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Internal high-pressure forming is a process for manufacturing lightweight components, especially automotive parts, with advantages of lower cost and weight reduction, better structural integrity and increased strength and sti ness over the conventional stamping process. One of the typical failure modes, including wrinkling, buckling and splitting, will occur through an unreasonable combination of the control parameters: the internal pressure and the axial punch feeding. In most previous papers, wrinkling is considered to be a failure mode. However, not all wrinkles are defects. The collection of materials in an expanding area by the formation of wrinkles is an alternative method for obtaining a preformed shape in the hydroforming die. In this case, the key point is to obtain`useful' wrinkles instead of`bad' wrinkles. In this paper, an investigation will be conducted on how to control the shape of the wrinkle waves and its e ect on the thickness distribution after hydroforming by using ®nite element simulation. LS-DYNA ®nite element software is used in this paper. An experiment has been carried out and the results obtained from experiment and simulation are in good agreement.

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An FEM software ARVIP‐3D was developed to simulate the process of 3‐D plastic thermoforming. The coupled thermo‐mechanical analysis, thermal stress and warpage analysis for plastic thermoforming was carried out by means of this software. Rigid visco‐plastic formula was adopted to simulate the deforming process. During this process, the method of comparing velocity, time and area was adopted as the contact algorithm at different nodes and triangular elements. Sticking contact was assumed when the nodes become in contact with tool surface. The Arrhenius equation and the Williams equation were employed to ascertain the temperature dependence of material properties. In order to analyze the temperature field of plastic thermoforming, the Galerkin FEM code and the dynamic heat conduction boundary condition were adopted; latent heat and deformation heat were treated as dynamic internal heat sources. Based on the above, the model of coupled thermomechanical analysis was established. Assuming that the thermal deformation occurs under elastic conditions, the thermal stress and the warpage following the cooling stage were estimated. Experiments of plastic thermoforming were made for high‐density polyethylene (HDPE). An infrared thermometer was used to record the temperature field and a spiral micrometer was used to measure the thickness of the part. Results of numerical calculation for thickness distribution, temperature field and warpage were in good agreement with experimental results.

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In this paper, the superplastic and isothermal hobbing process for manufacturing die cavities is described. The technical parameters, the design method of the set-up and the lubrication are also mentioned. Recently, these technologies have been applied in hobbing automobile link rod dies and other parts. By means of finite element analysis and experiments, the deformation paramaters for superplastic hobbing are obtained. They can be used in determining the process and choosing the blank sizes.

The integral hydro-bulge forming (IHBF) technology is used for manufacturing oblate spheroidal shells. A mild steel oblate spheroidal shell and a stainless steel shell were manufactured by using this new technology. The IHBF processes of the experimental shells are simulated by using an explicit finite element code, the numerical results are discussed and compared with the experimental results. Based on the numerical simulations and experimental results, a few suggestions are made for improving the new technology. [S1087-1357(00)71201-9]