Viscosity parameters for soft material property

Altair Forum User

Hello,

I am a beginer with Altair softwares (v12.0). I am working on modelling the compression of a soft silicon (similar to the skin).

I want to introduce viscosity in my model, so I chose a LAW42+prony serie (and I will try LAW82 too).

But when I create a property for the silicon, there are lambda_v and mu_v (navier stokes viscosity). And the only thing I know for now is that its viscosity is 20,000-30,000cps.
But I do not know what to set (even the unit recquired for those parameters... I am actualy [N mm g ms] system). Can you help me with this please?

Furthermore, I do not know what to set for the minimum time step (dt_min).

Thanks,

Best.

 

Corentin

Altair Forum User

Hi Corentin,

Please check online unit conversion tools, http://www.gordonengland.co.uk/conversion/dynamic_viscosity.htm and also please check this document https://hydramotion.com/uploads/view/20160224144736_Hydramotion_Viscosity_Units.pdf which is related to your topic. From my calculations, the value will be .02 for 20000cps. Please reconfirm after calculating.

Please find the attachment which shows the general unit consistency to be followed in an analysis.

 

If you are imposing a time step for the analysis, you need to specify dt_min. Please watch this webinar on time step control methods: https://altair-2.wistia.com/medias/o0bfml9ah5

As you are a beginner I recommend you to download our free ebook on RADIOSS which explains all aspects on RADIOSS explicit analysis. You can download it from: http://www.altairuniversity.com/free-ebooks-2/free-ebook-crash-analysis-with-radioss-a-study-guide/ 

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