Strengthening mechanisms, deformation behavior, and anisotropic mechanical properties of Al-Li alloys: A review

Generalised forming limit diagrams showing increased forming limits with non-planar stress states

A review on forming techniques for manufacturing lightweight complex—shaped aluminium panel components

The influence of tool rotation on an incremental forming process

Numerical simulations are being deployed widely for product design. However, the accuracy of the numerical tools is not yet always sufficiently accurate and reliable. This article focuses on the current state and recent developments in different stages of product design: springback prediction, springback compensation and optimization by finite element (FE) analysis. To improve the springback prediction by FE analysis, guidelines regarding the mesh discretization are provided and a new through-thickness integration scheme for shell elements is launched. In the next stage of virtual product design the product is compensated for springback. Currently, deformations due to springback are manually compensated in the industry. Here, a procedure to automatically compensate the tool geometry, including the CAD description, is presented and it is successfully applied to an industrial automotive part. The last stage in virtual product design comprises optimization. This article presents an optimization scheme which is capable of designing optimal and robust metal forming processes efficiently.

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Numerical product design: Springback prediction, compensation and optimization

Superplastic forming is a hot forming process to manufacture components characterized by a complex shape The ability of the material to deform depends on the process parameters and the intrinsic properties of the material However, superplastic forming is a stretch forming process that can involve tears or a non-uniform thickness in the part For this reason, in this paper a design of a superplastic forming process by using a multiphase process connected to a forming limit curve is proposed, with the aim of redistributing the thicknesses of the product component in a manner as uniform as possible

Influence of multiphase forming approach on the thickness uniformity of components from superplastic PbSn60 alloy

This work investigated the influence of the strain distribution on the material formability during hot free bulging of circular metal sheet. The strain distribution was altered by carrying out the hot free bulging on a blank characterized by a variable thickness. Some AA2017 aluminum alloy blanks, characterized by both a constant and a variable thickness, were subjected to the free bulging process at a temperature of 405 °C. The blanks with a variable thickness showed a greater degree of formability (measured in terms of forming depth) compared to the blanks with a constant thickness; thus, confirming the theoretical evidence.

Influence of blank variable thickness on the material formability in hot gas sheet metal forming process

In this study a fast procedure for determining the constants of superplastic 5083 Al alloy at 723 K is analyzed. To evaluate the displacement and the thickness evolutions at the dome apex of the metal sheet bulge forming experiments at constant pressure are performed. The displacement-time curves at the constant pressures of 0.30, 0.35, 0.40, 0.45 and 0.50 MPa are obtained by laser measurements whereas many bulging tests at the same gas pressures stopped up at prefixed intervals of time were carried out to evaluate the thickness at the dome apex. Direct measurements of the thickness were obtained using a centesimal micrometer. It is known that an equibiaxial stress state is present at the dome apex of the metal sheet. In contrast, at other locations, a nonequibiaxial stress state prevails. Due to the nonequibiaxial stress state, the thickest location occurs at the sheet periphery and the thinnest location at the dome apex. Therefore, by using the finite element method, it is possible to accurately analyse the superplastic forming process in the real stress state conditions. The material behaviour is modelled by the power law relationship between the effective flow stress, the effective strain and the effective strain-rate. In the power law relationship the strain-rate sensitivity index, m, is a constant, n and K are variables that are functions of the effective strain-rate. Experimental results allowed to easily determine the value of m. Moreover, by means of some numerical simulations it was possible to determine the values of n and K and associate them with specific strain-rates. The results of comparison of the numerical simulations of a bulge forming process with the experimental tests have shown good agreement and they indicate that the material constants are reliable.

Constitutive Modelling of Superplastic AA-5083

Superplastic materials show very large tensile elongation (in excess of 5000%) even if they are lowly stressed. Superplastic forming is carried out at high temperatures and relatively low strain rates. In order to control the industrial forming processes, the difficulty in predicting the failure strain of superplastic materials is main problem faced by technologists. In this paper, limit strain for superplastic materials were investigated under biaxial tension using the finite element method (FEM). To validate the results biaxial tension tests have been conducted using a fine-grained Pb-Sn alloy that shows superplastic properties at room temperature. The superplastic sheet was deformed using an experimental apparatus with dies of aspect ratios of 1:1, 15:11, 5:3 and 5:2.

Gillo Giuliano

Papers

Influence of multiphase forming approach on the thickness uniformity of components from superplastic PbSn60 alloy

Influence of blank variable thickness on the material formability in hot gas sheet metal forming process

Constitutive Modelling of Superplastic AA-5083

Analysis of forming limit diagram for superplastic materials

Formability of superplastic PbSn60 alloy