| No matter in the field of civil or military,during the servicing period of steel,it will be subjected to lots of dynamic issues,such as explosion and impact etc.It is very important to study the dynamic fracture toughness of steel to improve the safety of steel structural.Meanwhile the study method and standard of fracture toughness under dynamic loading is still a hot issue.Selecting Q345 and 40 Cr steel as experiment object and the dynamic tensile test was carried out with the split Hopkinson tension bar(SHTB),obtaining the dynamic fracture toughness under different loading rates.Use conventional finite element method to simulate the process of experiment,studying the influence of clamp loading mode to the experiment.The main contents of this paper are as follows:(1)The basic material parameters were tested used the universal testing machine and use fracture machine to prefabricating straight cracks.After that,quasi-static fracture test on compact tension specimens(CT specimens)was done.(2)The Q345 and 40 Cr steel compact tension specimens were tested with Hopkinson tension bar,and then obtaining fracture toughness under different loading rate though the change of the aluminum alloy short rod.At the same time,the influence of crack length on dynamic fracture toughness was studied.(3)Simulation has been done with finite element method for the process of experiment,verifying the accuracy of the simulation through comparing test results.Then observe the stress distribution of the device and CT specimens.Though the finite element method,the influence of direct loading method and clamp loading method on the stress waves in the specimen,fracture initiation time and stress-state equilibrium time were analyzed.Compared with the influence of direct loading method and clamp loading method to the stress waves in the specimen,dynamic fracture toughness.Optimization design was done on the fixture size. |
PDF Full Text Request