裂纹试样尺寸对局部解理断裂应力σ_f的影响

Influence of precracked specimen dimensions on stress σ_f of local cleavage fracture

应用弹塑性有限元计算了 3种不同尺寸COD试样裂尖前的应力分布 .在不同温度下进行了拉伸和COD试验 .通过精确测量起裂源距钝化裂尖前的距离 ,测定了局部解理断裂应力σf.结果表明 ,在一定范围内随裂纹深度a/h ,试样高度h和试验温度的增加 ,COD和断裂载荷Pf 明显变化 ,而σf 基本不变 .σf 是一个稳定的材料本质参数 ,它的值不随裂纹试样尺寸变化 .

An elastoplastic finite element method (FEM) is used to analyze the stress distributions in front of crack tips for three typ es of COD specimens with different precracked depth a/h and height h, an d the tensile and COD tests are carried out at various temperatures. By accurate ly measuring the distances of the cleavage initiation sites from the blunted cra ck tips, the stresses σf of local cleavage fracture are measured. The res ults show that, with increasing precrack depth a/h, specimen height h, a nd test temperature over a certain range, the COD and fracture load Pf var y appreciably while the σf is essentially unchanging. The σf is a stable inherent parameter of the material and its magnitude is independent of th e precracked specimen dimensions.