Análise da tenacidade à fratura para o carbeto de boro a partir dos ensaios de dureza vickers e knoop

Abstract

This dissertation has the objective of study the fracture toughness calculation models in ceramics of high hardness, from data obtained with the test Vickers and Knoop hardness. The Vickers and Knoop hardness tests are techniques used to evaluate the surface hardness from the penetration of a pyramidal indenter square base in Vickers method and lozenge base in Knoop method. For the evaluation of high hardness materials, such as special ceramics, these techniques are the most appropriate and complementary. In carrying out such assays in high hardness materials it is common the occurrence of surface cracks resulting from the indentation of the indenter on the surface of the material. The occurrence of this phenomenon can allow the evaluation of mechanical properties of these special materials such as tensile strength limit and fracture toughness. In this study were presented measurements performed on cracks of sintered boron carbide samples, evaluating highlighted fracture toughness property for using mathematical models, formulated based on fracture mechanics, for example, Gong. From measurements taken after the indentation test was possible to calculate fracture toughness values, allowing the development of a methodology of using these tests.