One of the fundamental aspects in cohesive zone modeling is the definition of the traction-separation relationship across fracture surfaces, which approximates the nonlinear fracture process. Cohesive traction-separation relationships may be classified as either nonpotential-based models or potential-based models. Potential-based models are of special interest in the present review article. Several potential-based models display limitations, especially for mixed-mode problems, because of the boundary conditions associated with cohesive fracture. In addition, this paper shows that most effective displacement-based models can be formulated under a single framework. These models lead to positive stiffness under certain separation paths, contrary to general cohesive fracture phenomena wherein the increase of separation generally results in the decrease of failure resistance across the fracture surface (i.e., negative stiffness). To this end, the constitutive relationship of mixed-mode cohesive fracture should be selected with great caution.

Cohesive Zone Models: A Critical Review of Traction-Separation Relationships Across Fracture Surfaces

A generalized potential-based constitutive model for mixed-mode cohesive fracture is presented in conjunction with physical parameters such as fracture energy, cohesive strength and shape of cohesive interactions It characterizes different fracture energies in each fracture mode, and can be applied to various material failure behavior (eg quasi-brittle) The unified potential leads to both intrinsic (with initial slope indicators to control elastic behavior) and extrinsic cohesive zone models Path dependence of work-of-separation is investigated with respect to proportional and non-proportional paths—this investigation demonstrates consistency of the cohesive constitutive model The potential-based model is verified by simulating a mixed-mode bending test The actual potential is named PPR (Park–Paulino–Roesler), after the first initials of the authors’ last names

A unified potential-based cohesive model of mixed-mode fracture

https://hal-upec-upem.archives-ouvertes.fr/hal-01213943/document

A phase-field method for computational modeling of interfacial damage interacting with crack propagation in realistic microstructures obtained by microtomography

To understand the thermal insulation and failure problems of the thermal barrier coatings (TBCs) deeply is vital to evaluate the reliability and durability of the TBCs. Actually, experimental methods can not reflect the real case of the TBCs during its fabrication and service process. Finite element modeling (FEM) play an important role in studying these problems. Especially, FEM is very effective in calculating the thermal insulation and the fracture failure problems of the TBCs. In this paper, the research progress of the FEM on the study of the thermal insulation and associated failure problems of the TBCs has been reviewed. Firstly, from the aspect of the investigation of the heat insulation of the TBCs, the thermal analysis via FEM is widely used. The effective thermal conductivity, insulation temperature at different temperatures of the coating surface considering the thermal conduct, convection between the coating and the environment, heat radiation at high temperature and interfacial thermal resistance effect can be calculated by FEM. Secondly, the residual stress which is induced in the process of plasma spraying or caused by the thermal expansion coefficient mismatch between the coating and substrate and the temperature gradient variation under the actual service conditions can be also calculated via FEM. The solution method is based on the thermal–mechanical coupled technique. Thirdly, the failure problems of the TBCs under the actual service conditions can be calculated or simulated via FEM. The basic thought is using the fracture mechanic method. Previous investigation focused on the location of the maximum residual stress and try to find the possible failure positions of the TBCs, and to predict the possible failure modes of the TBCs. It belonged to static analysis. With the development of the FEM techniques, the virtual crack closure technique (VCCT), extended finite element method (XFEM) and cohesive zone model (CZM) have been used to simulate the crack propagation behavior of the TBCs. The failure patterns of the TBCs can be monitored timely and dynamically using these methods and the life prediction of the TBCs under the actual service conditions is expected to be realized eventually.

Modeling of thermal properties and failure of thermal barrier coatings with the use of finite element methods: A review

Constitutive behaviour of mixed mode loaded adhesive layer

An improved description of the exponential Xu and Needleman cohesive zone law for mixed-mode decohesion

Interfacial fibrilation is a typical mechanism that frequently occurs during delamination of a polymer coating from a steel substrate. It involves large displacements at the interface as well as large deformations in the bulk material. Classical small displacement cohesive zone formulations fail to describe such large deformations correctly. Therefore, a generic cohesive zone model is introduced that is suitable to describe both uniform and non-uniform fracture at an interface with large deformations in the delaminating bulk and large displacements at the crack tip.

A cohesive zone model with a large displacement formulation accounting for interfacial fibrilation

Delamination is typically modelled using cohesive zone models. In this paper, it is shown that the validity of most models is limited to small displacements and/or deformations at the interface and the surrounding bulk materials. A large displacement formulation (LDF) is proposed that overcomes issues of the classical formulation with large displacements and deformations at the interface. Subsequently, a 3D cohesive zone element with this LDF is introduced and its numerical implementation is elaborated. Then, a 3D FEM model is proposed and the determination of several model parameters is substantiated. Finally, the implementation is validated by comparing numerical results with experimental observations.

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On the development of a 3D cohesive zone element in the presence of large deformations

In this paper, a mixed numerical–experimental approach is adopted to quantitatively investigate and characterize delamination in polymer coated steel. The integral bi-material system is analysed and special attention is given to the constitutive modelling of the polymer coating, the interface and the determination of all involved parameters. An extended cohesive zone model for large displacements is proposed, allowing for a mode-dependent behaviour in large deformations. Finally, peel tests are used to characterize the interface, whereby the interfacial properties are determined through an inverse parameter identification procedure.

van den Mj Marco Bosch

Papers

An improved description of the exponential Xu and Needleman cohesive zone law for mixed-mode decohesion

A cohesive zone model with a large displacement formulation accounting for interfacial fibrilation

On the development of a 3D cohesive zone element in the presence of large deformations

Identification and characterization of delamination in polymer coated metal sheet

On the prediction of delamination during deep-drawing of polymer coated metal sheet