A crack closure model for the fatigue behavior of notched components and welded joints
Hou, Chien-Yuan
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https://hdl.handle.net/2142/23285
Description
Title
A crack closure model for the fatigue behavior of notched components and welded joints
Author(s)
Hou, Chien-Yuan
Issue Date
1994
Doctoral Committee Chair(s)
Lawrence, Frederick V., Jr
Department of Study
Civil and Environmental Engineering
Discipline
Civil and Environmental Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Engineering, Mechanical
Engineering, Materials Science
Language
eng
Abstract
"Newman's Dugdale strip-yield model for crack closure was modified to estimate the crack-closure behavior of cracks emanating from notches. The results obtained using this crack-tip plastic deformation model showed that the estimated effective stress-intensity ratio $U(a)$ (=$\Delta K\sb{\rm eff}(a)/\Delta K(a))$ does not exhibit the commonly observed ""dip"" caused by the notch plasticity. A finite element procedure was used to calculate the magnitude of the notch plastic stretches. It was found that the magnitude of notch plastic stretches is much larger than that of the crack-tip plastic stretches, and that the notch plastic stretches are the main source of the plastic wake when the crack length is much smaller than the notch plastic zone."
A model termed the Strip-Yield Model for Notched Components (SYMNC) that incorporates the notch plastic stretches into the original strip-yield model was proposed for simulating the crack-closure behavior of cracks propagating in the vicinity of a notch. The validity and the efficiency of this model was verified by comparing the predicted results with the published experimental data of various notched components and stress-relieved weldments.
The effect of residual stress on the crack propagation behavior was studied using the crack-closure concept with the SYMNC model. The SYMNC model combined the weld toe plastic deformation and the residual stress effects, and in this form was used to study the crack-closure behavior of as-welded joints. The fatigue lives of weldments were simulated using the SYMNC model.
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