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Title: 3D finite element investigation of crack growth in compact tension fracture specimens
Author: Nicholas, P. J.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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The J-integral has been used over the past twenty years to predict crack initiation and crack growth in elastic-plastic materials. Fundamental to the J-integral gaining acceptance as a suitable fracture parameter for elastic-plastic solids were the papers of Rice and Rosengren, and Hutchinson. In 1968 Rice and Rosengren, and Hutchinson both presented theoretical models for J scaling of the stresses and strains around a stationary crack tip, under plane stress and plane constraint. However, the theories of Rice and Rosengren, and Hutchinson are unable to take into account any thickness effect, and other workers have investigated the limitations on the validity of J controlled fracture, culminating in empirical size requirements for test specimens and structural components. Druce and co-workers at U.K.A.E.A., Harwell carried out a comprehensive range of tests to investigate the size requirements for a C-Mn steel and found significant variations from currently accepted theory. Druce found, that while the crack initiation of J was fairly independent of specimen thickness, the slope of the J crack growth resistance curve decreased dramatically with increasing thickness. Thus there is much less potential for stable crack growth in thicker sections of the same material. This clearly contradicts the simplistic engineering approach, where an increased factor of structural safety may be obtained by increasing the dimensions of sections, which make up the structure. The main purpose of this thesis is to describe a finite analysis of the specimens tested by Druce, in order to explain the discrepancies from accepted theory. In addition, the numerical results were also used to verify theoretical models of crack tip stress and strain fields, and the assumptions used in J controlled crack growth.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available