裂尖前方塑性区内的局部弹性场

LOCAL ELASTIC ENERGY DENSITY FIELD NEAR THE CRACK TIP

该文给出平面应变下，不同材料（ｎ＝１３、１０、３）ＨＲＲ场对应的能量分布图，在裂尖前方扇形域（约为｜θ｜＜３０°，２＜ｒσ０／Ｊ＜６）内，静水拉应力（σｍ）很高、约为３σ０－７σ０，而等效应力（σｅ）却很小、接近屈服应力σ０，使此区内几乎仅能产生弹性体变能．此区在ＨＲＲ应变场［１］中对应一个几乎不变形的“刚性区”．大量的塑性功则分布于此扇形域的外区（约｜θ｜＞４５°，２＜ｒσ０／Ｊ＜６），构成Ｊ积分的主体．高约束本质上对应着此内区的主体变形能－弹性体变能，但基与塑性功的Ｊ值中却未能反映这部分能量，从而使Ｊ单参数断裂准则往往失真．

The energy density distribution related to the HRR field is obtained. The analysis indicates that within a sector ahead of a crack (about |θ|<30°, 2<rσ0/J<6), the hydrostatic stresses (σm)HRR are very high, up to 3σ0-7σ0, while the effective stresses(σ0)HRR are very small,near to the yield stress σ0, so the elastic strain energy density of the volume deformation prevails in the forward sector. However, this sector is almost abstracted as a“rigid area”in the HRR field[1].Meanwhile, a large amount of plastic dissipation distributes outside of the sector (about |θ|<45°, 2<rσ0/J<6), where the plastic dissipation make up the main part of the J value,.The high constraint means that the high elastic volume energy is stored in the local sector, thus the one parameter fracture criterion based on J is invalid.