Development of a novel differential velocity sideways extrusion process for forming curved profiles with fine grains and high strength

The aim of this study is to develop a novel process, differential velocity sideways extrusion (DVSE), for forming curved profiles with fine grains and high strength. In this new forming-bending-refining process, billets are used as the work-piece material to directly form curved profiles with certain cross-sections in order to increase the manufacturing efficiency and decrease the bending defects in conventional bending process. The DVSE process has been studied in this thesis by using forming experiments, microstructure characterisation experiments, finite element (FE) modelling and theoretical modelling. A tool set enabling sideways extrusion to be performed using opposing punches moving with different velocities was designed and manufactured. Plasticine was used as a model work-piece material and a series of compression tests were undertaken, to determine its constitutive properties and gain an estimate of work-piece die friction for use in process simulation. Feasibility studies for the DVSE process were carried out through a series of designed experimental programmes on plasticine, in which punch/extrusion velocity ratio, extrusion ratio and die land length were process parameters. Ultimately, trial tests using AA1050 at room temperature and AZ31 at elevated temperatures were conducted. Effects of extrusion velocity ratio, extrusion ratio, die land length, forming temperature and strain rate on profile curvature were studied. The microstructure evolution of the formed curved AA1050 bar by DVSE at room temperature was studied through EBSD. The evolution of grain structure and texture of formed curved AZ31 bars at different DVSE process conditions (temperature and strain rate) was investigated through optical microscopy and EBSD, and the optimum temperature and strain rate condition for obtaining fine equiaxed and homogeneous microstructure was identified. The different grain refinement mechanisms of AA1050 and AZ31 during the DVSE process were revealed. Micro-hardness of formed curved AA1050 and AZ31 bars was examined. Process mechanics of DVSE were modelled using FE modelling and upper bound theorem. The extent of work-piece flow velocity gradient across the die exit orifice, which causes curvature, was identified. A dead zone of roughly triangular shape, which exists on the chamber wall opposite the die exit orifice, was determined. The effective strain of the formed curved profiles was studied to confirm the rise of severe plastic deformation (SPD). The effective strain rate in the intersection regions of the channels was investigated to identify the source of severe plastic deformation. An analytical upper-bound-based model has been developed with the consideration of the determined dead zone. The extrusion force and curvature predicted by the analytical method agreed reasonably well with results from experiments and FE modelling. Discussions were made about the correlations between experimental and modelling approaches and results. The relationships between mechanical properties (yield strength, ultimate tensile strength, and elongation to failure) and microstructures (grain size, micro-texture) of formed curved profiles were correlated. From the experimental and modelling work, it has been demonstrated that the DVSE process proposed in this thesis is an effective way to efficiently form curved aluminium and magnesium profiles with controlled curvature and improved properties.Open Acces

3D Analysis of Combined Extrusion-Forging Processes

Combined extrusion-forging processes are now getting importance for its abilities to give improved material properties, high production rate and less material waste when compared with that produced by machining, casting or by assembling the individual parts produced by different manufacturing processes. In its simplest form of combined extrusion-forging process, a billet is forged by punch and dies with punch/die or both containing an opening for extrusion. This tooling arrangement permits the simultaneous lateral spread due to forging, and backward/forward extrusion or both forward and backward extrusion simultaneously through the die/punch opening(s). The flow pattern of the material is dependent on a number of factors, including the frictional conditions at the work piece/tooling interface; the geometry of the dies, particularly the size of the dies hole; the material type; and the percentage area reductions. Due to the complexity of the analysis, and because of the large number of process variables, it is difficult to estimate the forming force required to manufacture a given component. In this direction, the present work emphasizes on estimation of forming force for forward and forward-backward extrusion-forging process of regular shapes and different tooth spur gear shapes. Though technological barriers exist, as in most manufacturing areas, it is important to overcome them by developing proper understanding of the process with related attributes. In this direction, present work emphasis on the forward and forward-backward extrusion-forging process analysis of different methodology applied to different section heads with circular shaft. Based on these guiding principles, the methodology applied are upper bound analysis (particularly reformulated spatial elemental rigid region (SERR) technique), finite element analysis (commercial package DEFORM®-3D codes), and experimentation. The understandings generated in this work not only properly explain the complex material flow mechanism but also presents in detail the upper bound analysis. The results of UBA are well validated with that of finite element analysis and experimental results. The achievements realized from the present work can be summarized as follows: Experimental studies are carried out with a view to compare some of the theoretical results predicated using the upper bound method in general, modified SERR technique in particular, with that obtained from the experiment. SERR technique is used to analysis the last stage of the combined extrusion forging process, which requires maximum load. A computational model for forward and forward-backward extrusion-forging process with and without considering friction is developed by incorporating all special features for all the section extrusions. Three formulations for forward extrusion-forging process and six formulations for forward-backward extrusion-forging processes are analyzed and the optimal solution for non-dimensional extrusion pressure is found out for further computation. The model is developed using FORTRAN code. Experiments are performed for triangle, square, pentagon, hexagon, 4-tooth, 6-tooth, 8-tooth and 12-tooth spur gear (involutes profile and pressure angle 14½º) is form using flat / square dies. Both forward and forward-backward extrusion-forging processes are carried out. FEM based commercial package DEFORM®-3D code is used for finite element analysis of the processes. The results obtained from experimental investigation are found to be in good agreement with the similar one predicted by theoretical analysis using the proposed modified SERR technique and finite element analysis

An analysis of an axi-symmetric extrusion process

Ph.D

Upsetting of hollow flanged components.

Imperial Users onl

A computer package for simulation and analysis of rotary forging

This thesis presents the development of a software package to simulate and graphically represent the tool/workpiece kinematics in rotary forging. A hypothetical workpiece of non-constant volume is always used. Share changes are achieved by a process of material removal, analogous to metal cutting. Using a quantitative approach, the software is shown to be capable of calculating the tool/workpiece instantaneous contact zone and the volume of material being removed. The software has been developed and used to produce an analysis of radially configurated conic tools. This is believed to be a unique approach to the simulation of the rotary forging process. Various types of rotary forging machines can be identified by the motion of the conic tool and the hypothetical workpiece. A mathematical/ geometrical model is developed which can be used to simulate all possible rotary forging die motions. The model is used to determine the position in space of any point on the die, regardless of its motion and geometry. The software development has been used to graphically simulate the loci of points on a die, during movement of the die. The mathematical model is used to simulate a non-constant volume workpiece consisting of a large number of concentric cylinders of specified height and radius, with infinitesimal thickness. The interaction between tool and workpiece is achieved by using a method of geometric comparison. This allows an assessment of changes in the shape of the workpiece. Extension of the program, using a generated mesh, results in a numerical analysis of the rotary forging process. The data generated from the simulation phase, incorporating some previously developed software, is used to calculate the instantaneous area of contact and the volume of material being removed. Radially configurated tooling is achieved by the introduction of a database, into the software package. Guidelines are established for the practical design of radially configurated tools. The ability of the program to interact radially configurated tools with non-constant volume workpieces, is graphically/numerically investigated. The developed program could offer many potential applications in areas such as: the calculation of forming loads and stresses, pressure distribution, etc. Further, the program can establish some basic boundary conditions; which are essential information for the development of any finite element package for predicting metal flow in rotary forging

Finite Element Analysis and Experimental Study on the Effect of Extrusion Ratio during Hot Extrusion Process of Aluminium Matrix Composites

The finite element (FE) analysis on the effect of extrusion process parameter namely, extrusion ratio at different billet temperatures on the plastic strain and strain rate of aluminium matrix composite during hot extrusion process has been dealt. The dynamic explicit FE code in ANSYS 15.0 workbench was used for simulation. The FE analysis was carried out on the SiC reinforced aluminium matrix composites for three extrusion ratios 4:1, 8:1 and 15:1, for the billet temperatures in the range 350 °C - 450 °C in steps of 50 °C. The plastic strain and strain rate were found to increase with increase in the extrusion ratio. A minimum strain and strain rate was found to occur at the billet temperature of 450 °C. The silicon carbide particles reinforced aluminium matrix composites were then extruded at the optimised temperature of 450 °C for various extrusion ratios as mentioned above. The effect of extrusion ratio on the microstructure and surface quality of extruded rod was studied

Experimental investigation and 3d analysis of combined extrusion-forging process

Combined extrusion-forging is a metal forming process where the billet is forced through the extrusion and forging dies to get the required product. Combined extrusion-forging processes are now getting importance because of improved mechanical properties, less capital cost, high production rate and less material waste when compared to conventional manufacturing processes like casting and machining. Combined extrusion-forging is used in the manufacturing of a wide range of engineering components. Due to the complexity of the forming process and because of so many process variables, it is difficult to predict the forming load required to manufacture a given component. The present research work emphasizes on the estimation of forming force for combined extrusion-forging process of Collet chuck holder. Experimental studies are carried out to compare the results obtained from the Finite element analysis simulation. Experiments are performed for Collet chuck holder using aluminum billet using required die sets in ambient temperature. Metal flow patterns and filling of die cavities has been studied in the experimental analysis. The modelling has been done by using 3D modelling software Solid works and simulation through the finite element analysis. The results obtained from the simulation results are in good agreement with the experimental results

Numerical modelling of the aluminium extrusion process

The extrusion of aluminium alloys involves the shaping of the product from an homogenised billet into a complex shape. In addition the properties of the extrudate are closely related to the processing parameters (temperature, stain rate, and material morphology). Since all the parameters vary throughout the ram stroke and throughout the billet the prediction of the condition of the extrudate is complex. In this study the analysis is accomplished by the use of finite element analysis coupled with sub-illodelling of the structural features. The study is extended to include the lieat-treatment process necessary for precipitation hardened alloys subsequent to the process. The author has published these results in a number of learned journals and these are given in Appendix. After a concise introduction and crirical literature review chapter3 analyses the basic operation of the finite element package(FEM) discussing the procedures involved, the equilibrium equations and the more practical aspect of the mesh morphology and size. Finite Element analysis and material structural models have been integrated using parallel processing technology and program sub-routines. In this section the external inputs are also defined paying particular attention to the friction conditions and the constitutive equations. The thesis then proceeds to describe and analyse the integrated modelling of the process necessary to introduce the user introduction of the equations necessary to produce a comprehensive analysis of the material structural problems. This includes the cellular automata teclu-iiques. Various complex extrusion geometries are analysed and the effects of scaling considered. Development of the extrudate surface and criteria for ptedicting this important feature are coinprehebsivcly covered in chapter 5 whilst chapter 6 considers some special technologies such as the use of pockets to obtain homogenous structures. Isothermal extrusion is also included in this section

Rigid-plastic finite element analysis of some metal forming processes

Imperial Users onl

A computer package for simulation and analysis of rotary forging

This thesis presents the development of a software package to simulate and graphically represent the tool/workpiece kinematics in rotary forging. A hypothetical workpiece of non-constant volume is always used. Share changes are achieved by a process of material removal, analogous to metal cutting. Using a quantitative approach, the software is shown to be capable of calculating the tool/workpiece instantaneous contact zone and the volume of material being removed. The software has been developed and used to produce an analysis of radially configurated conic tools. This is believed to be a unique approach to the simulation of the rotary forging process. Various types of rotary forging machines can be identified by the motion of the conic tool and the hypothetical workpiece. A mathematical/ geometrical model is developed which can be used to simulate all possible rotary forging die motions. The model is used to determine the position in space of any point on the die, regardless of its motion and geometry. The software development has been used to graphically simulate the loci of points on a die, during movement of the die. The mathematical model is used to simulate a non-constant volume workpiece consisting of a large number of concentric cylinders of specified height and radius, with infinitesimal thickness. The interaction between tool and workpiece is achieved by using a method of geometric comparison. This allows an assessment of changes in the shape of the workpiece. Extension of the program, using a generated mesh, results in a numerical analysis of the rotary forging process. The data generated from the simulation phase, incorporating some previously developed software, is used to calculate the instantaneous area of contact and the volume of material being removed. Radially configurated tooling is achieved by the introduction of a database, into the software package. Guidelines are established for the practical design of radially configurated tools. The ability of the program to interact radially configurated tools with non-constant volume workpieces, is graphically/numerically investigated. The developed program could offer many potential applications in areas such as: the calculation of forming loads and stresses, pressure distribution, etc. Further, the program can establish some basic boundary conditions; which are essential information for the development of any finite element package for predicting metal flow in rotary forging