## Simulation Mechanical and Multiphysics

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# Nonlinear joints

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Hello

Is there any possibility to define a "nonlinear hinge" (like in Robot Structural Analysis - by moment-rotation curve)?

There is a rotational spring element, but it's got only one spring constant (linear spring).

I'd like to mimic geometrically and physically nonlinear behavior of joints in a steel frame.

# Re: Nonlinear joints

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Hi b.pankowski,

You can define a moment load curve based on the calculated rotation. Do a search in the Help for "Defining Load Curves" and scroll to the section "Result-Based Load Curves". You might be able to use this in combination with beam elements or a linear spring.

Mechanical Engineer

Pittsburgh, PA

16 years experience with Simulation Mechanical

# Re: Nonlinear joints

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I understand Your approach, but how can I use rotation as a lookup value (Simulation Multiphysics 2013)?

*The results that can be used at the probe are as follows:*

*X Displacement**Y Displacement**Z Displacement**X Velocity**Y Velocity**Z Velocity*

# Re: Nonlinear joints

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Oh, that's not good. I did not remember that limitation.

If you have not checked the software, you may want to do that. The rotation results are in the same file as the displacement results, so it should not have been diffucult for the developers to program those results, and the documentation is sometimes out of date.

Otherwise, you could approximate the rotation from the calculated displacements. It might require some dot and cross products of vectors, but straight-forward otherwise.

Mechanical Engineer

Pittsburgh, PA

16 years experience with Simulation Mechanical

# Re: Nonlinear joints

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I suppose, that e.g. beam rotation in the joint can be approximated as a sin(deltaY/L), where deltaY is Y displacement of the following joint and L = length of the 1st element.