三轴应力场中空穴扩张临界值与材料的微观断裂延性

选用一种球化碳钢的轴对称光滑和不同缺口拉伸试样研究了材料在三轴应力场中的宏、微观断裂延性。基于不同应力三轴性水平下空穴扩张与聚合的特性,给出了一个新的材料微观断裂延性表达式。结合空穴扩张的临界尺寸与断口韧窝几何的三维测量结果,证明了在不同的三轴应力水平下,材料微观断裂延性与实测宏观断裂延性之间均有着良好的一致性。从而揭示了材料断裂延性随应力三轴性水平升高而下降的微观机理。

CRITICAL VOID GROWTH AND MICRO-FRACTURE-DUCTILITY OF MATERIALS IN TRIAXIAL STRESS FIELD

The investigation were performed on the macro-and and micro-fracture-ductilityof materials in triaxial stress field by using axisymmetrical smooth and variousnotched tension specimens of a kind of spheroidized carbon steel. Based on thecharacteristics of void growth and coalescence at different stress triaxiality levels,a new expression for micro-fracture-ductility was given. The micro-fracture-ductility predicted was proven to be in better accordance with the macro-frac-ture-ductility measured experimentally at different triaxial stress levels, com-bining with the results in measuring the critical dimensions of growing voidsand dimple-geometry on the fracture surfaces. Thus the micro-mechanisms onthe decreasing of material's fracture-ductility with increased stress triaxialitylevels were revealed.