Fractography is the systematic study of fractures and fracture surfaces. It is a useful tool in failure analysis and provides a means for correlating the influence of microstructure on the fracture mode of a given material. This article discusses the preservation, preparation, and photography of fractured parts and surfaces, and describes some of the more common fractographic features revealed by light microscopy, including tensile-fracture surface marks in unnotched specimens, fatigue marks, and structural discontinuities within the metal. The article also explains how to interpret fracture information contained in optical and scanning-electron microscope fractographs.

The application of transmission electron microscope to the study of fracture surfaces and related phenomena has made it possible to obtain magnifications and depths of field much greater than those possible with light (optical) microscopes. This article reviews the methods for preparing single-stage, double-stage, and extraction replicas of fracture surfaces. It discusses the types of artifacts and their effects on these replicas, and provides information on shadowing of replicas. The article concludes with a comparison of the transmission electron and scanning electron fractographs with illustrations.

The scanning electron microscope (SEM) is one of the most versatile instruments for investigating the microscopic features of most solid materials. The SEM provides the user with an unparalleled ability to observe and quantify the surface of a sample. This article discusses the development of SEM technology and operating principles of basic systems of SEM. The basic systems covered include the electron optical column, signal detection and display equipment, and the vacuum system. The processes involved in the preparation of samples for observation using an SEM are described, and the application of SEM in fractography is discussed. The article covers the failure mechanisms of ductile failure, brittle failure, mixed-mode failure, and fatigue failure. Lastly, image dependence on microscope type and operating parameters is also discussed.

This article discusses the preparation of photomacrographs of fracture surfaces. It provides useful information on the equipment used, such as view cameras, 35-mm single-lens-reflex cameras, and stereomicroscopes. The article describes the role of lenses, focusing, camera magnification, and selection of lens aperture in a microscopic system. It illustrates the lighting techniques employed in photography and highlights the use of different films. The article concludes with a list of auxiliary equipment used in fracture surface photography.

Scanning electron microscopy (SEM) has unique capabilities for analyzing fracture surfaces. This article discusses the basic principles and practice of SEM, with an emphasis on its applications in fractography. The topics include an introduction to SEM instrumentation, imaging and analytical capabilities, specimen preparation, and the interpretation of fracture features. SEM can be subdivided into four systems, namely, illuminating/imaging, information, display, and vacuum systems. The article also describes the major criteria and techniques of SEM specimen preparation, and the general features of ductile and brittle fracture modes.

The purpose of fractography is to analyze fracture features and attempt to relate the topography of the fracture surface to the causes and/or basic mechanisms of fracture. This article reviews the historical development of fractography, from the early studies of fracture appearance dating back to the sixteenth century to the state-of-the-art work in electron fractography and quantitative fractography. It also describes the applications and limitations of scanning electron microscope and transmission electron microscope.

This article presents examples of the visual fracture examination that illustrate the procedure as it applies to failure analysis and quality determination. It describes the techniques and procedures for the visual and light microscopic examination of fracture surfaces with illustrations. The article also describes microscopic and macroscopic features of the different fracture mechanisms with illustrations with emphasis on visual and light microscopy examination. The types of fractures considered include ductile fractures, tensile-test fractures, brittle fractures, fatigue fractures, and high-temperature fractures.

Failure analysis is a process of acquiring specified information regarding the appropriateness of the design of a part, the competence with which the various steps of its manufacture have been performed, any abuse suffered by it in packing and transportation, or the severity of service under which failure has occurred. Beginning with a discussion of the various stages of failure analysis of glass and ceramic materials, this article focuses on descriptive and quantitative fracture surface analysis techniques that are used in the examination of glass and surfaces created by fracture and the interpretation of the fracture markings seen on these surfaces. Details are provided for the procedures for locating fracture origins, determining direction of crack propagation, learning the sequence of crack propagation, deducing the stress state at the time of fracture, and observing interactions between crack fronts and inclusions, etc. A separate fractography terminology is provided in this article.

Failure analysis is an investigative process that uses visual observations of features present on a failed component fracture surface combined with component and environmental conditions to determine the root cause of a failure. The primary means of recording the conditions and features observed during a failure analysis investigation is photography. Failure analysis photographic imaging is a combination of both science and art; experience and proper imaging techniques are required to produce an accurate and meaningful fracture surface photograph. This article reviews photographic principles and techniques as applied to failure analysis, both in the field and in the laboratory. The discussion covers the processes involved in field and laboratory photographic documentations, provides a description of professional digital cameras, and gives information on photographic lighting and microscopic photography. Special techniques can be employed to deal with highly reflective conditions and are also described in this article.

Metallographic examination is one of the most important procedures used by metallurgists in failure analysis. Typically, the light microscope (LM) is used to assess the nature of the material microstructure and its influence on the failure mechanism. Microstructural examination can be performed with the scanning electron microscope (SEM) over the same magnification range as the LM, but examination with the latter is more efficient. This article describes the major operations in the preparation of metallographic specimens, namely sectioning, mounting, grinding, polishing, and etching. The influence of microstructures on the failure of a material is discussed and examples of such work are given to illustrate the value of light microscopy. In addition, information on heat-treatment-related failures, fabrication-/machining-related failures, and service failures is provided, with examples created using light microscopy.

This article focuses on the analysis of materials and mechanical- (or biomechanical-) based medical device failures. It reviews the failure analysis practices, including evidence receipt, cleaning, nondestructive examination, destructive examination, exemplars analysis, and device redesign. The article examines the common failure modes, such as overload, fatigue, corrosion, hydrogen embrittlement, and fretting, of medical devices. The failure analysis of orthopedic implants, such as permanent prostheses and internal fixation devices, is described. The article reviews the failure mechanisms in some of the more common medical device materials, namely, stainless steels, titanium alloys, cobalt-base alloys, and nitinol. It presents case histories with examples for failure analysis.

Engineering component and structure failures manifest through many mechanisms but are most often associated with fracture in one or more forms. This article introduces the subject of fractography and aspects of how it is used in failure analysis. The basic types of fracture processes (ductile, brittle, fatigue, and creep) are described briefly, principally in terms of fracture appearances. A description of the surface, structure, and behavior of each fracture process is also included. The article provides a framework from which a prospective analyst can begin to study the fracture of a component of interest in a failure investigation. Details on the mechanisms of deformation, brittle transgranular fracture, intergranular fracture, fatigue fracture, and environmentally affected fracture are also provided.

This article discusses the fractal characteristics of fracture surfaces as a means for describing and quantifying irregular, complex curves and surfaces of fractured materials. It describes the important relationship between the profile and surface roughness parameters that yield the surface area of irregular fracture surfaces. The article reviews the experimental procedures required to obtain profiles and measurements that are made. In addition, fractal equations that linearize all the experimental data and provide constant fractal dimensions are presented in the article. Modified fractal dimensions that result from these analyses appear to possess some generality for natural irregular nonplanar surfaces and their profiles.

Fatigue failure of engineering components and structures results from progressive fracture caused by cyclic or fluctuating loads. Fatigue is an important potential cause of mechanical failure, because most engineering components or structures are or can be subjected to cyclic loads during their lifetime. This article focuses on fractography of fatigue. It provides an abbreviated summary of fatigue processes and mechanisms: fatigue crack initiation, fatigue crack propagation, and final fracture,. Characteristic fatigue fracture features that can be discerned visually or under low magnification are then described. Typical microscopic features observed on structural metals are presented subsequently, followed by a brief discussion on fatigue in polymers and polymer-matrix composites.

The principal objective of quantitative fractography is to express the characteristics of features in the fracture surface in quantitative terms, such as the true area, length, size, spacing, orientation, and location. This article provides a detailed account of the development of more quantitative geometrical methods for characterizing nonplanar fracture surfaces. Prominent techniques for studying fracture surfaces are based on the projected images, stereoscopic viewing, and sectioning. The article provides information on various roughness and materials-related parameters for profiles and surfaces. The applications of quantitative fractography for striation spacings, precision matching, and crack path tortuosity are also discussed.

This article focuses on characterizing the fracture-surface appearance at the microscale and contains some discussion on both crack nucleation and propagation mechanisms that cause the fracture appearance. It begins with a discussion on microscale models and mechanisms for deformation and fracture. Next, the mechanisms of void nucleation and void coalescence are briefly described. Macroscale and microscale appearances of ductile and brittle fracture are then discussed for various specimen geometries (smooth cylindrical and prismatic) and loading conditions (e.g., tension compression, bending, torsion). Finally, the factors influencing the appearance of a fracture surface and various imperfections or stress raisers are described, followed by a root-cause failure analysis case history to illustrate some of these fractography concepts.

Chemical analysis is a critical part of any failure investigation. With the right planning and proper analytical equipment, a myriad of information can be obtained from a sample. This article presents a high-level introduction to techniques often used for chemical analysis during failure analysis. It describes the general considerations for bulk and microscale chemical analysis in failure analysis, the most effective techniques to use for organic or inorganic materials, and examples of using these techniques. The article discusses the processes involved in the chemical analysis of nonmetallics. Advances in chemical analysis methods for failure analysis are also covered.

Metal-induced embrittlement is a phenomenon in which the ductility or the fracture stress of a solid metal is reduced by surface contact with another metal in either the liquid or solid form. This article summarizes some of the characteristics of liquid-metal- and solid-metal-induced embrittlement. This phenomenon shares many of these characteristics with other modes of environmentally induced cracking, such as hydrogen embrittlement and stress-corrosion cracking. The discussion covers the occurrence, failure analysis, and service failures of the embrittlement. The article also briefly reviews some commercial alloy systems in which liquid-metal-induced embrittlement or solid-metal-induced embrittlement has been documented and describes some examples of cracking due to these phenomena, either in manufacturing or in service.

This article describes some of the mechanical/ electrochemical phenomena related to the in vivo degradation of metals used for biomedical applications. It discusses the properties and failure of these materials as they relate to stress-corrosion cracking (SCC) and corrosion fatigue (CF). The article presents the factors related to the use of surgical implants and their deterioration in the body environment, including biomedical aspects, chemical environment, and electrochemical fundamentals needed for characterizing CF and SCC. It provides a discussion on the use of metallic biomaterials in surgical implant applications, such as orthopedic, cardiovascular surgery, and dentistry. It addresses the key issues related to simulation of the in vivo environment, service conditions, and data interpretation. Theses include frequency of dynamic loading, electrolyte chemistry, applicable loading modes, cracking mode superposition, and surface area effects. The article describes the fundamentals of CF and SCC, testing methodology, and test findings from laboratory, in vivo, and retrieval studies.

Hydrogen damage is a term used to designate a number of processes in metals by which the load-carrying capacity of the metal is reduced due to the presence of hydrogen. This article introduces the general forms of hydrogen damage and provides an overview of the different types of hydrogen damage in all the major commercial alloy systems. It covers the broader topic of hydrogen damage, which can be quite complex and technical in nature. The article focuses on failure analysis where hydrogen embrittlement of a steel component is suspected. It provides practical advice for the failure analysis practitioner or for someone who is contemplating procurement of a cost-effective failure analysis of commodity-grade components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also provided.