The Experimental And Numerical Simulation Research On Tensile Failure Of Notched Rectangular Specimen Of A Ductile Material

In engineering practice, many metal components mainly fail in the form of ductile fracture. Due to the manufacturing process, these metal components have existed and left "defects" inevitably. Under the action of external loads, the "defects" of the stress concentration from components will form a complex stress state, it often becomes the weak position and affects the service life of the components and structures. Just because of the "defects" are inevitable and harmful, it is necessary to research on the tensile failure of the notched specimen of ductile materials.As a basic research, this paper took the copper material as the subjects and the uniaxial tensile test as the breakthrough point. Through setting the copper rectangular notched tensile specimen with different gap sizes and geometric forms, the destructive influence were studied under different stress states. And then the section samples were made into metallographic samples by wire-electrode cutting and polishing. The evolutionary status of micro-holes and cracks near the specimen notch ligament were observed carefully under3D microscopic system. It provided reliable reference for the following numerical analysis.On the basis of experiments, a sub-model method was developed to investigate the plastic behavior (considering the representative volume element with polycrystalline aggregate) based on the classical plasticity constitutive theory and the crystal plasticity theory in macroscopic scale and grain scale respectively. The values and the relationship of stress triaxiality and equivalent plastic strain between the failure and the failure position will be analyzed.The results show that:1、with the increase of thickness, the fracture strain increases rather than decreases;2、preliminary confirmed, the analysis based on crystal plasticity calculation combined with the sub-model method was feasible;3、 the relationship of the failure position between the stress triaxiality and equivalent plastic strain reflected important influence on damage of ductile materials:in notch edge position, the degree of stress triaxiality and equivalent plastic strain were higher, this region can be identified as the crack initiation region based on the sample analysis before fracture.