Search Results for shear-banding experiments

This article provides a discussion on the generation of an incident wave with the help of the stored-torque torsional Kolsky bar and explosively loaded torsional Kolsky bar. It examines the procedures followed for measuring the waves in these bars. The article compares the compression Kolsky bar with the torsional Kolsky bar. It includes information on the various application areas of torsional Kolsky bar: limitations on strain rate, low- and high-temperature testing, quasi-static and incremental strain-rate testing, and localization and shear-banding experiments.

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 general aspects of creep, stress relaxation, and yielding for homogeneous polymers. It then presents creep failure mechanisms in polymers. The article discusses extrapolative methods for the prediction of long-term creep failure in polymer materials. Then, the widely used models to simulate the service life of polymers are highlighted. These include the Burgers power-law model, the Findley power-law model, the time-temperature superposition (or equivalence) principle (TTSP), and the time-stress superposition principle (TSSP). The Larson-Miller parametric method, one of the most common to describe the material deformation and rupture time, is also discussed.

The mechanism of contact fatigue can be understood in terms of several sources of stress concentration, or stress raisers, within the macroscopic Hertzian stress field. This article focuses primarily on rolling contact fatigue of hardened bearing steels. It discusses Hertzian shear stresses at and below the contact surfaces and briefly summarizes bearings and gear characteristics. The article provides an overview of the key types of gear and bearing steels. It analyzes two types of macropitting that result from the subsurface growth of fatigue cracks, namely, subsurface-origin macropitting and surface-origin macropitting. The article describes the factors influencing contact fatigue life of hardened steel bearings and gears, including hardness, inclusions, carbides, and residual stresses.

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 briefly reviews the analysis methods for spalling of striking tools with emphasis on field tests conducted by A.H. Burn and on the laboratory tests of H.O. McIntire and G.K. Manning and of J.W. Lodge. It focuses on the metallography and fractography of spalling. The macrostructure and microstructure of spall cavities are described, along with some aspects of the numerous specifications for striking/struck tools. The article also describes the availability of spall-resistant metals and the safety aspects of striking/struck tools in railway applications.

Workability in forging depends on a variety of material, process-variable, and die-design features. A number of test techniques have been developed for gaging forgeability depending on alloy type, microstructure, die geometry, and process variables. This article summarizes some common workability tests and illustrates their application in practical forging situations. Workability tests for open-die forging of cast structures, hot and cold open-die forging of recrystallized structures, fracture-controlled defect formation, establishing effects of process variables and secondary tensile stresses on forgeability, and flow-localization-controlled failure are some common tests. The workability test used for closed-die forging is also summarized.

The relative motion between the tool and the workpiece during cutting compresses the work material near the tool and induces a shear deformation that forms the chip. This article discusses the fundamental nature of the deformation process associated with machining. It describes the mechanics of the machining process, and presents the principles of the orthogonal cutting model. The article also analyzes the effect of workpiece properties on chip formation.

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.

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 discusses a set of experimental and computational studies aimed at understanding the effect of various processing parameters on the extent of burr and other defect formation during sheet edge-shearing and slitting processes. It describes the development of experimentally validated finite-element models for analyzing the classes of shearing processes. The article also discusses the use of microstructural characterization with stereology to render three-dimensional volumetric parameters. It concludes with information on the numerical simulation of an edge-shearing process, along with sensitivity studies with respect to process and tool parameters.

This article describes the mechanics and processing characteristics of equal-channel angular extrusion (ECAE). Tool design considerations for the ECAE are discussed. During ECAE, severe plastic strains and simple shear deformation mode contribute to strong, sometimes unusual effects of processing on structure and properties. The article explains these effects and concludes with a discussion on the applications of the ECAE.

This article provides a brief description of the different types of micromechanisms of monotonic and cyclic fracture. General information on the material variables that have the most beneficial effect on resistance to failure is presented. The article discusses the various stages, growth rates, and striation spacings of fatigue crack. The mechanisms of fatigue striation formation are also discussed. The fatigue crack growth in duplex microstructures and cyclic crack growth in polymers are reviewed. The article also describes the mechanisms and models of fatigue crack closure.

Filament winding is a process for fabricating a composite structure in which continuous reinforcements, either previously impregnated with a matrix material or impregnated during winding, is placed over a rotating form or mandrel in a prescribed way to meet certain stress conditions. This article describes the advancements in filament winding and lists the advantages and disadvantages of filament winding. It discusses the effects of fiber tension in filament winding and the selection of fibers, resins, and materials for filament winding. The article emphasizes the three basic filament-winding patterns, such as helical, polar, and hoop. It presents information on the applications of filament winding, including rocket motors, natural gas vehicle (NGV) tanks, and sporting goods. The article presents recommendations for the basic design guidelines for filament-winding design/manufacturing process and concludes with a discussion on fabrication recommendations.

Friction stir welding (FSW) involves plastic deformation at high strain rates and elevated temperatures with resultant microstructural changes leading to joining. This article provides a link between deformation and FSW process parameters and summarizes the results of experimental temperature measurements during FSW of various metals. It considers the physical explanation of the heat input during FSW and the possible methods of their estimation. The article presents the experimental results of two analytical models, supplemented by experimental/numerical flow models on material flow during FSW. The types of defects, processing parameters affecting the generation of these defects, and results of theoretical models and simulations to understand the formation and control of defects during FSW are discussed. The article concludes with information on the microstructure and its distribution produced during FSW.

The processing of steel involves five distinct sets of texture development mechanisms, namely, austenite deformation, austenite recrystallization, gamma-to-alpha transformation, ferrite deformation, and static recrystallization during annealing after cold rolling. This article provides an introduction on crystallographic textures. It discusses the effects of austenite rolling and recrystallization on the texture and transformation behavior of recrystallized austenite and deformed austenite. The article illustrates the overall summary of the rolling and transformation behavior. It details cold-rolling textures, annealing textures, and recrystallization textures of steel samples. The article concludes with a summary of texture development during cold rolling and annealing.

This article discusses the mechanics of chip formation and reviews the analytical modeling of the chip formation process by high-speed machining within the framework of continuum mechanics. It examines the relationship between the various high-speed machining parameters. The article describes the cutting tool systems for aluminum alloys, steel, superalloys, and titanium alloys and provides an overview of the alternative cutting tool geometries for increasing tool life. It highlights the factors considered by companies planning to employ high-speed machining systems and concludes with information on the applications of high-speed machining.

This article discusses the most important factors required for cutoff methods. It explains the operations of machines used for the punching, shearing, notching, or coping of plates, bars, and structural sections. The article describes the effects of the blade angle and speed on the shear blade life. It reviews the design requirements and best practices for the production of blades. The article compares double-cut dies with single-cut dies used for shearing of structural and bar shapes. The shearing of specific forms, such as angle iron and flat stock, is also discussed. The article describes the advantages of hydraulic bar and structural shears. It concludes with information on the principle and construction of impact cutoff machines.

This article provides practical guidance for interpreting macroscale fracture appearances. It focuses on metallic fracture features. The article covers the important distinctions between ductile and brittle fracture and the influence of the type of loading on the facture-surface orientation. It discusses both ductile fracture and brittle fracture macroscale features. Finally, it delves into fracture-initiation sites and metal-processing effects on fracture appearance, including castings, powder metals, additive manufacturing, and surface treatments.

This article provides information on the typical experimental observations of formation and propagation of small fatigue cracks under various stress states and explores the relation to long crack fracture mixed-mode fracture mechanics. It discusses state I crystallographic and stage II normal stress-dominated growth, along with some observations regarding the influence of combined stress state on the propagation of small cracks. The article discusses the differences between low-cycle fatigue and high-cycle fatigue (HCF) behaviors. Several other features of multiaxial fatigue are also explained, including mean stress effects, sequences of stress/strain amplitude or stress state, nonproportional loading and cycle counting, and HCF fatigue limits. In addition, the article covers the formation and propagation of cracks on the order of several grain sizes in diameter in initially isotropic and ductile structural alloys.