【摘要】 用弹塑性有限元法研究了中心带孔板在交变载荷作用下孔边的应力应变分布及其随循环次数变化的规律，其中考虑了材料的非线性和交变载荷下的瞬态σ－ε关系。通过对ＬＹ１２－ＣＺ材料的数值分析，表明在孔边存在循环硬化现象。找出了应变增量随循环次数变化的基本规律，且数值分析和实验测量结果吻合较好。提供的分析方法将有助于提高疲劳裂纹萌生寿命的估算精度。更多还原

【Abstract】 Accurate determination of crack initiation life is partly dependent on a good knowledge of variation of cyclic hardening strain with number of cycles of alternating loading. As far as we can ascertain, such knowledge is lacking. We used finite element elastoplastic analysis to calculate the strain distribution and its history at notch root of an LY12CZ (corresponding approximately to ASTM 2024T3) aluminum alloy plate specimen with a central hole (Fig.3a) under alternating loading. We prepared Figs.6 and 7 to show the attenuation of strain increment Δ ε during the 4th and 10th cycle respectively, which peaked as expected at point A in Fig.3(b). As distance from hole center increased, Δ ε quickly dropped and then flattened out. The solid curves were calculated and the test data, represented by crosses, were quite close to computed curves. Actually Δ ε was experimentally determined for N =1,2,…,100 and calculated for N =1,2,…,50. We made 50 comparisons, of which N =4 and N =10 were just two examples. We were therefore confident to compute Δ ε for any value of N by using regression method. For eq.(6), we determined its parameters C and D both with calculated and test values for Δ ε max at point A in Fig.3(a). Table 4 gave values of C and D determined by regression method and r =95.4% for computed values was only a little inferior to r =99.2% for test values,!but was still quite acceptable because r =95.4% was still much larger than r (0.01) =76.5%.更多还原