Approximation of stress-strain curves by various functions

Stress-strain curves obtained by measurements based on four different strain-rates relating to steels St 37-3 and X 10 CrAl 18 were approximated by various functions. The mathematical procedure used herein is of advantage inasmuch as no distortion through transformation of the approximating function occurs. The transition from the area of spread of Luders lines to homogeneous deformation, which occurs in steel St 37-3, is discussed.