This paper reports the results of modelling of the spinning of thin sheet aluminium with the MSC MARC finite element (FE) package and its domain decomposition facility using Patent MPI software. The use of networked computers, both single and dual processor machines, is compared. The network used consists of over twenty computers and a 3COM switch with a nominal capacity of 100Mbit/s. The effect of reduced network capacity is noted. The effect of increasing the number of computers involved is investigated in terms of resulting solution times. The results show the potential for large reductions in solution times. The impact of the background support of a network solution on the conventional computer user is examined.Partitioning of the model into ‘super-elements’ or separate domains is reviewed. Various partitions of the meshed geometry are compared, giving some indication of where pitfalls may lie in this critical aspect of multi-domain FE models.The results of the modelling are compared with experimental measurements of a conventional spinning operation using a CNC lathe. A flat disk is formed by a spinning operation into a dished shape. The material used is commercially pure aluminium.

Spinning is frequently used for manufacturing axi-symmetric shapes where press tooling might not be justified on grounds of size and production volumes. Spinning also has the possibility of producing parts that cannot be deep drawn. In this paper, conventional spinning is studied that is a rotational forming process that does not set out to change the sheet thickness. Both the blank and the finished product have roughly the same thickness.

This paper reports on the initial stages of a combined experimental and finite element analysis (FEA) of a deep drawing process. The objective of this research is to determine the most important factors influencing a drawing process, utilizing the help of a design of experiments and statistical analysis. The parameters varied include the punch and die radii, the punch velocity, clamping force, friction and draw depth. A deep drawing rig was designed and built for this purpose. Punches and dies of various geometries were manufactured. From previous FEA work and the experimental work performed to date, it seems that the punch/die radii have the greatest effect on the thickness of the deformed mild steel cups compared to blank-holder force or friction. The smaller is the punch/die radii, the greater is the punch force and shorter is the final draw. It has also been observed from the work to date that the speed of drawing plays an interesting role, in so far as, the higher is the speed the further is the draw, which is not entirely as expected. The cause of this will be further investigated. If the blank-holder force is not kept within the upper and lower limit of reasonable range it does have a significant effect on depth of draw, with the punch tearing through the bottom of the cup if the force is too high and if too low wrinkling of the flange area occurs. After observing the anisotropic effects of the rolling process on the sheet material through drawing it and seeing the extent of earing in the flange, some blanks were annealed for stress relief, then the draw depth was compared to that of the original mild steel blanks.

The particular cold forging process presented in this paper is the method used to form a spline shape on the head of an aerospace fastener in three forging blows. The workpiece material was Ti-6AL-4V. The first two figures of this paper illustrate the change in workpiece geometry during the final forging operation. This complicated process is a combination of extrusion (forward and backward) and forging of a very complex spline geometry.The first two stages of the forging operation were modelled using 2D finite element analysis (FEA) because of the symmetry in the workpiece geometry. Between stages two and three (shown in the first two figures), the stresses within the 2D workpiece were imported into a 3D model to enable the simulation of the spline formation.By analysing the strain, damage and flow patterns in all three stages, an in-depth understanding of the operation was obtained. The result from this analysis illustrates the powerful application of modem FEA packages for a large-scale deformation forging process. (C) 2002 Elsevier Science B.V. All rights reserved.

The results presented within this paper represent part of a larger collaborated investigation being conducted by Trinity College, Dublin and an industrial partner, The particular cold forging process analysed was the method used to 'trim' a hexagonal shape on the head of a fastener. The fastener head geometry is achieved by forcing the die, known as a trim die because of its function, onto the workpiece, whereupon a combined forging and cutting action produces the desired well-known hexagonal shape for the head. The size of the trim die modelled was that for an M6 fastener. The trim die material was taken as M2 high-speed steel.When the trim die reaches the end of its stroke, a knockout pin shears off the excess trimmed material. A finite element analysis package called DEFORM (R) was implemented to simulate the trim die forging process. DEFORM utilises Cockroft and Latham's fracture criteria to calculate the damage induced within the workpiece material during the process. Elements are deleted from the model when they exceed a specified damage value. The trim die geometry, if incorrect, can cause premature shearing of the waste material during forging. This premature shearing has a detrimental effect on tool life and the forging machinery. The relationship between the trim die geometry and its final stopping distance, the consequent induced stresses and the energy required to shear off this excess material was investigated. Finally the effect of altering the damage value C was analysed, see Eq. (1). From this investigation, conclusions as to the optimum trim die shape and final stopping distance, which would facilitate increased die life, were obtained. (C) 2001 Elsevier Science B.V. All rights reserved.

The cold-forging process analysed in this paper deals with the production of a hexagonal shape on the head of a bolt. The process utilises a die known as a "Standard Trim Die" which is forced at velocity onto the workpiece to form the bolt head. This process is a combination of cutting and forging. By definition, a cold-forging operation occurs at a temperature below the recrystallisation range of the metal being forged. Due to this fact very high forging loads are required, which in turn cause very high stresses within the die material. These high stresses can cause die failure due to overloading or fatigue. The main focus of this analysis was to predict the level of these stresses during the forging operation, and if possible to find the optimum operating conditions which would increase tool life. The analysis consisted of creating a range of different trim die geometry's using AutoCAD/mechanical desktop and importing them into the finite-element analysis (FEA) package DEFORM Due to geometrical considerations and computational limitations the initial tests consisted of two-dimensional (2D) models. Extensive analysis of these results enabled a more accurate simulation of the forging operation using three-dimensional (3D) models. Full elasto-plastic FEA, including contact and friction, was performed in order to produce the most realistic results possible for the stress distribution within both the tooling and workpiece. The FEA analysis indicated that the highest stress concentration occurred within the body of the tool and not along the contact surfaces as might first be expected. Results showing the variation in tool stress as a function of changes to the trim die cutting edge corner geometry are also presented. From these results it was possible to predict the corner fillet radii required to give the optimum geometry and hence produce the lowest stress concentration within the trim die. (C) 2001 Elsevier Science B.V. All rights reserved.

Particle Reinforced Metal Matrix Composites (PRMMC's) have proved to be extremely difficult to machine using conventional manufacturing processes due to heavy tool wear caused by the presence of the hard reinforcement. This paper presents details and results of an investigation into the machinability of SiC particle reinforced aluminium matrix composites using non-conventional machining processes such as Electro Discharge Machining (EDM), laser cutting and Abrasive Water Jet (AWJ). The surface integrity of the composite material for these different machining processes are examined and compared. The influence of the ceramic particle reinforcement on the machining process was analysed by tests performed on samples of the non-reinforced matrix material.

Spinning is frequently used for manufacturing axisymmetric shapes where press tooling might not be justified on grounds of size and production volumes. Spinning also has the possibility of producing parts that could not be deep drawn. For this paper, spinning is taken as a rotational forming process that does not set out to change the wall thickness. Both the blank and the finished product have roughly the same thickness.The objective of changing the shape of the blank to a new desired product shape is common to spinning and deep drawing. A metal part that is drawn is limited by the ductility of the material. A part that is spun is subject to far more compressive stresses and the limit of forming may in fact be due to a buckling failure rather than a tensile failure.Earlier authors have proposed various analyses of the spinning process. These highlight common process limitations. An analysis of spinning is presented which shows how the strains involved are quite different resulting in different spinning techniques. Results are interpreted to explain the rationals for multi-pass spinning operations.The material used in this work was light gauge sheet aluminium (Al 99.0-Werkstoff 30205, material condition HH, 0.2% yield 110 MPa). (C) 2000 Elsevier Science S.A. All rights reserved.

The paper reports on an investigation involving a comparison between a fibre metal laminate (FML) and typical aluminium alloy fuselage material (2024-T3). Results are presented on the effect of panel material, laminate stacking stiffness and forming load on the stress distribution within both the FML and the 2024-T3 riveted joints subjected to external loads. The stress distribution was predicted using deform, finite element code. To obtain a better understanding of the deformation process due to riveting and the stress state after elastic recovery a number of axisymmetrical models were simulated. It was noted that the forming load, ply stacking arrangement and the rivet material had a significant effect on hole fill and the initial stress distribution within the panels. The onset of delamination between the prepreg and the metal layers of the FML was predicted by examining both the radial and shear stress intensity on the interface between these two layers.

In this paper finite element methods were used to determine the influence of various coated and uncoated tungsten carbide cutting tools on the machining of a nickel-based super alloy Inconel 718. Disposable coated and uncoated carbide inserts were used both experimentally and as FEA models to study how the stress distribution within different coatings and carbide grades compared to each other, under a range of cutting conditions. Simulation of an orthogonal metal cutting process was performed using FORGE2, an elasto-visco plastic FEA code. All FE models were assumed to be plane strain. The results include the stress and temperature distributions through the primary shear zone, the chip/tool contact region and the coating/substrate boundaries. The tool wear and stress results from the FE modelling agree favourably with those obtained from experimental work.

This paper initially considers heat generation in single-point metal cutting and the direct/indirect techniques employed to measure cutting temperatures. The development of analytical models of the cutting process is briefly reviewed, including more recent work involving finite element (FE) methods. Details are given of the different FE packages and formulation methods used by different researchers. Following on from this, an FE model is presented using FORGE 2® to simulate cutting forces and temperature distributions when orthogonal turning a hardened hot work die steel, AISI H13 (52HRC), with polycrystalline cubic boron nitride (PCBN) tooling. Experimental data from infrared chip surface temperature measurements and cutting force output are used to validate the model. Good correlation was obtained between experimental and modelled results for temperature; however, the FE analysis underestimated feed force results due to a lack of adequate workpiece property data and simplistic tool/chip friction assumptions.

This paper reports on a numerical test program to model the micromechanics associated with the machining of a particle-reinforced metal matrix composite (PRMMC) The composite material modelled was a 35% by volume SiC particle-reinforced A356 aluminium alloy. A submodelling approach was adopted in order to analyse the micromechanical problem. Simulation of the metal cutting process was performed using FORGE2, an elasto-visco plastic FEA code. The micromechanical submodelling was performed using ANSYS 5.2, an elastoplastic FEA code. The machining model of the aluminium alloy without the reinforcement and the resulting hydrostatic pressure istribution were used as inputs for the ANSYS micromechanical submodels of the composite. The regions modelled included the primary shear zone, the machined surface, and the chip-tool contact region, in both the sticking and sliding regions along the rake face. All FE models were assumed to be plane strain. The results of the FE submodelling agree favourably with those obtained from machined test pieces when observed under a scanning electron microscope (SEM). Particle clustering has a detrimental effect on the rate of void growth. It was observed that SiC particles under the action of normal loads cause intense normal stresses at the point of contact between the aluminium matrix and the tungsten-carbide particles within the cutting tool. Overstraining of the matrix envelopes the SiC particle in contact with the cutting tool. A coarse grade of diamond tool had a superior wear resistance compared to a fine grade.

The work outlined in this paper involves an experimental, upper-bound analysis, with an elasto-plastic finite-element analysis of a plane-strain lateral extrusion process. Lead was used as the workpiece material so that a hot-working process could be simulated at room temperature. To obtain details of the deformation process as the material extrudes into the die branches, a square grid was scribed onto one of the mating faces of a `split' billet. The deformation of the grid was used in conjunction with the finite-element results to select the most appropriate velocity fields for use in an upper-bound analysis of the process. The results predicted by the finite-element analysis and the upper-bound results based on this analysis, compared very well with those obtained experimentally. It was found that the finite-element results provided the most upper-bound values for the forging pressure ratio and the die branch fill-out. Overall, the results show that both elasto-plastic finite-element analysis and the upper-bound method can be used with confidence to predict the important characteristics of a plane-strain lateral extrusion process.

The work reported on here is based on a finite element analysis of single and multicoated systems subjected to a simplified Hertizan normal pressure distribution to establish the influence of substrate and coating stiffness on the resulting stress distributions. The results obtained indicated that the magnitude of the direct and shear stress throughout the system, and particularly along the top contact surface and across the various interfaces, is strongly influenced by the stiffness of the substrate. The stiffness of a given coating layer also affects the magnitude of the various stresses. It was shown the thickness of a coating also influenced the resulting stresses and particularly the stress discontinuity across the various interfaces.

To establish the influence of lubrication on the surface finish of cold forged components a series of workpieces made of copper, aluminium and heading steel were forged within hexagonal and square shaped dies. Tests were performed under non-lubricated, or ''Dry'', and lubricated conditions. It was found that the surface finish was influenced by both the lubrication conditions and the particular material being forged. Under non-lubricated conditions there was a steady decrease in the surface roughness of the contact faces of the workpiece with increasing forging load, and hence less die fillout. In the case of the lubricated tests the surface finish showed variations over the forging range as the lubrication conditions changed from hydrodynamic to boundary type with increased deformation. It was also found that the tendency for tool/workpiece adhesion to occur was dependent on the particular material being forged.

In many non-steady-state metalforming processes, such as closed-die forging, the deforming material must change its flow direction at various stages during the process. The complex flow mechanism makes the calculation of tool stresses and forming forces extremely difficult. This paper presents results obtained from an experimental and analytical investigation of a combined forging-extrusion process applied to an axisymmetric component. It was established that this forging-extrusion process consisted of three distinct stages. A number of upper-bound expressions were derived to account for: the energy required for plastic deformation; to overcome friction; and to account for shearing on surfaces of internal velocity discontinuities; during each stage. Very good agreement was achieved between predicted upper-bound values for the forging pressure ratio, Pσ, and those determined experimentally.

This paper describes preliminary work on the application of an expert system to the solution of problems associated with the forging sequence design of turbine blades. An attempt is made to model the various stages of forging and to take into account material properties, forging temperatures, and inter-stage heat-treatment processes. For reasons of commercial links, the Imperial system of units is used throughout.

Because of the structure of metal-matrix composites (MMCs), the inclusion of a hard abrasive ceramic reinforcing phase makes these materials difficult to form and machine. This paper presents results from an ongoing investigation into the factors affecting the finish machining of an Al/SiC MMC. The influence of cutting tool coatings on flank wear and surface finish was investigated and it was found that a triple-coated carbide, having a top layer of TiN, performed best in terms of flank wear but gave the poorest surface finish. Overall, the worst results were obtained when machining with an uncoated carbide. The micromechanism of the cutting process was investigated with the aid of a “quick-stop” device used to produce a cut chip attached to the workpiece surface. The chip/workpiece specimens were examined subsequently using a scanning electron microscope, the SEM results indicating widespread failure due to tensile fracture rather than to shearing. The underlying cutting mechanism appeared to be quite different from that of an aluminium alloy similar in composition and mechanical properties to that of the aluminium matrix material of the MMC.

Because of the hard ceramic reinforcing component in a metal-matrix composite, these materials are difficult to machine and attempts to do so result frequently in accelerated tool wear and premature failure. This paper reports on the results from a series for drilling tests undertaken on a 25% volume fraction Al/SiC metal-matrix composite. A range of tool materials was tested, these including: coated and uncoated high-speed steel, carbide and PCD-tipped drills and solid-carbide drills. The results indicate that the hardness of the tool material has a significant influence on cutting-edge wear and on the drilling-torque and thrust-forces experienced. It was found also that the presence of a ceramic coating on a high-speed steel drill does not improve its performance appreaciably, compared to standard un-coated tools.

This paper investigates the mechanics of the deformation process associated with the formation of a permanent joint between a metal disc and a shaft when material from the disc is plastically deformed and forced to flow into a groove cut on the surface of the shaft. Cold forged disc/shaft joints were sectioned and etched to reveal the internal flow patterns within the deforming disc. In addition an elastoplastic finite element analysis was performed using a simplified model of the deformation regions to provide further evidence of the internal flow patterns. Both of these techniques indicated the presence of a flow divide centered around a neutral radius within the disc and these observations enabled the selection of suitable velocity fields for the deformation regions of the disc. These velocity fields were then used in the derivation of a series of upper-bound expressions to account for the energy dissipated in plastic deformation and in overcoming surface frictional resistance along the contact surfaces. The derived upper-bound expressions were used to estimated the change in the mean forging pressure ratio throughout the forming operation. The results obtained using the derived upper-bound expressions compared very closely to those determined experimentally.