On Relation Between Stress State And Fracture Strain-experimental And Numerical Of Pure Copper Plates With Hole

In this paper, A series specimens (smooth round specimens, center-hole plates with different thicknesses and diameters of hole) were tested under uniaxial tensile for searching the fracture strain of smooth specimens and the one under stress triaxiality close to 1/3Monitored under the microscopic observation system, the center-hole specimens are tensile loaded to three stages respectively to decide where and when the fractures initiate:Stretch up to fractures initiate; Stretch up to obvious cracks appear; Stretch up to fracture completely. These tests were aimed to revealing the crack growth trend. Scanning the specimens fracture to find out the difference among different stress states by electron microscope scanning system.Numerical study and microscopic observations were performed to decide the value of stress triaxiality and equivalent strain to fracture of the fracture initiation from the specimens (Reference to paper[12] experimental observations of smooth plates, notched hollow round specimens and notched solid round specimens). On this basis, further investigations comparing with smooth specimen under tension were carried on to research the relation between stress triaxiality and fracture strain of a material. The results show that:(1) The center-hole specimens fracture initiated at the same location, which is at minimum cross section with round hole near the border; (2) Equivalent strain to fracture increase with stress triaxiality, which is seemly different from the ductile fracture law concluded from void models; (3) The actual deformation on the hole surface is very inhomogeneous, which is significantly higher than the value according to the calculations by continuum mechanics methods.