Shock absorber Modelling

Parthiban B

Hi Guys, 

Currently I am trying to model shock absorber in hypermesh optistruct for performing stress analysis.

The model is placed in an assembly.

What kind of contact should I consider while performing the analysis in hypermesh. I want the shock absorber to have a sliding motion b/n the piston and the rod and stop when it reached the bump stop



Please help me.

Adriano A. Koga

it really depends on how detailed you need this to be modeled, and what effects you want to capture.

OptiStruct has a similar example here:

https://2021.help.altair.com/2021.2/hwsolvers/os/topics/solvers/os/compression_of_helical_springs_os_example_r.htm

 

But if you're running the full assembly, convergence might be tricky and even creating the model is cumbersome.

Maybe you could rely on some simplified model in order to represent this.

 

Or maybe even try Explicit model in OptiStruct to make it easier to handle contacts.

Parthiban B

Adriano A. Koga_21884 said:

it really depends on how detailed you need this to be modeled, and what effects you want to capture.

OptiStruct has a similar example here:

https://2021.help.altair.com/2021.2/hwsolvers/os/topics/solvers/os/compression_of_helical_springs_os_example_r.htm

 

But if you're running the full assembly, convergence might be tricky and even creating the model is cumbersome.

Maybe you could rely on some simplified model in order to represent this.

 

Or maybe even try Explicit model in OptiStruct to make it easier to handle contacts.

Thank you Adriano.

As you mentioned I could go to a simplified model ( may be 1 d springs) but in my case I need to allow the system to touch the Bump stopper. ( which is a Contact Non Linearity with the spring action)

So If I use the 1d spring with non linear stiffness will it be capturing the process. 

So what sort of difference will a 1d spring and total assembly modelling will cause in the results?

Adriano A. Koga

Parthiban B said:

Thank you Adriano.

As you mentioned I could go to a simplified model ( may be 1 d springs) but in my case I need to allow the system to touch the Bump stopper. ( which is a Contact Non Linearity with the spring action)

So If I use the 1d spring with non linear stiffness will it be capturing the process. 

So what sort of difference will a 1d spring and total assembly modelling will cause in the results?

using PBUSH/PBUSHT you could assign a NL force x displacement curve to both stiffness and damping.

So essentially you could force the behavior that you want, including some stopper at some stroke.

The only thing, of course you won't be able to see stresses, advanced contact effects and so on.