Showing papers in "Journal of Materials Shaping Technology in 1987"

Alternative binders for hard metals

Abstract: Cobalt has been the metal of choice for bonding of carbide based hard metals since their inception. Lately there has been concern about continued availability and price instability. A number of workers have looked at alternates for full or partial substitution and some of these are now commercially important. Improvement of chemical erosion resistance can be noted for nickel and chromium substitution. Additions of nickel on the one hand can stabilize the face centered cubic structure to give an austentic ductile binder whereas ruthenium can raise the F.C.C.-HCP transition temperature resulting in hexagonal binder structures associated with reduced friction effect. High strength martensitic binders can be fabricated using iron, cobalt, nickel alloys. Thus, some innovative alternates to cobalt have emerged with some technical advantage for specific areas of application.

Thermomechanical processing of iron, titanium, and zirconium alloys in the BCC structure

Abstract: The body centered cubic (bcc) metals undergo a high level of dynamic recovery during elevated temperature straining so that the stress increases monotonically to a steady-state value σs. The strain rate and σs are related by means of the power, the exponential, or the sinh law with an Arrhenius temperature relationship. The activation energy for a iron has values of 250–280 kJ/mol, whereas for β titanium and β zirconium it is in the range 134–184 kJ/mol. The structure developed during hot working consists of elongated grains containing subgrains of dimension inversely proportional to σs. In warm working of α iron (limited to below 0.66T m), the textures are similar to those for cold working. In working β titanium and β zirconium which is limited to above 0.6T m except in β stabilized alloys or as matrix in α+ β processing, the bcc textures transform into α textures. The α iron relies principally on substructure strengthening in association with carbides. The β phases can be thermomechanically processed to provide equiaxed or lamellar a in a variety of dimensions and combinations, with or without substructure. Hot working of the bcc refractory metal alloys, principally molybdenum, is similar to hot working of α iron.

Prediction of spread in hot flat rolling under variable geometry conditions

Abstract: Geometric deformation of steel blanks having a smoothly varying rectangular cross section under hot flat rolling was experimentally investigated. Specimens of different initial geometries were used. The experimental results were then utilized to develop mathematical expressions which represent the variant nature of the deformation process. These expressions were incorporated in El-Kalay and Sparling’s conventional steady-state spread formula. The resulting empirical formula related spread to the relevant process variables under the unsteady-state rolling conditions. The application of this formula is the process planning for manufacturing of a class of industrial components by rolling—whose distinct feature is the gradual change of cross-sectional size along the length.

Empirical and finite element approaches to forging die design: A state-of-the-art survey

Abstract: A survey of research concerned with the use of computer-aided techniques to simulate the forging process and design forging dies is presented here. Attention is focused on finite element models and empirical guidelines that have been developed in this connection.

Analysis of parameters and microcomputer control for the electric upsetting process for forging engine valves

Abstract: Using both theoretical analysis and practical experiment, it is clearly indicated that the electric upsetting process should be divided into two stages: preform upsetting and finish upsetting. The main process parameters influencing the forming quality of engine valves, balancing and matching of these parameters, and the microcomputer system used to control them are described. By using the microcomputer system to control the whole process automatically, the rate of efficient production could be considerably increased.

A new finite element method for binder wrap calculations

Abstract: In forming a large automobile sheet metal part in a draw die, a blank is first clamped by curved binders to form a binder wrap. This paper presents a numerical method to calculate the binder wrap. Theanalysis domain, aliaspseudo blank, is the portion of the blank which goes into the die cavity. Since its boundary is not known in advance, an iteration method is used to calculate the pseudo blank and binder wrap simultaneously.

Deformation and Interface Contact Friction in Metal Shearing Using Inclined Knife Profiles

Abstract: In industrial metal shearing operations, the profile geometry of knives has an important effect on the quality of the parting edge and the amount of shearing force involved. Compared to matching profiles (closed or open), inclined knife profile offers a lower shearing force and improves greatly the distortion at the parting edge. The degree of inclination cannot be chosen arbitrarily. Limited to certain optimum size, profile inclination is beneficial. The optimum size of inclination is dependent on the coefficient of knife-metal interface friction. In order to calculate coefficient of friction and also to facilitate the selection of other shearing parameters, evaluation of hydrostatic pressure at shear plane and interface contact pressure is of extreme importance. The evaluation of hydrostatic pressure and contact pressure necessitates a critical study of preshear deformation. In this paper, preshear deformation in an ideal shearing model has been briefly studied, using the slip line field concept, and corresponding hydrostatic pressure, contact pressure, and coefficient of friction have been evaluated. Formulae to obtain optimum size of inclination have been derived for shearing different shapes. Also, effects of section size and cutting speed are discussed.

Processing and Designing Parts Using Structural Reaction Injection Molding

Abstract: A new process called structural reaction injection molding (SRIM) has been developed to combine the high strength and modulus properties of fiber reinforced composites with the advantages of the reaction injection molding process. Along with the process, a new reactive resin has been developed expressly for the structural RIM process. With the new resin and SRIM process conventional design methods can be used, but the designer must also consider several facets of the structural RIM process.

New manufacturing techniques of large forged shell rings for pressure vessels

Abstract: A 250 ton hollow ingot was made for experimental purposes so that the properties of a large-sized hollow ingot could be simulated. The investigation results indicated that this ingot was suitable for forged shell rings of nuclear reactor pressure vessels (RPV). They were used in the manufacture of forged shell rings for an RPV of a 1300 MW type PWR and for an RPV of an 1100 MW type BWR using basic oxygen furnace, RH degassing, hollow ingot-making process. These shell rings had less segregation and clean inner surfaces which are attributed to the homogeneity of the hollow ingot.

Evaluation of woven fabric composites for automotive applications

Abstract: This paper summarizes the results of a recent study [1] funded by the National Science Foundation to investigate the feasibility of woven fabric composite materials for automotive applications. By identifying the advantages and limitations associated with woven fabric composites and by comparison with current automotive materials, the potential for successful application of these materials is investigated. In particular, strength, fatigue, moldability, and cost effectiveness have been identified as critical indicators of the potential for these materials in automotive applications. The results of an experimental evaluation of the static and fatigue properties of woven composites and comparable unidirectional tape composite laminates are discussed. An analytic model designed to quantify the effect of fabric weave configuration on relative conformability to complex geometries is also presented. Preliminary component designs utilizing woven fabric composites are considered in terms of potential weight savings, potential fabrication methods, and projected cost effectiveness. Finally, the key factors impeding the successful implementation of these materials in particular automotive structural applications are identified and reviewed.

Expert software concepts for design of P/M preforms for precision forging

Abstract: This article summarizes the results of a recent study funded by the National Science Foundation to investigate the feasibility of an expert system approach to design of P/M preforms for precision forging. The project utilized a computer-aided design (CAD) description of part geometry, artificial intelligence (AI) programming techniques, and numerical control methods of analysis. The details of implementing an expert design system were illustrated in a step-by-step example. The expert design system that emerged from this study is complex, incorporating aspects of a modular approach to expert system development. Although the feasibility of the approach was demonstrated, further work is required to produce a robust design system.