Ratcheting and Fatigue analysis with kinematic hardening model

smandelli_LINCE

Hi,

I'm looking for a way to perform a structural analysis to obtain the stabilized response of a structure subjected to periodic loading (thermomechanical loads), the material involved is exhibits kinematic hardening and it can't be modeled with a stabilized stress-strain curve so I need to capture the stabilized response (plastic shakedown) and then perform the damage calculation.

In Abaqus there is the Direct Cyclic analysis (link below) which is perfect for that type of analysis

https://abaqus-docs.mit.edu/2017/English/SIMACAEANLRefMap/simaanl-c-directcyclicfatigue.htm

I'm wondering if there is a way to implement it in Optistruct though the TSTEP- Fourier card.

thanks

Simone

solon

Hello,

You can run a non linear analysis with monotonic loading and then perform non linear e-N fatigue analysis, as described in the bellow link:

https://help.altair.com/hwsolvers/os/topics/solvers/os/fatigue_analysis_nonlinear_r.htm#:~:text=Nonlinear%20Analysis%20with%20Cyclic%20Load%20History%20in%20Fatigue%20Analysis%20and%20Monotonic%20load%20in%20nonlinear%20analysis

smandelli_LINCE

Hello,

thank you for the reply

I've read the Nonlinear Fatigue analysis as you suggest, my problem here is that I don't have a cyclic stress-strain curve, and for some materials the stabilized cyclic stress strain curve cannot be obtained if the material exhibit viscoplastic behavior and therefore in a first attempt you must consider ratcheting effect considering a cyclic load until stabilized plastic shakedown and after that you could perform the fatigue analysis. The problem is that in some case the plastic shakedown could be reached after 50 or more cycle and so it is not feasible in an engineering application to perform such analysis. In this case a "Direct cyclic analysis" approach based on Fourier analysis as in Abaqus could be a solution. I was wondering if such type of analysis could be performed also in Optistruct

thanks

Simone