Flexural Wave Propagation In Brittle Material

In the tensile fracture process of brittle material,the fracture characteristic time is affected.Based on tensile fracture,in the pure bending fracture of brittle material,its fracture process should also have characteristic time.However,due to the transient fracture of brittle material,it is difficult to analyze the phenomenon during the fracture process.As a kind of large commercial software ABAQUS,its provides several typical methods to simulate crack initiation and crack propagation technology,this paper based on the technology of cohesive element,to simulate brittle material fracture under pure bending,get the relationship between bending moment and cracking angle of the fracture surface.Then simplify the bending moment and fracture angle relationship,based on Euler-Bernoulli beam theory,the control equation is obtained,and using nondimensionalization,Laplace transform and inverse Laplace transform methods,get flexural wave propagation problems in brittle materials after the first-time fracture.The characteristic time of brittle material fracture under pure bending condition is proposed,and the influence of the loading speed on the propagation of flexural wave is considered.In addition,the problem of bending wave propagation of brittle materials is further studied from the pure bending fracture of brittle beam and dynamic buckling.Add strength weakness in brittle beam,it shows that after the first time fracture,bending moment unloading will cause the secondary fracture.At the same time,using high-speed photography and other techniques,the experiment on the breaking of spaghetti was done,which showed that the crack initiation was in order in the process of breaking the spaghetti.The main conclusions are as follows:(1)Using cohesive element techniques in ABAQUS,can simulation of breaking process of brittle material,and reveal the phenomenon of fracture process,show that brittle material under pure bending fracture,there is a certain relationship between fracture angle and bending moment of the fracture surface,and the area of the curve is related to the fracture energy of the material.(2)The process of pure bending of brittle materials is quite complicated,half of which is pulled,and half of the pressure state causes the propagation of crack velocity change greatly during the fracture process.(3)Based on Euler-Bernoulli beam theory,using the simplified bending moment and cracking angle of the fracture surface,with the help of numerical calculation,can get the characteristics time of the brittle material under pure bending fracture.At the same time,after the first fracture of brittle material,the propagation process of flexure wave is obtained.(4)Using the method of inserting the cohesive elements in the brittle material,the fracture of the brittle material fracture into more than two segments in the pure bending condition can be simulated,and the dynamic buckling of the brittle rod under impact loading is obtained.(5)By using high speed camera to get the breaking process of spaghetti,you can see the time sequence of the fracture,It shows that the propagation of curved wave after the first fracture causes the subsequent fracture.