A modified Swift law for high strength steels

Abstract

For most materials the tensile curve can be fitted with one of the usual constitutive laws: pure plasticity, linear hardening, Hollomon, Nadai, Swift or Ludwik. However, high strength steels, due to a specific hardening behavior, cannot be accurately characterized with one of the above-mentioned laws. The same is true for the unit bending moment that is often used to characterize materials under bending conditions. An additional problem of high strength steels is that tensile tests can be performed up to maximum strains ranging from 3 to about 5%, while in the bending process the typical values of stable strains (without visible damage) can be up to 20% and sometimes even higher. In order to overcome these difficulties, an appropriate material model has been developed for high strength steels that allows to accurately represent the constitutive law over the entire relevant strain range.For most materials the tensile curve can be fitted with one of the usual constitutive laws: pure plasticity, linear hardening, Hollomon, Nadai, Swift or Ludwik. However, high strength steels, due to a specific hardening behavior, cannot be accurately characterized with one of the above-mentioned laws. The same is true for the unit bending moment that is often used to characterize materials under bending conditions. An additional problem of high strength steels is that tensile tests can be performed up to maximum strains ranging from 3 to about 5%, while in the bending process the typical values of stable strains (without visible damage) can be up to 20% and sometimes even higher. In order to overcome these difficulties, an appropriate material model has been developed for high strength steels that allows to accurately represent the constitutive law over the entire relevant strain range.