Durability of Engineering Materials

Abstract

Basics of fracture mechanics, an engineering discipline that draws upon the principles of applied mechanics and materials science. The course gives the tools to a successful application of fracture mechanics concepts to failure analysis.

Objective

The students should know the possibilities and limitations of the use of “standard” materials as well as get an idea of new innovative development to prevent failure problems. It is an introduction to the field of fracture mechanics, an engineering discipline that draws upon the principles of applied mechanics and materials science. Cracks and crack-like defects are evaluated with a view to understanding and predicting the cracks' growth tendencies. Such growth may be either stable (relatively slow and safe) or unstable (instantaneous and catastrophic). The course gives the tools to a successful application of fracture mechanics concepts to failure analysis.

Content

Cracks cannot be neglected in engineering analysis, as they can weaken a material far more than one might expect. Even microscopic crack flaws can grow over time, ultimately resulting in fractured components. Structures that may have been blindly deemed "safe" could fail disastrously, causing injuries to its users, or the loss of life. Fracture mechanics can be used to: * Determine how large a crack can be in a structure before it leads to catastrophic failure * Predict the rate at which a crack can approach a critical size due to fatigue loads or aggressive environmental conditions The topics covered are * Introduction to Linear Elastic Fracture Mechanics (LEFM): crack tip stress, strain and displacement fields in linear elastic materials (Modes I, II and III); the stress-intensity factor, K; the fracture toughness KIc and their determination; fracture criterion * Estimates of crack plastic zones in ductile materials * The compliance method; experimental determination of compliance * Introduction to fracture mechanics of nonlinear materials: the J-integral; the JIc fracture criterion; JIc testing * Application of fracture mechanics concepts in the analysis of subcritical crack growth (fatigue, stress corrosion cracking, creep and their combinations) * Novel applications of fracture mechanics to small length scales and composite materials.

Resources