hourglass control and another option maybe mass scaling if hourglass control has no effect. ask also to eng-tips.com

Create a section controls definition as follows:

*SECTION CONTROLS, DISTORTION CONTROL=YES, NAME=your_name

Then specify one of the following definitions, depending on modeling of the shell elements:

*SHELL GENERAL SECTION,CONTROLS=your_name

*SHELL SECTION,CONTROLS=your_name

Note that distortion control cannot prevent elements from being distorted due to temporal instabilities, hourglass instabilities, or physically unrealistic deformation. Therefore you should check your model carefully.

George

Thanks for your answers, il attempt with your suggestions.