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Title:  Computation of Dynamic Stress Intensity Factors by the Time Domain Boundary Integral Equation Method (Crack, Propagating) 
Author(s):  Mettu, Sambi Reddy 
Department / Program:  Theoretical and Applied Mechanics 
Discipline:  Theoretical and Applied Mechanics 
Degree Granting Institution:  University of Illinois at UrbanaChampaign 
Degree:  Ph.D. 
Genre:  Dissertation 
Subject(s):  Applied Mechanics 
Abstract:  Application of the directtimedomain 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 semiinfinite cracks and finitelength 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 semiinfinite 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. Noderelease and superposition methods for a moving crack problem are also discussed. Both the singlestep and the multistep superposition methods give an accurate SIF history for a semiinfinite 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.) 
Issue Date:  1986 
Type:  Text 
Description:  154 p. Thesis (Ph.D.)University of Illinois at UrbanaChampaign, 1986. 
URI:  http://hdl.handle.net/2142/71686 
Other Identifier(s):  (UMI)AAI8623370 
Date Available in IDEALS:  20141216 
Date Deposited:  1986 
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Dissertations and Theses  Theoretical and Applied Mechanics

Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois