This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principle, the normalization method has been improved by introducing a forcible blunting correction. With the improved normalization method, the J-resistance curves of five different metallic materials of CT and SEB specimens are estimated. The forcible blunting correction of initial crack size plays an important role in the J-resistance curve estimation, which is closely related to the strain hardening level of material. The higher level of strain hardening leads to a greater difference in JQ determined by different slopes of the blunting line.If the blunting line coefficient recommended by ASTM E1820-11 is used in the improved normalization method, it will lead to greater fracture resistance than that processed by the blunting line coefficient recommended by ISO 12135-2002. Therefore, the influence of the blunting line on the determination of JQ must be taken into full account in the fracture toughness assessment of metallic materials.
该文利用有限元辅助测试(Finite element Aided Testing,FAT)方法测得了四种工程材料的等效全程单轴本构关系,基于此全程本构关系对拉伸过程中漏斗试样的应力三轴度演化进行了有限元分析,并同基于Bridgman应力修正后的单轴本构关系得到的漏斗试样漏斗根部截面中心处应力三轴度计算公式结果进行了比较。得到了四种材料的等效全程单轴本构关系、破断应变、破断应力和漏斗根部截面上应力三轴度分布随截面中心Von-Mises等效应变的变化规律。同时基于三轴度理论还讨论了漏斗型试样的拉伸破断机理以及断口的形貌。
采用T-F(Tests and finite element analysis)方法,通过小尺寸圆环试样单轴压缩试验,引入单轴本构关系模型进行有限元迭代计算使得模拟计算的试样变形与圆环试样压缩实验结果满足一致性,进而得到材料单轴弹塑性本构关系参数。研究表明,对不同厚度的304不锈钢圆环,应用T-F方法获得的材料本构关系与单轴拉伸试验结果吻合较好。基于小尺寸材料的T-F方法在获取小尺寸构件的力学性能方面有良好的工程应用前景。
