A rotary forming analysis model generally needs massive elements for solving large plastic deformation of three- dimensional problems with sufficient accuracy. Beforehand, we developed a compact form-rolling analysis model composed of small hoop-angle one-layer solid elements given a certain angular-velocity field. We have also developed a boss-forming analysis model with a unique extention of the above-mentioned method. This model can be used to analyze stress concentration with enough precision near the contact area between the roll and the blank. The computation time of the model was less than 1/1000 of that when using the full-scaled model. Our model will shorten both the modeling time and the model refining time in the early design stage of products prepared by the boss-forming production process.
The use of ultrasonic vibrations to join dissimilar metal plates was investigated. Plastic flow appeared when joining two aluminum plates by applying a zero-amplitude ultrasonic wave (stress amplitude is maximum). Over time, the plastic flow increased and resulted in a stirring phenomenon of the materials. Electron backscattering diffraction analysis revealed that ultrasonic-vibration-induced recrystallization occurred on the shear band. We call the joining method the mechanometallurgical joining method. By this joining method, an aluminum plate was joined to a steel plate. The resultant plate was analyzed by the cross-tension test and cross-sectional observation. When joining an aluminum plate to various kinds of metal plates, the cross-tensile load of the joint reached a maximum value of 200 N. The cross-tension tests revealed that fracture of the materials resulted in the plug failure mode. Therefore, the strength of bonding was greater than the tensile strength of the aluminum plate. These results led us to the conclusion that the joining of dissimilar metal plates has been achieved using ultrasonic vibrations.
Slide motion control for a servo press was investigated with the aim of improving shape accuracy in square cups formed by impact extrusion. We studied the effects of slide speed on wall thickness accuracy in the product. We explored the factors in defective product formation by analyzing strain curves during the punching operation. The results clarified that elastic deformation of the punch in the bending direction during the initial working portion of the stroke affects the accuracy of wall thickness. When observing the process using a high-speed camera, we deduced that unstable movement of the slug when initially impacted by the punch caused the punch to deform elastically in the bending direction. By employing pulse motion during the initial stage, whereby the punch is repeatedly advanced and retracted until the slug fills the die, elastic deformation of the punch in the bending direction could be reduced, improving the wall thickness accuracy in the product.