Abstract
In today’s industry, waste prevention and an efficient use of resources are becoming more important due to economic and environmental requirements. Especially in forming processes such as deep drawing, a reduced use of lubricants is highly promising for saving resources and reducing production costs. Deep drawing with macro-structured tools is a novel approach to reduce the amount of friction forces and realize a lubricant free process. The induced alternating bending in sheet metal during the deep drawing process with macro-structured tools leads to an increase of its geometrical moment of inertia and consequently stabilizes the sheet against wrinkling. The induced alternating bending increases the back force in the sheet metal during the process and as a result affects the springback behaviour of the formed part. Furthermore, the resulted cyclic loading in flange area can leads to a kinematic hardening of some material. Within the scope of this paper, the influence of alternating bending on springback behaviour of parts in deep drawing process with macro-structured tools is studied. For this purpose, numerical simulations as well as experimental tests to form a U-channel with macro-structured tools are carried out.
Highlights
Lubricant is essential in the conventional metal forming to reduce the friction between tool and workpiece and forming energy, increase the forming limit, and to prolong the tool life by prevention of galling and seizure
The induced alternating bending leads to a cyclic loading in the sheet metal, which can cause a kinematic hardening for some materials
Deep drawing with macro-structured tools is a new developed process which can reduce the friction force through minimization of contact area
Summary
Lubricant is essential in the conventional metal forming to reduce the friction between tool and workpiece and forming energy, increase the forming limit, and to prolong the tool life by prevention of galling and seizure. In [4] it is shown that in order to decrease the amount of friction force for a given friction coefficient, the integral of the contact pressure over the contact area can be reduced by means of macro-structured tools. In this way, the contact area between the workpiece and tools will be reduced to a small number of lines. By increasing the geometrical moment of inertia of the sheet, this effect can be avoided In this new developed process, it is achieved by immersing the macro-structured blankholder slightly into the drawing die and inducing an alternating bending mechanism in flange area.
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