: Free resources might not always be up-to-date or accurate. Academic works, especially in fields like engineering, benefit from the most current research and methodologies.
When the internal stress exceeds a specific threshold known as the yield point, the material enters the plastic regime. Unlike elastic deformation, plastic deformation is permanent. Even after the load is removed, the material will not return to its initial state. : Free resources might not always be up-to-date or accurate
If you need this material for your studies, here are the safest and most reliable sources: THEORY OF ELASTICITY AND PLASTICITY - Google Books especially in fields like engineering