In press forming, sampling inspection has been performed during production. However, in sampling inspection, there is the possibility that defective products will proceed to the next process despite inspection. In this paper, we investigated a method for detecting wrinkle defects occurring during deep drawing in order to prevent the outflow of defective products. Deep-drawing tests were performed using a drawing die incorporating an ultrasonic transducer. During deep drawing, ultrasonic waves were irradiated to the interface between the die and the workpiece, and the occurrence of wrinkles was examined on the basis of ultrasonic reflection characteristics. The ultrasonic reflection intensity was changed by the occurrence of the wrinkles. The influence of wrinkle height and wrinkle wavelength on relative reflection intensity was shown. It was demonstrated that ultrasonic measurement is an effective method of detecting wrinkles during press forming.

The application of water-solution lubricants to cold rolling processes is attractive because they have the potentialto conserve clean environments around rolling mills, and are also superior because of their easy maintenance and long life for circulated use. Polyalkylene glycols (PAGs) are representative components of metalworking solution lubricants. However, their application to industrial use is difficult because of their poor lubricity. In this study, conditions for the improvement of lubricity are investigated, especially for the high-speed cold rolling conditions of steel strips. It is found that the lubricant solutions can be improved to the level of oil-in-water emulsions if the amount of plated-out lubricant on the steel surface is sufficiently large by increasing the polymer concentrations in water and the surface temperature of the strip. Also, it is concluded that further investigations on additives are necessary to improve boundary lubrication properties in order to apply the lubricant solutions to industrial cold rolling processes.

We have devised new double-thread bolt fasteners (DTB) based on an innovative mechanism composed of a coarse single thread and a coarse multiple thread (called the multithread DTB). In the present work, thread-rolling experiments, FEM simulations, and performance evaluation tests were carried out. The number of coarse multithreads was set to 2, 3, and 4, which were called 2-thread, 3-thread, and 4-thread DTBs, respectively. The rolling dies have special profile grooves that follow the same outline as the thread profiles of each multithread DTB. Using these dies, the 3-thread DTB was successfully formed, although the height of the lower screw-thread portion of the 2-thread and 4-thread DTBs did not achieve the target level. The FE simulations well reproduced the actual deformation state. The tensile strength of the new DTB tended to decrease with increasing number of multithreads, and the 3-thread and 4-thread DTBs were damaged by shear failure of the screw thread in the double-nut mounted state. The loosening test results obtained using a Junker vibration test bench show that multithread DTB can withstand a certain amount of axial tensile force after the prescribed number of load cycles when controlling only the tightening torque of the outer nut.