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Crash Analysis

akhoje
1-Newbie

Crash Analysis

Hello,

I am looking to perform a crash analysis on a part inside an automobile and my static analysis seems to fail. I know that impact loading is the right way to go, but I have no idea why my results show uniform stress on the whole body under an enormous load during static analysis. Also, even though the stresses are uniform, the values are enormous and erratic. Displacement fringe looks fine though. My structure is a sheet metal part mounted on a sheet metal bracket and I am trying to constrain the displacement of the bottom face of the bracket's four legs and the gravity load I am applying on the whole assembly is 40g's

I have attached my setup and stress results screenshots below. Max strain I am getting is 2.4*e^9 lbm in/s2.

Thank you

Capture1.PNGCapture2.PNG

1 ACCEPTED SOLUTION

Accepted Solutions
dschenken
21-Topaz I
(To:akhoje)

Without doing a plastic large deformation analysis, what do you expect the results to be?

A static elastic analysis won't deal with plastic deformations.

It looks to have weak connections so the distribution of stress/strain is going to be limited to those connections.

View solution in original post

5 REPLIES 5
346gnu
12-Amethyst
(To:akhoje)

Hi,

I suspect your legend is hiding the interesting fringes.

You have sharp corners that have high stresses. These will be VERY high. The legend will be automatically divided evenly between a VERY high number and roughly zero. All the interesting stuff is in the first fringe probably which is why it is all blue.

Format - legend - set the top number to a useful value (yield?) and the bottom value to zero.

let us know if this helps

bfn

akhoje
1-Newbie
(To:346gnu)

This helped in changing the color tone of the results. However, the results don't make any sense to meas the stress in my assembly mostly lies between 4000 and 5000 Mpa which is way above the yield strength of structural steel. I am constraining the base frame to solid blocks using fasteners and assigning the solid blocks at the bottom zero displacement. The box mounted on the frame is again fastened to the frame using bolts. This assembly is a shell sheet metal assembly. I don't know where I am going wrong.

Thanks for the earlier reply though.

-Abhishek

346gnu
12-Amethyst
(To:akhoje)

Abhishek.

Check your units pedantically.

There is an order of magnitude somewhere perhaps ... however 40g is a lot. Generalising, components in a shocked structure will not see a static load of this because of their inertia.

dschenken
21-Topaz I
(To:akhoje)

Without doing a plastic large deformation analysis, what do you expect the results to be?

A static elastic analysis won't deal with plastic deformations.

It looks to have weak connections so the distribution of stress/strain is going to be limited to those connections.

Yes I felt the same way about that. I didn't incorporate the large plastic deformations as it is available only in the advanced version and wanted to make sure that before opting for the advanced version of Simulate for dynamics, I wasn't going wrong with my constraints.Thank you for your replies. I will try and solve this problem in a dynamic setup and see if the results are still erratic.

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