Since stress is proportional to load and strain is proportional to deformation, this implies that stress is proportional to strain. Hooke's Law is the statement of that proportionality. The constant, E , is the modulus of elasticity, Young's modulus or the tensile modulus and is the material's stiffness. If a material obeys Hooke's Law it is elastic. The modulus is insensitive to a material's temper.
Normal force is directly dependent upon the elastic modulus.
The greatest stress at which a material is capable of sustaining the applied load without deviating from the proportionality of stress to strain. The maximum stress a material withstands when subjected to an applied load. Dividing the load at failure by the original cross sectional area determines the value. The point on the stress-strain curve beyond which the material permanently deforms after removing the load . Yield strength Point at which material exceeds the elastic limit and will not return to its origin shape or length if the stress is removed.