低サイクル疲労におけるヤング率とポアソン比

抄録

Axial-and diametral-strain-controlled low-cycle fatigue tests were performed on carbon and low-alloy steels with both an axial and a diametral extensometer mounted on the same cylindrical specimen. The results obtained are summarized as follows. (1) Young's modulus, E, under cyclic plastic deformation was given by E=σ_a/ε^l_<ea>=σ_a/(ε^l_<ta>-ε^l_<ea>), where σ_a is stress amplitude, and ε^l_<ea>, ε^l_<ea> and ε^l_<pa> are total, elastic and plastic strain amplitudes in the axial direction, respectively. E was nearly equal to 206 GPa when ε^l_<pa>=0, while it decreased with increasing ε^l_<pa>. (2) Poisson's ratio for elastic and plastic strain, υ_e=-(ε^d_<ea>/ε^l_<ea>) and υ_p=-(ε^d_<pa>/ε^l_<pa>), were nearly equal to 0.3 and 0.5, respectinely, where ε^d_<ea> and ε^d_<pa> are diametral elastic and plastic strain amplitudes. (3) Strain-fatigue life properties for axial and diametral strain-controlled tests were coincident each other when the axial strain was calculated from the measured diametral strain through an equation of tranformation on the assumption that E=206GPa, υ_e=0.3 and υ_p=0.5.