The effects of constraint on three dimensional elastic-plastic crack tip fields

Chen, Ning (1997) The effects of constraint on three dimensional elastic-plastic crack tip fields. MSc(R) thesis, University of Glasgow.

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Detailed finite element analysis of the near tip region of a thin plate has revealed strong three-dimensional effects at the crack front. The field exhibits a gradual loss of plane strain conditions through the thickness which changes with increasing levels of deformation. A strain concentration is located at the intersection of free surface and crack plane. The distribution of J with a deformation levels coincides with the variation of the crack tip stress field. The effects of constraint were studied through modified boundary layer formulations using the first two terms of the William's expansion, K and T as boundary conditions. The results show that positive T stresses allow the strain close to the free surface to advance more than on the midplane. Negative T causes the strain to develop near the midplane more than close to the free surface. At large deformation levels, the crack tip deformation tends to a uniform plane stress field for both positive and negative T stresses. Numerical results show that the lateral contraction at the crack tip is approximately equal to the crack tip opening displacement in small scale yielding.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Mechanical engineering, fracture mechanics.
Subjects: T Technology > T Technology (General)
T Technology > TJ Mechanical engineering and machinery
Colleges/Schools: College of Science and Engineering
Supervisor's Name: Hancock, Professor J.
Date of Award: 1997
Depositing User: Enlighten Team
Unique ID: glathesis:1997-71761
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 17 May 2019 09:31
Last Modified: 05 Sep 2022 10:22
Thesis DOI: 10.5525/gla.thesis.71761

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