I am trying to simulate contact between a flat rigid plate and a sphere. I am applying a load on the flat rigid plate and the sphere is flexible. How can I avoid this flat from penetrating into the sphere?
It's not possible to give a discrete answer only by knowing what the geometries are. There are many factors affecting penetration. You still need to give more data about your analysis to get a better answer.
You should first make sure of Geometries, that are well assembled and are input with a good format.
A good practice is adjust to touch and pinball radius. If not you should then check other contact parameters.