body goes through itself when simulating

[akbarih]

I am doing a Static stress simulation, i want to simulate a shock absorber design i have, i constraint one side while putting force on other side, it is all one body and when there is force applied, the body goes through each other, i want the reaction to be realistic as possible , i want their to be friction factor, and i want the contact points to slide across each other within, so it would coil in and out.  there is an image below of my fusion and another image showing what i want the structure to look like after putting force on it, as you can see it bends within itself, can someone please help ! 

[henderh]

Hi @akbarih,

Have you set up a 'self contact' for the body? This is done via a manual contact, to specify the faces that will contact each other. i.e. select the body as both Primary Body, and Secondary Body. The Separation contact type supports adding friction.

https://help.autodesk.com/view/fusion360/ENU/?guid=GUID-2A413155-1C36-4C7E-A1C4-D424AC836908

In the case of large deformations, the nonlinear static stress study type should be used.

Hope this helps!

[akbarih]

i just tried that out now it still doesn't work, it still goes through itself. regarding the last thing you said, am i meant to select something specific to make it non linear static stress ? 

 

[henderh]

Hi @akbarih,

Could you attach the model so we can take a closer look? (File > Export... > f3d file type)

A nonlinear static stress is a different study type that can handle large deformations that go beyond the material's yield stress. You can either create a new NLSS study, or right-click on the static stress study > clone. In the cloned study, change the study type to nonlinear static stress via Manage > Settings.

[akbarih]

Hi @henderh 

In non linear static stress it doesn't give me option to choose the material i want, and i just want it not to go through and instead like slide across it when it comes in contact as it will be a plastic. 

[akbarih]

Hi @henderh 

In non linear static stress it doesn't give me option to choose the material i want. 

[henderh]

Hi @akbarih,

<In non linear static stress it doesn't give me option to choose the material i want.>

The reason that Nylon 12 wasn't appearing in the Study Material column drop-down is likely because the default material library was active. The default material library for a nonlinear study is the Nonlinear Materials Library. You can toggle it to the additive materials library.

The body material was defined as Nylon 12 in the Design workspace, Simulation will use it since the Study Material is showing 'Same as Model'

Since only a portion of the faces will come into contact, I've used split face in the Simplify workspace to use only a portion of the original faces to define the contact. The Separation contact has a Maximum Activation Distance set to 15mm, since the gap for the contacting faces is ~14.9mm. This will make it easier for the solver to converge on a solution.

For the linear static stress study, since there is large deformation compared to the overall model size, the deformed model is very distorted (notice it grew in size compared to the undeformed wireframe). Large deformations invalidate the static stress study results, and may be why there is some 'pass through'.

With a Nonlinear static stress study the model is not distorted, but the faces aren't coming into contact. I believe this is because the 100N load isn't large enough to make contact.

If the load magnitude is increased to 130N we can see the contact taking effect, and there isn't a large 'pass through'

I've attached the modified model.

Hope this helps!