Analysis of the failure of a metal structure or part usually requires identification of the type of failure. Failure can occur by one or more of several mechanisms, including surface damage (such as corrosion or wear), elastic or plastic distortion, and fracture. This leads to a wide range of failures, including fatigue failure, distortion failure, wear failure, corrosion failure, stress-corrosion cracking, liquid-metal embrittlement, hydrogen-damage failure, corrosion-fatigue failure, and elevated-temperature failure. This article describes the classification of fractures on a macroscopic scale as ductile fractures, brittle fractures, fatigue fractures, and fractures resulting from the combined effects of stress and environment.

The primary goal of failure analysis is to prevent the recurrence of product failures. This article discusses the sequence of activities in failure analysis and offers insight on how to gather background information, examine and assess damage, and identify the cause of the problem. It also explains where to look for evidence and how to collect samples for various types of testing. In addition, the article provides an introduction to fracture mechanics and explains how to predict and avoid fractures, including fatigue fracture, through testing and computational techniques.

Wear of metals occurs by plastic displacement of surface and near-surface material, and by detachment of particles that form wear debris. This article presents a table that contains the classification of wear. It describes the testing and evaluation of wear and talks about the abrasive wear, lubrication and lubricated wear, and selection of steels for wear resistance. The article discusses the effect of alloying elements, composition, and mechanical properties of carbon and low-alloy steels at elevated temperatures. It talks about the fatigue resistance characteristics of steels, and describes the forms of embrittlement associated with carbon and low-alloy steels. The article provides information on the effect of composition, manufacturing practices, and microstructure on notch toughness of steels. Finally, it explains the effects of alloy elements, inclusion content, microstructure and heat treatment on fracture toughness of steels.

This article begins with a discussion of the basic fracture modes, including dimple ruptures, cleavages, fatigue fractures, and decohesive ruptures, and of the important mechanisms involved in the fracture process. It then describes the principal effects of the external environment that significantly affect the fracture propagation rate and fracture appearance. The external environment includes hydrogen, corrosive media, low-melting metals, state of stress, strain rate, and temperature. The mechanism of stress-corrosion cracking in metals such as steels, aluminum, brass, and titanium alloys, when exposed to a corrosive environment under stress, is also reviewed. The final section of the article describes and shows fractographs that illustrate the influence of metallurgical discontinuities such as laps, seams, cold shuts, porosity, inclusions, segregation, and unfavorable grain flow in forgings and how these discontinuities affect fracture initiation, propagation, and the features of fracture surfaces.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of AISI/SAE alloy steels (4xxx steels) and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the brittle fracture, ductile fracture, impact fracture, fatigue fracture surface, reversed torsional fatigue fracture, transgranular cleavage fracture, rotating bending fatigue, tension-overload fracture, torsion-overload fracture, slip band crack, crack growth and crack initiation, crack nucleation, microstructure, hydrogen embrittlement, sulfide stress-corrosion failure, stress-corrosion cracking, and hitch post shaft failure of these steels. The components considered in the article include tail-rotor drive-pinion shafts, pinion gears, outboard-motor crankshafts, bull gears, diesel engine bearing cap bolts, splined shafts, aircraft horizontal tail-actuator shafts, bucket elevators, aircraft propellers, helicopter bolts, air flasks, tie rod ball studs, and spiral gears.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of medium-carbon steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the torsional-fatigue fracture, cup and cone tensile fracture, brittle fracture, and in-service rotary bending fatigue fracture of fractured roof-truss angles, pressure-vessel shells, automotive axle shafts, broken keyed spindles, crane gears, blooming-mill spindles, automotive bolts, and crane wheels of these steels.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of austenitic stainless steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the following: fatigue-crack fracture, rock candy fracture, cleavage fracture, brittle fracture, high-cycle fatigue fracture, fatigue striations, hydrogen-embrittlement failure, creep crack propagation, fatigue crack nucleation, intergranular creep fracture, torsional overload fracture, stress-corrosion cracking, and grain-boundary damage of these steels. The austenitic stainless steel components include spring wires, preheater-reactor slurry transfer lines and gas lines of coal-liquefaction pilot plants, oil feed tubes and suction couch rolls of paper machines, cortical screws and compression hip screws of orthopedic implants, and Jewett nails.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of low-carbon steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the following: the intergranular fracture, bending impact fracture, brittle fracture, tensile-test fracture, transgranular fracture, cleavage fracture, delayed fracture, corrosion fatigue, inclusion morphology, fatigue crack propagation, and in-service fatigue fracture of various automotive components. These components include tie rod adjusting sleeves, automotive bolts, hydraulic jack shafts, crank handle collars, boiler tubes, drive shafts, bicycle pedal axles, lift-truck hydraulic-piston rods, and steel springs.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of miscellaneous metals and alloys and in identifying and interpreting the morphology of fracture surfaces. The metals and alloys covered include tungsten, iridium, magnesium-base, iron-base, molybdenum-base, and tantalum-base materials. The fractographs illustrate fatigue striations, slow-bending fracture, quasi-cleavage fracture, corrosion-fatigue fracture, fatigue crack, intergranular cleavage, microvoid coalescence, tension-overload fracture, crack propagation, impact fracture, and high-cycle fatigue failure.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of copper alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the following: fatigue fracture, intergranular fracture, transgranular fracture, microvoid coalescence, corrosion fatigue, fatigue striations, tensile-overload fracture, stress-corrosion cracking, and pitting corrosion of these alloys.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of maraging steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the tensile-test fracture, low-cycle fatigue fracture, fibrous fracture, crack-initiation zone, microvoid coalescence, fatigue-crack surface, hydrogen embrittlement, and fatigue striations of these steels.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of wrought aluminum alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the corrosion-fatigue fracture, fatigue striations, tension-overload fracture surface, ductile fracture, cone-shaped fracture surface, intergranular crack propagation, transgranular crack propagation, stress-corrosion cracking, hydrogen damage, and grain-boundary separation of these alloys. Fractographs are also provided for a forged aircraft main-landing gear wheel and actuator beam, an aircraft wing spar, a fractured aircraft propeller blade, shot peened fillet, an aircraft lower-bulkhead cap, and clevis-attachment lugs.

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.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of high-carbon steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the following: torsional fatigue fracture, hydrogen-embrittlement fracture, fatigue crack propagation, and corrosion fatigue of components made from high-carbon steels. The high-carbon steel components include bull gear, drive shaft, power boiler stoker grate, steel wheel, spring wire, suspension spring, automotive engine valve spring, power spring, cantilever-type spring, railroad rail, and seamless drill pipe.

This article is an atlas of fractographs that covers nickel-base superalloys. The fractographs display the following: hydrogen-embrittlement fracture; segment of a fractured second-stage gas-turbine wheel; gas-producer turbine rotor cast; dendritic stress-rupture fracture surface; fatigue and creep fractures; simultaneous metallographic-fractographic evaluation; and effect of thermal cycling on fatigue fracture.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of martensitic stainless steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fracture surface, high-cycle fatigue fracture, tensile-shear fracture, intergranular crack, fatigue striations, and microvoid coalescence of conveyor-chain links, hub socket of aircraft propellers, and automotive intake valves of these steels.

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 tool steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the low-cycle and high-cycle fatigue fractures, tension-overload fractures, impact fractures, microstructure, quench cracking, brittle-in-service failure, hydrogen embrittlement, stress-corrosion cracking, and grain-boundary cracking of tool steel components. These components include diesel engine injector plungers, rivet-heading tools, circular saw blades, and open-header dies.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of cobalt alloys (cast Vitallium and cast ASTM F75 alloys) and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fatigue fracture, microcrack, and stair-step fracture surface of these alloys.

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.