Coupled deformation-diffusion-fracture theories for solids : application to polymeric gels and hydrogen embrittlement in steels
Year: 2018
Type: dissertation
Abstract: Solids with deformation-diffusion coupling areubiquitous in engineering applications. Understanding and modeling
the fracture of such solids is vitally important. This thesis
addresses the theoretical formulation, numerical implementation,
and application of fully-coupled deformation-diffusion-damage
theories for two different classes of materials: (i) polymeric gels
and (ii) hydrogen embrittlement in steels, as elaborated below. (i)
Fracture of polymeric gels: We first introduce a field called
stretch of Kuhn segments and/or crosslinks, which is necessary
for understanding and modeling of the fracture in polymeric
materials. Together with this newly introduced field, we formulate
a thermodynamically consistent phase-field type theory for fracture
of gels. A central feature of our theory is the recognition that
the free energy of polymeric materials is not entirely entropic in
nature, there is also an energetic contribution from the
deformation of the backbone bonds in a chain and/or the crosslinks.
It is this energetic part of the free energy that drives the
progressive damage and fracture of polymeric materials. We have
implemented our theory in a finite element code, and used this
simulation capability to study some interesting phenomena in
failure of elastomers and gels. (ii) Fracture of steels due to
hydrogen embrittlement: We have formulated a thermodynamically
consistent theory for the diffusion of hydrogen coupled with the
large elastic-plastic deformations, and a phase-field type theory
to model ductile fracture of metals. The theory accounts for the
macroscopic effects due to the generation and agglomeration of
microscopic hydrogen-vacancy complexes. We have implemented our
fully coupled theory in a finite element program, and calibrated
the material parameters in the theory by using experimental data
available in the literature. Finally we have utilized our
simulation capability to study the process of fracture due to
hydrogen embrittlement in some technically relevant
notched-components made from steel.
Author: Yunwei Mao
Language: English
Subfield: Metals and Alloys
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2907542002