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The forming limit diagram (FLD) is one of useful parameters for evaluating the formability of sheet metal, and has been currently used in the development of forming processes of autobody panels. Also FLD plays an important role for the prediction of fracture in the analyses by numerical forming simulation. In this paper the influencing factors on FLD were examined experimentally. The experimental results of FLD depend on the experimental conditions such as tool shape and dimension, lubricant, gauge length and measuring preciseness. The effect of straining path on FLD is seemed large, but it is complicated to obtain FLD in complex straining paths experimentally. For efficient application of FLD in tool design and making, and stamping shops, there are still remained some problems to be solved.

The application of tailored blanks to autobody parts has progressed because of its numerous advantages. The forming of tailored blanks has, however, a lot of technical problems. Among the problems, weld-line movement and formability deterioration are the most significant ones in case of deep drawing. The weld-line movement and formability change were examined experimentally as a function of weld-line location in square cup deep drawing. The weld-line movement of tailored blank consists of two sources. One is the geometrical reason, and the other is due to the hardening of weld bead. The formability of tailored blank is inferior to that of an original blank by the existence of hardened weld region. The mode of fracture changes from wall breakage to a fracture adjacent to punch radius when the weld-line was close to the punch corner.

In automobile companies new techniques of sheet metal forming have been developed and some of them are applied practically in order to solve the social demands to automobile. Sheet materials makers have also developed new materials with good formability in response to the requests of automobile companies. Current topics of sheet metal forming techniques in Japan are; (1) Stamping of high strength steel and aluminum alloy sheets for weight reduction of autobody, (2) Stamping of tailored blanks, (3) Application of new forming techniques such as hydro-mechanical forming and blank holding force control, and (4) Practical application of FEM simulation to die making and stamping processes for the reduction of preparation time and the optimization of forming processes.

The shape and dimensional failures were investigated by the hat-shape bend forming and the model forming of a door outer panel. In the hat-shape bend forming the springback and the side wall curl after forming depend on the strength of sheet material, the shape and dimension of tools, lubricants and the blank holding force. In the forming of door outer model panel the surface deflection around a handle portion appeared distinguishably. In order to suppress the surface deflection such a countermeasure as bottoming is required. It is difficult to change the material properties in a wide range in the manufacturing processes of aluminum alloy sheets. Therefore the development of forming techniques suitable for aluminum alloy sheets is desired.

The practical application of high strength steel sheets to autobody parts has been increased year by year in order to promote weight reduction and ensuring safety. New types of high strength steels with good formability have been developed and the average weight ratio of high strength steel in a whitebody is over 20 % in Japan. In the near future the weight ratio of high strength steel in a whitebody is estimated as over 40 %. In the forming of high strength steel sheets it is difficult to suppress geometrical failures and dimensional inaccuracy. The developments of forming techniques and their suitable application are required to succeed the forming of high strength steel sheets.