Quenching is one of the most important heat treating processes, because it is so closely related to dimensional control requirements and control of residual stresses. This article provides an overview of the fundamental material- and process-related parameters of quenching on residual stress, distortion control, and cracking. This overview is followed by various selected case histories of failures attributed to the quenching process.

This article presents the basic principle, characteristics, advantages, and disadvantages of resonant ultrasound spectroscopy (RUS) methods in additive manufacturing. It focuses on the two types of RUS methods: the swept-sine method and the impulse excitation method. Representative significant results for additively manufactured complex parts obtained with the different RUS systems are also shown. The article also presents the basic principle and examples of nonlinear RUS methods.

This article presents a general understanding of causes and possible solutions for defects in the most common metal additive manufacturing (AM) processes: laser powder-bed fusion (L-PBF), laser directed-energy deposition (DED-L), and binder jetting (BJ).

Additive manufacturing (AM) is a highly desired layer-by-layer fabrication process capable of creating near-net-shaped three-dimensional components for a wide range of industries, such as the automotive and aerospace industries. This article focuses on aluminum, titanium, and stainless steel alloys that are commonly used or highly desired for use with AM due to their widespread applicability and favorable mechanical properties. It presents an overview of two of the major AM processes: powder-bed and powder-fed. The article discusses processability using AM. It also provides an overview of material microstructures, defects, and the impact on mechanical behaviors.

This article provides an overview of different modeling approaches used to capture the phenomena present in the additive manufacturing (AM) process. Inherent to the thermomechanical processing that occurs in AM for metals is the development of residual stresses and distortions. The article then provides an overview of thermal modeling. It presents a discussion on solid mechanics simulation and microstructure simulation.

Fatigue failure is a critical performance metric for additively manufactured (AM) metal parts, especially those intended for safety-critical structural applications (i.e., applications where part failure causes system failure and injury to users). This article discusses some of the common defects that occur in laser powder bed fusion (L-PBF) components, mitigation strategies, and their impact on fatigue failure. It summarizes the fatigue properties of three commonly studied structural alloys, namely aluminum alloy, titanium alloy, and nickel-base superalloy.

This article covers defect formation and classification, followed by a brief description of the most common nondestructive testing (NDT) methods used for postbuild inspection. Descriptions of the established and emerging NDT techniques for in-process monitoring (IPM) and in-process inspection (IPI) in additive manufacturing (AM) also are provided, highlighting the advantages and limitations. The article concludes with a list of the main NDT methods and techniques used. As qualification and certification of AM parts is an urgent matter for the AM industry, a description of the current work carried out for developing standards is also included.

The use of additive manufacturing (AM) is increasing for high-value, critical applications across a range of disparate industries. This article presents a discussion of high-valued engineering components predominantly used in the aerospace and medical industries. Applications involving metal AM, including methods to identify pores and voids in AM materials, are the focus. The article reviews flaw formation in laser-based powder-bed fusion, summarizes sensors used for in situ process monitoring, and outlines advances made with in situ process-monitoring data to detect AM process flaws. It reviews investigations of ML-based strategies, identifies challenges and research opportunities, and presents strategies for assessing anomaly detection performance.

The discussion on the fracture of solid materials, both metals and polymers, customarily begins with a presentation of the stress-strain behavior and of how various conditions such as temperature and strain-rate affect the mechanisms of deformation and fracture. This article describes crazing and fracture in polymeric materials, with a review of the behavior of the elastic modulus as a function of temperature or time parameters, emphasizing the importance of the viscoelastic nature of their deformation and fracture. The discussion covers the behavior of polymers under stress, provides information on ductile and brittle behaviors, and describes craze initiation in polymers and crack formation and fracture by crazing. Macroscopic permanent deformation of polymeric materials caused by shear-yielding and crazing, which eventually can result in fracture and failure, is also covered.

The susceptibility of plastics to environmental failure, when exposed to organic chemicals, can limit their use in many applications. A combination of chemical and physical factors, along with stress, usually leads to a serious deterioration in properties, even if stress or the chemical environment alone may not appreciably weaken a material. This phenomenon is referred to as environmental stress cracking (ESC). The ESC failure mechanism for a particular plastics-chemical environment combination can be quite complex and, in many cases, is not yet fully understood. This article focuses on two environmental factors that contribute to failure of plastics, namely chemical and physical effects.

This article focuses on manufacturing-related failures of injection-molded plastic parts, although the concepts apply to all plastic manufacturing processes It provides detailed examples of failures due to improper material handling, drying, mixing of additives, and molecular packing and orientation. It also presents examples of failures stemming from material degradation improper use of metal inserts, weak weld lines, insufficient curing of thermosets, and inadequate mixing and impregnation in the case of thermoset composites.

Sheet forming failures divert resources from normal business activities and have significant bottom-line impact. This article focuses on the formation, causes, and limitations of four primary categories of sheet forming failures, namely necks, fractures/splits/cracks, wrinkles/loose metal, and springback/dimensional. It discusses the processes involved in analytical tools that aid in characterizing the state of a formed part. In addition, information on draw panel analysis and troubleshooting of sheet forming failures is also provided.

This article offers an overview of fatigue fundamentals, common fatigue terminology, and examples of damage morphology. It presents a summary of relevant engineering mechanics, cyclic plasticity principles, and perspective on the modern design by analysis (DBA) techniques. The article reviews fatigue assessment methods incorporated in international design and post construction codes and standards, with special emphasis on evaluating welds. Specifically, the stress-life approach, the strain-life approach, and the fracture mechanics (crack growth) approach are described. An overview of high-cycle welded fatigue methods, cycle-counting techniques, and a discussion on ratcheting are also offered. A historical synopsis of fatigue technology advancements and commentary on component design and fabrication strategies to mitigate fatigue damage and improve damage tolerance are provided. Finally, the article presents practical fatigue assessment case studies of in-service equipment (pressure vessels) that employ DBA methods.

The information provided in this article is intended for those individuals who want to determine why a casting component failed to perform its intended purpose. It is also intended to provide insights for potential casting applications so that the likelihood of failure to perform the intended function is decreased. The article addresses factors that may cause failures in castings for each metal type, starting with gray iron and progressing to ductile iron, steel, aluminum, and copper-base alloys. It describes the general root causes of failure attributed to the casting material, production method, and/or design. The article also addresses conditions related to the casting process but not specific to any metal group, including misruns, pour shorts, broken cores, and foundry expertise. The discussion in each casting metal group includes factors concerning defects that can occur specific to the metal group and progress from melting to solidification, casting processing, and finally how the removal of the mold material can affect performance.

The primary purpose of this article is to describe general root causes of failure that are associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be common sources of failure-inducing defects in the bulk working of wrought products. The article addresses the types of flaws or defects that can be introduced during the steel forging process itself, including defects originating in the ingot-casting process. Defects found in nonferrous forgings—titanium, aluminum, and copper and copper alloys—also are covered.

This article provides an overview of metal additive manufacturing (AM) processes and describes sources of failures in metal AM parts. It focuses on metal AM product failures and potential solutions related to design considerations, metallurgical characteristics, production considerations, and quality assurance. The emphasis is on the design and metallurgical aspects for the two main types of metal AM processes: powder-bed fusion (PBF) and directed-energy deposition (DED). The article also describes the processes involved in binder jet sintering, provides information on the design and fabrication sources of failure, addresses the key factors in production and quality control, and explains failure analysis of AM parts.

This article describes some of the welding discontinuities and flaws characterized by nondestructive examinations. It focuses on nondestructive inspection methods used in the welding industry. The sources of weld discontinuities and defects as they relate to service failures or rejection in new construction inspection are also discussed. The article discusses the types of base metal cracks and metallurgical weld cracking. The article discusses the processes involved in the analysis of in-service weld failures. It briefly reviews the general types of process-related discontinuities of arc welds. Mechanical and environmental failure origins related to other types of welding processes are also described. The article explains the cause and effects of process-related discontinuities including weld porosity, inclusions, incomplete fusion, and incomplete penetration. Different fitness-for-service assessment methodologies for calculating allowable or critical flaw sizes are also discussed.

This article introduces some of the general sources of heat treating problems with particular emphasis on problems caused by the actual heat treating process and the significant thermal and transformation stresses within a heat treated part. It addresses the design and material factors that cause a part to fail during heat treatment. The article discusses the problems associated with heating and furnaces, quenching media, quenching stresses, hardenability, tempering, carburizing, carbonitriding, and nitriding as well as potential stainless steel problems and problems associated with nonferrous heat treatments. The processes involved in cold working of certain ferrous and nonferrous alloys are also covered.