Study On Dynamic Fracture Of Mixed Cracks In Brittle Materials

In various engineering fields,the engineering structure which is often subjected to catastrophic failure by the impact or the shock waves caused by earthquakes and explosions due to the presence of cracks or other defects.Cracks in actual structures are often composed of two or three types of cracks in the basic type,mostly in the composite deformation state.At present,the more dynamic fracture is based on the metal materials,whiles the brittle material,represented by PMMA,because of its high transparency,high mechanical strength,low price and easy processing and other advantages of good performance,and is widely used in aviation,automotive and other industries.So it is verynecessary to carry out research on dynamic mixed mode fracture of brittle materials.In this paper,we use Richard and Julie's AFM specimen and its loading device to design an AFM specimenand its loading devicewhich are suitable for the dynamic test of the split Hopkinson tension bar(SHTB).The PMMA with good performance was prepared into AFM specimen,and the mixed mode fracture under static and dynamic loading was studied by means of experiment and simulation.Based on the WDW3100 electronic universal testing machine,the AFM specimens were subjected to the static tests of type ? and complex ?-?,?-?-?,the cracking phenomena were observed and the critical loads and initiation angles under three loading conditions were measured.Based on the Hopkinson rod(SHTB)test device,the AFM specimen and its loading device were subjected to dynamic tests of type ?,?-? and ?-?-?,and the cracks were observed.The dynamic fracture toughness of type and ? ?-was calculated by strain gauge ?method,The fracture process of type I was simulated by the finite element software ABAQUS,and the dynamic fracture toughness was studied by experimental numerical method,which proved the reliability of dynamic experiment.In this paper,the improved AFM specimen and the loading device are used to study the dynamic fracture under the three loading modes,and the preferablycomposite fracture results are obtained.It provides a reference for the dynamic fracture research of the composite crack of brittle materials,enriches the brittle fracture.