Numerical Evaluation of Strength in the Interface during Indentation Spherical Testing in Thin Films

Abstract

The need for more components that are more resistant to wear and corrosion has promoted a growing interest in surface engineering. The search for improved tribological properties in materials contributes to the development of processes that extend the useful life of components and their applications in increasingly severe environments. In this respect, thin ceramic coatings have been used to enhance the tribological properties of components that operate under these conditions. However, new experimental assays are needed to assess the behaviour of these films and their surface as substrate. These experimental analyses require the use of sophisticated equipment and specialized personnel. On the other hand, with advances in computational mechanics, the application of numerical analysis to solve numerous technological problems has been increasingly frequent, owing to its low operational costs. This study aims to simulate an indentation assay with spherical penetrator in systems composed of thin ceramic film deposited on metallic substrate using a Finite Element commercial code. The main objective of this study was to evaluate the field behaviour of stresses in the contact region of the indenter with the sample, on the outline of the impression made by the penetrator and, primarily, on the film-substrate interface.

Determination of Film Thickness Through Simulation of Vickers Hardness Testing

“…K and n are constants that describe the strain-hardening characteristics of the material, n being its coefficient. 8,11,12,18,20,23 Table 1 shows the Young's Modulus (E) and the Poisson coefficient (ν) that were obtained in the literature and were used in the present simulation. [24][25] The values of K and n were obtained from Equation (2) In this Equation (2), ε u is the ultimate strain, ε o is the yield strain, σ u is the ultimate strength, σ o is the yield stress and n is the strain-hardening coefficient, as seen previously.…”

“…[10][11] However, conjugates composed of thin films have limitations in the conventional use of surface hardness. Whether due to the geometry of the indenter or to the capacity of the film to fracture during experimental testing, the surface hardness of these conjugates depends on the thickness of the film and on the load used during the hardness test.…”

Avaliação dos processos de fratura em filmes finos através da simulação de ensaios de indentação com penetradores esféricos

“…Simulou-se o ciclo de indentação, carregamento e descarregamento do ensaio, através do deslocamento prescrito do indentador, permitindo-se, assim, um melhor controle numérico no início e durante a simulação. Desconsiderou-se o coeficiente de atrito entre o indentador e a amostra, pois, conforme literatura especializada, o atrito não influencia significativamente nos resultados numéricos de carga de indentação [7,14].…”

“…Este trabalho tem como objetivo usar o Método dos Elementos Finitos (MEF) em conjunto com os conceitos da mecânica dos meios contínuos e da mecânica da fratura linear elástica (MFLE) para simular ensaios de indentação com penetradores esféricos e analisar processos de fratura que podem ocorrer durante esses ensaios através de dois modelos de danos, o modelo de trinca difusa e o modelo de delaminação [12,[14][15]. Finalmente, este trabalho comparou os resultados obtidos com os apresentados na literatura especializada, avaliando os resultados encontrados através dos dois modelos de dano adotados.…”

“…Uma maneira de melhorá-las é a criação de filmes de composição complexas (nitretos ternários), ligando o nitreto binário com outro elemento, como CrTiN, CrAlN, CrTiAlN, etc [16]. Destes, o CrAlN representa uma nova geração de revestimento baseado na liga de cromo que foi investigada por muitos autores [5,6,[14][15][16][17][18][19]. A adição de alumínio afeta a estrutura do revestimento e, em seguida, aumenta os valores de módulo de elasticidade (E) que estão relacionados com o percentual de alumínio.…”