Solids behave differently when they are subjected to large deformations as opposed to small ones. This is due to the change in their shape and it often introduces a form of nonlinearity known as geometric nonlinearity. The degree to which this nonlinearity affects the solution accuracy is controlled by certain variables, including the nature of the loading, the material used, boundary conditions, etc. Apart from this there are material and contact nonlinearity also.
For a detailed understanding of large deformations, refer to this Ansys innovation course:
Large Deformation | Ansys Innovation Courses
Also, have a look at this documentation:
8.2.2. Large Deformations (ansys.com)
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