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韧性材料断裂过程通常可看作是材料内部微孔洞的形核、扩展及相互贯通的积累。经典的GursonTvergaard(GT)模型能够很好地模拟具有变形均匀、各向同性的孔洞的萌生及扩展过程;但无法模拟由孔洞贯通而引起的局部变形过程,因此需要对其修正,引入相应的孔洞贯通准则。该文采用两种贯通准则对经典GT模型进行修正,即Thomason的塑性极限载荷准则和临界等效塑性应变准则。借助用户自定义程序UMAT将采用这两种贯通准则修正的GT本构关系嵌入至商用有限元软件ABAQUS中,从而可通过对金属材料应力状态和断裂机理的分析控制孔洞的贯通。以一组含有不同缺口根半径的圆棒拉伸试验件为例,分析了该类金属构件自孔洞萌生至最终断裂的整个损伤演化过程,并与试验数据进行了对比,验证了该模型的有效性。该文还讨论了金属断裂过程中应力三轴度对微裂纹萌生与扩展的影响。
The fracture process of ductile materials can usually be regarded as the nucleation, expansion and mutual accumulation of micro-holes in the material. The classic Gursonververgaard (GT) model can well simulate the initiation and propagation of holes with uniform deformation and isotropy. However, it is impossible to simulate the local deformation caused by hole penetration. Therefore, it needs to be corrected and introduced into the corresponding holes Through criteria. In this paper, two pass-through criteria are used to correct the classical GT model, namely Thomason’s plastic limit load criterion and critical equivalent plastic strain criterion. The user-defined program UMAT embeds the GT constitutive relations modified by these two penetration rules into the commercial finite element software ABAQUS, so that the penetration of the holes can be controlled by analyzing the stress state and the fracture mechanism of the metal material. Taking a group of round bar tensile test pieces with different notch root radii as an example, the whole damage evolution process of the metal parts from the hole initiation to the final fracture was analyzed and compared with the experimental data to verify the effectiveness of the model Sex. The paper also discusses the influence of stress triaxiality on the initiation and propagation of micro-cracks during metal fracture.