This article provides a description of the microscale models and mechanisms for deformation and fracture. Macroscale and microscale appearances of ductile and brittle fracture are discussed for various specimen geometries and loading conditions. The article reviews the general geometric factors and materials aspects that influence the stress-strain behavior and fracture of ductile metals. It highlights fractures arising from manufacturing imperfections and stress raisers. The article presents a root cause failure analysis case history to illustrate some of the fractography concepts.

Wire rod is a semifinished product rolled from billet on a rod mill and is used primarily for the manufacture of wire. Steel wire rod is usually cold drawn into wire suitable for further drawing; for cold rolling, cold heading, cold upsetting, cold extrusion, or cold forging; or for hot forging. The article explains these operations, along with the several recognized quality and commodity classifications applicable to steel wire rods. The heat treatments commonly applied to steel wire rod, either before or during processing into wire, include annealing, spheroidize annealing, patenting, and controlled cooling. When the end product must be heat treated, the heat treatment and mechanical properties should be clearly defined. Carbon steel rods are produced in various grades or compositions: low-carbon, medium-low-carbon, medium-high-carbon, and high-carbon steel wire rods. Rod for the manufacture of carbon steel wire is produced with manufacturing controls and inspection procedures intended to ensure the degree of soundness and freedom from injurious surface imperfections necessary for specific applications. This article also describes the various quality descriptors applicable to the rods as well as standard qualities and commodities available in alloy steel wire rod.

This article describes the general root causes of failure associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be the common sources of failure-inducing defects in bulk working of wrought products. The article discusses the types of imperfections that can be traced to the original ingot product. These include chemical segregation; ingot pipe, porosity, and centerline shrinkage; high hydrogen content; nonmetallic inclusions; unmelted electrodes and shelf; and cracks, laminations, seams, pits, blisters, and scabs. The article provides a discussion on the imperfections found in steel forgings. The problems encountered in sheet metal forming are also discussed. The article concludes with information on the causes of failure in cold formed parts.

Hot-rolled steel bars and other hot rolled steel shapes are produced from ingots, blooms, or billets converted from ingots, or from strand cast blooms and billets, and comprise a variety of sizes and cross sections. This article provides a brief discussion on mechanical properties, quality descriptors and chemical compositions of hot-rolled steel bars, cold-finished steel bars, steel wire rod and steel wire. It contains tables that provide size tolerances for cold-finished carbon steel bar and cold-finished alloy steel bar.

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 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.

Hot-rolled steel bars and other hot-rolled steel shapes are produced from ingots, blooms, or billets converted from ingots or from strand cast blooms or billets and comprise a variety of sizes and cross sections. Most carbon steel and alloy steel hot-rolled bars and shapes contain surface imperfections with varying degrees of severity. Seams, laps, and slivers are probably the most common defects in hot-rolled bars and shapes. Another condition that could be considered a surface defect is decarburization. Hot-rolled steel bars and shapes can be produced to chemical composition ranges or limits, mechanical property requirements, or both. Hot-rolled carbon steel bars are produced to two primary quality levels: merchant quality and special quality. Merchant quality is the least restrictive descriptor for hot-rolled carbon steel bars. Special quality bars are employed when end use, method of fabrication, or subsequent processing treatment requires characteristics not available in merchant quality bars.

This article provides a schematic illustration of factors that should be considered in component design. It discusses the effect of component geometry on the behavior of materials and groups the main parameters that affect the value of the factor of safety. The article illustrates the estimation of probability of failure with an example. It reviews the designing and selection of materials for static strength and stiffness. The article also describes the causes of failure of engineering components, including design deficiencies, poor selection of materials, and manufacturing defects.

This article outlines the requirements and methods associated with the inspection of brazements. It emphasizes the incorporation of these requirements into the overall quality system. The article reviews the acceptance limits, design limitations, and nondestructive and destructive inspection techniques involved in the brazement inspection. Selected case studies are also provided for further reference.

Titanium metal passes through three major steps during processing from ore to finished product: reduction of titanium ore to sponge (porous form), melting of sponge and scrap to form ingot, and remelting and casting into finished shape. This article describes primary fabrication, including all operations that convert ingot into general mill products, such as billet, bar, plate, sheet, strip, tube, and wire. The section on secondary fabrication describes processes such as die forging, extrusion, hot and cold forming, machining, chemical milling, and joining. The article presents a short note on powder metallurgy products of titanium. Casting processes and properties are covered in the final section.

Welded connections are a common location for failures for many reasons, as explained in this article. This article looks at such failures from a holistic perspective. It discusses the interaction of manufacturing-related cracking and service failures and primarily deals with failures that occur in service due to stresses caused by externally applied loads. The purpose of this article is to enable a failure analyst to identify the causative factors that lead to welded connection failure and to identify the corrective actions needed to overcome such failures in the future. Additionally, the reader will learn from the mistakes of others and use principles that will avoid the occurrence of similar failures in the future. The topics covered include failure analysis fundamentals, welded connections failure analysis, welded connections and discontinuities, and fatigue. In addition, several case studies that demonstrate how a holistic approach to failure analysis is necessary are presented.

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 outlines the basic steps to be followed and the range of techniques available for failure analysis, namely, background data assembling, visual examination, microfractography, chemical analysis, metallographic examination, electron microscopy, electron microprobe analysis, X-ray techniques, and simulations. It also describes the steps for analyzing the data, preparing the report, preservation of evidence, and follow-up on recommendations.

The various methods of furnace, torch, induction, resistance, dip, and laser brazing are used to produce a wide range of highly reliable brazed assemblies. However, imperfections that can lead to braze failure may result if proper attention is not paid to the physical properties of the material, joint design, prebraze cleaning, brazing procedures, postbraze cleaning, and quality control. Factors that must be considered include brazeability of the base metals; joint design and fit-up; filler-metal selection; prebraze cleaning; brazing temperature, time, atmosphere, or flux; conditions of the faying surfaces; postbraze cleaning; and service conditions. This article focuses on the advantages, limitations, sources of failure, and anomalies resulting from the brazing process. It discusses the processes involved in the testing and inspection required of the braze joint or assembly.

This article provides an overview of fractography and explains how it is used in failure analysis. It reviews the basic types of fracture processes, namely, ductile, brittle, fatigue, and creep, principally in terms of fracture appearances, such as microstructure. The article also describes the general features of fatigue fractures in terms of crack initiation and fatigue crack propagation.

This article is a compilation of terms related to analysis and prevention of engineering failures.

This article provides information on the development of finite element analysis (FEA) and describes the general-purpose applications of FEA software programs in structural and thermal, static and transient, and linear and nonlinear analyses. It discusses special-purpose finite element applications in piping and pressure vessel analysis, impact analysis, and microelectronics. The article describes the steps involved in the design process using the FEA. It concludes with two case histories that involve the use of FEA in failure analysis.

The principal task of a failure analyst during a physical-cause investigation is to identify the sequence of events involved in the failure. Technical skills and tools are required for such identification, but the analyst also needs a mental organizational framework that helps evaluate the significance of observations. This article discusses the processes involved in the characterization and identification of damage and damage mechanisms. It describes the relationships between damage causes, mechanisms, and modes with examples. In addition, some of the more prevalent and encompassing characterization approaches and categorization methods of damage mechanism are also covered.

Cold-finished steel bars are carbon and alloy steel bar products (round, square, hexagonal, flat, or special shapes) that are produced by cold finishing previous hot-wrought bars. by means of cold drawing, cold forming, turning, grinding, or polishing (singly or in combination) to yield straight lengths or coils that are uniform throughout their length. Cold-finished bars fall into five classifications: cold-drawn bars; turned and polished bars; cold-drawn, ground, and polished bars; turned, ground, and polished bars; cold-drawn, turned, ground, and polished bars. Different size tolerances are applicable to cold-finished products, depending on shape, carbon content, and heat treatment. When used to identify cold-finished steel bars, the various quality descriptors are indicative of many characteristics, such as degree of internal soundness, relative uniformity of chemical composition, and relative freedom from detrimental surface imperfections. Cold drawing significantly increases machinability, tensile and yield strengths of steel bars. Two special die-drawing processes have been developed to give improved properties over those offered by standard drawing practices. These processes are cold drawing using heavier-than-normal drafts, followed by stress relieving; and drawing at elevated temperatures.