Symbol of material stiffness: where-the stress in the elastic deformation range (MPa) ε-the strain generated under the stress, that is, the relative deformation (Δl / l.), Dimensionless. Material stiffness is called stiffness for short, which is the elastic modulus in material mechanics. It can be seen from the formula that its physical meaning refers to the stress required for a metal material to produce a relative deformation per unit elasticity. It is a mechanical property index that characterizes the ability of materials to resist elastic deformation