D.H. Jang

The Forming Characteristics of Simultaneous Radial-Forward Extrusion Processes

Numerical simulations are applied to investigate the simultaneous radial-forward extrusion process in a combined extrusion such as subsequent radial-forward extrusion after radial extrusion. Design factors for the process such as gap height, deflection angle into annular gap and frictional condition are employed in the analysis. The analysis is focused to see the influence of design factors on the maximum force requirement for the forming process. One of the selected simulation results is compared with the experiments in terms of load-stroke relationships. The pressure distributions exerted on the die-wall interfaces are also investigated to reveal if the tooling system is safe, especially the die set. The plastic stress-strain relationship is derived analytically from the material constants used in elastic deformation analysis. It is revealed from the simulation results that the influence of the deflection angle on the maximum force requirement for the process is greatest among design parameters. AA 6063 alloy is selected as a model material for the analyses in this study.

The process sequence design of a power-assisted steering part

Abstract Conventional and new forging processes of a power-steering worm blank are analyzed by the rigid–plastic finite element method. The conventional process contains three stages such as indentation, extrusion and upsetting, and was designed by a forming equipment expert. Process conditions such as reduction in area, extrusion angle and upsetting ratio are considered to prevent internal or geometrical defects. The results of simulation of the conventional forging process are summarized in terms of deformation patterns, load–stroke relationships and die pressures for each forming operation. Based on the simulation results of the current three-stage process, a power-steering worm blank forging process for improving the conventional process sequence is designed. The die pressures and forming loads of the proposed process are within the limit value, which was set by experts and the proposed process is found to be suitable for manufacturing the power-steering worm blank.

A Study on the Forming Characteristics of Clinching Joint Process

This paper is concerned with joining of thin metal sheets by single stroke clinching process. This method has been used in sheet metal work as it is a simple process and offers the possibility of joining similar-dissimilar thin sheet metals. Clinching generates a joint by overlapping metal sheets deforming plastically by punching and squeezing sequence. AA 5754 aluminum alloy of 0.5 mm thick sheets have been selected as a modal material and the process has been simulated under different process conditions and the results have been analyzed in terms of the quality of clinch joints which are influenced mainly by tool geometries. The rigid-plastic finite element method is applied to analyses in this paper. Analysis is focused mainly on investigation of deformation and material flow patterns influenced by major geometrical parameters such as die diameter, die depth, groove width, and groove corner radius, respectively. To evaluate the quality of clinch joints, four controlling or evaluation parameters have been chosen and they are bottom, neck thickness of bottom and top sheets, and undercut thickness, respectively. It has been concluded from the simulation results that the die geometries such as die depth and diameters are the most decisive process parameters influencing on the quality of clinch joints, and the bottom thickness is the most important evaluation parameter to determine if the quality of clinch joints satisfies the demand for industrial application.

Influence of Punch Nose Radius on the Surface Expansion

This paper is related to an analysis on the surface expansion in backward can extrusion process using spherical punches. It is generally known that the backward can extrusion process usually experiences severe normal pressure and heavy surface expansion. This is a reason why the backward can extrusion process is one of most difficult operations among many forging processes. Different punch nose radii have been applied to the simulation to investigate the effect of punch nose radius on the surface expansion, which is a major effort in this study. AA 2024 aluminum alloy is selected as a model material for investigation. Different frictional conditions have also been selected as a process parameter. The pressure applied on the punch has been also investigated since heavy surface expansion as well as high normal pressure on the tool usually leads to severe tribological conditions along the interface between material and tool. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including strain distributions and maximum pressure exerted on the workpiece and punch, the effect of punch nose radius and the frictional condition on the surface expansion and the location and magnitude of maximum pressure exerted, respectively.

A Study on the Process Design of Cold-Forged Automobile Parts

The cold forging processes of automobile parts such as piston-pin, valve-spring retainer(VSR) and power-assisted steering part (PAS) are analyzed by the rigid-plastic finite element method. The results of the simulation on the piston-pin are summarized in terms of the strain distribution and load-stroke relationship. Based on the analysis on the current processes of VSR and PAS, the new novel processes for improving the conventional process sequences are designed. As a design criterion, the improved processes satisfy the new condition such as an initial billet size, the production time and the limit value of forming load and pressure etc. The present simulation results and the newly developed process gave rise to an improvement in manufacturing processes for cold-forged automobile parts. Furthermore, the numerical analysis for the processes in this study provides a new design concept for forming processes and a basis for the selection of forging equipments.

An Analysis of the Riveting Process as 2-D Frictional Contact Problem

A frictional contact model is adopted for the analysis of conventional solid rivet setting. Material properties for the selected plates and rivets are obtained from analytical method using elastic constants and tensile strengths for each material. Rigid- and elasto-plastic models are selected for process analysis in this paper. Process variables are selected to investigate the effect of variables on the successful rivet setting and servicing in any structure as force transmitting member. Major variables in riveting process are material variables such as material properties and geometrical variables, which are dimensions of head, shank, and blank diameters. Analysis in this study is concentrated on the influence of variety of materials and of shank dimensions on the contact area after rivet setting, i.e. after forming process of rivet head. Soft and hard materials are selected as mother materials to investigate how the selection of material influences on the riveting process in quantitative manner. The geometry of head is closely investigated through simulation in terms of contact status, i.e. contact area between rivet head and mother material, which would affect the snap fit joint by riveting.

FE Analysis on the Serrated Forming Process using Multi-action Pressing Die

In this paper, the serrated forming process is analyzed with finite element method. The seal should secure the overlapping portions of ligature, which has teeth for ligature to prevent from slipping each other after clamping. In the simulation, rigid-plastic finite element model has been applied to the serration forming process. Serration or teeth forming characteristics has been analyzed numerically in terms of teeth geometry based on different forming conditions. Analyses are focused to find the influence of different die movements and geometries on the tooth geometry, which is crucial for securing overlapping portions of ligature. Two major process variables are selected, which are the face angle and entry angle of punch, respectively. Extensive investigation has been performed to reveal the influences of different entry and face angles on the geometry of teeth formation in the simulation. Three different face angles of punch have been selected to apply to each simulation of serrated sheet forming process with every case of punch entry angles. Furthermore, tooth geometries predicted from simulation have been applied to the indention process for comparing proper tooth geometries to secure the sealing.

Inhomogeneous Deformation Between Construction Materials in the Cu/Al and Fe/Al Co-extrusion Processes

This paper is concerned with the analysis of plastic deformation of bimetal co-extrusion process. Two sets of material combination have been adopted for analysis, i.e. combinations of Cu/Al and Fe/Al. In the first set of material combination, the selected materials are AA 1100 aluminum alloy as hard material and CDA 110 as soft one. This type of material selection is to examine the effect of hard core and soft sleeve and vice versa on the deformation pattern in terms of plastic zone and velocity discontinuity along the contact surface between construction materials. Four different cases of co-extrusion process in terms of material combination and interference bonding were simulated to investigate the effect of material arrangement between core and sleeve, and of bonding on the plastic zones and velocity discontinuity. In the other set of material combination, model materials used as core and sleeve were AA 1100 and AISI 1010, which are relatively soft and hard, respectively. Process parameters except diameter ratio of core to sleeve material such as semi-die angle, reduction in area in global sense and die comer radius have been set constant throughout the simulation to concentrate our effort on the analysis of influence of diameter ratio on deformation behavior such as deformation zone, surface expansion, exit velocity discontinuity between composite materials, and extrusion forces.

Finite Element Analysis of the Compaction Processes for Hollow Three-Level (Class IV) Components

The yield criterion describing asymmetric behavior of powdered metal compacts in tension and compression is introduced by modifying that used for sintered powdered metals. The plasticity theory related to the modified yield criterion is reviewed and summarized for a powdered metal compact. The constitutive equation is applied to the variational principle and its discritization is also introduced. Axisymmetric die pressings with copper powders were performed to see the deformation mechanics of hollow three-level parts. The simulation includes two different types of multiple-motion tooling compaction of a Class IV part of hollow three-level component. Predictions are made for density distributions, load-stroke relationships, average density as function of height, pressure distributions along the die-walls and punches, average compact densities at each level, and energy consumption for each pressing. The information from simulation can be used to synthesize the various punch motions in a multiple action tooling system.

Numerical Analysis on the Dissimilar Channel Angular Pressing by Multi-Pass Rolling

The dissimilar channel angular pressing (DCAP or CCSS) based on the equal channel angular pressing (ECAP) was numerically modeled and analyzed by means of a rigid-plastic two-dimensional finite element method. Multi-pass rolling is performed in two different manners; the feeding direction of samples into the DCAP-channel is maintained in Route A and the feeding direction is reversed in the Route B. The deformation of AA1100 sheets during the DCAP process comprises three distinct processes of rolling, bending and shearing. The shear deformation of an amount of 0.5 was concentrated at the corner of the DCAP-channel where the abrupt change in the direction of material flow occurred. Because differences in the shear deformation in Route A and Route B led to the different strain states throughout the thickness of the aluminum sheet, the strain history in the DCAP-channel was analyzed in various thickness layers by the shear and effective strain components.