Computation of Dynamic Stress Intensity Factors by the Time Domain Boundary Integral Equation Method (Crack, Propagating)
Mettu, Sambi Reddy
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https://hdl.handle.net/2142/71686
Description
Title
Computation of Dynamic Stress Intensity Factors by the Time Domain Boundary Integral Equation Method (Crack, Propagating)
Author(s)
Mettu, Sambi Reddy
Issue Date
1986
Department of Study
Theoretical and Applied Mechanics
Discipline
Theoretical and Applied Mechanics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Applied Mechanics
Abstract
Application of the direct-time-domain boundary integral equation method (BIEM) to the solution of a number of elastodynamic crack problems is presented. In addition to the usual element having constant space and time interpolation of tractions and displacements on the boundary, a new boundary element which incorporates quadratic variation in space and linear variation in time is developed. These two boundary elements are implemented in computer codes and are used in solving the examples. A consistent method of estimation of the dynamic stress intensity factor (SIF) in conjunction with the two types of element is described.
The examples considered include those involving semi-infinite cracks and finite-length cracks in infinite bodies, and finite bodies with finite cracks. It is found that both types of elements discussed model the crack tip displacement fields well when no reflected waves are involved. An example involving a discontinuously loaded semi-infinite crack displays the wave propagation features quite well using both types of element. The effects of finite cracks and wave interaction with the finite boundaries of the specimen are also found to be modeled quite well using the constant/constant element but some oscillation in the computed SIF values at later times is observed when these problems are solved using the quadratic/linear elements. In the case of a finite crack in an infinite body the discontinuity in the slope of the SIF history curve predicted by Thau and Lu is successfully reproduced by the present BIEM. For each case some typical boundary meshes and stress intensity factor histories are presented. Node-release and superposition methods for a moving crack problem are also discussed. Both the single-step and the multi-step superposition methods give an accurate SIF history for a semi-infinite crack moving at constant velocity. Values of the computer memory and the execution time required are presented in the form of graphs. (Abstract shortened with permission of author.)
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