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fatigue analysis


Is it necessary to carryout the linear static analysis first before doing the fatigue analysis.

If the stress exceeds the UTS , still can we caryyout the fatigue analysis.



GOPALAERO2000's picture

Hi Sagar,


Yes, it is absolutely necessary to carry out  linear static analysis, prior to fatigue analysis.


For your second question, considering your loads and boundary condition as correct one, then the component is expected to fail in the static load itself if the operating stress in the component goes beyond UTS. In this scenario, no point in talking about fatigue life.

 Or else, there might be mistake in your loads and boundary conditions.Hence, correct it and bring down the stress value to the correct magnitude, then proceed your fatigue analysis.

 By the way, what is the software do you use for fatigue life prediction?(If you are interested to share)


Thanks and Regards

M Gopalakrishnan

Alejandro Ortiz-Bernardin's picture

What I can tell you is the following: If you are using linear (assuming elastic) static analysis and you passed the UTS, i would tell you that this is fictitious behavior. There is no way that an linear elastic static analysis can predict plastic behavior. If you even pass the yielding stress, then you should do a nonlinear analysis since the linear model will increase the stress without having a control over it in the plastic range (you can get high meaningless stresses). When doing a linear elastic analysis, you should always be in the elastic range. Once you have managed to keep all in the elastic range, you can do the fatigue analysis.

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