Search results

Aerospace industry was pioneered in the use of superplastic forming (SPF) process. Weight saving is the most important need in this industry. For this reason, there is special attention paid to this method. Blow forming is a common method for SPF process. Process parameters such as temperature and pressure have significant effects on part accuracy, quality and desired characteristics. The purpose of this paper is to present a numerical and experimental investigation of process parameters in superplastic free bulge forming.

In this paper, superplastic free bulge forming of Al‐5083 has been studied. First, free bulge tests have been done at two different pressures. Bulge height variations were recorded for different pressure and temperature. The forming time was determined according to the forming pressure and temperature. Then, simulation of free bulge process has been carried out using creep behavior model at high temperature. Bulge height and thickness distribution are obtained at two different pressure settings. These results have been compared with experimental results presenting a good agreement. Also the effects of temperatures and pressure on the required process time are compared for a certain bulge height. Finally, thickness distribution profile for different temperatures, pressures and initial thicknesses have been studied.

A numerical and experimental investigation has been presented that can be used to study the process parameters. These findings show the effects of temperatures, pressure and initial thicknesses on sheet forming.

The results of this work show that higher temperature and forming pressure will reduce the required process time for a certain bulge height. Reduction of these parameters can improve thickness distribution. Also, by considering the effects of both pressure and temperature, it is shown that using lower forming pressure at higher temperature is more suitable for forming. The findings of this work can provide more understanding of the process for aircraft part designers and manufacturing process planners.

BRITAIN's new metal—superplastic aluminium—is making headway in some of the most sophisticated industries, from aeronautics to computers. The unique properties of the new material, which allows complex components to be formed in one operation, is cutting costs for an increasing number of customers.

Brief Particulars of Recently Introduced Materials likely to have Aircraft, Missile or Space Vehicle Applications. The whole business of metal forming may be turned completely upside down due to the development of new alloys which can be pushed, pulled or stretched into the required shape almost as easily as a piece of chewing gum. Because these ‘superplastic’ metals need precise heating to facilitate the shaping operation the Electricity Council Research Centre at Capenhurst, Cheshire is studying the conditions under which materials exhibit superplasticity as well as the associated processing techniques to ensure that the necessary know‐how is available to industry when superplastics come into widespread use.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

A purpose‐built superplastic forming and diffusion bonding manufacturing facility has been commissioned at the Hatfield Division of British Aerospace Dynamics Group.

The paper describes developments in the numerical analysis of metal forming processes mainly motivated by industrial applications. It deals with a complete consideration of the unsteady contact developing between the material and the die, the regeneration of the finite element mesh during the course of the calculation, and with the simulation of superplastic forming processes. In particular, an approach relating both the contact pressure and the friction force to the motion of the material relative to the die surface leads to a convenient computational procedure and to a smooth numerical behaviour under friction. The topological part of the contact algorithm appears well‐suited also for the redefinition of the discretization mesh. As a selected application, superplastic forming is considered in conclusion. Industrial practice requires the adjustment of the forming pressure to a prescribed value of the maximum rate of deformation in the material.

A numerical model for solving either elastic‐plastic, elastic‐viscoplastic or purely viscoplastic deformation of thin sheets is presented, using a membrane mechanical approach. The finite element method is used associated with an incremental procedure. The mechanical equations are the principle of virtual work written in terms of plane stress, which is solved at the end of each increment, and an incremental semi‐implicit flow rule obtained by the time integration of the constitutive equations over the increment. These equations are written using curvilinear coordinates, and membrane elements are used to discretize them. The resolution method is the Newton‐Raphson algorithm. The contact algorithm is presented and allows for applications to cold stretching and deep‐drawing problems and to the superplastic forming of thin sheets.

A numerical method is presented for analysis of the pneumatic forming process of axisymmetric superplastic thin shells. The governing non‐linear partial differential equations are derived from membrane shell theory, using total Lagrangian description and considering a hardening creep material model. The method of lines used in the computational algorithm, involves two steps: first the Cauchy problem in time is considered, then the boundary problem is solved by finite differences. The effectiveness of the proposed algorithm is illustrated by several examples.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming and powder metallurgy are briefly discussed. The range of applications of finite elements on the subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for the last five years, and more than 1100 references are listed.