Hi george85
In general, stiffness and rigidity means the same thing. Both answers to the question how stiff or how rigid the material is when subject to load or deformation. In specific terms using numerical values, we normally use stiffness like what is the axial stiffness, flexural stiffness, torsional, or shear stiffness of the material rather than saying axial, flexural, torsional, or shear rigidity of the material. Sometimes, rigidity is referred to the toughness against volumetric deformation of the material.
Cheers
Jpver
In general, stiffness and rigidity means the same thing. Both answers to the question how stiff or how rigid the material is when subject to load or deformation. In specific terms using numerical values, we normally use stiffness like what is the axial stiffness, flexural stiffness, torsional, or shear stiffness of the material rather than saying axial, flexural, torsional, or shear rigidity of the material. Sometimes, rigidity is referred to the toughness against volumetric deformation of the material.
Cheers
Jpver