Welded connections are a common location for failures for many reasons, as explained in this article. This article looks at such failures from a holistic perspective. It discusses the interaction of manufacturing-related cracking and service failures and primarily deals with failures that occur in service due to stresses caused by externally applied loads. The purpose of this article is to enable a failure analyst to identify the causative factors that lead to welded connection failure and to identify the corrective actions needed to overcome such failures in the future. Additionally, the reader will learn from the mistakes of others and use principles that will avoid the occurrence of similar failures in the future. The topics covered include failure analysis fundamentals, welded connections failure analysis, welded connections and discontinuities, and fatigue. In addition, several case studies that demonstrate how a holistic approach to failure analysis is necessary are presented.

Rolling-contact fatigue (RCF) is a common failure mode in components subjected to rolling or rolling-sliding contact. This article provides a basic understanding of RCF and a broad overview of materials and manufacturing techniques commonly used in industry to improve component life. A brief discussion on coatings to improve surface-initiated fatigue and wear is included, due to the similarity to RCF and the increasing criticality of this failure mode. The article presents a working knowledge of Hertzian contact theory, describes the life prediction of rolling-element bearings, and provides information on physics and testing of rolling-contact fatigue. Processes commonly used to produce bearings for demanding applications are also covered.

This article provides a description of the microscale models and mechanisms for deformation and fracture. Macroscale and microscale appearances of ductile and brittle fracture are discussed for various specimen geometries and loading conditions. The article reviews the general geometric factors and materials aspects that influence the stress-strain behavior and fracture of ductile metals. It highlights fractures arising from manufacturing imperfections and stress raisers. The article presents a root cause failure analysis case history to illustrate some of the fractography concepts.