The first term on the right side, σ σ / E , is equal to the elastic part of the strain, while the second term, K ( σ σ / E ) n , accounts for the plastic part, the parameters K and n describing the hardening behavior of the material. Introducing the yield strength of the material, σ σ 0 , and defining a new parameter, α α , related to K as α α = K ( σ σ 0 / E ) n − − 1 , it is convenient to rewrite the term on the extreme right side as follows: