Inrel support

Rodrigo Gavino
Rodrigo Gavino Altair Community Member
edited September 2023 in Community Q&A

I’m facing an issue with INRELL and SUPPORT

 

I will describe the issue with the following example:

 

              Thrust force = 10 Lbs

              Mass = 2

              G = 5

 

Case 1 (Gravity LC):

 

I’m running a gravity case the applies 5Gs to a mass of 2 resulting in 10 Lbs thrust. For the gravity case I’m applying a BC as an SPC connected to a CBUSH (10^7 Stiffness all 6DOF). CBUSH has coincident nodes and the other node is tied to a RBE3 with dependent node at the center of a cylinder.

 

Case 2 (Thrust LC):

 

I run the same BC with a for applied a the other end of the cylinder (10 bs). The force result in equivalent force to the G and mass.

 

Results from Case 1 and 2 are similar.

 

Case 3 (Thrust LC, BC with SUPPORT and INRELL):

 

              I run the same configuration as Case 2, but instead of a SPC I use SUPPORT connected to the CBUSH and INRELL -1.

 

When I compare results from Case 2 and 3, they are 10 times smaller for case 3.

 

I’m using the following PARAMs:

WTMASS

WTM_V1 = 0.00259

And the Gravity load is:

G: 386.1

N1: 5

Why this 1 fold difference in results?

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Answers

  • Jason_Craanen
    Jason_Craanen
    Altair Employee
    edited September 2023

    Hello

    With INREL, -1, the SUPORT points that you place determine the fixed reference for the solution when you solve for inertia relief.
    The inertial relief analysis solves a different set of equations than linear static analysis, so that could be why you're seeing a different result.
    In inertia relief, the balancing forces are calculated and applied on the structures as if it is freely accelerating. The reference SUPORT points are set as a way to have a frame of reference for deflection in the result. This is different from the SPC in linear analysis where displacement = 0.

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