Elastomers belong to a group of materials known as polymers that acquire their properties and strength from their molecular weight, chain entanglements, and crystalline regions. This article focuses on the use of elastomers as seals and describes its performance capabilities from the point of a sealant. The important technical concepts that define the performance capabilities of the elastomeric part include polymer architecture (molecular building blocks), compounding (the ingredients within the polymer), and vulcanization of the elastomer shape. The article discusses the aggressiveness of the chemical environment, temperature, and minor constituents in the environment and in the material itself that affect the chemical resistance of the elastomer. It provides a discussion on performance evaluation methods, namely, immersion testing and application specific testing that are determined using ISO and ASTM standards. The article concludes with information on elastomer failure modes and failure analysis.

Portland cement concrete has low environmental impact, versatility, durability, and economy, which make it the most abundant construction material in the world. This article details the types and causes of concrete degradation. Concrete can be degraded by corrosion of reinforcing steel and other embedded metals, chlorides, carbonation, galvanic corrosion, chemical attack, alkali-aggregate reaction, abrasion, erosion, and cavitation as well as many other factors. The article addresses the durability of concrete by two approaches, namely, the prescriptive approach and the performance approach. In the former, designers specify materials, proportions, and construction methods based on fundamental principles and practices that exhibit satisfactory performance. In the latter, designers identify functional requirements such as strength, durability, and volume changes and rely on concrete producers and contractors to develop concrete mixtures to meet those requirements.

This article focuses on casting design in general and on sand and permanent mold aluminum casting in particular. It examines the casting design process from a variety of design and processing perspectives. Excessive design iterations can adversely impact the casting design. The article summarizes several strategies for improving the traditional casting design process. It also proposes some possible approaches for implementing these strategies. The article presents a vision for the development of comprehensive casting design guidelines along with specific development objectives.

For most nondestructive evaluation (NDE) applications, the term thermography actually refers to surface-excited thermography (SET) that involves thermal mapping of surface temperature as heat flows from, to, or through a test object in response to excitation applied to the sample surface. This article discusses the strategies for implementing thermography for NDE, including the steady-state/whole-body approach and transient heat conduction. It describes the most common signal-processing methods, such as thermographic signal reconstruction, lock-in thermography, and pulsed-phase thermography. The article concludes with a discussion on the use of thermal methods for thermal diffusivity measurement and characterization of multilayer structures.

Computational fluid dynamics (CFD) is a computationally intensive three-dimensional simulation of thermal fluids systems where non-linear momentum transport plays an important role. This article presents the governing equations of fluid dynamics and an introduction to the CFD techniques. It introduces some common techniques for discretizing the fluid-flow equations and methods for solving the discrete equations. These include finite-difference methods, finite-element methods, spectral methods, and computational particle methods. The article describes the approaches for grid generation with complex geometries. It discusses the four-step procedures used in the CFD process for engineering design: geometry acquisition, grid generation and problem specification, flow solution, and post-processing and synthesis. The article also provides information on the engineering applications of the CFD. It concludes with a discussion on issues and directions for engineering CFD.

Both nondestructive testing (NDT) and nondestructive evaluation (NDE) use noninvasive measurement techniques to gain information about defects and various properties of materials, components, and structures. This article begins with a discussion on the historical development of quantitative measurement techniques, evaluation reliability, and quantitative interpretation of nondestructive inspection methods. The common nondestructive evaluation methods, along with their uses and limitations, are summarized in a table. The article conceptually illustrates the interplay of NDE and fracture mechanics in the damage tolerant approach. It concludes with information on pressure vessel applications that can be separated into three protocols used by military nuclear power, commercial nuclear power, and non-nuclear pressure vessels and/or fired boilers.

This article introduces filling and feeding concepts from the general perspective of what constitutes good casting practice. It briefly reviews concepts that may help clarify and quantify objectives for more effective mold-filling designs. The article describes the preprimed filling system through various partial solutions to the prepriming approach. The naturally pressurized filling system is characterized by the narrowness of its flow channels. The article discusses the six individual parts of the naturally pressurized filling system, namely, offset stepped pouring basin, sprue, sprue/runner junction, runner, gates, and feeding via feeders. It also lists key features of the naturally pressurized filling system.

This article focuses on transport phenomena and modeling approaches that are specific to vapor-phase processes (VPP). It discusses the VPP for the synthesis of materials. The article reviews the basic notions of molecular collisions and gas flows, and presents transport equations. It describes the modeling of vapor-surface interactions and kinetics of hetereogeneous processes as well as the modeling and kinetics of homogenous reactions in chemical vapor deposition (CVD). The article provides information on the various stages of developing models for numerical simulation of the transport phenomena in continuous media and transition regime flows of VPP. It explains the methods used for molecular modeling in computational materials science. The article also presents examples that illustrate multiscale simulations of CVD or PVD processes and examples that focus on sputtering deposition and reactive or ion beam etching.

This article provides a detailed discussion on the most commonly employed tests and specific examples of the use of these tests in evaluating the corrosion resistance of powder metallurgy (P/M) stainless steels. It describes the influence of various processing parameters on the corrosion resistance of P/M stainless steels. The approaches used to improve the corrosion resistance of sintered stainless steels are discussed briefly. The article also presents a discussion on the manufacturing and corrosion characteristics of P/M superalloys.

Fretting is a wear phenomenon that occurs between two mating surfaces; initially, it is adhesive in nature, and vibration or small-amplitude oscillation is an essential causative factor. Fretting generates wear debris, which oxidizes, leading to a corrosion-like morphology. This article focuses on fretting wear related to debris formation and ejection. It reviews the general characteristics of fretting wear, with an emphasis on steel. The review covers fretting wear in mechanical components, various parameters that affect fretting; quantification of wear induced by fretting; and the experimental results, map approach, measurement, mechanism, and prevention of fretting wear. This review is followed by several examples of failures related to fretting wear.

Fatigue failures may occur in components subjected to fluctuating (time-dependent) loading as a result of progressive localized permanent damage described by the stages of crack initiation, cyclic crack propagation, and subsequent final fracture after a given number of load fluctuations. This article begins with an overview of fatigue properties and design life. This is followed by a description of the two approaches to fatigue, namely infinite-life criterion and finite-life criterion, along with information on damage tolerance criterion. The article then discusses the characteristics of fatigue fractures followed by a discussion on the effects of loading and stress distribution, and material condition on the microstructure of the material. In addition, general prevention and characteristics of corrosion fatigue, contact fatigue, and thermal fatigue are also presented.

This article identifies the coatings applied to many substrates for both beautification and protection, and the inherent conflicts that exist between the coatings and the buildings they are designed to protect; emphasis is placed on masonry walls. It provides information on the purposes of the coatings in the commercial buildings. The article briefly describes some of the most common types of substrates found in buildings and the coatings commonly associated with each substrate. The selection of the coating system depends on the substrate and service expectations. The article addresses the primary causes of masonry coating problems and also provides a detailed discussion on the wall design considerations, moisture considerations, and coating system challenges in the masonry buildings.

This article discusses the inspection/reference standards that are absolutely critical for proper application of ultrasonic inspection systems. Many of the standards and specifications for ultrasonic inspection require the use of standard reference blocks. The article lists the variables that should be considered when selecting standard reference blocks and describes the three types of standard blocks ordinarily used for calibration or reference: area-amplitude blocks, distance-amplitude blocks, and blocks of the type sanctioned by the International Institute of Welding. It reviews the determination of area-amplitude and distance-amplitude curves of a straight-beam pulse-echo ultrasonic inspection system. The article discusses the three principal conventional manual ultrasonic sizing techniques: 6 dB drop technique, maximum-amplitude technique, and 20 dB drop technique. It provides information on the dimension-measurement applications of ultrasonic inspection methods.

Integrated computational materials engineering refers to the use of computer simulations that integrate mathematical models of complex metallurgical processes with computer models used in component and process design. This article outlines an example of a computer-aided engineering tool, such as virtual aluminum castings (VAC), developed and implemented for quickly developing durable cast aluminum power train components. It describes the procedures for the model development of the VAC system. These procedures include linking the manufacturing process to microstructure, linking microstructures to mechanical properties, linking material properties to performance prediction, and model validation and integration into the engineering process. The article discusses the benefits of the VAC system in process selection, process optimization, and improving the component design criteria.

This article provides background information on the chemistry, coating properties, resin types, applications techniques, and performance characteristics of fluoroethylene vinyl ether (FEVE) resins. It describes the formulation methods of FEVE resins, namely, solvent-based coating formulations, water-based coating formulations, and powder coating formulations. The basic concerns to be addressed when formulating and using FEVE coatings are also discussed. The article concludes with a section on health and related safety regulations.

Acrylic coatings are one of the major generic classes of organic coatings and are prevalent in both architectural and industrial applications. This article provides information on the chemistry of acrylic polymers, the methods used in their manufacture, the relationship between structure and properties when they are formulated into coatings, and how they are being used in coatings. The main discussion points are the differences between solventborne and waterborne technologies and some of the challenges in formulating and applying waterborne acrylic coatings. The article describes the mechanism of film formation of acrylic latex polymers and its effect on final coating properties. It discusses the types of waterborne acrylic latex coatings based on chemical properties and based on applications such as primers, intermediate coats, topcoats, stains, and direct-to-substrate finishes. The article concludes with a description of the advances in the development of waterborne acrylic coatings for maintenance and protective applications.

This article presents a background of green chemistry and green coatings, and a summary of the key concerns of the green coating procurement process. It includes a discussion on green marketing and the seven sins of greenwashing, an overview of the environmental certification standards and regulatory environments, and the importance of performance during the duty cycle.

The presence of macroscopic residual stresses in heat treatable aluminum alloys can give rise to machining distortion, dimensional instability, and increased susceptibility to in-service fatigue and stress-corrosion cracking. This article details the residual-stress magnitudes and distributions introduced into aluminum alloys by thermal operations associated with heat treatment. The available technologies by which residual stresses in aluminum alloys can be relieved are also described. The article shows why thermal stress relief is not a feasible stress-reduction technology for precipitation-hardened alloys. It examines the consequences of aging treatments on the residual stress, namely, annealing, precipitation heat treatment, and cryogenic treatment. The article provides information on uphill quenching, which attempts to reverse thermal gradients encountered during quenching. It examines how quench-induced residual stresses in heat treatable aluminum alloys are reduced when sufficient load is applied to cause plastic deformation. The article also shows how plastic deformation reduces residual stress.

Wear is mechanically-induced surface damage that results in the progressive removal of material. Because different types of wear occur in machinery, many different types of wear tests have been developed to evaluate its effects on materials and surface treatments. This article provides an explanation on mechanisms, forms (sliding, impact, and rolling) and the causes of wear. It describes the wear measuring methods, including the mass loss method, wear width method, and scar depth method. The units used to report wear vary with type of wear and with the purpose for which the data are to be used. Listing the considerations of tribosystem analysis, the article provides information on selection of ASTM wear test methods grouped by wear type. The article concludes by tabulating the testing geometries and parameters that are commonly controlled and reported when conducting wear tests.