fabric hinge

Simon Križnik

Hi,

 

I am simulating in Radioss a fabric hinge (similar to a living hinge with flexible woven material). 

 

Using M19_FABRI material card in combination with P9_SH_ORTH property card I can simulate the out-of-plane bending of the fabric hinge. But simulating the in-plane shear is challenging.

In the attached image, the gravity is acting in negative Z direction and the sample is fixed encastre on the left side. The expected behaviour is collapse of the fabric hinge in the middle (between two wood panels). However the sample is behaving like it is made out of uniform elastic material and is only deforming slightly (defromation is 1000x scaled).

 

Does anyone have an explanation? I would also like to use the same material in Optistruct, but I could not find equivalent material law for flexible fabric.

 

any suggestion would be appreciated

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Altair Forum User

Hi Ivan,

 

Can you check with LAW58 in RADIOSS?

 

Meanwhile, I will check about the OptiStruct material.

 

Simon Križnik

Thanks for the tip, however the results are the same with LAW58.

 

The model is attached if anyone would like to check in case I made some mistake. Alternative material/property combination is Kevlar2 & Hinge2. 

 

In this research paper (page 34) it is suggested to use Mooney-Rivlin material in Optistruct (probably MATX42) as substitution for fabric material. 

Unable to find an attachment - read this blog

Altair Forum User

Hi Ivan,

 

yeah you can use LAW42 to model  rubbers, polymers, foams, and elastomers.

Simon Križnik

Hi Prakash, 

 

second order elements almost simulated the collapse I was looking for /emoticons/default_ohmy.png' srcset='/emoticons/ohmy@2x.png 2x' title=':o' width='20' /> sort of 

In the attached animation it can be seen that second order shell elements were converted to nodes and detached from wood panels. 

What did I miss?

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Altair Forum User

Hi,

What is the element formulation used?

 

Can you share the model file?

 

Use this File Transfer LINK

Simon Križnik

Hi,

 

the element formulations are:

ISHELL: 4

Ismstr: 4

I sent the file- thanks for assistance.

Altair Forum User

Hi Ivan,

 

thanks for sharing the file, I will check and let you know.

Simon Križnik

Hi,

 

I truly appreciate your help in resolving the issue.

Altair Forum User

Hi Ivan,

 

I can see that with 1st Order elements doesn't give the expected results but in HV elements are shown.

 

This is not the case with 2nd order elements. The elements are represented as dots/points. 

 

I will discuss with expects to confirm if it just a visualization issue or pre-processing issue and will convey the same to you.

Altair Forum User

Hi,

 

Can you update to latest patch and trying again?

 

There were some issues with shell elements in RADIOSS as they are not supported in HV if they are 2nd order.

 

Simon Križnik

Hi Prakash,

 

thanks for assistance- I will check it out.

Simon Križnik

Is it possible to model the fabric hinge in Radioss with cable (tension only) instead of shell elements? 

In Optistruct this can be achieved with CGAP element, however I could not convert or use it with Radioss solver.

Simon Križnik

Just wanted to update: the problem was I did not give reduction factor (R_E) which is 1 by default on material law 19 (fabric), so elastic modulus is the same in compression and tension. Bellow is the simulation with R_E at 0.001 giving good results.

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