Non-destructive material characterisation and material loss evaluation in large historic military vehicles

Engineering Failure Analysis

2017

This paper contains a review of the most vital concepts regarding the analysis and design of film systems. Various techniques have been presented to analyse and predict the failure of films for all common types of failure: fracture, delamination, general yield, cathodic blistering, erosive and corrosive wear in both organic and inorganic films. Interfacial fracture or delamination is the loss of bonding strength of film from substrate, and is normally analysed based on the fracture mechanics concepts of bi-material systems. Therefore, keeping the focus of this review on bonding strength, the emphasis will be on the interfacial cracking of films and the corresponding stresses responsible for driving the delamination process. The bi-material characteristics of film systems make the nature of interfacial cracks as mixed mode, with cracks exhibiting various complex patterns such as telephone cord blisters. Such interfacial fracture phenomenon has been widely studied by using fracture mechanics based applicable analysis to model and predict the fracture strength of interface in film systems. The incorporation of interfacial fracture mechanics concepts with the thermodynamics/diffusion concepts further leads to the development of corrosive degradation theories of film systems such as cathodic blistering. This review presents the suggestions for improvements in existing analysis techniques to overcome some of the limitations in film failure modelling. This comprehensive review will help researchers, scientists, and academics to understand, develop and improve the existing models and methods of film-substrate systems.

Section: Introductionmentioning

confidence: 99%

A review of theoretical analysis techniques for cracking and corrosive degradation of film-substrate systems

Engineering Failure Analysis

2017

“…[28][29][30][31] The purpose of this investigation is to predict the adhesion failure and assess the reliability of coatingsubstrate system using the principles of debondment of the bi-layered cantilever induced by diffusion. For this purpose, two most important parameters that influence the adhesion in terms of debonding driving force are used for investigation.…”

Section: Introductionmentioning

confidence: 99%

Optimisation of interface roughness and coating thickness to maximise coating–substrate adhesion – a failure prediction and reliability assessment modelling

Journal of Adhesion Science and Technology

Stokes

2015

A mathematical model for failure prediction and reliability assessment of coating-substrate system is developed based on a multidisciplinary approach. Two models for diffusion and bending of bi-layer cantilever beam have been designed separately based on the concepts of material science and solid mechanics respectively. Then, these two models are integrated to design an equation for debonding driving force under mesomechanics concepts. Mesomechanics seeks to apply the concepts of solid mechanics to microstructural constituent of materials such as coatings. This research takes the concepts of mesomechanics to the next level in order to predict the performance and assess the reliability of coatings based on the measure of debonding driving force. The effects of two parameters i.e. interface roughness and coating thickness on debonding driving force have been analysed using finite difference method. Critical/ threshold value of debonding driving force is calculated which defines the point of failure of coating-substrate system and can be used for failure prediction and reliability assessment by defining three conditions of performance i.e. safe, critical and fail. Results reveal that debonding driving force decreases with an increase in interface roughness and coating thickness. However, this is subject to condition that the material properties of coating such as diffusivity should not increase and Young's modulus should not decrease with an increase in the interface roughness and coating thickness. The model is based on the observations recorded from experimentation. These experiments are performed to understand the behaviour of debonding driving force with the variation in interface roughness and coating thickness.

“…This work is the continuation of research within group as [43][44][45][46]. The basic idea of cathodic blistering is similar to that of cathodic delamination.…”

Section: Mathematical Modelling For Blisteringmentioning

confidence: 99%

A unified mathematical modelling and simulation for cathodic blistering mechanism incorporating diffusion and fracture mechanics concepts

Journal of Adhesion Science and Technology

Stokes

2015

A novel mathematical model has been developed to understand the mechanism of blister initiation and propagation. The model employs a two-part theoretical approach encompassing the debondment of a coating film from the substrate, coupled with the design components incorporating diffusion and fracture mechanics, where the latter is derived from equi-biaxial tensile loading. Integrating the two components, a comprehensive mathematical design for the propagation of blister boundaries based on specific toughness functions and mode adjustment parameters has been developed. This approach provided a reliable and efficient prediction method for blister growth rate and mechanisms. The model provided a foundation for holistic design based on diffusion and mechanic components to enable better understanding of the debondment of thin elastic films bonded to a metallic substrate.