Modeling and Simulation of Chemomechanical Problems with Chemical Reactions

包含化學反應的力化學耦合問題的建模與模擬分析

Student thesis: Doctoral Thesis

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Author(s)

Detail(s)

Awarding Institution
Supervisors/Advisors
  • Kim Meow LIEW (Supervisor)
  • Shengping Shen (External person) (Supervisor)
Award date15 Oct 2020

Abstract

Multiphysics problems governed by different disciplines of physics are becoming common and challenging due to the advancement of science and technology and the great demand of modern industries, such as the industries of aerospace, energy, chemical engineering and electronics. Among all the multiphysics problems, the coupled chemomechanical processes have arisen in a number of complex material systems, such as thermal barrier coating system, lithium-ion batteries (LIBs), biological tissues, gels, and attracted more and more research interests. The coupling plays an important role in the system behaviors. Thus, it’s essential to have a deep understanding of the coupling. In the thesis, modeling and simulation of chemomechanical processes with chemical reactions are concentrated. Except for the study of basic coupled phenomena, two important issues, i.e., problems of moving interface and fracture, are discussed. Besides, an implementation of electrochemomechanical theory is presented.

A linear continuum model for the coupled chemomechanical processes is proposed within the framework of the irreversible thermodynamics accounting for deformation, mass diffusion and chemical reactions, and the finite element formulations are derived from the Gibbs function variational principle. One- and two-dimensional numerical simulations with different boundary conditions are implemented into the finite element method (FEM) with user-defined element (UEL) subroutines in ABAQUS. The results present the validity and capability of the UEL subroutines and show the chemomechanical interactions.

Due to the limitations of the linear coupled theory, a more general and nonlinear coupled theory for the chemomechanical processes is proposed and the numerical simulation is conducted with UEL subroutines in ABAQUS. Compositional strain and growth strain are induced by the diffusion and chemical reactions in the solid, and in turn, both the diffusion and chemical reactions are stress-dependent. Several illustrative numerical simulation examples are investigated. The results show how the mechanical deformation, diffusion and chemical reaction interact.

The moving interface problem in the fully coupled chemomechanical processes is solved with the combination of the extended finite element method (XFEM) and the level set method (LSM). The coupled problem is actually the Stefan problem. The interface jump condition is introduced and the metal-scale interface is described with the LSM. Besides, the discontinuity is represented with the XFEM. All the numerical procedures are implemented via the UEL subroutines in ABAQUS. The method is capable of capturing the moving interface and describing the jump conditions across the interface and the results show the coupled processes are diffusion-controlled.

Based on the nonlinear coupled theory for the chemomechanical processes, a modified path-independent J-integral derived from the transient energy release rate is presented for calculating the quasi-static crack growth. Numerical simulations are performed for a single edge-cracked plate subject to remote tension and a chemical reservoir under plane strain conditions. The distributions of crack opening profiles and concentrations near the crack tip are analyzed and compared with the linear elastic fracture mechanics (LEFM) under different tensions and boundary concentrations at the instantaneous and equilibrium states. The modified J-integral evolves with time due to diffusion and reaction and the numerical results show the great effect of the diffusion and reaction on J-integral.

A finite element approach to study the electrochemomechanical coupling behavior among mechanical deformation, ionic diffusion and electric performance in mixed ionic electronic conductors (MIECs) is presented based on the coupled constitutive and governing equations, which is implemented with UEL subroutines in ABAQUS. The method is verified in comparison with some previous results. To investigate the performance of MIECs, the influence of mechanical boundary conditions and some parameters, i.e., the coefficients of compositional expansion (CCE), the applied voltage, the diffusion coefficients and the dielectric constant are discussed. The developed finite element method allows one to assess and design the MIECs.

    Research areas

  • Chemomechanical coupling, Stress-assisted chemical reactions, Moving interface, J-integral, Electrochemomechanical coupling, UEL subroutines, XFEM, Level set method