Computational Solid Mechanics Laboratory 本文へジャンプ
Research on plastic working of light-metal alloys

An analysis for circular-cup deep drawing of aluminum alloy sheets

Innumerable problems regarding aluminum cans to solve
   Aluminum cans, which are familiar to us, are made by circular-cup deep drawing. Seeing aluminum cans on a routine basis, we tend to think that can manufacturing is one of mature technology. However, we still have various technical problems, and the irregularity of edge shape along the circumferential direction of cans, so-called "ear", is typical of them (see Fig.1).
   This results from the textures of metal sheets. In general, metal sheets have a crystal orientation distribution with a bias toward a certain direction depending on the manufacturing process. It is known that the deep drawing of metal sheets made through a different manufacturing process produces change in the shape of ear.
   Can manufacturers mount can lid components after removing the ears. Therefore, in order to avoid an increase in the production cost due to low yields and implement environmental protection measures such as the energy saving, materials without causing ears during the process are required.

            A moving image of circular-cup deep drawing→


    Fig.1 A deep-drawn cup with four ears     Fig.2 The texture of a material with four ears
                                           (111 pole figure)

A contribution to society that simulation techniques can give
   The objective of our study is to develop a computer software that can predict the actual shape of ears formed during deep drawing using material data obtained from a metal sheet (Fig.2). This software enables us to predict the shape of ears without experiments and propose a guideline for developing materials that form no ears in the future. Since these are quite effective in the reduction of production costs and environmental measures, a contribution to society directly connected with environmental issues can be made by simulation technique.

Fig.3 The shape of deformation for a quarter region     Fig.4 A comparison of the shape of ear

Formability of magnesium alloy rolled sheets

   Magnesium is the lightest in the practical metals, and its specific gravity is approximately two-thirds of that of aluminum and one-fourth of that of iron. Moreover, magnesium has a high strength per weight, i.e., specific strength and excellent recyclability, being now in increasing demand as an environmentally friendly material.
   However, magnesium alloys have poor plastic formability at room temperature, and it has not yet been in the actual use to form magnesium alloys by cold press, which has good productivity. Considering this circumstance, we conduct numerical simulation and some experiments to show an index for making magnesium alloys with good formability.

Modeling of materials
   It is important for numerical simulation how to construct material models that can express the deformation behavior of materials with high accuracy. For this reason, material properties are investigated through experiments or literature, being formulated and incorporated into simulation programs. Once the material models are constructed, it is possible to perform numerical experiments, or simulation with computers.

                                                Fig.5 A tensile test
Numerical simulation

   Modeling the texture inside the material, we discuss what texture should be made to improve the formability of magnesium alloys. It is observed that a change in the texture inside the material improves the formability, as shown in the figure below.

Fig.6 The effect of the textures inside a material on the strain distributions