What do design engineers and failure analysis experts have in common? Answer: material failure. These two groups are the bookends to a material’s life. While materials selection is sometimes left up to a bona fide materials engineer, designers are typically responsible for determining what environments and operating conditions a component will encounter during service. In many cases designers are also responsible for performing the task of materials selection. This combined role essentially determines the fate of a material and quite possibly the system. Failure analysis specialists explore the questions of how and why a particular system, and more precisely, a material failed. To preclude failure the designer should consider the questions of when and how the system, and more specifically, the material will fail. The first step toward preventing failure is understanding how it might occur. If a material were resistant to all failure modes in all environments, a system or component could theoretically have an infinitely long life. Unfortunately, all materials are susceptible to failure. Even the best engineered materials are prone to failure given a sufficiently harsh service environment, or if they are poor choices for a specific application. Furthermore, there are a number of mechanisms and combinations of mechanisms that cause materials to fail. The goal of the design engineer is to cost-effectively design a system that operates at its maximum efficiency for the longest possible period of time without having to be replaced or overhauled. To meet this goal it is important for the designer to be aware and have a certain level of understanding about how materials can fail. The intent of this article is to provide an educational reference for designers and other engineers on the common modes of material failure. Understanding potential failure modes in the early stages of system design can lead to a more appropriate selection of materials, prevent premature system failure and possibly lengthen system life; ultimately resulting in increased safety in some cases and reduced cost of ownership. INTRODUCTION TO FAILURE The failure of a material is not restricted to fracture or total disintegration; it can also consist of a change in shape, loss of material or the alteration of mechanical properties. When a material becomes unable to execute the function that it was originally intended or designed to perform, it has failed. Environmental conditions and operating loads are often the primary causes leading to a material’s failure. Examples of harsh environments that commonly induce failure include corrosive, high temperature, and high energy environments. Stress, impact, and frictional loading are examples of operating conditions that frequently cause a material failure. Combinations of harsh environments and mechanical loads often lead to a more rapid material wearout and failure. There are several failure prevention methods that can be employed, but often the first critical step is to properly select the material or material system that will be used to construct the given system component. Further prevention measures (e.g. protective coatings, cold working, etc.) can be implemented depending on the application, the conditions found in the operational environment, mechanical loading, and the failure modes that the selected material is traditionally susceptible to in a given system configuration. The rest of this article is devoted to providing a background on the most common material failure modes.