Search Results for deformation mode

Plastic deformation can occur in metals from various mechanisms, such as slip, twinning, diffusion creep, grain-boundary sliding, grain rotation, and deformation-induced phase transformations. This article emphasizes on the mechanism of slip and twinning under cold working conditions. It discusses the factors on which the structures developed during plastic deformation depend. These factors include crystal structure, amount of deformation, composition, deformation mode, and deformation temperature and rate. The article illustrates the microstructural features that appear after substantial deformation when revealed through metallographic investigation.

Compression tests are used for subscale testing and characterizing the mechanical behavior of anisotropic materials. This article discusses the characteristics of deformation during axial compression testing, including deformation modes, compressive properties, and compression-test deformation mechanics. It describes the procedures for the use of compression testing for the measurement of the deformation and fracture properties of materials. The article provides a detailed discussion on the technique involved in determining the stress-strain behavior of metallic materials based on the ASTM E 9, "Compression Testing of Metallic Materials at Room Temperature." It also reviews the factors that influence the generation of test data for tests conducted in accordance with the ASTM E 9 and the capabilities of conventional universal testing machines for compression testing.

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 examines aluminum forging processes, including open-die, closed-die, upset, roll, orbital, spin, and mandrel forging, and compares and contrasts their capabilities and the associated design requirements for forged parts. It discusses the effect of key process variables such as workpiece and die temperature, strain rate, and deformation mode. The article describes the relative forgeability of the ten most widely used aluminum alloys, and reviews common forging equipment, including hammers, mechanical and screw presses, and hydraulic presses. It also discusses postforge operations such as trimming, forming, repairing, cleaning, and heat treatment.

Dynamic mechanical analysis (DMA) is a powerful tool for studying the viscoelastic properties and behavior of a range of materials as a function of time, temperature, and frequency. This article describes various systems and equipment used in DMA setup and discusses the processes involved in preparation of test specimen for DMA measurements. Some factors to be considered when calibrating the DMA instrument are provided, along with a description on processes for interpreting the temperature and frequency dependence of DMA curves as well as the applications of DMA.

This article examines the understanding of persistent material changes produced in stainless alloys during light water reactor (LWR) irradiation based on the fundamentals of radiation damage and existing experimental measurements. It summarizes the overall trends and correlations for irradiation-assisted stress-corrosion cracking. The article addresses the effects of various radiation factors on corrosion. These include radiation-induced segregation at grain boundaries, radiation hardening, mode of deformation, radiation creep relaxation, and radiolysis. The article discusses a variety of approaches for mitigating stress-corrosion cracking in LWRs, in categories of water chemistry, operating guidelines, new alloys, design issues, and stress mitigation. It concludes with a discussion on the irradiation effects of irradiation on corrosion of zirconium alloys in LWR environments.

This article begins with a discussion on the energy sources used for thermal forming. These include electric induction coil, gas flame, plasma torch, and laser beam. The article discusses the mechanisms of forming and different modes of deformation. It describes the effect of process and material parameters on forming and the effect of metallurgical changes on mechanical property and microstructure of stainless steel. The article concludes with information on the applications of thermal forming.

Coextrusion is defined as the simultaneous extrusion of two or more metals to form an integral product that can be carried out using conventional extrusion or drawing equipment at a temperature appropriate to the metal system being formed. This article discusses the applications, billet configurations, and metal flow modes of coextrusion. It presents the analytical studies of coextrusion: deformation energy methods, lower-bound (slab) analyses, upper-bound analyses, and finite-element analyses. These studies are used to identify the regime of material properties and process variables for which sound extrusions can be obtained. The article concludes with a discussion on the state-of-the-art of coextrusion that assists in developing process models, which accurately describe both the macroscopic and microscopic aspects of a process.

This article provides an in-depth treatment on the deformation and recrystallization of titanium alloys. It provides information on the predominant mode of plastic deformation that occurs in titanium in terms of the most common crystallographic planes. The article explains the relationship of the recovery process to the recrystallization, grain-growth process, and the effects of time and temperature on stress relief. It describes the factors that influence the rate of recrystallization and the conditions required for neocrystallization to occur. The article explains the mechanism of strain hardening and its effects on the mechanical properties of titanium alloys. It also discusses the factors that influence the superplasticity of titanium alloys.

This article outlines several polycrystal formulations commonly applied for the simulation of plastic deformation and the prediction of deformation texture. It discusses the crystals of cubic and hexagonal symmetry that constitute the majority of the metallic aggregates used in technological applications. The article defines the basic kinematic tensors, reports their relations, and presents expressions for calculating the change in crystallographic orientation associated with plastic deformation. It surveys some of the polycrystal models in terms of the relative strength of the homogeneous effective medium (HEM). The article analyzes the anisotropy predictions of rolled face-centered-cubic and body centered-cubic sheets and presents simulations of the axial deformation of hexagonal-close-packed zirconium. The applications of polycrystal constitutive models to the simulation of complex forming operations, through the use of the finite element method, are also presented.

Successful application of forging and hot pressing involves careful consideration of powder preparation and forming process parameters. This article describes the important process features for powder forging and hot pressing, along with specific applications and materials used.

Wear, a form of surface deterioration, is a factor in a majority of component failures. This article is primarily concerned with abrasive wear mechanisms such as plastic deformation, cutting, and fragmentation which, at their core, stem from a difference in hardness between contacting surfaces. Adhesive wear, the type of wear that occurs between two mutually soluble materials, is also discussed, as is erosive wear, liquid impingement, and cavitation wear. The article also presents a procedure for failure analysis and provides a number of detailed examples, including jaw-type rock crusher wear, electronic circuit board drill wear, grinding plate wear failure analysis, impact wear of disk cutters, and identification of abrasive wear modes in martensitic steels.

This article reviews the mechanical behavior and fracture characteristics that discriminate structural polymers from metals. It provides information on deformation, fracture, and crack propagation as well as the fractography involving the examination and interpretation of fracture surfaces, to determine the cause of failure. The fracture modes such as ductile fractures and brittle fractures are reviewed. The article also presents a detailed account of various fracture surface features. It concludes with several cases of field failure in various polymers that illustrate the applicability of available analytical tools in conjunction with an understanding of failure mechanisms.