# Unitless FE solvers **URL:** \ **Category:** Model setup\ **Created:** [September 10, 2023, 11:58am UTC](https://calculix.discourse.group/t/unitless-fe-solvers/1804 "2023-09-10T11:58:22Z")\ **Posts on this page:** 1\ **Showing post:** 4
**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, 3:00pm UTC](https://calculix.discourse.group/t/unitless-fe-solvers/1804/4 "2023-09-10T15:00:38Z")
Hi rsmith and thanks for comment on this, This comes from a previous post that was experiencing some convergence issues. > [@Pre-stretch membrane simulation error](https://calculix.discourse.group/t/pre-stretch-membrane-simulation-error/1190/12): > > 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. 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 e… If D=0.8237E-05 has [mm2/N] units in our particular case would deliver a Posson Ratio of .5 with the corresponding convergence issues. If D=0.8237E-05 has [m2/N] ,as I think , that value is not enought for the large stretch ratios involved. (Jacobian ends up at 1.42). I think units should be shown or maybe better : \*WARNING reading \*HYPERELASTIC: default value was used (Poisson coefficient of 0.475) --- _[View the full topic](https://calculix.discourse.group/t/unitless-fe-solvers/1804)._