The Relationship between High Temperature Creep-Fatigue Properties and the Tensile and Creep Ductilities

Abstract

Ductility normalized strainrange partitioning (DN-SRP) life relations in a perfect vacuum were determined based on the SRP life relations experimentally obtained both in air and in an imperfect vacuum for three materials: the annealed, the normalized and tempered 21/4 Cr-1 Mo steels and SUS 304 stainless steel.
As the results, it is found that they can be given by either set of equations as follows: Δε_pp=0.5D_pN_pp^-0.5 Δε_pc=0.145D_pN_pc^-0.5Δε_cp=0.111D_cN_cp^-0.5Δε_cc=0.5D_cN_cc^-0.5} or Δε_pp=D_p^0.6N_pp^-0.6Δεpc=(0.192D_p)^0.6N_pc^-0.6Δε_cp=(0.078D_c)^0.6N_cp=0.6Δε_cc=D_c^0.6N_cc^-0.6}
It is also shown that these DN-SRP life relations can predict a shorter life in the large inelastic strain range than that predicted by extrapolation of air data. So they are important properties even in evaluating the life in air of highly strained structural parts such as notches.