Linear Structural Analysis and Virtual Connectors (Joints & Pins) - Unable to solve the equation system

Pierre Li

Hi there!

I am very new to SIMSOLID and wanted to try a linear structural analysis on an excavator; model that includes some hinge joints and linear guides as well. I've used the model provided for the Virtual Connector - Joint Tutorial here:

https://2021.help.altair.com/2021/ss/topics/tutorials/ss/intro_virtual_connector_joints_r.htm#reference_ycq_c5y_qlb

The .ssp model can also be found here:

https://2021.help.altair.com/2021/ss/topics/tutorials/ss/simsolid_access_tutorial_files.htm

In the tutorial, a modal analysis is conducted but I wanted to try a linear structural analysis, which would be of interest in my study. Therefore, I've used the same connection setup shown here:

The constraints (immovable at the base) and forces (remote load of 100N in the Z axis) are shown here:

Solving this gives me the error below:

My hypothesis is that since it's a static analysis, parts should "not" be moving and using joints allows relative motion between parts. My question is therefore: is there another way to indicate a relative displacement that would work/not give the error when performing linear structural analysis? I have tried hinge constraints but it's not possible to have a hinge constraint and a hinge joint at the same time. I have also tried hinge constraint without joints but efforts doesn't transfer from one part to another as there is no more connection.

 

Kindly,

 

Pierre 

Adriano_Koga

linear static needs equilibrium for your structure, indeed.

 

what about spring connections at your hinges with some stiffness? or even rigid connections (or bonded contact) at some points to avoid undesired movement.

Pierre Li

Adriano A. Koga_21884 said:

linear static needs equilibrium for your structure, indeed.

 

what about spring connections at your hinges with some stiffness? or even rigid connections (or bonded contact) at some points to avoid undesired movement.

I still need to verify if the solution is physically correct but the following solution did eliminate the error I previously had:

I replaced Joints - Hinge (Virtual Connectors), by bushing. If the joint was a hinge, I chose to set the stiffness of all but the rotating axis to "Rigid". For the hinge (rotating axis - Angular), I did set the stiffness to a very small value (0.0005Nm/rad). I applied the same logic with the linear guides. I did set the value of stiffness of the linear axis at 200N/m and the rest to rigid. If I needed pins, I kept them and also set them to rotating.

Modal analysis did give me somewhat the same animation as the baseline and the linear structural analysis did also give me a solution.

 

Thank you for the fast reply Mr. Koga.

 

I'll verify my results with my teachers and close the thread afterwards!

 

Pierre