Experimental Study of Dynamic Fracture Toughness of Specimen Subjected to Compact Tension under Plane Strain
平面应变下紧凑拉伸试样的动态断裂韧性的实验研究

Dynamic fracture toughness of material is a importan index evaluating material's crack growth resistance under dynamic load. In the past, most dynamic fracture toughness measurement was based on three-point bending specimen, and the dynamic fracture toughness study of compact tension (CT) specimen was rarely carried out. In this paper, CT specimen is simplified as an equivalent spring-mass model, then an approximate expression of dynamic stress intensity factor of CT specimen is obtained. The existent Hopkinson pressure bar equipment was improved first, then elastic-plastic dynamic fracture experiments under plane-strain state of CT specimen were carried out by using the improved equipment. The dynamic stress intensity factor K(t) is used as a token parameter of fracture top, and the dynamic stress intensity factor K(t) is determined by dynamic impact loading curve (or the displacement of loading point), since the load is monotonically increased before crack propagation and even during a period of time after fracture formation. The resistance strain gage method was used to determine the crack initiation. Finally, the dynamic fracture toughness KId of the typical specimen was obtained. Results indicate that the token and the testing method of dynamic fracture toughness are feasible in dynamic fracture mechanics. Above method was adopted to test the CT specimen fracture toughness of 2A12 aluminum alloy and 16Mn steel, respectively. Experimental esults show that the improved device and testing method is reliable and effective.