This article discusses several examples of fatigue load histories that intentionally create artificial fracture-surface markings during testing such that they are measurable by post-test quantitative fractography (QF). It reviews a number of methods for providing fatigue fracture-surface markers to aid QF of fatigue crack growth (FCG). These methods are based on load changes, including reordering the basic load histories and/or adding loads to them. The article also provides some guidelines for obtaining recognizable FCG markers for a variety of load histories and crack-growth regimes for coupons, components, and, particularly, full-scale fatigue tests.

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.

Rolling-contact fatigue (RCF) is a common failure mode in components subjected to rolling or rolling-sliding contact. This article provides a basic understanding of RCF and a broad overview of materials and manufacturing techniques commonly used in industry to improve component life. A brief discussion on coatings to improve surface-initiated fatigue and wear is included, due to the similarity to RCF and the increasing criticality of this failure mode. The article presents a working knowledge of Hertzian contact theory, describes the life prediction of rolling-element bearings, and provides information on physics and testing of rolling-contact fatigue. Processes commonly used to produce bearings for demanding applications are also covered.

This article describes the effects of cyclic fatigue properties on aluminum alloys. It provides a discussion on strain-control fatigue and the effects of two microstructural features on the strain life of aluminum alloys: shearable precipitates and precipitate-free zones. The article discusses various models of fatigue crack growth (FCG) and the effects of alloy microstructure and composition on FCG.

This article describes mechanical/electrochemical phenomena related to 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 key issues related to the simulation of an in vivo environment, service conditions, and data interpretation. These include the frequency of dynamic loading, electrolyte chemistry, applicable loading modes, cracking mode superposition, and surface area effects. The article explains the fundamentals of CF and SCC, and presents the test findings from laboratory, in vivo, and retrieval studies.

This article discusses the basic approach for predicting the corrosion-fatigue life of structural components. It describes two types of tests that are normally used in combination: cycles-to-failure tests, which focus on crack initiation, and crack propagation tests, which focus on crack growth rates under cyclic load. The article examines corrosion-fatigue cracking along with the effects of cracking due to stress corrosion and hydrogen embrittlement, which often occur together. It explains how test parameters such as loading and environmental conditions impact crack growth mechanisms and data interpretation.

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.

In the design of composite structures for durability and damage tolerance, the primary concerns are out-of-plane failures, such as delamination, material degradation associated with environment, stability under compression loading, large degree of scatter in fatigue life, and bearing failure of joints. This article presents an introductory discussion on the fatigue damage process, methodologies assessing fatigue behavior, and life prediction models. It describes the damage mechanisms introduced for a quasi-isotropic laminate under tension-compression fatigue loading. Delamination is a critical issue in fatigue and generally results from high interlaminar normal and shear stresses. The article schematically illustrates the structural elements in which high interlaminar stresses are common. It concludes with a discussion on the classification of fatigue models such as mechanistic or phenomenological, for composite materials under cyclic loading.

This article provides the general mechanical testing guidelines for the characterization of lamina and laminate properties. Guidelines are provided for tensile property, compressive property, shear property, flexure property, fracture toughness, and fatigue property test methods. The article also tabulates selected standards for lamina and laminate mechanical testing.

This article describes the fatigue properties of particle-reinforced metal-matrix composites (PR-MMCs) in terms of mechanisms of crack initiation, fatigue life, and fatigue crack growth. It reviews specimen preparation and microscopic procedures that are used in fatigue testing of MMCs. It also describes the evaluation of the long fatigue crack growth behavior of MMCs by using the test methods and specimens that are used for unreinforced metallic alloys. Fractography of MMCs under plane-strain conditions is also described with information on the observed features of MMC fatigue fracture surfaces and their observation methods.

This article provides an overview of two major classes of bearings: rolling bearings and sliding, or plain, bearings. It reviews the experimental data resulted from testing of rolling and sliding bearing materials with illustration. The article presents a table that summarizes rolling contact fatigue test methods that ASTM published in STP 771. It also describes the role of lubrication in the bearings.

This article provides a review of fatigue test methodologies and an overview of general fatigue behavior, fatigue crack initiation and fatigue crack propagation of advanced engineering plastics. It also describes the factors affecting fatigue performance of polymers and concludes with information on fractography, a useful tool in failure analysis.

This article reviews the basic equipment and methods for creep and creep rupture testing. It begins with a discussion on the creep properties, including stress and temperature dependence, as well as of the extrapolation techniques that permit estimation of the long-term creep and rupture strengths of materials. The article describes the different types of equipment for determination of creep characteristics, including test stands, furnaces, and extensometers. It also discusses the different testing methods for creep rupture: constant-load testing and constant-stress testing. The article presents other testing considerations and concludes with information on stress relaxation testing.

Mechanical tests are performed to evaluate the durability of gears under load. Gear tooth failures occur in two distinct regions, namely, the tooth flank and the root fillet. This article describes the common failure modes such as scoring, wear, and pitting, on tooth flanks. Failures in root fillets are primarily due to bending fatigue but can be precipitated by sudden overloading (impact). The article presents contact stress computations for gear tooth flank and bending stress computations for root fillets. Specimen characterization is a critical part of any fatigue test program because it enables meaningful interpretation of the results. The article describes four areas of the characterizations: dimensional, surface finish/texture, metallurgical, and residual stress. The rolling contact fatigue test, single-tooth fatigue test, single-tooth single-overload test, and single-tooth impact test are some of the gear action simulating tests discussed in the article.

This article describes the fatigue mechanism and behavior of environmentally induced fatigue and cyclic fatigue. It discusses three basic strength test methods, namely, static, dynamic, and cyclic, along with their analytical relations for determining the fatigue parameters and behavior of ceramics and glasses. The article explains the double torsion and double-cantilever beam fracture mechanics methods, which employ test specimens with relatively large, induced cracks. Crack growth data are typically determined directly by the observation of the crack or by devices that monitor test specimen compliance, such as clip gages and strain gages.

The main objective for the study of combined-stress fatigue is to obtain fatigue data for axles and to find the criterion for fatigue limit under combined stress. This article begins with a description of the stress states of combined stress and stress fields near crack tips. It provides an account of the various biaxial and multiaxial fatigue testing methods, specimen geometries, and stress intensity factors important in the study multiaxial fatigue. Widely used test methods are the torsion-rotating bending fatigue test and biaxial and triaxial fatigue tests. Common specimen geometries include rectangular plate specimens, cruciform specimens, compact tension shear specimens, compact shear specimens, mode II crack growth specimen, circumferentially notched cylindrical specimens, tubular specimens containing a slit, and solid cylindrical specimens containing a small hole or initial crack.

Impact tests are used to study dynamic deformation and failure modes of materials. This article discusses low-velocity impact experiments in single-stage gas guns. It describes surface velocity measurements with laser interferometric techniques. The article details plate impact soft-recovery experiments, pressure-shear friction experiments, and low-velocity penetration experiments. It reviews two types of plate impact soft-recovery experiments: normal plate impact and pressure-shear plate impact experiments. The article provides information on low-velocity penetration experiments, which include the setup for direct penetration experiment (rod-on-plate) and the reverse penetration experiment (plate-on-rod). It also considers high-temperature plate impact testing and impact techniques with in-material stress and velocity measurements.

This article describes the phenomena of crack initiation and early growth. It examines specimen design and preparation as well as the apparatus used in crack initiation testing. The article provides descriptions of the various commercially available fatigue testing machines: axial fatigue testing machines and bending fatigue machines. Load cells, grips and alignment devices, extensometry and strain measuring devices, environmental chambers, graphic recorders, furnaces, and heating systems of ancillary equipment are discussed. The article presents technologies available to accomplish closed loop control of materials testing systems in performing standard materials tests and for the development of custom testing applications. It explores the advanced software tools for materials testing. The article includes a description of baseline isothermal fatigue testing, creep-fatigue interaction, and thermomechanical fatigue. The effects of various variables on fatigue resistance and guidelines for fatigue testing are also presented.

Testing and characterization of fatigue crack growth are used extensively to predict the rate at which subcritical cracks grow due to fatigue loading. ASTM standard E 647 is the accepted guideline for fatigue crack growth testing (FCGR) and is applicable to a wide variety of materials and growth rates. The two most widely used types of specimens are the middle-crack tension and compact-type specimens. This article describes the factors affecting the selection of appropriate geometries of these specimens: consideration of material availability and raw form, desired loading condition, and equipment limitations. Various crack measurement techniques, including optical, ultrasonic, acoustic emission, electrical, and compliance methods, are also reviewed. The article discusses the two major aspects of FCGR test analysis: to ensure suitability of the test data and to calculate growth rates from the data.