Micromechanics of the Hydrogen Effect on Plasticity and Interfacial Decohesion
Liang, Yueming
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https://hdl.handle.net/2142/87712
Description
Title
Micromechanics of the Hydrogen Effect on Plasticity and Interfacial Decohesion
Author(s)
Liang, Yueming
Issue Date
2003
Doctoral Committee Chair(s)
Sofronis, Petros
Department of Study
Theoretical and Applied Mechanics
Discipline
Theoretical and Applied Mechanics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
A traction-separation law that describes the cohesion of an interface in the presence of hydrogen is suggested and implemented through interfacial cohesive finite elements to study interfacial debonding around an elastic particle imbedded in an elastoplastically deforming matrix, while transient hydrogen transport takes place in the matrix, the particle, and the opening interfacial channel. Finite element analyses demonstrate that both hydrogen-induced reduction of interfacial cohesion and matrix softening acting concurrently lead to a reduction of the void nucleation stress at the particle-matrix interface. However, while hydrogen-induced decohesion decreases the void nucleation strain, matrix-softening increases it. Some other issues such as the effect of interfacial diffusivity and strain rate on decohesion are also addressed. Numerical simulations of hydrogen-induced intergranular fracture in nickel-base alloy 690 have been carried out. It is found that hydrogen induced intergranular fracture process in alloy 690 is controlled by the separation process at the interfaces between the grain boundary carbides and the nickel matrix.
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