Residual stress, fatigue and stress relief

[Peter Cole[_2_]]

"Metal Fatigue in Engineering", Ralph I. Stephens, Ali Fatemi, Robert R.
Stephens, Henry O. Fuchs, Ali Faterni
http://www.amazon.com/gp/reader/0471510599/ref=sib_dp_pop_toc?ie=UTF8&p=S008#reader-link

Page 247-8 describe creation of beneficial residual stress at a notch by
overloading in tension, whereby the stress concentrating effect of the
notch brings the material above yield in the immediate notch vicinity,
followed by a residual compressive stress when the overload is relaxed.
The undesirable residual stresses created by bending to form parts (skin
tension caused by forming compression) are also mentioned.

Page 257 describes stress relieving via yielding.

Page 259 describes modifying residual stress by overloading:

"In springs, as in other parts that are primarily loaded in one
direction, an overload applied early in life is beneficial because it
introduces desirable residual compressive stresses at the proper
surface. Springs, hoists and pressure vessels are strengthened by proof
loading with a higher load than the expected service load"

[jim beam]

Peter Cole wrote:
> "Metal Fatigue in Engineering", Ralph I. Stephens, Ali Fatemi, Robert R.
> Stephens, Henry O. Fuchs, Ali Faterni
> http://www.amazon.com/gp/reader/0471510599/ref=sib_dp_pop_toc?ie=UTF8&p=S008#reader-link
>
>
> Page 247-8 describe creation of beneficial residual stress at a notch by
> overloading in tension, whereby the stress concentrating effect of the
> notch brings the material above yield in the immediate notch vicinity,
> followed by a residual compressive stress when the overload is relaxed.
> The undesirable residual stresses created by bending to form parts (skin
> tension caused by forming compression) are also mentioned.
>
> Page 257 describes stress relieving via yielding.
>
> Page 259 describes modifying residual stress by overloading:
>
> "In springs, as in other parts that are primarily loaded in one
> direction, an overload applied early in life is beneficial because it
> introduces desirable residual compressive stresses at the proper
> surface. Springs, hoists and pressure vessels are strengthened by proof
> loading with a higher load than the expected service load"

see previous post.

existence of residual stress does not mean it causes spoke fatigue.
simple observation shows the truth. spokes are not observed to have
their cracking initiate in regions of high residual stress, but in
regions of high applied stress. as one might expect given that spoke
elbows, by definition, are subject to bending as a function of being
offset from the spoke axis.

simple observation of the facts. i suggest you try educating people on
basic scientific method rather than leaping to conclusions. or trolling.

[Leo Lichtman]

"jim beam" wrote: existence of residual stress does not mean it causes
spoke fatigue.
> simple observation shows the truth. spokes are not observed to have their
> cracking initiate in regions of high residual stress, but in regions of
> high applied stress. as one might expect given that spoke elbows, by
> definition, are subject to bending as a function of being offset from the
> spoke axis.
>
> simple observation of the facts. i suggest you try educating people on
> basic scientific method rather than leaping to conclusions. or trolling.
^^^^^^^^^^^^^^^^^^^^^^
Residual COMPRESSIVE stress would tend to reduce fatigue failure, since
fatigue cracks grow ONLY under tensile stress. That observation does not
depart from the scientific method. leap to conclusions, and certainly is not
trolling. Under tension, spoke bends try to straighten out, which creates
tensile stress on the inside of the bend. Any residual compressive stress
in that area as a result of the formation of the bend would have the effect
that Peter Cole referred to.

[jim beam]

Leo Lichtman wrote:
> "jim beam" wrote: existence of residual stress does not mean it causes
> spoke fatigue.
>> simple observation shows the truth. spokes are not observed to have their
>> cracking initiate in regions of high residual stress, but in regions of
>> high applied stress. as one might expect given that spoke elbows, by
>> definition, are subject to bending as a function of being offset from the
>> spoke axis.
>>
>> simple observation of the facts. i suggest you try educating people on
>> basic scientific method rather than leaping to conclusions. or trolling.
> ^^^^^^^^^^^^^^^^^^^^^^
> Residual COMPRESSIVE stress would tend to reduce fatigue failure, since
> fatigue cracks grow ONLY under tensile stress. That observation does not
> depart from the scientific method. leap to conclusions, and certainly is not
> trolling. Under tension, spoke bends try to straighten out, which creates
> tensile stress on the inside of the bend. Any residual compressive stress
> in that area as a result of the formation of the bend would have the effect
> that Peter Cole referred to.
>
>

but the region of highest residual stress is near the neutral plane, not
the outer parts of the bend where fatigue is always observed to
initiate. and in fact, fatigue is still observed to initiate where, if
there is any, compressive residual is compressive, on the outer part of
the elbow.

again, observe the facts, bother to understand the whole story, and
don't leap to conclusions.

[Ben C]

On 2008-04-23, Leo Lichtman > wrote:
>
> "jim beam" wrote: existence of residual stress does not mean it causes
> spoke fatigue.
>> simple observation shows the truth. spokes are not observed to have their
>> cracking initiate in regions of high residual stress, but in regions of
>> high applied stress. as one might expect given that spoke elbows, by
>> definition, are subject to bending as a function of being offset from the
>> spoke axis.
>>
>> simple observation of the facts. i suggest you try educating people on
>> basic scientific method rather than leaping to conclusions. or trolling.
> ^^^^^^^^^^^^^^^^^^^^^^
> Residual COMPRESSIVE stress would tend to reduce fatigue failure, since
> fatigue cracks grow ONLY under tensile stress. That observation does not
> depart from the scientific method. leap to conclusions, and certainly is not
> trolling. Under tension, spoke bends try to straighten out, which creates
> tensile stress on the inside of the bend. Any residual compressive stress
> in that area as a result of the formation of the bend would have the effect
> that Peter Cole referred to.

I think jim's point is that no-one has shown that spoke fatigue starts
on the inside of the bend significantly (or at all) more often than it
starts on the outside.

The evidence we would expect to see for residual stress being a factor
just isn't there.

Having said that many people (who aren't jim beam) don't scrutinize the
broken spoke carefully through a magnifying glass, but just chuck it in
the trash, so we wouldn't know.

[Peter Cole[_2_]]

Ben C wrote:

> The evidence we would expect to see for residual stress being a factor
> just isn't there.

The point I made by posting the source was that overloading was a
recognized technique to manipulate residual stress -- either to reduce
or increase it depending on the desired outcome.

If a spoke is laced with an elbow angle that is too large, there will be
a bending stress in operation (load stress) that will put the outside
skin in tension. If the angle is too small, the load stress will be
tension on the inside skin. If the load path for a spoke is straight
from the hub to the rim, there will be no moment (bending stress), only
uniform tension across the cross section and shear stress.

By overloading the spoke, any existing notch conditions (small cracks,
threads) yield in tension and after unloading have residual compressive
stress which retards crack growth (see reference). The important factor
is that the static load plus overload plus residual totals to greater
than yield, if only in very local spots where stresses become naturally
concentrated.

As for the claim that spokes always crack from the outside of the elbow
(which doesn't agree with my limited experience), it's a certainty that
cold forming a ~90 degree bend will leave micro cracks on the outside
skin. Stress relief will yield these and generate beneficial
(compressive) residual stress in the immediate vicinity (see reference).
It does not matter if the residual skin stress from forming was
compressive, the stress relief will mitigate the fatigue effect of
surface flaws and provide additional benefit. As Jobst has frequently
pointed out, these effects are at the microscopic level, the source I
cited explains the mechanism.

Stress relief by brief overload before a part is put into service is a
well established method for improving fatigue life. The only requirement
is that the overload be applied in the same direction as the service
load. The literature abounds with examples, I just cited one source.
This can only be controversial via willful ignorance.

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>
>> The evidence we would expect to see for residual stress being a factor
>> just isn't there.
>
> The point I made by posting the source was that overloading was a
> recognized technique to manipulate residual stress -- either to reduce
> or increase it depending on the desired outcome.
>
> If a spoke is laced with an elbow angle that is too large, there will be
> a bending stress in operation (load stress) that will put the outside
> skin in tension. If the angle is too small, the load stress will be
> tension on the inside skin. If the load path for a spoke is straight
> from the hub to the rim, there will be no moment (bending stress), only
> uniform tension across the cross section and shear stress.
>
> By overloading the spoke, any existing notch conditions (small cracks,
> threads) yield in tension and after unloading have residual compressive
> stress which retards crack growth (see reference). The important factor
> is that the static load plus overload plus residual totals to greater
> than yield, if only in very local spots where stresses become naturally
> concentrated.
>
> As for the claim that spokes always crack from the outside of the elbow
> (which doesn't agree with my limited experience), it's a certainty that
> cold forming a ~90 degree bend will leave micro cracks on the outside
> skin. Stress relief will yield these and generate beneficial
> (compressive) residual stress in the immediate vicinity (see reference).
> It does not matter if the residual skin stress from forming was
> compressive, the stress relief will mitigate the fatigue effect of
> surface flaws and provide additional benefit. As Jobst has frequently
> pointed out, these effects are at the microscopic level, the source I
> cited explains the mechanism.
>
> Stress relief by brief overload before a part is put into service is a
> well established method for improving fatigue life. The only requirement
> is that the overload be applied in the same direction as the service
> load. The literature abounds with examples, I just cited one source.
> This can only be controversial via willful ignorance.

yet again, fatigue is NOT observed to be initiating in regions affected
by high residual stress, "relieved" or not. and it's independent of
whether any residual is either compressive or tensile. but it IS
observed to be originating in regions of high /applied/ stress. and
that high applied stress is entirely a function of the design of the
component.

if you want to fix spoke breakage, change the design - don't waste your
time clutching at straws demonstrating ignorance and inability to
observe. move to straight pull spokes. that's what the smart
manufacturers with research budgets and engineers that have done their
homework have done.

[Ben C]

On 2008-04-23, Peter Cole > wrote:
> Ben C wrote:
>
>> The evidence we would expect to see for residual stress being a factor
>> just isn't there.
>
> The point I made by posting the source was that overloading was a
> recognized technique to manipulate residual stress -- either to reduce
> or increase it depending on the desired outcome.

Interesting point and thank you for posting it. The idea of creating
residual compressive stress at a notch as you describe is not something
I've heard before.

> If a spoke is laced with an elbow angle that is too large, there will be
> a bending stress in operation (load stress) that will put the outside
> skin in tension. If the angle is too small, the load stress will be
> tension on the inside skin. If the load path for a spoke is straight
> from the hub to the rim, there will be no moment (bending stress), only
> uniform tension across the cross section and shear stress.
>
> By overloading the spoke, any existing notch conditions (small cracks,
> threads) yield in tension and after unloading have residual compressive
> stress which retards crack growth (see reference). The important factor
> is that the static load plus overload plus residual totals to greater
> than yield, if only in very local spots where stresses become naturally
> concentrated.
>
> As for the claim that spokes always crack from the outside of the elbow
> (which doesn't agree with my limited experience)

I don't know who's claiming that. My understanding was that if residual
stress were a factor, we would expect to see the majority of outbound
spoke failures starting from the inside and the majority of inbound
spokes failures starting from the outside.

Let me just check I got that the right way round... Yes I think so since
residual stress is tensile on the outside of the bend for a spoke whose
angle you made less acute (inbound), and the other way round for the
other ones.

The highest residual stresses I think jim beam has been saying are in
the interior of the spoke and not on the skin at all.

But, we don't see any particular pattern of whether failure starts on
the outside or inside, or on the exterior or in the interior, for
outbound or inbound spokes one way or the other.

But as I said we don't have much evidence that there isn't such a
pattern either, since most people don't look at their broken spokes in
such detail.

It's a pity Jobst didn't since he reports experiencing a big change in
number of broken spokes after he started stress-relieving. Examination
of the broken spokes might have helped confirm the theory that residual
stress was a significant factor in why they broke.

But I think you're saying with this new link that fatigue would be
mitigated at notches on either side of either kind of spoke anyway.

> , it's a certainty that cold forming a ~90 degree bend will leave
> micro cracks on the outside skin. Stress relief will yield these and
> generate beneficial (compressive) residual stress in the immediate
> vicinity (see reference). It does not matter if the residual skin
> stress from forming was compressive, the stress relief will mitigate
> the fatigue effect of surface flaws and provide additional benefit.
>
> As Jobst has frequently
> pointed out, these effects are at the microscopic level, the source I
> cited explains the mechanism.

I don't remember Jobst mentioning anything about this mechanism of
notches resulting in compressive residual stress but never mind.

> Stress relief by brief overload before a part is put into service is a
> well established method for improving fatigue life. The only requirement
> is that the overload be applied in the same direction as the service
> load. The literature abounds with examples, I just cited one source.
> This can only be controversial via willful ignorance.

The controversy here is not that brief overload relieves stress or that
stress relief improves fatigue life. It's the claim that this is known
to be _the significant beneficial effect_ of spoke-squeezing, the Mavic
method, and other "stabilization" practices that people do when
wheel-building.

[[email protected]]

On Apr 23, 7:57 am, Peter Cole > wrote:
> Ben C wrote:
> > The evidence we would expect to see for residual stress being a factor
> > just isn't there.
>
> The point I made by posting the source was that overloading was a
> recognized technique to manipulate residual stress -- either to reduce
> or increase it depending on the desired outcome.
>
> If a spoke is laced with an elbow angle that is too large, there will be
> a bending stress in operation (load stress) that will put the outside
> skin in tension. If the angle is too small, the load stress will be
> tension on the inside skin. If the load path for a spoke is straight
> from the hub to the rim, there will be no moment (bending stress), only
> uniform tension across the cross section and shear stress.
>
> By overloading the spoke, any existing notch conditions (small cracks,
> threads) yield in tension and after unloading have residual compressive
> stress which retards crack growth (see reference). The important factor
> is that the static load plus overload plus residual totals to greater
> than yield, if only in very local spots where stresses become naturally
> concentrated.
>
> As for the claim that spokes always crack from the outside of the elbow
> (which doesn't agree with my limited experience), it's a certainty that
> cold forming a ~90 degree bend will leave micro cracks on the outside
> skin. Stress relief will yield these and generate beneficial
> (compressive) residual stress in the immediate vicinity (see reference).
> It does not matter if the residual skin stress from forming was
> compressive, the stress relief will mitigate the fatigue effect of
> surface flaws and provide additional benefit. As Jobst has frequently
> pointed out, these effects are at the microscopic level, the source I
> cited explains the mechanism.
>
> Stress relief by brief overload before a part is put into service is a
> well established method for improving fatigue life. The only requirement
> is that the overload be applied in the same direction as the service
> load. The literature abounds with examples, I just cited one source.
> This can only be controversial via willful ignorance.

There are other requirements than direction of applied proof load,
namely ductility and defect size. For a large defect in a ductile
material, you will in fact get plasticity and residual compression
when you release the load. If the defect is very small, or the
material is brittle, proof loading may form a crack. There will be
some residual compression at the crack tip, but not enough to make the
part stronger than it was before it was cracked.

[[email protected]]

On Apr 23, 11:06 am, Ben C > wrote:
> On 2008-04-23, Peter Cole > wrote:
>
> > Ben C wrote:
>
> >> The evidence we would expect to see for residual stress being a factor
> >> just isn't there.
>
> > The point I made by posting the source was that overloading was a
> > recognized technique to manipulate residual stress -- either to reduce
> > or increase it depending on the desired outcome.
>
> Interesting point and thank you for posting it. The idea of creating
> residual compressive stress at a notch as you describe is not something
> I've heard before.
>
>
>
> > If a spoke is laced with an elbow angle that is too large, there will be
> > a bending stress in operation (load stress) that will put the outside
> > skin in tension. If the angle is too small, the load stress will be
> > tension on the inside skin. If the load path for a spoke is straight
> > from the hub to the rim, there will be no moment (bending stress), only
> > uniform tension across the cross section and shear stress.
>
> > By overloading the spoke, any existing notch conditions (small cracks,
> > threads) yield in tension and after unloading have residual compressive
> > stress which retards crack growth (see reference). The important factor
> > is that the static load plus overload plus residual totals to greater
> > than yield, if only in very local spots where stresses become naturally
> > concentrated.
>
> > As for the claim that spokes always crack from the outside of the elbow
> > (which doesn't agree with my limited experience)
>
> I don't know who's claiming that. My understanding was that if residual
> stress were a factor, we would expect to see the majority of outbound
> spoke failures starting from the inside and the majority of inbound
> spokes failures starting from the outside.
>
> Let me just check I got that the right way round... Yes I think so since
> residual stress is tensile on the outside of the bend for a spoke whose
> angle you made less acute (inbound), and the other way round for the
> other ones.
>
> The highest residual stresses I think jim beam has been saying are in
> the interior of the spoke and not on the skin at all.
>
> But, we don't see any particular pattern of whether failure starts on
> the outside or inside, or on the exterior or in the interior, for
> outbound or inbound spokes one way or the other.
>

This is because residual compression on one side of the bend is
residual tension on the other, and trying to produce just the right
amount of residual stress in a spoke by hand is like aligning
microscope lenses with a framing hammer. It works great as long as
you never look into the eye piece.


>
> But as I said we don't have much evidence that there isn't such a
> pattern either, since most people don't look at their broken spokes in
> such detail.
>
> It's a pity Jobst didn't since he reports experiencing a big change in
> number of broken spokes after he started stress-relieving. Examination
> of the broken spokes might have helped confirm the theory that residual
> stress was a significant factor in why they broke.
>
> But I think you're saying with this new link that fatigue would be
> mitigated at notches on either side of either kind of spoke anyway.
>
> > , it's a certainty that cold forming a ~90 degree bend will leave
> > micro cracks on the outside skin. Stress relief will yield these and
> > generate beneficial (compressive) residual stress in the immediate
> > vicinity (see reference). It does not matter if the residual skin
> > stress from forming was compressive, the stress relief will mitigate
> > the fatigue effect of surface flaws and provide additional benefit.
>
> > As Jobst has frequently
> > pointed out, these effects are at the microscopic level, the source I
> > cited explains the mechanism.
>
> I don't remember Jobst mentioning anything about this mechanism of
> notches resulting in compressive residual stress but never mind.
>
> > Stress relief by brief overload before a part is put into service is a
> > well established method for improving fatigue life. The only requirement
> > is that the overload be applied in the same direction as the service
> > load. The literature abounds with examples, I just cited one source.
> > This can only be controversial via willful ignorance.
>
> The controversy here is not that brief overload relieves stress or that
> stress relief improves fatigue life. It's the claim that this is known
> to be _the significant beneficial effect_ of spoke-squeezing, the Mavic
> method, and other "stabilization" practices that people do when
> wheel-building.

[Leo Lichtman]

> wrote:
This is because residual compression on one side of the bend is
> residual tension on the other, (clip)
^^^^^^^^^^^^^^^^
No. You are evidently applying the equations for bending stress, with
symmetry about the neutral axis. If there are tensile stresses present, the
bending stresses add on one side and subtract on the other. Then, if the
higher value (either tensile or compressive) passes the yield point, the
symmetry is gone, and the residual stress could have an effect on fatigue
afterward.

[Peter Cole[_2_]]

Ben C wrote:

> The controversy here is not that brief overload relieves stress or that
> stress relief improves fatigue life.

Not true.

> It's the claim that this is known
> to be _the significant beneficial effect_ of spoke-squeezing, the Mavic
> method, and other "stabilization" practices that people do when
> wheel-building.

Not true. The specific claim (originally by Jobst) is that spoke
squeezing causes stress relief by the exact mechanism described in the
sources I cited. "Stabilization" is your word -- and a meaningless one,
too. Stress relief is a specific term. That there are residual stresses
in spokes is not a matter of faith. Overloading in the direction of the
working load will either diminish undesirable residual stresses or
create desirable residual stresses or both. That is the whole point. It
needs no other qualifications.

[Peter Cole[_2_]]

wrote:

> There are other requirements than direction of applied proof load,
> namely ductility and defect size. For a large defect in a ductile
> material, you will in fact get plasticity and residual compression
> when you release the load. If the defect is very small, or the
> material is brittle, proof loading may form a crack. There will be
> some residual compression at the crack tip, but not enough to make the
> part stronger than it was before it was cracked.

That's not what my sources say. I'd be happy to look at yours.

[Peter Cole[_2_]]

wrote:

> This is because residual compression on one side of the bend is
> residual tension on the other, and trying to produce just the right
> amount of residual stress in a spoke by hand is like aligning
> microscope lenses with a framing hammer. It works great as long as
> you never look into the eye piece.

It doesn't matter for the overload method of stress relief. That's what
makes it such a useful technique.

[Peter Cole[_2_]]

Ben C wrote:

> I don't remember Jobst mentioning anything about this mechanism of
> notches resulting in compressive residual stress but never mind.

Never mind, yourself. If threads aren't notches, I don't know what are.
Jobst claimed that his technique of stress relief would improve failure
rates at the threads, too. The published material I cited supports this
claim.

[Peter Cole[_2_]]

wrote:

> If the defect is very small, or the
> material is brittle, proof loading may form a crack. There will be
> some residual compression at the crack tip, but not enough to make the
> part stronger than it was before it was cracked.

If you take the trouble to read the text I cited, you'll see the
specific case of gun barrels is described, where overloading serves 2
purposes -- either it will improve the fatigue life, or if the crack is
already severe it will cause a complete failure then and there. This is
exactly the principle Jobst Brandt describes in stress relieving spokes
that have already been in service.

[Peter Cole[_2_]]

Ben C wrote:

> I think jim's point is that no-one has shown that spoke fatigue starts
> on the inside of the bend significantly (or at all) more often than it
> starts on the outside.

"jim beam" doesn't correct his spoke lines. He will have a moment under
normal load. That will likely be larger than any residual stress
contribution.

> The evidence we would expect to see for residual stress being a factor
> just isn't there.
>
> Having said that many people (who aren't jim beam) don't scrutinize the
> broken spoke carefully through a magnifying glass, but just chuck it in
> the trash, so we wouldn't know.

People like Jobst & I are at a disadvantage from a "forensics" angle --
we don't break spokes, so have no samples to analyze. "jim beam" seems
to have plenty. Follow his faith-based analysis if you want.

[Ben C]

On 2008-04-23, Peter Cole > wrote:
> Ben C wrote:
>
>> The controversy here is not that brief overload relieves stress or that
>> stress relief improves fatigue life.
>
> Not true.
>
>> It's the claim that this is known
>> to be _the significant beneficial effect_ of spoke-squeezing, the Mavic
>> method, and other "stabilization" practices that people do when
>> wheel-building.
>
> Not true. The specific claim (originally by Jobst) is that spoke
> squeezing causes stress relief by the exact mechanism described in the
> sources I cited. "Stabilization" is your word -- and a meaningless one,
> too.

The idea is to choose a term that does not rule out that spoke squeezing
(etc.) may have a beneficial effect but that isn't because it relieves
residual stress.

> Stress relief is a specific term. That there are residual stresses
> in spokes is not a matter of faith.

No, but that they make any practical difference to how quickly the spoke
breaks or not is.

[Ben C]

On 2008-04-23, Peter Cole > wrote:
> Ben C wrote:
>
>> I think jim's point is that no-one has shown that spoke fatigue starts
>> on the inside of the bend significantly (or at all) more often than it
>> starts on the outside.
>
> "jim beam" doesn't correct his spoke lines. He will have a moment under
> normal load. That will likely be larger than any residual stress
> contribution.

The presence of moment under normal load is my preferred likely
candidate for what causes most spoke failures.

And in fact part of what Jobst calls "residual stress" is I believe
just a convoluted description of moment under load.

He says that when you put the bend in the elbow of an outbound spoke the
bend can't spring back because the flange is in the way but is held
there by spoke tension. He calls that "residual stress", which is
confusing, but that's what he calls it.

For that to be possible there must be quite a bit of moment, since spoke
tension is not high enough to hold a bend in an elbow that is close to
flush with the flange. Overloading reduces that tension by bending the
elbow and/or deforming the hub and reducing the moment. Jobst says
instead overloading deforms the fibres or something and relieves the
"residual stress". But it is actually basically the same thing (although
I think Jobst denies the hub can possibly deform at this point).

That is my conclusion from all the discussions I have read about this on
RBT. Residual stress deserves mention as a possible mechanism that may
also be involved, but no more than that.

Beam is right: straight-pull spokes are a better design. On the other
hand with aluminium hubs and quality steel spokes breakages are rare
these days so it's not really as big a problem as a casual reader of RBT
might take it for.

>> The evidence we would expect to see for residual stress being a factor
>> just isn't there.
>>
>> Having said that many people (who aren't jim beam) don't scrutinize the
>> broken spoke carefully through a magnifying glass, but just chuck it in
>> the trash, so we wouldn't know.
>
> People like Jobst & I are at a disadvantage from a "forensics" angle --
> we don't break spokes, so have no samples to analyze.

I thought Jobst did used to break them before he started
stress-relieving.

> "jim beam" seems to have plenty. Follow his faith-based analysis if
> you want.

I know you don't really want to be a troll. Fight the urge.

[daveornee[_184_]]

Peter Cole Wrote:
> Ben C wrote:
>
> > The controversy here is not that brief overload relieves stress or
> that
> > stress relief improves fatigue life.
>
> Not true.
>
> > It's the claim that this is known
> > to be _the significant beneficial effect_ of spoke-squeezing, the
> Mavic
> > method, and other "stabilization" practices that people do when
> > wheel-building.
>
> Not true. The specific claim (originally by Jobst) is that spoke
> squeezing causes stress relief by the exact mechanism described in the
> sources I cited. "Stabilization" is your word -- and a meaningless
> one,
> too. Stress relief is a specific term. That there are residual
> stresses
> in spokes is not a matter of faith. Overloading in the direction of
> the
> working load will either diminish undesirable residual stresses or
> create desirable residual stresses or both. That is the whole point.
> It
> needs no other qualifications.
"Stabilizing" is a term used Barnett Bicycle Institute in thier wheel
building classes. It is not meaningless. Stabilizing makes sure the
spokes are embeded and residual windup removed. The process also
temporarily overloads spokes in the direction of the working load....
likely better than the spoke squeezing method. I can see and
immediately measure the results of the process. I know that if a wheel
isn't stabilized it will detension as it is ridden... sometimes to the
point where nipples will back-off and the wheel will have spokes that
are totally slack.


--
daveornee

[[email protected]]

On Apr 23, 4:11 pm, "Leo Lichtman" >
wrote:
> > wrote:
>
> This is because residual compression on one side of the bend is> residual tension on the other, (clip)
>
> ^^^^^^^^^^^^^^^^
> No. You are evidently applying the equations for bending stress, with
> symmetry about the neutral axis. If there are tensile stresses present, the
> bending stresses add on one side and subtract on the other. Then, if the
> higher value (either tensile or compressive) passes the yield point, the
> symmetry is gone, and the residual stress could have an effect on fatigue
> afterward.

I'm applying the equations for static equilibrium. If some part of
your spoke is under residual compression, the material around that
zone must be in tension to keep it there.

[[email protected]]

On Apr 23, 4:20 pm, Peter Cole > wrote:
> wrote:
> > This is because residual compression on one side of the bend is
> > residual tension on the other, and trying to produce just the right
> > amount of residual stress in a spoke by hand is like aligning
> > microscope lenses with a framing hammer. It works great as long as
> > you never look into the eye piece.
>
> It doesn't matter for the overload method of stress relief. That's what
> makes it such a useful technique.

So the magnitude doesn't matter? Proof loading of things like gun
barrels is done to a fairly precise stress level. To think that
without doing any calculations on spoke yielding and cracking or using
any instrumentation in application other than your bare hands will
achieve this level of precision is absurd. I'm willing to believe
that residual stresses may improve fatigue life under the right proof
loading conditions, but I will not accept that the average wheel
builder (myself included) has taken the time to figure out exactly
what those conditions are and ensured that they're being followed.

[Michael Press]

In article >,
daveornee > wrote:

> Peter Cole Wrote:
> > Ben C wrote:
> >
> > > The controversy here is not that brief overload relieves stress or
> > that
> > > stress relief improves fatigue life.
> >
> > Not true.
> >
> > > It's the claim that this is known
> > > to be _the significant beneficial effect_ of spoke-squeezing, the
> > Mavic
> > > method, and other "stabilization" practices that people do when
> > > wheel-building.
> >
> > Not true. The specific claim (originally by Jobst) is that spoke
> > squeezing causes stress relief by the exact mechanism described in the
> > sources I cited. "Stabilization" is your word -- and a meaningless
> > one,
> > too. Stress relief is a specific term. That there are residual
> > stresses
> > in spokes is not a matter of faith. Overloading in the direction of
> > the
> > working load will either diminish undesirable residual stresses or
> > create desirable residual stresses or both. That is the whole point.
> > It
> > needs no other qualifications.
> "Stabilizing" is a term used Barnett Bicycle Institute in thier wheel
> building classes. It is not meaningless. Stabilizing makes sure the
> spokes are embeded and residual windup removed.

Thereby putting the wheel out of true.
Spoke wind up is never present when
attention is paid while turning the
nipples. Turn until the nipple turns
with respect to the spoke, then back
the spoke wrench until the spoke is
not wound up.


> The process also
> temporarily overloads spokes in the direction of the working load....

No it does not. All strain is elastic when the
spoke wrench turns the nipple.

> likely better than the spoke squeezing method. I can see and
> immediately measure the results of the process. I know that if a wheel
> isn't stabilized it will detension as it is ridden...

No it won't. Nipples unwind when the spoke tension is insufficient
to the job of carrying the cyclic load at the contact patch.

> sometimes to the
> point where nipples will back-off and the wheel will have spokes that
> are totally slack.

Oil the threads and spoke bed. Use a sufficient number
of spokes to carry the load.

--
Michael Press

[daveornee[_185_]]

Michael Press Wrote:
> In article >,
> daveornee > wrote:
>
> > Peter Cole Wrote:
> > > Ben C wrote:
> > >
> > > > The controversy here is not that brief overload relieves stress
> or
> > > that
> > > > stress relief improves fatigue life.
> > >
> > > Not true.
> > >
> > > > It's the claim that this is known
> > > > to be _the significant beneficial effect_ of spoke-squeezing,
> the
> > > Mavic
> > > > method, and other "stabilization" practices that people do when
> > > > wheel-building.
> > >
> > > Not true. The specific claim (originally by Jobst) is that spoke
> > > squeezing causes stress relief by the exact mechanism described in
> the
> > > sources I cited. "Stabilization" is your word -- and a meaningless
> > > one,
> > > too. Stress relief is a specific term. That there are residual
> > > stresses
> > > in spokes is not a matter of faith. Overloading in the direction
> of
> > > the
> > > working load will either diminish undesirable residual stresses or
> > > create desirable residual stresses or both. That is the whole
> point.
> > > It
> > > needs no other qualifications.
> > "Stabilizing" is a term used Barnett Bicycle Institute in thier
> wheel
> > building classes. It is not meaningless. Stabilizing makes sure
> the
> > spokes are embeded and residual windup removed.
>
> Thereby putting the wheel out of true.
> Spoke wind up is never present when
> attention is paid while turning the
> nipples. Turn until the nipple turns
> with respect to the spoke, then back
> the spoke wrench until the spoke is
> not wound up.
>
>
> > The process also
> > temporarily overloads spokes in the direction of the working
> load....
>
> No it does not. All strain is elastic when the
> spoke wrench turns the nipple.
>
> > likely better than the spoke squeezing method. I can see and
> > immediately measure the results of the process. I know that if a
> wheel
> > isn't stabilized it will detension as it is ridden...
>
> No it won't. Nipples unwind when the spoke tension is insufficient
> to the job of carrying the cyclic load at the contact patch.
>
> > sometimes to the
> > point where nipples will back-off and the wheel will have spokes
> that
> > are totally slack.
>
> Oil the threads and spoke bed. Use a sufficient number
> of spokes to carry the load.
>
> --
> Michael Press
I build my way and it always works. I properly lubricate the threads
and I make sure there isn't windup as I tighten nipples.
If the wheel goes out of true while stabilizing it isn't likely to stay
true when riding.
I use the proper numbers of spokes for the intended loads in my
builds.
I don't uderstand what you mean:
"No it does not. All strain is elastic when the spoke wrench turns the
nipple."
Pick apart as you want!


--
daveornee

[jim beam]

wrote:
> On Apr 23, 4:20 pm, Peter Cole > wrote:
>> wrote:
>>> This is because residual compression on one side of the bend is
>>> residual tension on the other, and trying to produce just the right
>>> amount of residual stress in a spoke by hand is like aligning
>>> microscope lenses with a framing hammer. It works great as long as
>>> you never look into the eye piece.
>> It doesn't matter for the overload method of stress relief. That's what
>> makes it such a useful technique.
>
> So the magnitude doesn't matter?

of course they do. peter cole is just clutching at straws at this point.


> Proof loading of things like gun
> barrels is done to a fairly precise stress level. To think that
> without doing any calculations on spoke yielding and cracking or using
> any instrumentation in application other than your bare hands will
> achieve this level of precision is absurd. I'm willing to believe
> that residual stresses may improve fatigue life under the right proof
> loading conditions, but I will not accept that the average wheel
> builder (myself included) has taken the time to figure out exactly
> what those conditions are and ensured that they're being followed.

[jim beam]

daveornee wrote:
> Peter Cole Wrote:
>> Ben C wrote:
>>
>>> The controversy here is not that brief overload relieves stress or
>> that
>>> stress relief improves fatigue life.
>> Not true.
>>
>>> It's the claim that this is known
>>> to be _the significant beneficial effect_ of spoke-squeezing, the
>> Mavic
>>> method, and other "stabilization" practices that people do when
>>> wheel-building.
>> Not true. The specific claim (originally by Jobst) is that spoke
>> squeezing causes stress relief by the exact mechanism described in the
>> sources I cited. "Stabilization" is your word -- and a meaningless
>> one,
>> too. Stress relief is a specific term. That there are residual
>> stresses
>> in spokes is not a matter of faith. Overloading in the direction of
>> the
>> working load will either diminish undesirable residual stresses or
>> create desirable residual stresses or both. That is the whole point.
>> It
>> needs no other qualifications.
> "Stabilizing" is a term used Barnett Bicycle Institute in thier wheel
> building classes. It is not meaningless. Stabilizing makes sure the
> spokes are embeded and residual windup removed. The process also
> temporarily overloads spokes in the direction of the working load....
> likely better than the spoke squeezing method. I can see and
> immediately measure the results of the process. I know that if a wheel
> isn't stabilized it will detension as it is ridden... sometimes to the
> point where nipples will back-off and the wheel will have spokes that
> are totally slack.
>
>


indeed. and it's easy to test this observation at home - it's not like
this is inaccessible rocket surgery.

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>
>> I think jim's point is that no-one has shown that spoke fatigue starts
>> on the inside of the bend significantly (or at all) more often than it
>> starts on the outside.
>
> "jim beam" doesn't correct his spoke lines. He will have a moment under
> normal load. That will likely be larger than any residual stress
> contribution.
>
>> The evidence we would expect to see for residual stress being a factor
>> just isn't there.
>>
>> Having said that many people (who aren't jim beam) don't scrutinize the
>> broken spoke carefully through a magnifying glass, but just chuck it in
>> the trash, so we wouldn't know.
>
> People like Jobst & I are at a disadvantage from a "forensics" angle --
> we don't break spokes, so have no samples to analyze. "jim beam" seems
> to have plenty.

so how freakin' hard is it to go to a bike shop and get them to save a
bunch of broken spokes for you??????????? neither you nor jobst can
manage this? how about find a magnifier and bother to look at the
fatigue patterns?????


> Follow his faith-based analysis if you want.

try observing fact - it makes life a lot easier than trying to swallow
misinterpreted garbage from a pair of lazy presumptive bull****ting
amateurs!!!

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>
>> I don't remember Jobst mentioning anything about this mechanism of
>> notches resulting in compressive residual stress but never mind.
>
> Never mind, yourself. If threads aren't notches, I don't know what are.
> Jobst claimed that his technique of stress relief would improve failure
> rates at the threads, too. The published material I cited supports this
> claim.

er, actually, the residual stress at the root of cold rolled threads is
compressive, not tensile. you *don't* want to "relieve" that.

and your cite is for the phenomenon of residual stress and mechanical
stress relief. nobody contests that it exists. what's being contested,
and the point you /still/ don't seem to be able to grasp, is that
OBSERVATION OF THE FACTS contradicts the supposition that it plays any
material role in spoke fatigue. supposition, not matter how hotly
defended, is simply not fact, and no amount of repetition by either you
or jobst can make it so.

[jim beam]

Ben C wrote:
> On 2008-04-23, Peter Cole > wrote:
>> Ben C wrote:
>>
>>> I think jim's point is that no-one has shown that spoke fatigue starts
>>> on the inside of the bend significantly (or at all) more often than it
>>> starts on the outside.
>> "jim beam" doesn't correct his spoke lines. He will have a moment under
>> normal load. That will likely be larger than any residual stress
>> contribution.
>
> The presence of moment under normal load is my preferred likely
> candidate for what causes most spoke failures.
>
> And in fact part of what Jobst calls "residual stress" is I believe
> just a convoluted description of moment under load.

no, he's completely unclear on either concept.


>
> He says that when you put the bend in the elbow of an outbound spoke the
> bend can't spring back because the flange is in the way but is held
> there by spoke tension. He calls that "residual stress", which is
> confusing, but that's what he calls it.

it's not confusing, it's just plain wrong. see above.


>
> For that to be possible there must be quite a bit of moment, since spoke
> tension is not high enough to hold a bend in an elbow that is close to
> flush with the flange. Overloading reduces that tension by bending the
> elbow and/or deforming the hub and reducing the moment. Jobst says
> instead overloading deforms the fibres or something and relieves the
> "residual stress". But it is actually basically the same thing (although
> I think Jobst denies the hub can possibly deform at this point).
>
> That is my conclusion from all the discussions I have read about this on
> RBT. Residual stress deserves mention as a possible mechanism that may
> also be involved, but no more than that.

why bother to muddy the water with something not observed to be the
case? if we want to discuss irrelevancies, let's discuss stress
corrosion cracking and hydrogen embrittlement as well!


>
> Beam is right: straight-pull spokes are a better design. On the other
> hand with aluminium hubs and quality steel spokes breakages are rare
> these days so it's not really as big a problem as a casual reader of RBT
> might take it for.
>
>>> The evidence we would expect to see for residual stress being a factor
>>> just isn't there.
>>>
>>> Having said that many people (who aren't jim beam) don't scrutinize the
>>> broken spoke carefully through a magnifying glass, but just chuck it in
>>> the trash, so we wouldn't know.
>> People like Jobst & I are at a disadvantage from a "forensics" angle --
>> we don't break spokes, so have no samples to analyze.
>
> I thought Jobst did used to break them before he started
> stress-relieving.

and he failed to correlate his use of the new breed of spoke, made of
fatigue resistant vacuum degassed stainless steel, with prolonged life,
instead attributing it to the process he "invented" [copied] instead.
that kind of, er, "oversight" might be good for selling books to those
with insufficient scientific or engineering background, but it's just
plain insulting to those who do.


>
>> "jim beam" seems to have plenty. Follow his faith-based analysis if
>> you want.
>
> I know you don't really want to be a troll. Fight the urge.

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>
>> The controversy here is not that brief overload relieves stress or that
>> stress relief improves fatigue life.
>
> Not true.
>
>> It's the claim that this is known
>> to be _the significant beneficial effect_ of spoke-squeezing, the Mavic
>> method, and other "stabilization" practices that people do when
>> wheel-building.
>
> Not true. The specific claim (originally by Jobst) is that spoke
> squeezing causes stress relief by the exact mechanism described in the
> sources I cited. "Stabilization" is your word -- and a meaningless one,
> too. Stress relief is a specific term. That there are residual stresses
> in spokes is not a matter of faith. Overloading in the direction of the
> working load will either diminish undesirable residual stresses or
> create desirable residual stresses or both. That is the whole point. It
> needs no other qualifications.

jobstian "stress relief" theory is presumptive nonsense that has no
correlation with observed fact. it's as well grounded as his assumption
that fatigue can be eliminated from spokes made of stainless steel, a
material with no fatigue endurance limit.

absent sufficient knowledge and absent proper application of scientific
method, you're just perpetuating jobstian mistakes - and looking foolish
to boot.

[Ron Ruff]

On Apr 23, 4:44*pm, wrote:
> So the magnitude doesn't matter?

I suppose it would be nice to be more precise about this, but I'm not
sure it matters a whole lot. I'm presently thinking that more is
better for spokes... bending spokes at the hub, cross, and nipple, and
then stressing them as much as I can after full (and even excessive)
final build tension is acheived. Pressing on the spokes with the wheel
laying on a soft surface seems to work best. Pressing on the rim will
also work except for DS and carbon rims.

[[email protected]]

On Apr 24, 1:07 am, Ron Ruff > wrote:
> On Apr 23, 4:44 pm, wrote:
>
> > So the magnitude doesn't matter?
>
> I suppose it would be nice to be more precise about this, but I'm not
> sure it matters a whole lot. I'm presently thinking that more is
> better for spokes... bending spokes at the hub, cross, and nipple, and
> then stressing them as much as I can after full (and even excessive)
> final build tension is acheived. Pressing on the spokes with the wheel
> laying on a soft surface seems to work best. Pressing on the rim will
> also work except for DS and carbon rims.

It only matters if your "more is better" is enough to initiate cracks,
but not enough to immediately fracture the whole spoke.

[Peter Cole[_2_]]

Ben C wrote:
> On 2008-04-23, Peter Cole > wrote:

>> Stress relief is a specific term. That there are residual stresses
>> in spokes is not a matter of faith.
>
> No, but that they make any practical difference to how quickly the spoke
> breaks or not is.

If there are residual stresses, there must be both tension and
compression residuals. Since the working load is tension, tension
residuals are bad for fatigue, compression residuals are harmless or
beneficial. By overloading in the working direction, tension residuals
-- wherever they occur -- are reduced.

Additionally, notches act as stress concentrators, so will multiply the
working stress. By overloading, the immediate vicinity yields, creating
a beneficial compression residual.

All of the above statements are true. Stress relief can only improve
fatigue life, whether the root cause of premature failure is residual
stress or notches (defects).

The only other possible cause for early spoke fatigue is the presence of
a bending moment in the working load. If the spoke is properly formed
and supported this won't exist. If it did, the peak stress would be at
the skin, and an overload would yield those spots close to yield (just
as it would near a notch). Again, identically, it would improve fatigue
life.

All 3 of the above scenarios are not speculative.

A speculative scenario that has been proposed is that the overload "beds
in" the spoke heads to the (aluminum, presumably) hub flange, by
deforming the material. Consider that the overload is only (nominally)
50%. We are to believe that the spoke head will sink further into the
beveled hole in the flange? If it did, what benefit would that yield?
Perhaps it's the "bedding" of the spoke into the hole bore? The spoke
shaft into the hub flange? The theory (presumably) is that the spoke
elbow is not well supported initially (after tensioning) and that the
50% overload will deform the hub enough to change the elbow support
enough to remove a significant amount of bending moment.

Problems with the above speculation:

It assumes that the 50% overload somehow achieves a critical amount of
hole deformation that the initial tension didn't.

It assumes that the hole wall deforms, but the spoke doesn't plastically
yield (bend further).

Assuming the flange holes are parallel to the axle (check it if you
don't believe -- I did), and that spoke elbows are initially formed (at
the factory) to 90-95 degrees, that angle can't be optimal for both in
and out bound spokes (bracing angle +-5-8 degrees), the speculation
assumes that the out bound hole is wallowed (by shear force*) to match
the spoke angle, while the in bound hole (subject to the same shear
force) is not. If they both deform to the same degree, then the angular
mismatch remains, and a bending moment remains. *must be shear, else
spoke would bend.

If spoke tension lowers after stress relief (commonly observed) and the
spokes are not unwinding (or unscrewing), then something must have
yielded. The spoke can not have stretched (insufficient force), so the
candidates are: spoke interfaces (hub, nipple/rim) or spoke bending
(elbow, nipple). The "hub bedding" speculation assumes that the force is
high enough to deform (additionally) the hole edge (and change the
"bedding angle") without changing the spoke elbow angle (bending). How
can the bedding angle change while the spoke elbow angle doesn't? It
can't. If the bedding angle changes while the spoke is being tensioned
and/or stress relieved, the spoke elbow angle must change, too (it is in
contact). It doesn't really matter if the change is plastic (it is,
since elbows take a set), since even an elastic change would leave the
skin close to yield. Stress relieving adds a tension component to the
bending stress, yielding the areas brought close to yield from the
bending stress.

It doesn't matter how the overload is applied, only that it be in the
same direction as the working load. It will reduce operating stresses
whether from residual manufacturing stress, stress raisers or skin
stress from (static) bending moments.

[Peter Cole[_2_]]

wrote:
> On Apr 24, 1:07 am, Ron Ruff > wrote:
>> On Apr 23, 4:44 pm, wrote:
>>
>>> So the magnitude doesn't matter?
>> I suppose it would be nice to be more precise about this, but I'm not
>> sure it matters a whole lot. I'm presently thinking that more is
>> better for spokes... bending spokes at the hub, cross, and nipple, and
>> then stressing them as much as I can after full (and even excessive)
>> final build tension is acheived. Pressing on the spokes with the wheel
>> laying on a soft surface seems to work best. Pressing on the rim will
>> also work except for DS and carbon rims.
>
> It only matters if your "more is better" is enough to initiate cracks,
> but not enough to immediately fracture the whole spoke.

"Initiate cracks" with a single load cycle to ~50% yield? Please, let's
be serious.

[Ben C]

On 2008-04-24, Peter Cole > wrote:
> Ben C wrote:
>> On 2008-04-23, Peter Cole > wrote:
>
>>> Stress relief is a specific term. That there are residual stresses
>>> in spokes is not a matter of faith.
>>
>> No, but that they make any practical difference to how quickly the spoke
>> breaks or not is.
>
> If there are residual stresses, there must be both tension and
> compression residuals. Since the working load is tension, tension
> residuals are bad for fatigue, compression residuals are harmless or
> beneficial. By overloading in the working direction, tension residuals
> -- wherever they occur -- are reduced.
>
> Additionally, notches act as stress concentrators, so will multiply the
> working stress. By overloading, the immediate vicinity yields, creating
> a beneficial compression residual.
>
> All of the above statements are true. Stress relief can only improve
> fatigue life, whether the root cause of premature failure is residual
> stress or notches (defects).

OK, yes I think I agree with that-- that it is unlikely to make the
residual stress situation worse than it was before in any way.

> The only other possible cause for early spoke fatigue is the presence of
> a bending moment in the working load.

That's my prime suspect.

> If the spoke is properly formed
> and supported this won't exist. If it did, the peak stress would be at
> the skin, and an overload would yield those spots close to yield (just
> as it would near a notch). Again, identically, it would improve fatigue
> life.

Yes, by bending the spoke (or crushing the hub) a bit thereby reducing
the moment.

> All 3 of the above scenarios are not speculative.
>
> A speculative scenario that has been proposed is that the overload "beds
> in" the spoke heads to the (aluminum, presumably) hub flange, by
> deforming the material.

That is possible. I agree that it is speculative. We know that hub holes
deform, but not that that happens during wheel stabilization rather than
in the earlier stages of tensioning.

> Consider that the overload is only (nominally)
> 50%. We are to believe that the spoke head will sink further into the
> beveled hole in the flange? If it did, what benefit would that yield?

Reducing moment.

> Perhaps it's the "bedding" of the spoke into the hole bore? The spoke
> shaft into the hub flange? The theory (presumably) is that the spoke
> elbow is not well supported initially (after tensioning) and that the
> 50% overload will deform the hub enough to change the elbow support
> enough to remove a significant amount of bending moment.

You got it!

> Problems with the above speculation:
>
> It assumes that the 50% overload somehow achieves a critical amount of
> hole deformation that the initial tension didn't.

Agreed.

> It assumes that the hole wall deforms, but the spoke doesn't plastically
> yield (bend further).

Well, I think the spoke probably _does_ bend further. Stabilization is
justa another way of improving spoke line. Most likely scenario in my
opinion is that it does that by bending the elbow, but it is also
possible (though more speculative) that the hub may yield a bit too at
this point.

> Assuming the flange holes are parallel to the axle (check it if you
> don't believe -- I did), and that spoke elbows are initially formed (at
> the factory) to 90-95 degrees, that angle can't be optimal for both in
> and out bound spokes (bracing angle +-5-8 degrees), the speculation
> assumes that the out bound hole is wallowed (by shear force*) to match
> the spoke angle, while the in bound hole (subject to the same shear
> force) is not. If they both deform to the same degree, then the angular
> mismatch remains, and a bending moment remains. *must be shear, else
> spoke would bend.
>
> If spoke tension lowers after stress relief (commonly observed) and the
> spokes are not unwinding (or unscrewing), then something must have
> yielded. The spoke can not have stretched (insufficient force), so the
> candidates are: spoke interfaces (hub, nipple/rim) or spoke bending
> (elbow, nipple). The "hub bedding" speculation assumes that the force is
> high enough to deform (additionally) the hole edge (and change the
> "bedding angle") without changing the spoke elbow angle (bending). How
> can the bedding angle change while the spoke elbow angle doesn't? It
> can't.

It depends how small the moment is. The smaller the moment, the more
deformation of the hub can (possibly) occur.

> If the bedding angle changes while the spoke is being tensioned
> and/or stress relieved, the spoke elbow angle must change, too (it is in
> contact). It doesn't really matter if the change is plastic (it is,
> since elbows take a set), since even an elastic change would leave the
> skin close to yield. Stress relieving adds a tension component to the
> bending stress, yielding the areas brought close to yield from the
> bending stress.
>
> It doesn't matter how the overload is applied, only that it be in the
> same direction as the working load. It will reduce operating stresses
> whether from residual manufacturing stress, stress raisers or skin
> stress from (static) bending moments.

I agree with all that, I just think the last of those three is likely to
be the significant one.

Another question I've asked a few times but don't remember anyone
answering satisfactorily (my apologies if they have) is what happens to
these residual manufacturing stresses after you correct the spoke line?

I have a spoke with a bend in it from the factory. There are residual
stresses due to this bend. So far so good. Then I bend it some more to
change the angle. What has now happened to the original residual
stresses?

[Peter Cole[_2_]]

Ben C wrote:
> On 2008-04-24, Peter Cole > wrote:

>> It doesn't matter how the overload is applied, only that it be in the
>> same direction as the working load. It will reduce operating stresses
>> whether from residual manufacturing stress, stress raisers or skin
>> stress from (static) bending moments.
>
> I agree with all that, I just think the last of those three is likely to
> be the significant one.

Well, you're entitled to your opinions, but stress relief will be
beneficial in all cases. The overload technique will reduce all tension
stress in the tensioned wheel that are close to yield.

Since the spoke line can't be initially right for both out & in bound
spokes, and, to the extent that hole deformation occurs, it helps one &
harms the other, the spoke line must be corrected. That will introduce
additional residual stresses, which need be relieved. If there is any
residual mismatch between spoke elbow angle and spoke bed angle, that
will introduce static stresses. These are reduced by stress relieving,
whether there is additional hole deformation or not.

[Michael Press]

In article >,
daveornee > wrote:

> Michael Press Wrote:
> > In article >,
> > daveornee > wrote:
> >
> > > Peter Cole Wrote:
> > > > Ben C wrote:
> > > >
> > > > > The controversy here is not that brief overload relieves stress
> > or
> > > > that
> > > > > stress relief improves fatigue life.
> > > >
> > > > Not true.
> > > >
> > > > > It's the claim that this is known
> > > > > to be _the significant beneficial effect_ of spoke-squeezing,
> > the
> > > > Mavic
> > > > > method, and other "stabilization" practices that people do when
> > > > > wheel-building.
> > > >
> > > > Not true. The specific claim (originally by Jobst) is that spoke
> > > > squeezing causes stress relief by the exact mechanism described in
> > the
> > > > sources I cited. "Stabilization" is your word -- and a meaningless
> > > > one,
> > > > too. Stress relief is a specific term. That there are residual
> > > > stresses
> > > > in spokes is not a matter of faith. Overloading in the direction
> > of
> > > > the
> > > > working load will either diminish undesirable residual stresses or
> > > > create desirable residual stresses or both. That is the whole
> > point.
> > > > It
> > > > needs no other qualifications.
> > > "Stabilizing" is a term used Barnett Bicycle Institute in thier
> > wheel
> > > building classes. It is not meaningless. Stabilizing makes sure
> > the
> > > spokes are embeded and residual windup removed.
> >
> > Thereby putting the wheel out of true.
> > Spoke wind up is never present when
> > attention is paid while turning the
> > nipples. Turn until the nipple turns
> > with respect to the spoke, then back
> > the spoke wrench until the spoke is
> > not wound up.
> >
> >
> > > The process also
> > > temporarily overloads spokes in the direction of the working
> > load....
> >
> > No it does not. All strain is elastic when the
> > spoke wrench turns the nipple.
> >
> > > likely better than the spoke squeezing method. I can see and
> > > immediately measure the results of the process. I know that if a
> > wheel
> > > isn't stabilized it will detension as it is ridden...
> >
> > No it won't. Nipples unwind when the spoke tension is insufficient
> > to the job of carrying the cyclic load at the contact patch.
> >
> > > sometimes to the
> > > point where nipples will back-off and the wheel will have spokes
> > that
> > > are totally slack.
> >
> > Oil the threads and spoke bed. Use a sufficient number
> > of spokes to carry the load.
> >
> I build my way and it always works. I properly lubricate the threads
> and I make sure there isn't windup as I tighten nipples.
> If the wheel goes out of true while stabilizing it isn't likely to stay
> true when riding.
> I use the proper numbers of spokes for the intended loads in my
> builds.
> I don't uderstand what you mean:
> "No it does not. All strain is elastic when the spoke wrench turns the
> nipple."

I was confused when you said "the process",
and take back what I said there.


[...]

--
Michael Press

[Peter Cole[_2_]]

Ben C wrote:

> Another question I've asked a few times but don't remember anyone
> answering satisfactorily (my apologies if they have) is what happens to
> these residual manufacturing stresses after you correct the spoke line?
>
> I have a spoke with a bend in it from the factory. There are residual
> stresses due to this bend. So far so good. Then I bend it some more to
> change the angle. What has now happened to the original residual
> stresses?

Depends how much you bend it and in which direction.

Check out the graph:
http://www.lanl.gov/contour/beam.html

Typical residual stress profile for a bent beam (TCTC).

If you consider that spoke wire has some amount of spring back, to get
the original ~95 degree angle, the spoke must have been bent to around
85 and sprang back 10. If you bent the spoke to that original 85, you'd
be just to the point of creating additional plastic deformation. If you
bent it the other way instead, opposite the original bend, you would not
have to go as far to get into the plastic region because the residual
stresses have already got you part way there.

If you bend beyond the 85 (to 80 say), you will deform (plastic)
material from the skin down to beyond the original elastic/plastic
deformation transition boundary. After relaxing, the residual profile
would be similar, but the stress reversal layer would be deeper in the
material.

If, instead of bending in the same direction you bent the other way (95
to 100 say), you'd be adding to the residuals and enter the plastic mode
as soon as the residual + applied exceeded the yield threshold. At
that point, beginning at the skin, material would plastically deform in
an opposite fashion to the original (manufacturing) deformation. Skin
that had been compressed would be stretched and vice versa. This would
cause (after relaxation) another layer of residual stress to be
superimposed on the first one. You will have restored some of the
material (near the skin) to its original unbent state (more or less),
but not the deeper layers.

If, instead of bending either way, you just load the spoke with pure
tension, you will superimpose that stress on the residual stress curve,
shifting the whole thing upward. If the residual peaks (tension) go
beyond yield with this added stress, they will plastically deform. When
you relax, you will have "knocked off the tops" of the residual stress
profile.

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>
>> Another question I've asked a few times but don't remember anyone
>> answering satisfactorily (my apologies if they have) is what happens to
>> these residual manufacturing stresses after you correct the spoke line?
>>
>> I have a spoke with a bend in it from the factory. There are residual
>> stresses due to this bend. So far so good. Then I bend it some more to
>> change the angle. What has now happened to the original residual
>> stresses?
>
> Depends how much you bend it and in which direction.
>
> Check out the graph:
> http://www.lanl.gov/contour/beam.html
>
> Typical residual stress profile for a bent beam (TCTC).
>
> If you consider that spoke wire has some amount of spring back, to get
> the original ~95 degree angle, the spoke must have been bent to around
> 85 and sprang back 10. If you bent the spoke to that original 85, you'd
> be just to the point of creating additional plastic deformation. If you
> bent it the other way instead, opposite the original bend, you would not
> have to go as far to get into the plastic region because the residual
> stresses have already got you part way there.
>
> If you bend beyond the 85 (to 80 say), you will deform (plastic)
> material from the skin down to beyond the original elastic/plastic
> deformation transition boundary. After relaxing, the residual profile
> would be similar, but the stress reversal layer would be deeper in the
> material.
>
> If, instead of bending in the same direction you bent the other way (95
> to 100 say), you'd be adding to the residuals and enter the plastic mode
> as soon as the residual + applied exceeded the yield threshold. At that
> point, beginning at the skin, material would plastically deform in an
> opposite fashion to the original (manufacturing) deformation. Skin that
> had been compressed would be stretched and vice versa. This would cause
> (after relaxation) another layer of residual stress to be superimposed
> on the first one. You will have restored some of the material (near the
> skin) to its original unbent state (more or less), but not the deeper
> layers.
>
> If, instead of bending either way, you just load the spoke with pure
> tension, you will superimpose that stress on the residual stress curve,
> shifting the whole thing upward. If the residual peaks (tension) go
> beyond yield with this added stress, they will plastically deform. When
> you relax, you will have "knocked off the tops" of the residual stress
> profile.

and /where/ exactly does fatigue initiate???

[jim beam]

Peter Cole wrote:
> wrote:
>> On Apr 24, 1:07 am, Ron Ruff > wrote:
>>> On Apr 23, 4:44 pm, wrote:
>>>
>>>> So the magnitude doesn't matter?
>>> I suppose it would be nice to be more precise about this, but I'm not
>>> sure it matters a whole lot. I'm presently thinking that more is
>>> better for spokes... bending spokes at the hub, cross, and nipple, and
>>> then stressing them as much as I can after full (and even excessive)
>>> final build tension is acheived. Pressing on the spokes with the wheel
>>> laying on a soft surface seems to work best. Pressing on the rim will
>>> also work except for DS and carbon rims.
>>
>> It only matters if your "more is better" is enough to initiate cracks,
>> but not enough to immediately fracture the whole spoke.
>
> "Initiate cracks" with a single load cycle to ~50% yield?

absolutely.


> Please, let's
> be serious.

you be serious michael - look up miner's cumulative damage rule. and
"yield" is not "yield" - fatigue simply would not happen if there was no
yielding before "yield".

[do you want to discuss why most metals don't obey hooke's law now?]

[jim beam]

Michael Press wrote:
> In article >,
> daveornee > wrote:
>
>> Michael Press Wrote:
>>> In article >,
>>> daveornee > wrote:
>>>
>>>> Peter Cole Wrote:
>>>>> Ben C wrote:
>>>>>
>>>>>> The controversy here is not that brief overload relieves stress
>>> or
>>>>> that
>>>>>> stress relief improves fatigue life.
>>>>> Not true.
>>>>>
>>>>>> It's the claim that this is known
>>>>>> to be _the significant beneficial effect_ of spoke-squeezing,
>>> the
>>>>> Mavic
>>>>>> method, and other "stabilization" practices that people do when
>>>>>> wheel-building.
>>>>> Not true. The specific claim (originally by Jobst) is that spoke
>>>>> squeezing causes stress relief by the exact mechanism described in
>>> the
>>>>> sources I cited. "Stabilization" is your word -- and a meaningless
>>>>> one,
>>>>> too. Stress relief is a specific term. That there are residual
>>>>> stresses
>>>>> in spokes is not a matter of faith. Overloading in the direction
>>> of
>>>>> the
>>>>> working load will either diminish undesirable residual stresses or
>>>>> create desirable residual stresses or both. That is the whole
>>> point.
>>>>> It
>>>>> needs no other qualifications.
>>>> "Stabilizing" is a term used Barnett Bicycle Institute in thier
>>> wheel
>>>> building classes. It is not meaningless. Stabilizing makes sure
>>> the
>>>> spokes are embeded and residual windup removed.
>>> Thereby putting the wheel out of true.
>>> Spoke wind up is never present when
>>> attention is paid while turning the
>>> nipples. Turn until the nipple turns
>>> with respect to the spoke, then back
>>> the spoke wrench until the spoke is
>>> not wound up.
>>>
>>>
>>>> The process also
>>>> temporarily overloads spokes in the direction of the working
>>> load....
>>>
>>> No it does not. All strain is elastic when the
>>> spoke wrench turns the nipple.
>>>
>>>> likely better than the spoke squeezing method. I can see and
>>>> immediately measure the results of the process. I know that if a
>>> wheel
>>>> isn't stabilized it will detension as it is ridden...
>>> No it won't. Nipples unwind when the spoke tension is insufficient
>>> to the job of carrying the cyclic load at the contact patch.
>>>
>>>> sometimes to the
>>>> point where nipples will back-off and the wheel will have spokes
>>> that
>>>> are totally slack.
>>> Oil the threads and spoke bed. Use a sufficient number
>>> of spokes to carry the load.
>>>
>> I build my way and it always works. I properly lubricate the threads
>> and I make sure there isn't windup as I tighten nipples.
>> If the wheel goes out of true while stabilizing it isn't likely to stay
>> true when riding.
>> I use the proper numbers of spokes for the intended loads in my
>> builds.
>> I don't uderstand what you mean:
>> "No it does not. All strain is elastic when the spoke wrench turns the
>> nipple."
>
> I was confused when you said "the process",
> and take back what I said there.
>
>
> [...]
>


"confused"??? that's gotta be potm!!!

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>> On 2008-04-23, Peter Cole > wrote:
>
>>> Stress relief is a specific term. That there are residual stresses in
>>> spokes is not a matter of faith.
>>
>> No, but that they make any practical difference to how quickly the spoke
>> breaks or not is.
>
> If there are residual stresses, there must be both tension and
> compression residuals. Since the working load is tension, tension
> residuals are bad for fatigue, compression residuals are harmless or
> beneficial. By overloading in the working direction, tension residuals
> -- wherever they occur -- are reduced.

what's the point of bothering if it's not causing fatigue??? you can't
just presume a problem then prescribe a cure. well you can, but you're
wasting everybody's time, including your own. and you look stupid to
people that know better.


>
> Additionally, notches act as stress concentrators, so will multiply the
> working stress.

depending on orientation and location.



> By overloading, the immediate vicinity yields, creating
> a beneficial compression residual.

it depends where. and more to the point, it depends whether it's worth
it if it's not causing fatigue, as is the case with spokes.


>
> All of the above statements are true. Stress relief can only improve
> fatigue life, whether the root cause of premature failure is residual
> stress or notches (defects).

actually,

1. overload can introduce more residual stress than it relieves.
2. miner's cumulative damage rule says you're simply reducing fatigue life.
3. you can actually *activate* dislocation movement and thus initiate
fatigue.


>
> The only other possible cause for early spoke fatigue is the presence of
> a bending moment in the working load.

it's not the "other" cause, it's /the/ cause. a simple examination of
any broken spoke will tell you that.


> If the spoke is properly formed
> and supported this won't exist.

rubbish. any elbowed spoke has a bending moment - by definition.


> If it did, the peak stress would be at
> the skin, and an overload would yield those spots close to yield (just
> as it would near a notch). Again, identically, it would improve fatigue
> life.

you're confused.


>
> All 3 of the above scenarios are not speculative.

but only one is observed to be relevant!



>
> A speculative scenario that has been proposed is that the overload "beds
> in" the spoke heads to the (aluminum, presumably) hub flange, by
> deforming the material. Consider that the overload is only (nominally)
> 50%. We are to believe that the spoke head will sink further into the
> beveled hole in the flange?

of course. do you understand that metals yield when over-loaded?


<snip remaining boring confused garbage>

[jim beam]

Peter Cole wrote:
> Ben C wrote:
>> On 2008-04-24, Peter Cole > wrote:
>
>>> It doesn't matter how the overload is applied, only that it be in the
>>> same direction as the working load. It will reduce operating stresses
>>> whether from residual manufacturing stress, stress raisers or skin
>>> stress from (static) bending moments.
>>
>> I agree with all that, I just think the last of those three is likely to
>> be the significant one.
>
> Well, you're entitled to your opinions, but stress relief will be
> beneficial in all cases.

no. three reasons cited above.


> The overload technique will reduce all tension
> stress in the tensioned wheel that are close to yield.
>
> Since the spoke line can't be initially right for both out & in bound
> spokes,

untrue. canted flanges. ever heard of them?


> and, to the extent that hole deformation occurs, it helps one &
> harms the other, the spoke line must be corrected. That will introduce
> additional residual stresses, which need be relieved.

manufacturers actually state that spokes /shouldn't/ be bent.


> If there is any
> residual mismatch between spoke elbow angle and spoke bed angle, that
> will introduce static stresses. These are reduced by stress relieving,
> whether there is additional hole deformation or not.

all of which presumptive nonsense ignorantly ignores the fundamental
fact that fatigue cracking is not observed to be initiating in regions
of high residual stress!!! no matter how you try michael, you can't fit
a 3" turd into a 1" pipe, just like you can't fudge facts to fit a
misconceived mistake.

[Tom Sherman[_2_]]

"jim beam" wrote:
> Peter Cole wrote:
>> wrote:
>>> On Apr 24, 1:07 am, Ron Ruff > wrote:
>>>> On Apr 23, 4:44 pm, wrote:
>>>>
>>>>> So the magnitude doesn't matter?
>>>> I suppose it would be nice to be more precise about this, but I'm not
>>>> sure it matters a whole lot. I'm presently thinking that more is
>>>> better for spokes... bending spokes at the hub, cross, and nipple, and
>>>> then stressing them as much as I can after full (and even excessive)
>>>> final build tension is acheived. Pressing on the spokes with the wheel
>>>> laying on a soft surface seems to work best. Pressing on the rim will
>>>> also work except for DS and carbon rims.
>>>
>>> It only matters if your "more is better" is enough to initiate cracks,
>>> but not enough to immediately fracture the whole spoke.
>>
>> "Initiate cracks" with a single load cycle to ~50% yield?
>
> absolutely.
>
>
>> Please, let's be serious.
>
> you be serious michael[...]

How does "Peter Cole" equate to "michael"? The world wonders.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

[jim beam]

Tom Sherman wrote:
> "jim beam" wrote:
>> Peter Cole wrote:
>>> wrote:
>>>> On Apr 24, 1:07 am, Ron Ruff > wrote:
>>>>> On Apr 23, 4:44 pm, wrote:
>>>>>
>>>>>> So the magnitude doesn't matter?
>>>>> I suppose it would be nice to be more precise about this, but I'm not
>>>>> sure it matters a whole lot. I'm presently thinking that more is
>>>>> better for spokes... bending spokes at the hub, cross, and nipple, and
>>>>> then stressing them as much as I can after full (and even excessive)
>>>>> final build tension is acheived. Pressing on the spokes with the wheel
>>>>> laying on a soft surface seems to work best. Pressing on the rim will
>>>>> also work except for DS and carbon rims.
>>>>
>>>> It only matters if your "more is better" is enough to initiate cracks,
>>>> but not enough to immediately fracture the whole spoke.
>>>
>>> "Initiate cracks" with a single load cycle to ~50% yield?
>>
>> absolutely.
>>
>>
>>> Please, let's be serious.
>>
>> you be serious michael[...]
>
> How does "Peter Cole" equate to "michael"? The world wonders.
>

good point. but they're both singing the same [underinformed] song.

[TBerk]

So what do you _do_ when you are stressed and fatigued, for relief?


TBerk

[Gary Young]

On Thu, 24 Apr 2008 20:59:25 -0700, jim beam wrote:

> Peter Cole wrote:
>> Ben C wrote:
>>> On 2008-04-24, Peter Cole > wrote:
>>
>>>> It doesn't matter how the overload is applied, only that it be in the
>>>> same direction as the working load. It will reduce operating stresses
>>>> whether from residual manufacturing stress, stress raisers or skin
>>>> stress from (static) bending moments.
>>>
>>> I agree with all that, I just think the last of those three is likely
>>> to be the significant one.
>>
>> Well, you're entitled to your opinions, but stress relief will be
>> beneficial in all cases.
>
> no. three reasons cited above.
>
>
>> The overload technique will reduce all tension stress in the tensioned
>> wheel that are close to yield.
>>
>> Since the spoke line can't be initially right for both out & in bound
>> spokes,
>
> untrue. canted flanges. ever heard of them?
>
>
>> and, to the extent that hole deformation occurs, it helps one & harms
>> the other, the spoke line must be corrected. That will introduce
>> additional residual stresses, which need be relieved.
>
> manufacturers actually state that spokes /shouldn't/ be bent.
>
>

The dog returns to its vomit.

We've been over this before -- you've come up with one spoke manufacturer
-- Sapim, in a web document rife with errors. Other spoke manufacturers
disagree. Wheelsmith, for instance:

"Wheelsmith spokes are “cold headed” with great accuracy, and marked with
the distinctive “W”. Elbows are formed over a radiussed mandrel rather
than a flat surface as with other popular spokes. This results in a
larger bend radius, and preserves the round cross-section of the elbow.
Consequently, Wheelsmith spokes require a minimum of bending to conform
to a hub, thereby maximizing fatigue life."

http://www.wheelsmith.com/spokes_introduction.html




>> If there is any
>> residual mismatch between spoke elbow angle and spoke bed angle, that
>> will introduce static stresses. These are reduced by stress relieving,
>> whether there is additional hole deformation or not.
>
> all of which presumptive nonsense ignorantly ignores the fundamental
> fact that fatigue cracking is not observed to be initiating in regions
> of high residual stress!!! no matter how you try michael, you can't fit
> a 3" turd into a 1" pipe, just like you can't fudge facts to fit a
> misconceived mistake.

[[email protected]]

Peter Cole wrote:

>>>> So the magnitude doesn't matter?

>>> I suppose it would be nice to be more precise about this, but I'm
>>> not sure it matters a whole lot. I'm presently thinking that more
>>> is better for spokes... bending spokes at the hub, cross, and
>>> nipple, and then stressing them as much as I can after full (and
>>> even excessive) final build tension is acheived. Pressing on the
>>> spokes with the wheel laying on a soft surface seems to work best.
>>> Pressing on the rim will also work except for DS and carbon rims.

>> It only matters if your "more is better" is enough to initiate
>> cracks, but not enough to immediately fracture the whole spoke.

> "Initiate cracks" with a single load cycle to ~50% yield? Please,
> let's be serious.

Don't wait until then. With bright grazing incident illumination,
crazing around spoke eyelets, caused by the riveting the eyelet, is
apparent on new unused rims. They only get worse thereafter as they
propagate into the substrate and open wider on the surface.

Jobst Brandt

[Tom Sherman[_2_]]

TBerk wrote:
>
> So what do you _do_ when you are stressed and fatigued, for relief?
>
Start a flame war on Usenet?

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

[jim beam]

wrote:
> Peter Cole wrote:
>
>>>>> So the magnitude doesn't matter?
>
>>>> I suppose it would be nice to be more precise about this, but I'm
>>>> not sure it matters a whole lot. I'm presently thinking that more
>>>> is better for spokes... bending spokes at the hub, cross, and
>>>> nipple, and then stressing them as much as I can after full (and
>>>> even excessive) final build tension is acheived. Pressing on the
>>>> spokes with the wheel laying on a soft surface seems to work best.
>>>> Pressing on the rim will also work except for DS and carbon rims.
>
>>> It only matters if your "more is better" is enough to initiate
>>> cracks, but not enough to immediately fracture the whole spoke.
>
>> "Initiate cracks" with a single load cycle to ~50% yield? Please,
>> let's be serious.
>
> Don't wait until then. With bright grazing incident illumination,
> crazing around spoke eyelets, caused by the riveting the eyelet, is
> apparent on new unused rims. They only get worse thereafter as they
> propagate into the substrate and open wider on the surface.
>

except that the anodizing crack orientation doesn't correlate with the
metal crack orientation!!!

but observation is a powerful tool jobst - you should be encouraged to
do this more often. a quick read on the subject of fracture mechanics
would be handy too.

[Peter Cole[_2_]]

Peter Cole wrote:

> If there are residual stresses, there must be both tension and
> compression residuals. Since the working load is tension, tension
> residuals are bad for fatigue, compression residuals are harmless or
> beneficial. By overloading in the working direction, tension residuals
> -- wherever they occur -- are reduced.

There still seems to be some confusion about stress relief. Where
beneficial residual stresses exist (e.g. rolled threads), stress relief
will not reduce them, if anything, it will increase them. Since residual
compression stress is created by yielding other parts of the section
from tension, a uniform tension overload will reach yield in the areas
with residual tension before those with residual compression.

overload tension + load tension + residual tension > yield tension,
overload tension + load tension - residual compression < yield tension

This is the basis of overload stress relief. If you don't grasp that
then everything else remains obscure.

[jim beam]

Peter Cole wrote:
> Peter Cole wrote:
>
>> If there are residual stresses, there must be both tension and
>> compression residuals. Since the working load is tension, tension
>> residuals are bad for fatigue, compression residuals are harmless or
>> beneficial. By overloading in the working direction, tension residuals
>> -- wherever they occur -- are reduced.
>
> There still seems to be some confusion about stress relief. Where
> beneficial residual stresses exist (e.g. rolled threads), stress relief
> will not reduce them, if anything, it will increase them. Since residual
> compression stress is created by yielding other parts of the section
> from tension, a uniform tension overload will reach yield in the areas
> with residual tension before those with residual compression.
>
> overload tension + load tension + residual tension > yield tension,
> overload tension + load tension - residual compression < yield tension
>
> This is the basis of overload stress relief. If you don't grasp that
> then everything else remains obscure.


the only obscurity here is why some people are still confused about
relevance of "stress relief" where it's not observed to be the cause of
fatigue initiation!!!!

buy a magnifier and examine a broken spoke. then correlate the observed
fatigue initiation point to the residual stress profile of a spoke bend.

[Ron Ruff]

On Apr 24, 9:59*pm, jim beam > wrote:
> manufacturers actually state that spokes /shouldn't/ be bent.

Everybody I know who uses Sapim spokes bends them. Dave Ornee, what do
you do?

[[email protected]]

On Apr 24, 11:58 pm, jim beam > wrote:
> Peter Cole wrote:
>
> > If there are residual stresses, there must be both tension and
> > compression residuals. Since the working load is tension, tension
> > residuals are bad for fatigue, compression residuals are harmless or
> > beneficial. By overloading in the working direction, tension residuals
> > -- wherever they occur -- are reduced.
>
>
> actually,
>
> 1. overload can introduce more residual stress than it relieves.
> 2. miner's cumulative damage rule says you're simply reducing fatigue life.

jim beam is mis-applying Miner's rule.

Miner's rule is intended to give approximate estimations of fatigue
life for repeated patterns of cyclical loads. AFAIK, it's never been
intended for evaluating the effect of a single application of a load
causing yielding.

From http://en.wikipedia.org/wiki/Metal_fatigue:

"Though Miner's rule is a useful approximation in many circumstances,
it has two major limitations:

1. It fails to recognise the probabilistic nature of fatigue and
there is no simple way to relate life predicted by the rule with the
characteristics of a probability distribution.
2. There is sometimes an effect in the order in which the reversals
occur. In some circumstances, cycles of low stress followed by high
stress cause more damage than would be predicted by the rule. It does
not consider the effect of overload or high stress which may result in
a compressive residual stress."

Note that last sentence.

- Frank Krygowski

[jim beam]

Ron Ruff wrote:
> On Apr 24, 9:59�pm, jim beam > wrote:
>> manufacturers actually state that spokes /shouldn't/ be bent.
>
> Everybody I know who uses Sapim spokes bends them.

that's probably because of jobst's bad advice about "correcting the
spoke line". there's no technical reason to do it though because in
reality, once the spoke becomes tensioned, and the hub holes are
deformed, it becomes unnecessary. especially on modern hubs with canted
flanges.

http://www.flickr.com/photos/38636024@N00/331112190/

that's why spokes are formed with 95 degree bends, not 90. it's not
like manufacturers are so dumb they couldn't form it right first time.


> Dave Ornee, what do
> you do?

[jim beam]

wrote:
> On Apr 24, 11:58 pm, jim beam > wrote:
>> Peter Cole wrote:
>>
>>> If there are residual stresses, there must be both tension and
>>> compression residuals. Since the working load is tension, tension
>>> residuals are bad for fatigue, compression residuals are harmless or
>>> beneficial. By overloading in the working direction, tension residuals
>>> -- wherever they occur -- are reduced.
>>
>> actually,
>>
>> 1. overload can introduce more residual stress than it relieves.
>> 2. miner's cumulative damage rule says you're simply reducing fatigue life.
>
> jim beam is mis-applying Miner's rule.
>
> Miner's rule is intended to give approximate estimations of fatigue
> life for repeated patterns of cyclical loads. AFAIK, it's never been
> intended for evaluating the effect of a single application of a load
> causing yielding.
>
> From http://en.wikipedia.org/wiki/Metal_fatigue:
>
> "Though Miner's rule is a useful approximation in many circumstances,
> it has two major limitations:
>
> 1. It fails to recognise the probabilistic nature of fatigue and
> there is no simple way to relate life predicted by the rule with the
> characteristics of a probability distribution.
> 2. There is sometimes an effect in the order in which the reversals
> occur. In some circumstances, cycles of low stress followed by high
> stress cause more damage than would be predicted by the rule. It does
> not consider the effect of overload or high stress which may result in
> a compressive residual stress."
>
> Note that last sentence.
>

and note the krygowski snippage on #3,

"3. you can actually *activate* dislocation movement and thus initiate
fatigue. "

and i quote from an authoritative academic reference:
"while many deviations from miner's rule have been observed, and
numerous modification to this relationship have been proposed, *none
have been proven better or gained wide acceptance*." [my emphasis.]

isbn 0-07-016893-8 p414.

[jim beam]

jim beam wrote:
> Ron Ruff wrote:
>> On Apr 24, 9:59�pm, jim beam > wrote:
>>> manufacturers actually state that spokes /shouldn't/ be bent.
>>
>> Everybody I know who uses Sapim spokes bends them.
>
> that's probably because of jobst's bad advice about "correcting the
> spoke line". there's no technical reason to do it though because in
> reality, once the spoke becomes tensioned, and the hub holes are
> deformed, it becomes unnecessary. especially on modern hubs with canted
> flanges.
>
> http://www.flickr.com/photos/38636024@N00/331112190/
>
> that's why spokes are formed with 95 degree bends, not 90. it's not
> like manufacturers are so dumb they couldn't form it right first time.

http://www.flickr.com/photos/38636024@N00/327722444/


>
>
>> Dave Ornee, what do
>> you do?
>

[daveornee[_187_]]

Ron Ruff Wrote:
> On Apr 24, 9:59*pm, jim beam > wrote:
> > manufacturers actually state that spokes /shouldn't/ be bent.
>
> Everybody I know who uses Sapim spokes bends them. Dave Ornee, what do
> you do?

I bend the heads in ones to a slightly smaller angle (depending on the
hub, crossing pattern and rim ERD) with spokes laced and nipples turned
5 full turns. Some hubs like Phil Wood have canted flanges so I don't
bend spokes on them unless it looks like it will improve the spoke line.
Yes, I saw what Sapim says on their web site about not bending, but I
find that the improved spoke line is benenficial in the long run. I
have had one returned wheel from over 1,000 built with a broken spoke...
and it broke at the end of the spoke shaft just at the elbow. I tossed
the spoke and all 31 of the others in the wheel (no pictures as I forgot
to take the time and wanted to get the wheel back to the rider) and
rebuilt it with all new spokes and new nipples.
Hub is Dura Ace 7700 rear (25th Annivesary) rim is Velocity Fusion.
I saw the spokes in Jim Beams pictures. That is interesting. Some day
I will photograph spokes before & after... inbound and outbound + spoke
holes prebuild and post build, including post stabilizing.
If any of you have such pictures already I would like to see them and
get some suggestions how to get the details photographed such that you
can really discern what is going on.


--
daveornee

[jim beam]

daveornee wrote:
> Ron Ruff Wrote:
>> On Apr 24, 9:59*pm, jim beam > wrote:
>>> manufacturers actually state that spokes /shouldn't/ be bent.
>> Everybody I know who uses Sapim spokes bends them. Dave Ornee, what do
>> you do?
>
> I bend the heads in ones to a slightly smaller angle (depending on the
> hub, crossing pattern and rim ERD) with spokes laced and nipples turned
> 5 full turns. Some hubs like Phil Wood have canted flanges so I don't
> bend spokes on them unless it looks like it will improve the spoke line.
> Yes, I saw what Sapim says on their web site about not bending, but I
> find that the improved spoke line is benenficial in the long run. I
> have had one returned wheel from over 1,000 built with a broken spoke...
> and it broke at the end of the spoke shaft just at the elbow. I tossed
> the spoke and all 31 of the others in the wheel (no pictures as I forgot
> to take the time and wanted to get the wheel back to the rider) and
> rebuilt it with all new spokes and new nipples.
> Hub is Dura Ace 7700 rear (25th Annivesary) rim is Velocity Fusion.
> I saw the spokes in Jim Beams pictures. That is interesting. Some day
> I will photograph spokes before & after... inbound and outbound + spoke
> holes prebuild and post build, including post stabilizing.

this is the hub those spokes came from:
http://www.flickr.com/photos/38636024@N00/104463818/

that hub hole deformation is *definitely* going to affect exit angle.
and thus "correcting" the spoke line /before/ tensioning [and
stabilizing], as most people do, is going to be premature.


> If any of you have such pictures already I would like to see them and
> get some suggestions how to get the details photographed such that you
> can really discern what is going on.
>
>

[daveornee[_188_]]

jim beam Wrote:
> daveornee wrote:
> > Ron Ruff Wrote:
> >> On Apr 24, 9:59*pm, jim beam > wrote:
> >>> manufacturers actually state that spokes /shouldn't/ be bent.
> >> Everybody I know who uses Sapim spokes bends them. Dave Ornee, what
> do
> >> you do?
> >
> > I bend the heads in ones to a slightly smaller angle (depending on
> the
> > hub, crossing pattern and rim ERD) with spokes laced and nipples
> turned
> > 5 full turns. Some hubs like Phil Wood have canted flanges so I
> don't
> > bend spokes on them unless it looks like it will improve the spoke
> line.
> > Yes, I saw what Sapim says on their web site about not bending, but
> I
> > find that the improved spoke line is benenficial in the long run. I
> > have had one returned wheel from over 1,000 built with a broken
> spoke...
> > and it broke at the end of the spoke shaft just at the elbow. I
> tossed
> > the spoke and all 31 of the others in the wheel (no pictures as I
> forgot
> > to take the time and wanted to get the wheel back to the rider) and
> > rebuilt it with all new spokes and new nipples.
> > Hub is Dura Ace 7700 rear (25th Annivesary) rim is Velocity Fusion.
> > I saw the spokes in Jim Beams pictures. That is interesting. Some
> day
> > I will photograph spokes before & after... inbound and outbound +
> spoke
> > holes prebuild and post build, including post stabilizing.
>
> this is the hub those spokes came from:
> http://www.flickr.com/photos/38636024@N00/104463818/
>
> that hub hole deformation is *definitely* going to affect exit angle.
> and thus "correcting" the spoke line /before/ tensioning [and
> stabilizing], as most people do, is going to be premature.
>
>
> > If any of you have such pictures already I would like to see them
> and
> > get some suggestions how to get the details photographed such that
> you
> > can really discern what is going on.
> >
> >
Here are links to 6 pictures I took today of a Dura Ace HB-7700 32H
wheel I built today with Sapim Race 14/15 DB spokes. One side I used my
previous pattern of "correcting the spoke line" and the other side I
made no such correction.
Judge for yourself.


http://www.flickr.com/photos/17085834@N08/2443679334/


http://www.flickr.com/photos/17085834@N08/2443679236/


http://www.flickr.com/photos/17085834@N08/2442851273/


http://www.flickr.com/photos/17085834@N08/2443679416/


http://www.flickr.com/photos/17085834@N08/2442851411/


http://www.flickr.com/photos/17085834@N08/2442851349/


After this experiment I think the next build will be done without
correcting the spoke line.


--
daveornee

[jim beam]

daveornee wrote:
> jim beam Wrote:
>> daveornee wrote:
>>> Ron Ruff Wrote:
>>>> On Apr 24, 9:59*pm, jim beam > wrote:
>>>>> manufacturers actually state that spokes /shouldn't/ be bent.
>>>> Everybody I know who uses Sapim spokes bends them. Dave Ornee, what
>> do
>>>> you do?
>>> I bend the heads in ones to a slightly smaller angle (depending on
>> the
>>> hub, crossing pattern and rim ERD) with spokes laced and nipples
>> turned
>>> 5 full turns. Some hubs like Phil Wood have canted flanges so I
>> don't
>>> bend spokes on them unless it looks like it will improve the spoke
>> line.
>>> Yes, I saw what Sapim says on their web site about not bending, but
>> I
>>> find that the improved spoke line is benenficial in the long run. I
>>> have had one returned wheel from over 1,000 built with a broken
>> spoke...
>>> and it broke at the end of the spoke shaft just at the elbow. I
>> tossed
>>> the spoke and all 31 of the others in the wheel (no pictures as I
>> forgot
>>> to take the time and wanted to get the wheel back to the rider) and
>>> rebuilt it with all new spokes and new nipples.
>>> Hub is Dura Ace 7700 rear (25th Annivesary) rim is Velocity Fusion.
>>> I saw the spokes in Jim Beams pictures. That is interesting. Some
>> day
>>> I will photograph spokes before & after... inbound and outbound +
>> spoke
>>> holes prebuild and post build, including post stabilizing.
>> this is the hub those spokes came from:
>> http://www.flickr.com/photos/38636024@N00/104463818/
>>
>> that hub hole deformation is *definitely* going to affect exit angle.
>> and thus "correcting" the spoke line /before/ tensioning [and
>> stabilizing], as most people do, is going to be premature.
>>
>>
>>> If any of you have such pictures already I would like to see them
>> and
>>> get some suggestions how to get the details photographed such that
>> you
>>> can really discern what is going on.
>>>
>>>
> Here are links to 6 pictures I took today of a Dura Ace HB-7700 32H
> wheel I built today with Sapim Race 14/15 DB spokes. One side I used my
> previous pattern of "correcting the spoke line" and the other side I
> made no such correction.
> Judge for yourself.
>
>
> http://www.flickr.com/photos/17085834@N08/2443679334/
>
>
> http://www.flickr.com/photos/17085834@N08/2443679236/
>
>
> http://www.flickr.com/photos/17085834@N08/2442851273/
>
>
> http://www.flickr.com/photos/17085834@N08/2443679416/
>
>
> http://www.flickr.com/photos/17085834@N08/2442851411/
>
>
> http://www.flickr.com/photos/17085834@N08/2442851349/
>
>
> After this experiment I think the next build will be done without
> correcting the spoke line.
>
>

aren't modern digicams fantastic???

one other thing i've noticed, not that it really makes much difference,
is that the spoke head on the "uncorrected" spoke always sits in the hub
hole just that little bit better.

[[email protected]]

On Sun, 27 Apr 2008 04:22:58 +1000, daveornee
> wrote:

>Here are links to 6 pictures I took today of a Dura Ace HB-7700 32H
>wheel I built today with Sapim Race 14/15 DB spokes. One side I used my
>previous pattern of "correcting the spoke line" and the other side I
>made no such correction.
>Judge for yourself.
>
>http://www.flickr.com/photos/17085834@N08/2443679334/
>
>http://www.flickr.com/photos/17085834@N08/2443679236/
>
>http://www.flickr.com/photos/17085834@N08/2442851273/
>
>http://www.flickr.com/photos/17085834@N08/2443679416/
>
>http://www.flickr.com/photos/17085834@N08/2442851411/
>
>http://www.flickr.com/photos/17085834@N08/2442851349/
>
>After this experiment I think the next build will be done without
>correcting the spoke line.

Dear Dave,

Nice pictures--thanks!

Yikes!
http://www.flickr.com/photos/17085834@N08/2443679416/
http://www.flickr.com/photos/17085834@N08/2442851349/

Cheers,

Carl Fogel

[jim beam]

wrote:
> On Sun, 27 Apr 2008 04:22:58 +1000, daveornee
> > wrote:
>
>> Here are links to 6 pictures I took today of a Dura Ace HB-7700 32H
>> wheel I built today with Sapim Race 14/15 DB spokes. One side I used my
>> previous pattern of "correcting the spoke line" and the other side I
>> made no such correction.
>> Judge for yourself.
>>
>> http://www.flickr.com/photos/17085834@N08/2443679334/
>>
>> http://www.flickr.com/photos/17085834@N08/2443679236/
>>
>> http://www.flickr.com/photos/17085834@N08/2442851273/
>>
>> http://www.flickr.com/photos/17085834@N08/2443679416/
>>
>> http://www.flickr.com/photos/17085834@N08/2442851411/
>>
>> http://www.flickr.com/photos/17085834@N08/2442851349/
>>
>> After this experiment I think the next build will be done without
>> correcting the spoke line.
>
> Dear Dave,
>
> Nice pictures--thanks!
>
> Yikes!
> http://www.flickr.com/photos/17085834@N08/2443679416/
> http://www.flickr.com/photos/17085834@N08/2442851349/

perfectly normal, perfectly healthy.


>
> Cheers,
>
> Carl Fogel

[daveornee[_189_]]

Wrote:
> On Sun, 27 Apr 2008 04:22:58 +1000, daveornee
> > wrote:
> [color=blue]
> <SNIP>
> http://www.flickr.com/photos/17085834@N08/2443679416/
> http://www.flickr.com/photos/17085834@N08/2442851349/
>
> Cheers,
>
> Carl Fogel
If you just built em and rode them without stabilizing them, they would
look quite similar after riding them a short while. The difference is
that you can put a controlled force amount in stabilizing them and get
the wheels trued, tensioned, tension balanced, centered and they will
stay that way for a long time.


--
daveornee

[daveornee[_190_]]

Wrote:
> On Sun, 27 Apr 2008 04:22:58 +1000, daveornee
> > wrote:
> [color=blue]
> <SNIP>
> http://www.flickr.com/photos/17085834@N08/2443679416/
> http://www.flickr.com/photos/17085834@N08/2442851349/
>
> Cheers,
>
> Carl Fogel
If you just built em and rode them without stabilizing them, they would
look quite similar after riding them a short while. The difference is
that you can put a controlled force amount in stabilizing them and get
the wheels trued, tensioned, tension balanced, centered and they will
stay that way for a long time.


--
daveornee

[Ron Ruff]

On Apr 25, 10:09*pm, jim beam > wrote:
> that hub hole deformation is *definitely* going to affect exit angle.
> and thus "correcting" the spoke line /before/ tensioning [and
> stabilizing], as most people do, is going to be premature.

Exactly when and how much can be debated I suppose, but... Every hub I
use supports the spoke in such a way as to make the heads-in spokes
"stick out" ie they aren't heading straight to the rim but rather bow
outward. Increasing tension (even overloading) will not eliminate this
completely... so the spoke will end up with an additional bending
load, if nothing else is done about it. This is not a good thing.
Similarly, most rims I use do not allow spokes on the NDS and front
spokes to enter without some bending load at the rim. Some large
flange hubs create a pretty acute angle even on the DS.

I prefer to "correct the spoke line" at the hub rather late in the
building process, but before overloading. I agree that high tension is
probably better for achieving the best "shape" at that point. At the
rim I bend the spokes fairly early, just because it is too difficult
to do well when the tension is high. It seems to me that it is better
for the rim if the nipple lies more closely to perpendicular against
the surface of the rim, to reduce the chance of eyelet deformation and
cracking.

[jim beam]

Ron Ruff wrote:
> On Apr 25, 10:09�pm, jim beam > wrote:
>> that hub hole deformation is *definitely* going to affect exit angle.
>> and thus "correcting" the spoke line /before/ tensioning [and
>> stabilizing], as most people do, is going to be premature.
>
> Exactly when and how much can be debated I suppose, but... Every hub I
> use supports the spoke in such a way as to make the heads-in spokes
> "stick out" ie they aren't heading straight to the rim but rather bow
> outward.

only when the hub is new and the hub holes un-deformed. to bend the
spoke a head of this deformation is premature because hub hole
deformation changes the exit angle. and it's the angle to which spokes
are pre-formed!

> Increasing tension (even overloading) will not eliminate this
> completely... so the spoke will end up with an additional bending
> load, if nothing else is done about it.

that's not correct. both dave ornee and i have posted pics of spokes
that are unbent, and when disassembled, they prove that bending was
unnecessary.


> This is not a good thing.

no, it's a misunderstanding and non-observation of the facts. see above.


> Similarly, most rims I use do not allow spokes on the NDS and front
> spokes to enter without some bending load at the rim. Some large
> flange hubs create a pretty acute angle even on the DS.
>
> I prefer to "correct the spoke line" at the hub rather late in the
> building process, but before overloading. I agree that high tension is
> probably better for achieving the best "shape" at that point. At the
> rim I bend the spokes fairly early, just because it is too difficult
> to do well when the tension is high. It seems to me that it is better
> for the rim if the nipple lies more closely to perpendicular against
> the surface of the rim, to reduce the chance of eyelet deformation and
> cracking.
>

you have to overload to ensure bedding in - if you want your wheels to
remain true at any rate. and if your spoke tension is high enough to
cause rim deformation, it's too high - use a tension meter.

[jim beam]

jim beam wrote:
> Ron Ruff wrote:
>> On Apr 25, 10:09�pm, jim beam > wrote:
>>> that hub hole deformation is *definitely* going to affect exit angle.
>>> and thus "correcting" the spoke line /before/ tensioning [and
>>> stabilizing], as most people do, is going to be premature.
>>
>> Exactly when and how much can be debated I suppose, but... Every hub I
>> use supports the spoke in such a way as to make the heads-in spokes
>> "stick out" ie they aren't heading straight to the rim but rather bow
>> outward.
>
> only when the hub is new and the hub holes un-deformed. to bend the
> spoke a head

typo - "ahead"

> of this deformation is premature because hub hole
> deformation changes the exit angle. and it's the angle to which spokes
> are pre-formed!
>
>> Increasing tension (even overloading) will not eliminate this
>> completely... so the spoke will end up with an additional bending
>> load, if nothing else is done about it.
>
> that's not correct. both dave ornee and i have posted pics of spokes
> that are unbent, and when disassembled, they prove that bending was
> unnecessary.
>
>
>> This is not a good thing.
>
> no, it's a misunderstanding and non-observation of the facts. see above.
>
>
>> Similarly, most rims I use do not allow spokes on the NDS and front
>> spokes to enter without some bending load at the rim. Some large
>> flange hubs create a pretty acute angle even on the DS.
>>
>> I prefer to "correct the spoke line" at the hub rather late in the
>> building process, but before overloading. I agree that high tension is
>> probably better for achieving the best "shape" at that point. At the
>> rim I bend the spokes fairly early, just because it is too difficult
>> to do well when the tension is high. It seems to me that it is better
>> for the rim if the nipple lies more closely to perpendicular against
>> the surface of the rim, to reduce the chance of eyelet deformation and
>> cracking.
>>
>
> you have to overload to ensure bedding in - if you want your wheels to
> remain true at any rate. and if your spoke tension is high enough to
> cause rim deformation, it's too high - use a tension meter.