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 Title: A crack closure model for the fatigue behavior of notched components and welded joints Author(s): Hou, Chien-Yuan Doctoral Committee Chair(s): Lawrence, Frederick V., Jr Department / Program: Civil and Environmental Engineering Discipline: Civil and Environmental Engineering Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Engineering, Civil Engineering, Mechanical Engineering, Materials Science 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. Issue Date: 1994 Type: Text Language: English URI: http://hdl.handle.net/2142/23285 Rights Information: Copyright 1994 Hou, Chien-Yuan Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9503219 OCLC Identifier: (UMI)AAI9503219
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