Hyperelastic materials such as rubbers are used in a variety of engineering applications for sealing and other purposes. These materials often experience large and nonlinear deformation. In addition, modeling such cases usually involves accounting for geometric and contact nonlinearities. Due to these reasons, care must be taken while calibrating the material models, and one must know how to handle excessive element distortion error encountered during simulations. In this course, we will discuss the procedure to curve-fit and calibrate hyperelastic material models. We will also discuss why element distortion errors occur and learn how to understand various error messages and use them to diagnose and fix the underlying issues.