This article aims to identify and illustrate the types of overload failures, which are categorized as failures due to insufficient material strength and underdesign, failures due to stress concentration and material defects, and failures due to material alteration. It describes the general aspects of fracture modes and mechanisms. The article briefly reviews some mechanistic aspects of ductile and brittle crack propagation, including discussion on mixed-mode cracking. Factors associated with overload failures are discussed, and, where appropriate, preventive steps for reducing the likelihood of overload fractures are included. The article focuses primarily on the contribution of embrittlement to overload failure. The embrittling phenomena are described and differentiated by their causes, effects, and remedial methods, so that failure characteristics can be directly compared during practical failure investigation. The article describes the effects of mechanical loading on a part in service and provides information on laboratory fracture examination.

Mechanical testing is an evaluative tool used by the failure analyst to collect data regarding the macro- and micromechanical properties of the materials being examined. This article provides information on a few important considerations regarding mechanical testing that the failure analyst must keep in mind. These considerations include the test location and orientation, the use of raw material certifications, the certifications potentially not representing the hardware, and the determination of valid test results. The article introduces the concepts of various mechanical testing techniques and discusses the advantages and limitations of each technique when used in failure analysis. The focus is on various types of static load testing, hardness testing, and impact testing. The testing types covered include uniaxial tension testing, uniaxial compression testing, bend testing, hardness testing, macroindentation hardness, microindentation hardness, and the impact toughness test.

Stress-corrosion cracking (SCC) occurs under service conditions, which can result, often without any prior warning, in catastrophic failure. Hydrogen embrittlement is distinguished from stress-corrosion cracking generally by the interactions of the specimens with applied currents. To determine the susceptibility of alloys to SCC and hydrogen embrittlement, several types of testing are available. This article describes the constant extension testing, constant load testing, constant strain-rate testing for smooth specimens and precracked or notched specimens of SCC. It provides information on the cantilever beam test, wedge-opening load test, contoured double-cantilever beam test, three-point and four-point bend tests, rising step-load test, disk-pressure test, slow strain-rate tensile test, and potentiostatic slow strain-rate tensile test for hydrogen embrittlement.

This article discusses a number of workability tests that are especially applicable to the forging process. The primary tests for workability are those for which the stress state is well known and controlled. The article provides information on the tension test, torsion test, compression test, and bend test. It examines specialized tests including plane-strain compression test, partial-width indentation test, secondary-tension test, and ring compression test. The article explains that workability is determined by two main factors: the ability to deform without fracture and the stress state and friction conditions present in the bulk deformation process. These two factors are described and brought together in an experimental workability analysis.

This article begins with a description of the classes and grades of ductile iron. It discusses the factors affecting the mechanical properties of ductile iron. The article reviews the hardness properties, tensile properties, shear and torsional properties, compressive properties, fatigue properties, fracture toughness, and physical properties of ductile iron and compares them with other cast irons to aid the designer in materials selection. It concludes with information on austempered ductile iron.

This article briefly introduces the concepts of failure analysis, including root-cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It initially provides definitions of failure on several different levels, followed by a discussion on the role of failure analysis and the appreciation of quality assurance and user expectations. Systematic analysis of equipment failures reveals physical root causes that fall into one of four fundamental categories: design, manufacturing/installation, service, and material, which are discussed in the following sections along with examples. The tools available for failure analysis are then covered. Further, the article describes the categories of mode of failure: distortion or undesired deformation, fracture, corrosion, and wear. It provides information on the processes involved in RCA and the charting methods that may be useful in RCA and ends with a description of various factors associated with failure prevention.

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.

This article focuses on the factors that determine the extent of deformation a metal can withstand before cracking or fracture occurs. It informs that workability depends on the local conditions of stress, strain, strain rate, and temperature in combination with material factors. The article discusses the common testing techniques and process variables for workability prediction. It illustrates the simple and most widely used fracture criterion proposed by Cockcroft and Latham and provides a workability analysis using the fracture limit line. The article describes various workability tests, such as the tension test, ring compression test, plane-strain compression test, bend test, indentation test, and forgeability test. It concludes with information on the role of the finite-element modeling software used in workability analysis.

This article discusses two types of hot-tension tests, namely, the Gleeble test and conventional isothermal hot-tension test, as well as their equipment. It summarizes the data for hot ductility, strength, and hot-tension for commercial alloys. The article presents isothermal hot-tension test data, which helps to gain information on a number of material parameters and material coefficients. It details the effect of test conditions on flow behavior. The article briefly describes the detailed interpretation of data from the isothermal hot-tension test using numerical model. It also explains the cavitation mechanism and failure modes that occur during hot-tension testing.

This article is an atlas of fractographs that covers pearlitic and ferritic ductile irons. The fractographs display the following: brittle cleavage fracture; fatigue crack propagation; fatigue and monotonic fracture surfaces; fracture modes in slow monotonic loading and impact loading; and microcrack initiation and propagation.

This article focuses on the evaluation of mechanical properties of freestanding films and films adherent to their substrates. Common methods of testing freestanding films, including uniaxial tensile testing, uniaxial creep testing, biaxial testing, and beam-bending methods, are discussed. For films which are adherent to their substrates, indentation testing is used to evaluate hardness, creep, and strength.

This article discusses the mechanics, surface preparation and principles of metal forming operations such as drawing, bending (draw bending, compression bending, roll bending, and stretch bending), spinning, and straightening of bars, tubes, wires, rods and structural shapes. The article also discusses the machines and tools, including dies and mandrels, and lubricants used for these metal forming operations.

This article reviews the various types of mechanical testing methods, including hardness testing; tension testing; compression testing; dynamic fracture testing; fracture toughness testing; fatigue life testing; fatigue crack growth testing; and creep, stress-rupture, and stress-relaxation testing. Shear testing, torsion testing, and formability testing are also discussed. The discussion of tension testing includes information about stress-strain curves and the properties described by them.

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 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.

Mechanical properties are often the most important properties in the design and selection of engineering plastics. Temperature, molecular structure, crystallinity, viscoelasticity, and effects of environment, fillers and reinforcements are considered as the basic factors affecting the mechanical properties of engineering plastics. The testing methods for determining mechanical properties, including stress-strain test, modulus-directed tensile test, strength test, strength-directed tensile test, impact test, and dynamic mechanical test are discussed.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of pure irons and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the grain-boundary cavitation; slip lines; intergranular fracture; cleavage fracture; notch-impact fracture; oxide inclusions and blowholes; ductile rupture; impact fracture and tensile-test fracture surfaces; fatigue striations; and crack initiation and propagation of pure irons.

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 discusses the identifying characteristics of the forms or mechanisms of corrosion that commonly attack copper metals, as well as the most effective means of combating each. It tabulates corrosion ratings of wrought copper alloys in various corrosive media. The article describes the corrosion behavior of copper alloys in specific environments. It reviews the corrosion characteristics of copper and copper alloys in various acids, alkalis, salts, organic compounds, and gases. The article provides information on the behavior of copper alloys that is susceptible to stress-corrosion cracking in various industrial and chemical environments. It concludes with a discussion on various corrosion testing methods, including aqueous corrosion testing, dynamic corrosion tests, and stress-corrosion testing.