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bbell1-Visitor
1-Visitor
October 15, 2015
Solved

How to find load at yield stress?

  • October 15, 2015
  • 3 replies
  • 2930 views

My goal is to do a sensitivity analysis of a part where one dimension (x) is varied. What I want out, is the force that would cause the part to reach the yield point for each change in 'x'.

In other words, the user is allowed to reconfigure an assembly, and we want to plot the expected failure load for each configuration. Anyone know of a way to do this?


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Best answer by mlindqvist

You want to increase the load until some location in the model reaches yield stress, and then identify what that load is, correct?

If it is a linear problem, then create a computed measure M = Mtrl_yield_limit/Stress_model_max_von_Mises.

For example if you apply 1 kN, and M turns out to be 0.1, then you will  need to scale down the load to 0.1 or else your max stress will be above yield. Conversely, if M turns out to be 10, then you must scale up your unit load by a factor of 10 to reach yield stress.

Apply a unit load, say 1 kN. Run sensitivity study. Plot yout measure M vs. x. Then M corresponds to the factor*(unit load) that will cause the material to reach the yield limit for each x. 

In linear problems, everything is proportional- double the load you double the stress, displacement etc. For nonlinear problems you can't do that.

If it is a nonlinear model, then there are no shortcuts. Increase the load in steps, and see when max von Mises stress exceeds yield limit.

/Mats L

3 replies

A
AnandKumar1-Visitor
1-Visitor
October 15, 2015

Just create a local parameter called Load. While applying load specify "Load" instead of value .then proceed static & Sensitivity study

M
mlindqvist1-VisitorAnswer
1-Visitor
October 15, 2015

You want to increase the load until some location in the model reaches yield stress, and then identify what that load is, correct?

If it is a linear problem, then create a computed measure M = Mtrl_yield_limit/Stress_model_max_von_Mises.

For example if you apply 1 kN, and M turns out to be 0.1, then you will  need to scale down the load to 0.1 or else your max stress will be above yield. Conversely, if M turns out to be 10, then you must scale up your unit load by a factor of 10 to reach yield stress.

Apply a unit load, say 1 kN. Run sensitivity study. Plot yout measure M vs. x. Then M corresponds to the factor*(unit load) that will cause the material to reach the yield limit for each x. 

In linear problems, everything is proportional- double the load you double the stress, displacement etc. For nonlinear problems you can't do that.

If it is a nonlinear model, then there are no shortcuts. Increase the load in steps, and see when max von Mises stress exceeds yield limit.

/Mats L

B
bbell1-VisitorAuthor
1-Visitor
October 16, 2015

Both of these answers were useful. I was able to run a sensitivity analysis on the load parameter and determine that the response was indeed linear. Then I could extend the results of the dimensional sensitivity to find the failure load at each configuration.

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