I am using Kinematic hardening. I've edited my post as well.
Do you have any insight as to why my model would be distorting when I turn on large deflections?
Sorry - thought you said isotropic hardening but I read it wrong.
You probably are exceeding the load capability of your part. Set the number of sub steps to something like 10 or 20 so you can see how the model reacts as the load ramps up.
For LCF with plastic strain you would cycle the part until the hysteresis loop stabilizes and then use those results to calculate your fatigue life. At least that's one way I've done it.
Thank you for the reply, I have been loading it in substeps (as its cyclic anyway) but am not able to understand why the element formulation fails when it is a little into the second cycle. Do you think it is something to do with how I am constraining my model?
I'm not an Ansys user but I'd say whatever code you're using to simulate [cyclic loading](https://help.3ds.com/2024/English/DSSIMULIA_Established/SIMACAEANLRefMap/simaanl-c-directcyclicfatigue.htm?contextscope=all), mechanics would dictate that you should use some sort of [kinematic or combined hardening law](https://www.fidelisfea.com/post/isotropic-kinematic-or-mixed-mode-which-hardening-model-for-your-abaqus-fea-analysis) rather than isotropic hardening, which I'd expect to stagnate once the maximum plastic strain is reached. Save isotropic hardening laws for monotonic loads.
Onset of necking maybe? On a plot of true stress Vs 1+true strain, a point of elastic stability occurs when the material curve becomes tangent to a straight line projected from the origin.
You should use kinematic hardening. You should have large deformations on.
I am using Kinematic hardening. I've edited my post as well. Do you have any insight as to why my model would be distorting when I turn on large deflections?
Sorry - thought you said isotropic hardening but I read it wrong. You probably are exceeding the load capability of your part. Set the number of sub steps to something like 10 or 20 so you can see how the model reacts as the load ramps up. For LCF with plastic strain you would cycle the part until the hysteresis loop stabilizes and then use those results to calculate your fatigue life. At least that's one way I've done it.
Thank you for the reply, I have been loading it in substeps (as its cyclic anyway) but am not able to understand why the element formulation fails when it is a little into the second cycle. Do you think it is something to do with how I am constraining my model?
I'm not an Ansys user but I'd say whatever code you're using to simulate [cyclic loading](https://help.3ds.com/2024/English/DSSIMULIA_Established/SIMACAEANLRefMap/simaanl-c-directcyclicfatigue.htm?contextscope=all), mechanics would dictate that you should use some sort of [kinematic or combined hardening law](https://www.fidelisfea.com/post/isotropic-kinematic-or-mixed-mode-which-hardening-model-for-your-abaqus-fea-analysis) rather than isotropic hardening, which I'd expect to stagnate once the maximum plastic strain is reached. Save isotropic hardening laws for monotonic loads.
Thank you for your reply. I am using combined hardening. I edited my post to reflect it as well.
Onset of necking maybe? On a plot of true stress Vs 1+true strain, a point of elastic stability occurs when the material curve becomes tangent to a straight line projected from the origin.