# Pre-stretch membrane simulation error

**URL:** <https://calculix.discourse.group/t/pre-stretch-membrane-simulation-error/1190>\
**Category:** Uncategorized\
**Created:** [August 2, 2022, 12:50am UTC](https://calculix.discourse.group/t/pre-stretch-membrane-simulation-error/1190 "2022-08-02T00:50:31Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\
**Post date:** [September 10, 2023, 2:43pm UTC](https://calculix.discourse.group/t/pre-stretch-membrane-simulation-error/1190/12 "2023-09-10T14:43:01Z")

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Nice area of research!!.

I find some discrepancies on the data and your model.

Your final thickness is 2mm in the pres-stretch step1.

That shows some issue in the compressibility. It should be 0.16mm or close as advanced on the paper.

 ![screenshot.292](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/e/ef6434e8afb696c504284c8ba5879891f4845de6.jpeg)

Your analysis should consider material nonlinearity (Mooney Rivlin) not only geometric nonlinearity.

Hint to check the accuracy of your results: This is a Pure Biaxial Stretch (in cylindrical coordinates).  
Principal Stress 1 and 2 must be equal and uniform and third negligible. Image on the right shows your VM stress field.

 ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/7/7bd67e0e6b72214dbb20deb6aa73528c1d79331a.png)

Minor comment: A principal Stretch of 3.5 delivers a final radius of 200mm not 195mm.You could do some small adjustment here.

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