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 focuses primarily on what an analyst should know about applying X-ray diffraction (XRD) residual stress measurement techniques to failure analysis. Discussions are extended to the description of ways in which XRD can be applied to the characterization of residual stresses in a component or assembly. The article describes the steps required to calibrate instrumentation and to validate stress measurement results. It presents a practical approach to sample selection and specimen preparation, measurement location selection, and measurement depth selection, as well as an outline on measurement validation. The article also provides information on stress-corrosion cracking and corrosion fatigue. The importance of residual stress in fatigue is described with examples. The article explains the effects of heat treatment and manufacturing processes on residual stress. It concludes with a section on the XRD stress measurements in multiphase materials and composites and in locations of stress concentration.

X-ray diffraction (XRD) residual-stress analysis is an essential tool for failure analysis. This article focuses primarily on what the analyst should know about applying XRD residual-stress measurement techniques to failure analysis. Discussions are extended to the description of ways in which XRD can be applied to the characterization of residual stresses in a component or assembly and to the subsequent evaluation of corrective actions that alter the residual-stress state of a component for the purposes of preventing, minimizing, or eradicating the contribution of residual stress to premature failures. The article presents a practical approach to sample selection and specimen preparation, measurement location selection, and measurement depth selection; measurement validation is outlined as well. A number of case studies and examples are cited. The article also briefly summarizes the theory of XRD analysis and describes advances in equipment capability.

This article describes the characteristics of tubing of heat exchangers with respect to general corrosion, stress-corrosion cracking, selective leaching, and oxygen-cell attack, with examples. It illustrates the examination of failed parts of heat exchangers by using sample selection, visual examination, microscopic examination, chemical analysis, and mechanical tests. The article explains corrosion fatigue of tubing of heat exchangers caused by aggressive environment and cyclic stress. It also discusses the effects of design, welding practices, and elevated temperatures on the failures of heat exchangers.

Crystallographic texture measurement and analysis is an important tool for correlating material properties with microstructural features. This article describes the general approach to quantifying crystallographic texture, namely, the collection of statistical data from grain measurements and subsequent analysis based on Euler plots (i.e., pole figures), orientation distribution functions, and stereographic projections. Using detailed illustrations and examples, it explains the significance of preferred crystallographic orientations and their influence on properties and material behavior. The article also discusses sample selection and preparation as well as the challenges and limitations of various methods.

Inert gas fusion is a method of determining the quantitative content of gases in ferrous and nonferrous materials where gases, such as hydrogen, nitrogen, and oxygen, are physically and chemically adsorbed by the materials and later removed and swept by from the fusion area by an inert carrier gas. This article describes the operating principles and sample selection of inert gas fusion. It explains the mechanisms involved in the introduction of fusion gas, separation and detection of fusion gas by thermal-conductive and infrared detection methods. Additionally, the article explains the methods used for analyzing trace amounts of nitrogen, oxygen, and hydrogen in the carrier mediums, providing examples that aid in solving several problems.

Metallographic analysis is primarily a collection of visual and imaging techniques that provide an insight into the background of a material or part and its behavior. Metallic specimens, both porous and pore-free, are opaque, and as a result, an optical examination must be performed on carefully prepared planar (two-dimensional) surfaces. This article discusses the preparation sequence of ferrous powders, which is normally separated into several well-defined steps: sample selection, sectioning, mounting, grinding, polishing, drying, and chemical etching and/or coating. It provides several suggestions to promote and encourage the safety of those performing metallographic preparation and analysis.

This article presents definitions, equations, and notational conventions that are used widely in statistical analysis. It provides information on a basic framework for the selection of a statistical test. The article outlines the basic elements common to all statistical tests. Illustrations of specific statistical tests and the concept of confidence limits are introduced. The article provides an overview of sampling issues, with guidance on both selecting a sampling method and determining the number of units to sample. One-way analysis of the variance, correlation, and simple regression are also illustrated.

Visual examination, using the unaided eye or a low-power optical magnifier, is typically one of the first steps in a failure investigation. This article presents the guidelines for selecting samples for scanning electron microscope examination and optical metallography and for cleaning fracture surfaces. It discusses damage characterization of metals, covering various factors that influence the damage, namely stress, aggressive environment, temperature, and discontinuities.

Potentiometric membrane electrodes are electrochemical devices that can be used to quantify numerous ionic and nonionic species. This class of electrochemical sensors can be divided into ion-selective and gas-sensing membrane electrodes. The first half of this article mainly focuses on the subclasses, the membrane potential, electrode selectivity limitations and the methods of analysis of the ion-selective membrane electrodes. These methods of analysis include the use of calibration curves, addition techniques, subtraction techniques, and titration. The second half outlines gas sensing membrane electrodes, and discusses important elements that must be considered in addition to the potentiometric membrane electrode to ensure proper electrode response. These elements are reference electrodes, temperature controls, recording of the potential with respect to time, electrode storages, and sample pretreatment. The article also explains the applications of the potentiometric membrane electrodes with the aid of an example.

This article describes the historical background, uncertainties in structural parameters, classifications, and application areas of probabilistic analysis. It provides a discussion on the basic definition of random variables, some common distribution functions used in engineering, selection of a probability distribution, the failure model definition, and a definition of the probability of failure. The article also explains the solution techniques for special cases and general solution techniques, such as first-second-order reliability methods, the advanced mean value method, the response surface method, and Monte Carlo sampling. A brief introduction to importance sampling, time-variant reliability, system reliability, and risk analysis and target reliabilities is also provided. The article examines the various application problems for which probabilistic analysis is an essential element. Examples of the use of probabilistic analysis are presented. The article concludes with an overview of some of the commercially available software programs for performing probabilistic analysis.

This article describes the metallographic specimen preparation procedures for cast iron test samples, including mounting, grinding, polishing, and etching. It discusses the makeup and use of black-and-white and selective color etchants and where one might be preferred over the other. The article provides information on nearly 100 micrographs, discussing the microstructure of flake graphite in gray iron, nodular graphite in ductile iron, and temper graphite in malleable iron. It also examines the matrix microstructures of gray, ductile, compacted, and malleable cast iron samples.

High-temperature combustion is primarily used to determine carbon and sulfur contained in a variety of materials. This article illustrates the principle of combustion and focuses on the characteristics of accelerators. It provides information on the process of separating oxide compounds formed in the combustion zone. The article provides information on infrared and thermal-conductive detectors, which are used for the detection of CO2 and SO2. Finally, it addresses the requirements of a sample to undergo total and selective combustion, and presents examples showing the applications of high-temperature combustion. .

The analysis of composite materials using optical microscopy is a process that can be made easy and efficient with only a few contrast methods and preparation techniques. This article is intended to provide information that will help an investigator select the appropriate microscopy technique for the specific analysis objectives with a given composite material. The article opens with a discussion of macrophotography and microscope alignment, and then goes on to describe various illumination techniques that are useful for specific analysis requirements. These techniques include bright-field illumination, dark-field illumination, polarized-light microscopy, interference and contrast microscopy, and fluorescence microscopy. The article also provides a discussion of sample preparation materials such as dyes, etchants, and stains for the analysis of composite materials using optical microscopy.

This article reviews various phases and constituents found in the microstructures of low-carbon and coated steels. It provides information on the criteria for selecting proper metallographic procedures. Techniques used to prepare metallographic specimens of low-carbon steels and coated steels, such as sectioning, mounting, grinding, polishing, and etching, are discussed. The article also reviews the simple and proven manual sample preparation techniques of coated steel specimens.

Examination of a damaged component involves a chain of activities that, first and foremost, requires good observation and documentation. Following receipt and documentation, the features of damage can be recorded and their cause(s) investigated, as this article briefly describes, for typical types of damage experienced for metallic components. This article discusses the processes involved in visual or macroscopic examination of damaged material; the interpretation of fracture features, corrosion, and wear damage features; and the analysis of base material composition. It covers the processes involved in the selection of metallurgical samples, the preparation and examination of metallographic specimens in failure analysis, and the analysis and interpretation of microstructures. Examination and evaluation of polymers and ceramic materials in failure analysis are also briefly discussed.

Identification of alloys using quantitative chemical analysis is an essential step during a metallurgical failure analysis process. There are several methods available for quantitative analysis of metal alloys, and the analyst should carefully approach selection of the method used. The choice of appropriate analytical techniques is determined by the specific chemical information required, the condition of the sample, and any limitations imposed by interested parties. This article discusses some of the commonly used quantitative chemical analysis techniques for metals. The discussion covers the operating principles, applications, advantages, and disadvantages of optical emission spectroscopy (OES), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray spectroscopy, and ion chromatography (IC). In addition, information on combustion analysis and inert gas fusion analysis is provided.

This article endeavors to familiarize the reader with a selection of different ionization designs and instrument components to provide knowledge for sorting the various analytical strategies in the field of solid analysis by mass spectrometry (MS). It begins with a description of the general principles of MS. This is followed by sections providing a basic understanding of instrumentation and discussing the operating requirements as well as practical considerations related to solid sample analysis by MS. Instrumentation discussed include the triple quadrupole mass spectrometer and the time-of-flight mass spectrometer. Inductively coupled plasma and thermal ionization MS provide atomic information, and direct analysis in real-time and matrix-assisted laser-desorption ionization MS are used to analyze molecular compositions. The article describes various factors pertinent to ionization methods, namely glow discharge mass spectrometry and secondary ion mass spectrometry. It concludes with a section on various examples of applications and interpretation of MS for various materials.

Uniform corrosion refers to the attack on an exposed metal surface that results in homogeneous thickness loss that is evaluated by mass loss or measurement of thickness change. This article focuses on the various processes involved in mass loss tests, namely, selection and preparation of suitable test specimens, planning of the experimental technique, posttest sample cleaning, data acquisition, and reporting. It further discusses the test variables addressed during the experimental planning and provides an overview of the other test and evaluation methods of evaluating uniform corrosion.