Overload failures refer to the ductile or brittle fracture of a material when stresses exceed the load-bearing capacity of a material. This article reviews some mechanistic aspects of ductile and brittle crack propagation, including a discussion on mixed-mode cracking, which may also occur when an overload failure is caused by a combination of ductile and brittle cracking mechanisms. It describes the general aspects of fracture modes and mechanisms. The article discusses some of the material, mechanical, and environmental factors that may be involved in determining the root cause of an overload failure. It also presents examples of thermally and environmentally induced embrittlement effects that can alter the overload fracture behavior of metals.

This article aims to identify and illustrate the types of overload failures, which are categorized as failures due to insufficient material strength and underdesign, failures due to stress concentration and material defects, and failures due to material alteration. It describes the general aspects of fracture modes and mechanisms. The article briefly reviews some mechanistic aspects of ductile and brittle crack propagation, including discussion on mixed-mode cracking. Factors associated with overload failures are discussed, and, where appropriate, preventive steps for reducing the likelihood of overload fractures are included. The article focuses primarily on the contribution of embrittlement to overload failure. The embrittling phenomena are described and differentiated by their causes, effects, and remedial methods, so that failure characteristics can be directly compared during practical failure investigation. The article describes the effects of mechanical loading on a part in service and provides information on laboratory fracture examination.

This article provides information on the typical experimental observations of formation and propagation of small fatigue cracks under various stress states and explores the relation to long crack fracture mixed-mode fracture mechanics. It discusses state I crystallographic and stage II normal stress-dominated growth, along with some observations regarding the influence of combined stress state on the propagation of small cracks. The article discusses the differences between low-cycle fatigue and high-cycle fatigue (HCF) behaviors. Several other features of multiaxial fatigue are also explained, including mean stress effects, sequences of stress/strain amplitude or stress state, nonproportional loading and cycle counting, and HCF fatigue limits. In addition, the article covers the formation and propagation of cracks on the order of several grain sizes in diameter in initially isotropic and ductile structural alloys.

Solid-state welding (SSW) processes are those that produce coalescence of the faying surfaces at temperatures below the melting point of the base metal being joined without the addition of brazing or solder filler metal. This article discusses the fundamentals of welding and joining materials via the application of a nonmelting process. The specific processes usually associated with the nonmelting process are discussed.