Search Results for strain-control testing

The separation of the fatigue process into crack initiation and propagation phases has been an important and useful advance in engineering. The combined approach of strain-control testing and the development fracture mechanics of fatigue crack growth rates is a key advance that allows better understanding and simulation of both crack nucleation and the subsequent crack growth mechanisms. This article reviews three basic types of fatigue properties: stress-life, strain life, and fracture mechanic crack growth.

This article discusses the underlying concepts and basic techniques for performing ultrasonic fatigue tests and describes test equipment design, specimen design, and effective control over test variables. It reviews the results obtained with ultrasonic fatigue test methods with respect to strain-rate-dependent material behavior. The article also provides information on the applications of the ultrasonic fatigue test.

This article describes the use of compression tests, namely, cylindrical compression, ring compression, and plane-strain compression tests at elevated temperatures. It discusses the effects of the temperature, strain rate, and deformation heating on metals during the cylindrical compression test, with the help of flow curves. The article illustrates the testing apparatus used in the cylindrical compression test. It describes the issues regarding friction and temperature, and strain-rate control with proper test equipment and experimental planning during the ring compression test and plane-strain compression test. The article also reviews the testing conditions, procedures, and advantages of hot plane-strain compression test.

An important activity in metalworking facilities is the testing of raw materials for characteristics that ensure the integrity and quality of the products made. This article reviews the common material parameters that can have a direct or indirect influence on workability and product quality. These include strength, ductility, hardness, strain-hardening exponent, strain-rate effects, temperature effects, and hydrostatic pressure effects. The article also reviews the material behavior characteristics typically determined by mechanical testing methods. It discusses various mechanical testing methods, including the tension test, plane-strain tension test, compression test, plane-strain compression test, partial-width indentation test, and torsion test. Aspects of testing particularly relevant to workability and quality control for metalworking processes are also described. Finally, the article details the various factors influencing workability in bulk deformation processes and formability in sheet-metal forming.

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 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.

This article focuses on the effects of mechanical plasticity on workability; that is, process control of localized stress and strain conditions to enhance workability. It describes the nature of local stress and strain states in bulk forming processes, leading to a classification scheme, including testing procedures and specific process measurements, that facilitate the application of workability concepts. Using examples, the article applies these concepts to forging, rolling, and extrusion processes. The stress and strain environments described in the article suggest that a workability test should be capable of subjecting the material to a variety of surface strain combinations. By providing insights on fracture criteria, these tests can be used as tools for troubleshooting fracture problems in existing processes, as well as in the process development for new product designs.

THE TENSION TEST is one of the most commonly used tests for evaluating materials. The material characteristics obtained from tension tests are used for quality control in production, for ranking performance of structural materials, for evaluation of alloys, and for dealing with the static-strength requirements of design. This article describes the stress-strain behavior during a tension test and provides the definition of terms such as stress, force, strain, and elongation. It explains the tensile properties obtained from the test results: the tensile strength and yield strength, which includes offset yield strength, extension-under-load yield strength, and upper yield strength. The article concludes with a description of the general procedures for conducting the tension test based on ASTM standards and the variability of tensile properties.

This article focuses on the specific aspects of nitinol that are of interest to medical device designers. It describes the physical metallurgy, physical properties, and tensile properties of the nitinol. The article discusses the factors influencing superelastic shape memory effects, fatigue, and corrosion in medical device design. It reviews the biocompatibility of nitinol based on corrosion behavior. The article explains the general principles, potential pitfalls, and key properties for manufacturing, heat treatment, and processing of nitinol.

Fatigue properties are an integral part of materials comparison activities and offer information for structural life estimation in many engineering applications. This article presents three general approaches to fatigue design, with a discussion on their respective attributes. These include infinite-life criterion, finite-life criterion, and damage tolerant criterion. The article describes the individual property requirements of these approaches. It also presents selected examples of properties that reflect some detail of these approaches.

This article provides ASTM standard definitions for fatigue and describes the approaches that are used to design finite or infinite life, used in a complementary sense in fatigue design. It explains four distinct phases of fatigue: nucleation, structurally dependent crack propagation, crack propagation, and final instability. The article discusses the significant role that fatigue plays in industrial design applications.

The design of components against fatigue failure may involve several considerations of irregular loading, variable temperature, and environment. This article focuses on design considerations against fatigue related to material performance under mechanical loading at constant temperature. It reviews the traditional methods of fatigue design on smooth and notched components. The article discusses high-cycle fatigue in terms of fatigue strength and tensile strength, mean stress effects, stress concentration, and multiaxial fatigue. It describes low-cycle fatigue in terms of deformation behavior and concludes with a discussion on lifetime analysis based on a strain approach.