Papers by Keyword: Dynamic Fracture Mechanics

Abstract: The purpose of this paper is to solve dynamic fracture problems of plates under both tension and bending using the boundary element method (BEM). The dynamic problems were solved in the Laplace-transform domain, which avoided the calculation of the domain integrals resulting from the inertial terms. The dual boundary element method, in which both displacement and traction boundary integral equations are utilized, was applied to the modelling of cracks. The dynamic fracture analysis of a plate under combined tension and bending loads was conducted using the BEM formulations for the generalized plane stress theory and Mindlin plate bending theory. Dynamic stress intensity factors were estimated based on the crack opening displacements.

Abstract: The Finite Block Method (FBM) for computing the Stress Intensity Factors (SIFs) and the T-stress under transient dynamic load is presented. In order to capture the stress intensity factor and the T-stress, the Williams' series of stress function is introduced in the circular core for statics generally. In the Laplace domain, the Deng's series of stress and displacement is too complicated to be used easily like Williams' series. However, the numerical solutions show that Williams' solution of series is still valid with smaller core size. Comparisons have been made with the solutions given by the finite element method (ABAQUS).

Abstract: The aim of this paper is to present a procedure to perform the evaluation of dynamic stress intensity factors of composite cracked sheets. The numerical method that is used to perform the modeling of the crack is the dual boundary element method. The inertial effects are modeled using the dual reciprocity boundary elements method. The Houbolt Method is used to integrate time, and the energy domain integral is used to evaluate stress intensity factors.

Abstract: In this paper, transparent dynamic photoelastic experimental hybrid method for propagating cracks in orthotropic material was developed. Using transparent dynamic photoelastic experimental hybrid method, we can obtain stress intensity factor and separate the stress components from only isochromatic fringe patterns without using isoclinics. When crack is propagated with constant velocity, the contours of stresses components in the vicinity of crack tip in orthotropic material are similar to those of isotropic material or orthotropic material with stationary crack under the static load. Dynamic stress intensity factors are decreased as crack growth. It was certified that the dynamic photoelastic experimental hybrid method was very useful for the analysis of the dynamic fracture mechanics.

Abstract: A periodic array of cracks in a functionally graded material under transient mechanical loading is investigated. Anti-plane shear loading condition is considered. A singular integral equation is derived, in which the crack surface displacement is the unknown function. Numerical results are obtained to illustrate the variations of the stress intensity factors as a function of the crack periodicity for different values of the material nonhomogeneity, either at the transient state or at the steady state. The material non-homogeneity can increase or reduce the stress intensity factors. Comparing with the single crack solution, it can be shown that multiple cracking can reduce the stress intensity factor significantly.

Abstract: Preventing pipeline from rapid crack propagation is a critical issue to avoid casualties and disasters. In this paper, by combining the energy balance theory with FEM simulation and arrest criteria, the numerical analysis is developed to solve the problem of crack dynamic propagation in gas pipeline. This simulation, in combination with the full-scale blast tests, provides a broad prediction of the dynamic fracture process. The crack tip opening angle (CTOA) criterion is consummated through the comparison between CTOA in FEM calculation and the critical value of (CTOA)C obtained by the experiment. The result of the simulation for the crack speed and location is consistent with data by Alliance and Japanese full-scale blast tests.