平面应变下的主应力比对微孔洞损伤演化行为的影响

Effect of principal stress ratio in plane strain condition on void damage evolution

通过有限元计算,分析平面应变下的主应力比对微孔洞损伤演化行为的影响.计算结果表明,三向应力度q相同时,不同的主应力比2σ/1σ会引起不同的孔洞长大和聚合行为,从而使开裂路径和断裂时的应变不同.当2σ/1σ>1时,最大主应力为2σ,由孔洞长大和聚合所决定的开裂路径倾向于同2σ方向垂直.当2σ/1σ<1时,最大主应力为σ1,开裂路径倾向于同1σ方向垂直.随主应力比2σ/1σ的增加,孔洞面积分数fa随主应变1ε1的增加速率变大,断裂时的主应变(1ε1)f降低.因此在分析应力状态对材料的损伤断裂行为的影响及建立相应的力学模型时,不仅要考虑三向应力度σm/eσ,而且要考虑不同主应力比2σ/1σ的影响.

The effect of principal stress ratio in planar strain condition on void damage evolution was analyzed by using finite element method. The results showed that the void growth and coalescence behavior was different for various principal stress ratios σ2/σ1 in the case of the same stress triaxiality. This caused different crack growth paths and fracture strains. When the σ2/σ1 was larger then unity, the maximum principal stress was σ2, and the crack growth path determined by the void growth and coalescence tended to be vertical to the σ2 direction. When σ2/σ1 was less then unity, the maximum principal stress was al, and the crack growth path determined by the void growth and coalescence tended to be vertical to the σ1 direction. With increasing the principal stress ratio σ2/σ1, the increase rate of the void area fraction fa with the principal strain ell increased, and the principal strain （ε11）f at the moment of fracturing decreased. Therefore, when the effect of the stress state on the damage and fracture behavior of materials would be analyzed and the mechanical model established, not only the effect of stress triaxiality but also the principal stress ratio should be considered.