Ductile material can undergo large elastic but small plastic deformation.

Poisson’s ratio value is between half and one.

Material volume does not change during deformation.

A tough material has a large ultimate stress but small area under the stress-strain curve.

The stress-strain equations are independent of the orientation of the coordinate system in isotropic materials

The material constants are functions of coordinates in non-homogenous materials.

The most general anisotropic material needs 36 independent constants to relate the six independent stress components to the six independent and strain at a point.

There are three independent material constant relating stresses and strains in isotropic material

The Generalized Hooke’s law is valid for any orthogonal coordinate system for isotropic material.

The Generalized Hooke’s law is valid for non-homogenous, isotropic material.