| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 100 === There are various applications of small motors in an automobile. Dozens of motors are needed in actuating the needs of the passengers inside the automobile. Due to the limitation of space, the lifting mechanism of windows and sun-roof and the adjustment of seats require the motors to be flat-like. Therefore, the deep drawing operation of motor case becomes complicated and requires more forming stages. This work attempted to reach the pre-form with two-stage elliptical drawing. The influence of strain ratio of strip was also considered to reduce forming stages and forming defects.
Finite element method software, DYNAFORM, was used in simulating the sheet forming process. Cold-rolled steel sheet SPCE was used as the workpiece strip. Fifteen degrees of angle between rolling direction and base line of forming dies was used as the increment to investigate the effects of strain ratio on forming. The thinning on the round corner and the height of the elliptical wall were compared between the two proposed forming schemes: preliminary circular drawing followed by elliptical redrawing and preliminary elliptical drawing followed by elliptical redrawing. Moreover, two types of forming schemes, namely preforms from two elliptical drawing and from the traditional drawing, were investigated to obtain the optimum forming scheme on the bearing of the motor case.
The results of simulation show that the corner angle of the long axis tended to be thinning and fracturing and the corner angle of the short axis tended to be thickening and whinkling for the preliminary circular drawing followed by elliptical redrawing. However, the corner angle of long axis tended to be less thinning and fracturing and the corner angle of short axis tended to be less thickening and whinkling for the preliminary elliptical drawing followed by elliptical redrawing. The thinning on the corner angle of the long axis was significant when the rolling direction was aligned with the long axis. However, the thinning on the corner angle of the long axis as well as the wrinkling tendency was reduced when the rolling direction was aligned with the short axis. The experimental results with the forming dies also approved the simulation.
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