A zipper pull tab is used to open a flap by tearing the zipper dash lines, which are produced by using a nicked blade. There are various empirical design patterns of the zipper pull tab depending on the geometrical features. In order to arrange and classify these various patterns of the zipper pull tab, the tearing characteristics of the zipper- connecting portion must be clarified, while changing some representative parameters, such as the pitch of nicks and the profile of the entry guide parts. In this work, in order to reveal the effect of the guiding route on the tearing characteristics, several fundamental patterns were chosen and the tearing tensile force response and breaking modes of the connecting portion were experimentally investigated while varying the geometric parameters and the grain direction of paperboard. Appropriate guiding routes embedded in the band zone contributed to the cutoff of connecting portions when the perforation of the zipper band was across the grain direction of the paperboard. The success rate of tearing connecting portions was statistically analyzed with respect to the pattern of the guiding route. It was found that the inhibition of delamination after passing through the torn zone was necessary to successfully cut off the connecting portions.

The newly proposed punching process to form a burr-free hole for the air valve mounted on the wheel rim of an automobile was experimentally studied to evaluate the process parameters required to realize the burr-free punching process. The proposed burr-free punching process employs the mechanism of concise reciprocating shearing that had been originally developed as burr-free blanking. The two-step of experiments on the laboratory scale with actual steel material were conducted to evaluate the parameters of the punching process. In the first step simple rectangular test pieces were adopted and then an actual automobile product shape was employed in the second step. As a result of a series of these simulated experiments, some admissible sets of process parameters to realize burr-free punching were quantitatively found and the mechanism of forming a desirable separated surface shape was qualitatively discussed from the viewpoint of the clearance condition in the partial shearing.

The purpose of this research is the development of technology to make complex-shape closed-section parts directly from sheet blanks (direct sheet forming). It is expected to form closed-section parts with large expansion of the circumferential length by direct sheet forming. In this paper, the deformation type of horn tubes, which consists of circular, conical and transient portions, is studied. The horn tube is one of the typical shapes for automotive parts. With reference to deformation types in the conventional stamping process, those in the forming process of horn tubes are discussed on the basis of the results of FEM analysis. The validity of FEM analysis is confirmed by comparison with experimental results. It is clarified that the forming process can be broken down into several stages and deformation types (uniform bending of sheet, stretch flanging, axial bending of U-section, deformation into double curved surface and plane-strain compression).