# Plastic snap

**URL:** <https://www.simscale.com/forum/t/plastic-snap/63312>\
**Category:** Solid Mechanics / FEA\
**Created:** [February 7, 2017, 2:19pm UTC](https://www.simscale.com/forum/t/plastic-snap/63312 "2017-02-07T14:19:20Z")\
**Posts on this page:** 1\
**Showing post:** 28

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**Author:** ![rszoeke](https://www.simscale.com/forum/user_avatar/www.simscale.com/rszoeke/32/14_2.png) [@rszoeke](https://www.simscale.com/forum/u/rszoeke)\
**Post date:** [August 7, 2017, 11:11am UTC](https://www.simscale.com/forum/t/plastic-snap/63312/28 "2017-08-07T11:11:57Z")

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Sure,  
this is a new case, so new challenges might appear.

In this case it is relatively easy to find the error cause. If you look at the convergence plots you can see that the absolute residual is very low (~1e-26) while the relative is very high (~1). This hints to the fact that there are actually no forces in your model at all and thus you can not use a _relative_ convergence criteria. In fact, the snap does not move far enough in the first time step to get into contact, so there are no forces at all.

To resolve this, just change in the _numerics_ under _nonlinear resolution type_ the _convergence criteria type_ from **relative** to **absolute**.

When this analysis comes to the final stage there are again some problems. This time the master surfaces was missing the rear end surface. After adding this the simulation runs smooth in a few minutes.

Here the link to the resolved project: [SimScale](https://www.simscale.com/projects/rszoeke/snap_new_1/)

Best,  
Richard

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