基于累积塑性应变的表面裂纹板CTOD疲劳分析

Research on CTOD for low-cycle fatigue analysis of surface cracked plates based on accumulative plastic strain

结合Dugdale模型,以表面裂纹尖端累积塑性应变为控制参量,提出一个低周疲劳载荷下含半椭圆形表面裂纹船体板的裂纹尖端张开位移(CTOD)分析模型.利用有限元法模拟了表面裂纹尖端累积塑性变形、表面裂纹几何特性、应力均值以及材料应变硬化系数等相关因素的影响,结合最小二乘法拟合出基于表面裂纹尖端累积塑性应变的考虑表面裂纹几何特性、应力均值以及材料应变硬化系数影响的CTOD二阶多项式.

An analytical model was presented to determine the crack tip opening displacement （CTOD） for the semi-elliptical surface cracked plates subjected to cyclic axial in-plane loadings. Combined with Dugdale model, the plastic strain accumulation at the crack tips were used as controlling parameter to estimate cyclic CTOD for tow-cycle failure analysis of the semi-elliptical surface cracked plates. Also in the present work, the finite element analysis was conducted to investigate the influence of the accu- mulative plastic strain at crack tips, crack geometry, mean stress and material strain hardening expo- nent. The second order polynomial for the normalized CTOD defined as a function of the accumulative plastic strain, the ratio of mean stress to the yield stress and the ratio of crack geometry was fitted by the least square method.