Simulation Mechanical and Multiphysics

Reply
Member
b.pankowski
Posts: 3
Registered: ‎07-01-2013

Nonlinear joints

157 Views, 4 Replies
12-17-2013 11:00 AM

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.

Please use plain text.
Valued Mentor
AstroJohnPE
Posts: 498
Registered: ‎08-30-2012

Re: Nonlinear joints

12-18-2013 07:21 AM in reply to: b.pankowski

 

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.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Please use plain text.
Member
b.pankowski
Posts: 3
Registered: ‎07-01-2013

Re: Nonlinear joints

12-18-2013 08:08 AM in reply to: AstroJohnPE

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

Please use plain text.
Valued Mentor
AstroJohnPE
Posts: 498
Registered: ‎08-30-2012

Re: Nonlinear joints

12-18-2013 11:34 AM in reply to: b.pankowski

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so it should not have been diffucult for the developers to program those results, and the documentation is sometimes out of date.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.

 

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Please use plain text.
Member
b.pankowski
Posts: 3
Registered: ‎07-01-2013

Re: Nonlinear joints

12-19-2013 03:49 AM in reply to: AstroJohnPE

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.

Please use plain text.