Search Results for tensile Hopkinson bar

This article describes the techniques involved in measuring the high-strain-rate stress-strain response of materials using a split-Hopkinson pressure bar (SHPB). It focuses on the generalized techniques applicable to all SHPBs, whether compressive, tensile, or torsion. The article discusses the methods of collecting and analyzing compressive high-rate mechanical property data. A review of the critical experimental variables that must be controlled to yield valid and reproducible high-strain-rate stress-strain data is also included. Comparisons and contrasts to the differences invoked when using a tensile Hopkinson bar in terms of loading technique, sample design, and stress-state stability, are discussed.

This article addresses the specialized aspects required to accurately quantify the behavior of soft materials, including polymers and polymeric composites, using the split-Hopkinson pressure bar (SHPB). It details some of the specialized SHPB techniques that facilitate testing soft materials. These techniques include the data-reduction techniques and assumptions required to use polymer pressure bars, the importance of sample-size considerations to polymer testing, and temperature-control methodologies to measure the high-strain-rate uniaxial stress response of polymers and other soft materials.

This article illustrates the momentum-trapping scheme in the incident bar and stress-reversal technique which is used to change the strain rate during the course of Hopkinson bar compression or tension experiments. It describes techniques to recover the sample after it has been subjected to a cycle of compression followed by tension or tension followed by compression with illustrations. The article provides information on the recovery dynamic testing of hard materials such as ceramics and ceramic composites and explains high-temperature dynamic recovery tests. The recovery of the sample that has been subjected to a single stress pulse allows a number of interesting applications, a few of which are reviewed.

High strain rate testing is important for many engineering structural applications and metalworking operations. This article describes various methods for high strain rate testing. Several methods have been developed, starting with the pioneering work of John Hopkinson and his son, Bertram Hopkinson. Based on these contributions and also on an important paper by R.M. Davies, H. Kolsky invented the split-Hopkinson pressure bar, which allows the deformation of a sample of a ductile material at a high strain rate, while maintaining a uniform uniaxial state of stress within the sample.

This article reviews high strain rate compression and tension test methods with a focus on the general principles, advantages, and limitations of each test method. The compression test methods are cam plastometer test, drop tower compression test, the Hopkinson bar in compression, and rod impact (Taylor) test. The flyer plate impact test, expanding ring test, split-Hopkinson bar in tension, and a test using a rotating wheel used for high strain rate tension are also discussed.

Split-Hopkinson pressure bar (SHPB) testing is traditionally used for determining the plastic properties of metals (which are softer than the pressure bar material) at high strain rates. However, the use of this method for testing ceramic has various limitations. This article provides a discussion on the operational principle of the traditional SHPB technique and the relevant assumptions in the derivation of the stress-strain relationship. It describes the inherent limitations on the validity of these assumptions in testing ceramics and discusses the necessary modifications in SHPB design and test procedure for evaluating high-strength brittle ceramics. The article includes information on the maximum strain rate that can be obtained in ceramics using an SHPB and the necessity of incident pulse shaping. It also reviews the specimen design considerations, interpretation of experimental results obtained from SHPB testing of ceramics, and effectiveness of the proposed modifications.

This article describes a method for determining the dynamic indentation response of metals and ceramics. This method, based on split Hopkinson pressure bar testing, can determine rate-dependent characteristics of metals and ceramics at moderate strain rates. For example, dynamic indentation testing reveals a significant effect of loading rates on the hardness and the induced plastic zone size in metals and on the hardness and induced crack sizes of brittle materials. The article also explains the rebound and pendulum methods for dynamic hardness testing.

This article reviews the dynamic factors, experimental methods and setup, and result analysis of different types of high strain rate shear tests. These include high strain rate torsion testing, double-notch shear testing and punch loading, drop-weight compression shear testing, thick-walled cylinder testing, and pressure-shear plate impact testing.

This article describes the most commonly used test methods for determining flow stress in metal-forming processes. The methods include tension, ring, uniform compression, plane-strain compression, torsion, split-Hopkinson bar, and indentation tests. The article discusses the effect of deformation heating on flow stress. It provides metallurgical considerations at hot working temperatures and presents flow curves at conventional metalworking strain rates. The article describes the effect of microstructural scale, crystallographic texture, and equiaxed phases on flow stress at hot working temperatures. It tabulates a summary of certain values describing the flow stress-strain rate relation for steels, aluminum alloys, copper alloys, titanium alloys, and other metals at various temperatures.

This article begins with a review of the purposes of mechanical characterization tests and the general considerations related to the mechanical properties of anisotropic systems, specimen fabrication, equipment and fixturing, environmental conditioning, and analysis of test results. It provides information on the specimen preparation, instrumentation, and procedures for various mechanical test methods of fiber-reinforced composites. These include the compression test, flexure test, shear test, open hole tension test, and compression after impact test. The article describes three distinct fracture modes, namely, crack opening mode, shearing mode, and tearing mode. It presents an overview of fatigue testing and fatigue damage mechanisms of composite materials and reviews the types of mechanical measurements that can be made during the course of testing to assess fatigue damage. The article concludes with a discussion on the split-Hopkinson pressure bar test.

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 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.

Measurement and analysis of fracture behavior under high loading rates is carried out by different test methods. This article provides a discussion on the history and types of notch-toughness tests and focuses exclusively on notch-toughness tests with emphasis on the Charpy impact test. It reviews the requirements of test specimens, test machine, testing procedure and machine verification, application, and determination of fracture appearance and lateral expansion according to ASTM A370, E 23, and A 593 specifications. In addition, the article includes information on the instrumentation, standards and requirements, and limitations of instrumented Charpy impact test, which is carried out in specimens with induced fatigue precrack. The article concludes with a review of the requirements of drop weight testing and the specimens used in other notch-toughness tests.

This article reviews the factors that have a significant effect on the selection and interpretation of results of different hardness tests, namely, Brinell, Rockwell, Vickers, and Knoop tests. The factors concerned include hardness level (and scale limitations), specimen thickness, size and shape of the workpiece, specimen surface flatness and surface condition, and indent location. The article focuses on the selection for specific types of materials, such as steels, cast irons, nonferrous alloys, and plastics, and industrial applications, of hardness tests.

This article provides an overview of cavitation erosion with a specific focus on the estimation of mass loss. It describes the mechanisms of cavitation erosion and the types of laboratory devices to evaluate the resistance to cavitation erosion of materials. The laboratory devices include rotating disks, vibratory devices, cavitating liquid jets, and high-speed cavitation tunnels. The article discusses materials selection and surface protection to prevent cavitation erosion. It reviews the fluid-structure interaction that plays a role in cavitation erosion particularly for compliant materials. The article provides information on the numerical prediction of cavitation erosion damage by the finite element method (FEM).