yielding of SS 304 part
yielding of SS 304 part
(OP)
For a test, I loaded some SS 304 parts and found that they didn't yield at 50 lbs and did yield at 75 lbs. Therefore, I only know the yield strength is between 50 and 75 lbs.
A customer has returned some parts (same design as above). The parts hadn't failed but they have plastically deformed. The parts were subjected to 20 Hz vibration where the max load should be less than 20 lbs.
My question is this: When parts see very high cycles at stresses below the yield strength, is there a mechanism that can (or does) cause eventual yielding of the material?
My thinking is that while the parts might fracture at less the yield strength, they shouldn't be significantly yielding.
Thanks for any help.
Tom
A customer has returned some parts (same design as above). The parts hadn't failed but they have plastically deformed. The parts were subjected to 20 Hz vibration where the max load should be less than 20 lbs.
My question is this: When parts see very high cycles at stresses below the yield strength, is there a mechanism that can (or does) cause eventual yielding of the material?
My thinking is that while the parts might fracture at less the yield strength, they shouldn't be significantly yielding.
Thanks for any help.
Tom





RE: yielding of SS 304 part
RE: yielding of SS 304 part
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: yielding of SS 304 part
CoyPad: I know that the fatigue can eventually cause the part to break but can it also cause the yielding that we're seeing? My limited understanding of fatigue failure is that there is little or no warning which I take to mean that there is little to no yielding prior to failure. Does this sound correct?
Thanks,
Tom
RE: yielding of SS 304 part
RE: yielding of SS 304 part
RE: yielding of SS 304 part
Let me try to rephrase it.
If you take a steel part and subject it to cycling loading below the yield stress, can the part plastically deform (yield), other than completely fracturing? If instead it was a static load of the same magnitude, we know that there will be elastic deformation only.
I know the part can fail due to a stress that is below the yield strength due to fatigue.
Thanks again,
Tom
RE: yielding of SS 304 part
Another possible mechanism is distortion due to residual stress.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: yielding of SS 304 part
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RE: yielding of SS 304 part
What is the nature of the deformation? How does it compare to the deformation experienced during overload?
What is the stress gradient? What are the residuals after forming?
Metengr has hinted that residual stresses being relieved may be the cause. This certainly seems worth further investigation.