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Number of Cycle to Failure (Fatigue Analysis)
Posted 25 avr. 2022, 04:40 UTC−4 Structural & Acoustics, Acoustics & Vibrations, Structural Mechanics Version 6.0 2 Replies
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Hi all, I am doing a Fatigue stress based analysis of a tuned mass dampener with the end goal of obtaining S-N Curve (or Wöhler curve) to determine the relation between Stress and number of cycles to failure for my geometry. I used the findley's criterion and successfully coputed fatigue usage factor but not able to figure out the way to obtain number of cycles to failure.
Can someone help me by telling if (and how) I can get this in Comsol or am I supposed to use other software for this purpose?
Thank you.
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Hello.
The Findley criterion applies to the fatigue limit of the material, where the fatigue usage factor that is computed suggests failure if it exceeds one, etc. Now, if you want to use the Findley criterion for finite life computations, using an S-N curve, it is doable, but you would currently need to do it manually. The criterion computes a measure of stress deemed the most critical. After performing the fatigue computation, you could then use this stress in an S-N curve to get the number of cycles. Note, however, that in order to do this, you would need to shift the S-N curve, depending on the R value that it represents. If you are then able to express the inverse of this shifted S-N curve, N(S), you immediately get the number of cycles. Otherwise, you would need to solve an equation to get the number of cycles.
Mats
Please login with a confirmed email address before reporting spam
Hello.
The Findley criterion applies to the fatigue limit of the material, where the fatigue usage factor that is computed suggests failure if it exceeds one, etc. Now, if you want to use the Findley criterion for finite life computations, using an S-N curve, it is doable, but you would currently need to do it manually. The criterion computes a measure of stress deemed the most critical. After performing the fatigue computation, you could then use this stress in an S-N curve to get the number of cycles. Note, however, that in order to do this, you would need to shift the S-N curve, depending on the R value that it represents. If you are then able to express the inverse of this shifted S-N curve, N(S), you immediately get the number of cycles. Otherwise, you would need to solve an equation to get the number of cycles.
Mats
Thank you Mats. I was able to get number of cycles for a range of load (using parametric sweep), but to plot them in an S-N curve I need stress data from the result of Study 1 (Stationary analysis) and number of cycle data from Study 2 (Fatigue analysis). Is it possible to plot this graph in Comsol or the only way to do it is to export data and use other plotting software to do that. I have attached my model builder sceenshot for reference ?
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