PS32 マグネシウム合金の微小き裂領域における下限界応力拡大係数幅の特性(フェロー賞対象ポスターセッション)

Rotating bending fatigue tests on specimens with small cracks were carried out in order to investigate characteristics of threshold stress intensity factor range (ΔK_<th>) for magnesium alloys: AMX602B (X=Ca), AZX912D (X=Ca) and Mg-Ni6.4%-Y11.3% and carbon steel S10C. Obtained result are as follows. (1) ΔK_<th> of Ni6.4%-Y11.3% was a half of S10C though Mg-Ni6.4%-Y11.3% had the same Vickers hardness as S10C. (2) For dependence of crack size, ΔK_<th> of AMX602 and AZX912 increased with the crack size ranging from 150μm to 500μm. On the other hand, ΔK_<th> of Mg-Ni6.4%-Y11.3% had the constant value with the crack size ranging from 80μm to 350μm. (3) The stress intensity factor range at crack propagating lower limit (ΔK_p) from a pre-crack was 0.6MPa・m^<1/2> for magnesium alloys and 2.6MPa・m^<1/2> for S10C. It is likely that ΔK_<th> of magnesium alloys was lower than that of S10C owing to difference of ΔK_p. (4) The prediction equation for ΔK_<th> on magnesium alloys with a small crack was proposed. It can be easily to estimate ΔK_<th> within less than 20% eor using the proposed method.