Dynamic Crack Propagation in PMMA

discrete crack approach has been used to model crack propa- gation in prestressed PMMA (poly-methyl-metha-acrylate) plates. paper is concerned with the comparison computational results. The experiments have carried out on prestressed plates of viscoelastic PMMA material. plates a hole have been preloaded and fracture was by a pres- sure pulse excited through an explosive wire placed the end of a transfer bar. Cracking starts at hole and propagates through material. photorecording fracture process the shows the crack length development in time. tional analyses influence of fracture parameters - energy, tensile strength and shape of the softening diagram - on velocity of crack propagation and the size of the cohesive zone was determined. The influence of the fineness of the on the results and the modelling of PMMA impact have discussed. 10n leave from the Department of Solitl 1/Iechanics, Technical University of Liberec, The Czech Republic 729 1 The analysis of dynamic fracture extremely difficult due to complexity of Analytical gation elastic continua Although the analytical solutions are essential for of various features of dynamic crack propagation, applicabil- ity is restricted a class of problems with special boundary con- ditions. Therefore, numerical methods are used for analysis of real structures, particular the finite element method (FEM). The crack motion is modeled either by a special singular technique or by a separation of element edges, the so-called "nodal release technique". The first method requires a continuous change of discretization crack tip which increases the cost considerably. An implementation of the is usu- ally easier and introduces no inhomogenities which become a source of false stress waves. However, in methods still two ways can be used to crack propagation.