Forming Limit Of SUS304 Stainless Steel Thin Sheets On Mesoscale

Micro sheet forming technology has got extensive application prospect in the field of MEMS with its advantages such as simple process, high production efficiency, low cost etc. However, research on micro sheet forming is not comprehensive, due to the limitation of equipment and measuring methods. Especially, study on mesoscopic scale sheet forming limit is not very full. Therefore, it is quite necessary to conduct research in this area.Taking those into consideration, this essay focus on the forming limit of SUS304 stainless steel on mesoscale. Two methods, micro uniaxial tensile test and micro bulging experiment, are used to achieve the FLDs of SUS304 thin sheets. For micro uniaxial tensile test, DIC technology is used to realize the measurement of limit strains and the dynamic reflection of strain distribution in the process of forming. Finally, the left side of FLD is got with this method. For micro bulging experiment, samples with tiny grinds are obtained with the method of spraying gold. After forming process, the change of tiny grind is meatured so as to calculate limit strains. Then the right side of FLD is got, and a complete FLD is made together with the left side.Besides, flow stress curves of samples with 4 thickness(50μm、75μm、100μm、150μm) under different heat treatments are obtained. Looking into those curves, much can be discovered. Under the same heat treatment, flow stress curves trend to move down with the increasing of thickness. For samples with the same thickness, flow strss curves move down at first and then move back up with the increasing of grain size. Moreover samples with designed sizes are made to get different strain paths, so as to study the effect of strain path on forming limit; samples with different grain sizes are also obtained to study the effect of grain size on forming limit. Then reasonable explanations are made upon those effects and their mechanism.