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Title: Fatigue & fracture mechanics analysis of components containing residual stress fields
Author: Han, Sungkon
ISNI:       0000 0001 3529 3235
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2003
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This research thesis is concerned with residual stress effects on the fatigue life of components. Residual stress can have either a favourable or deteriorating effect on fatigue life depending on its nature. Compressive residual stresses are preferred in fatigue-prone structural details due to their protective qualities against both fatigue crack initiation and propagation. A residual stress measurement model has been developed based on uni-axial stress tests using a non-contacting measurement system using the magnetostriction of ferromagnetic steels. This new "ACSM model" allows the measurement of bi-axial residual stresses in the surface of plates. The strain-life method was applied to analysis of the effects of a number of related variables on fatigue crack initiation life. The method enabled a systematic evaluation of each parameter leading to a clear understanding of complex crack initiation problems such as notches in tensile residual stress fields and cold rolled thread roots subjected to a high mean cyclic stress. The SIF weight function becomes critical in LEFM analysis of cracks propagating in residual stress fields due to the resultant complex stress distribution. A number of weight function solutions for surface cracks were studied and applied to real applications. A one-dimensional weight function was used to calculate the deepest point SIF of surface cracks in threaded pins, using a SIF weight function composition method. The RMS SIF weight function was reformulated and applied to analysis of non-uniform stress test results. The RMS SIF was demonstrated to be robust and applicable to the analysis of fatigue crack propagation and surface crack shape evolution. An extended Vainshtok weight function was derived for external circumferential cracks in pipes and was successfully applied to predict the shape evolution of cracks.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available