Existing experimental results showed that

for some metallic materials

nonproportional loading resulted in significantly shorter lives while no additional nonproportional cyclic hardening was observed. The equivalent strain method modified by additional hardening coefficient and nonproportionality factor cannot be used to correlate the fatigue data of these materials

which usually gives nonconservative predictions. To overcome this shortcoming

a new multiaxial low cycle fatigue life prediction model on the basis of the ASME effective strain range is proposed by introducing the fatigue life reduction factor and nonproportionality factor. The procedure was also proposed to determine the fatigue life reduction factor. A new equation is proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range are presented for the general multiaxial loadings. The proposed method is verified by the measured data of 12 kinds of nonproportional loading paths. In contrast to the existed method

the proposed one can be better used to describe the nonproportionality of the loading path. The accuracy of the proposed fatigue life prediction method is systematically checked by the experimental data found in literature for 10 different metallic materials (including 7 kinds of material showing no additional nonproportional cyclic hardening) under various constant amplitude multiaxial loading paths.