This article outlines the fundamentals of polymer science and emphasizes the aspects that are necessary and useful to applications of engineering plastics. The basic structure of polymers influences the properties of both polymers and the plastics made from them. An understanding of this basic structure permits the engineers to understand which polymers may be acceptable for a certain application, and which may not. There are various possible classification schemes for polymers. Typical classification categories include polymerization process, chemical elements that make up the monomer, or crystalline versus noncrystalline structure. The article describes the various aspects of chemical structure that are important to an understanding of polymer properties and, thus, affect eventual end uses. It discusses different types of names assigned to polymers. The article details the aspects of polymer structure and examines the properties of polymers and the way they are altered by structure.

Corrosion modeling is an essential benchmarking element for the selection and life prediction associated with the introduction of new materials or processes. These models are most naturally expressed in terms of differential equations or in other nonexplicit forms of mathematics. This article discusses the principles and applications of various models developed for understanding the corrosion mechanism. These models include mechanistic models, including Pourbaix model, thermophysical module, electrochemical module, and ion association model; risk-based models; and knowledge models. The risk-based model and knowledge models are illustrated with examples for better understanding. The article also describes boundary-element modeling and pitting corrosion fatigue models.

While there are many fracture mechanisms that can lead to the failure of a plastic component, environmental stress cracking (ESC) is recognized as one of the leading causes of plastic failure. This article focuses on unpacking the basic concepts of ESC to provide the engineer with a better understanding of how to evaluate and prevent it. It then presents factors that affect and contribute to the susceptibility of plastic to ESC: material factors, chemical factors, stress, and environmental factors. The article includes the collection of background information to understand the circumstances surrounding the failure, a fractographic evaluation to assess the cracking, and analytical testing to evaluate the material, design, manufacturing, and environmental factors.

Corrosion is the electrochemical reaction of a material and its environment. This article addresses those forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. Various forms of corrosion covered are galvanic corrosion, uniform corrosion, pitting, crevice corrosion, intergranular corrosion, selective leaching, and velocity-affected corrosion. In particular, mechanisms of corrosive attack for specific forms of corrosion, as well as evaluation and factors contributing to these forms, are described. These reviews of corrosion forms and mechanisms are intended to assist the reader in developing an understanding of the underlying principles of corrosion; acquiring such an understanding is the first step in recognizing and analyzing corrosion-related failures and in formulating preventive measures.

This article discusses the organization required at the outset of a failure investigation and provides a methodology with some organizational tools. It focuses on the use of problem-solving tools such as a fault tree analysis combined with critical thinking. The discussion covers nine steps to organize a good failure investigation. They are as follows: understand and negotiate goals of the investigation, obtain a clear understanding of the failure, identify all possible root causes, objectively evaluate the likelihood of each root cause, converge on the most likely root cause(s), objectively and clearly identify all possible corrective actions, objectively evaluate each corrective action, select optimal corrective action(s), and evaluate effectiveness of selected corrective action(s). Common problems detrimental to a failure investigation are also covered.

The formation of defects within additive-manufactured (AM) components is a major concern for critical structural and cyclic load applications. Thus, understanding the mechanisms of defect formation in fusion-based processes is important for prescribing the appropriate process parameters specific to the alloy system and selected processing technique. This article discusses the formation of defects within metal additive manufacturing, namely fusion-based processes and solid-state/sintering processes. Defects observed in fusion-based processes include lack of fusion, keyhole collapse, gas porosity, solidification cracking, solid-state cracking, and surface-connected porosity. The types of defects in solid-state/sintering processes are sintering porosity and improper binder burnout. The article also discusses defect-mitigation strategies, such as postprocess machining, surface treatment, and postprocessing HIP to eliminate defects detrimental to properties from the as-built condition. The use of noncontact thermal, optical, and ultrasound techniques for inspecting AM components are also considered. The final section summarizes the knowledge gap in our understanding of the defects observed within AM components.

This article presents a glossary of terms related to fractography.

This article provides a brief historical perspective, a classification of metallurgical processes, basic model development efforts, and an overview of the potential future directions for the modeling of metals processing. It describes the classification of material behavior models, which can be grouped broadly into three classes: statistical, phenomenological, and mechanistic models. The article also presents an overview of the potential directions for the modeling of metals processing.

This article describes the various steps involved in image analysis, including sample selection and preparation, image preprocessing, measurement, and data analysis and output. It reviews various types of image analyzers and explains how operator bias and poor sample selection and preparation practices can lead to measurement error. It also examines several applications, illustrating how microstructural measurements can be used to assess quality control and better understand how processing changes affect microstructure and, in turn, material properties and behavior.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of pearlitic malleable and ferritic malleable white irons, and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fracture sequence, localized plastic deformation, and microcrack initiation and propagation of these irons.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of sulfur concrete and asphalt and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the crystal morphology, noninterconnecting voids, and microvoids of these surfaces.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of precipitation-hardening stainless steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the cup-and-cone tension-overload fracture, low-cycle and high-cycle fatigue fracture, fracture surface, brittle intergranular fracture, hydrogen embrittlement, and intergranular stress-corrosion cracking of stainless steel components of these steels. The components include high-pressure compressor parts, springs, deflector yokes of aircraft main landing gears, and aircraft engine mount beams.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of pure irons and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the grain-boundary cavitation; slip lines; intergranular fracture; cleavage fracture; notch-impact fracture; oxide inclusions and blowholes; ductile rupture; impact fracture and tensile-test fracture surfaces; fatigue striations; and crack initiation and propagation of pure irons.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of a type of resin-matrix composites, carbon-epoxy composites. The fractographs illustrate the fracture modes found in composite prepregs, composite panels, solid rocket motor nozzles, and tension, flexural, compressive, and shear loadings.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of cast aluminum alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the brittle fracture, microvoid coalescence, fatigue striations, and microstructure of these alloys. The components considered include fractured sand-cast carrier trays, broken extension-housing yokes, helicopter tail-rotor drive assemblies, fractured bell-crank fittings, chain-hoist hooks, and automotive connecting rods.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of gray irons and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fatigue fracture, solidification structure, and crack propagation of gray irons.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of nickel alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fatigue crack, transgranular cleavage, intergranular fracture, grain boundaries, notch and fatigue precrack, dimpled rupture, and fatigue striations of these alloys.