Hydroforming is a cost-effective way of shaping malleable metals such as steel into lightweight, structurally stiff and strong pieces. With the increased use of the hydro formed components in automotive and aerospace industries, it is important to know the variations of the mechanical properties in the hydro forming process for the safe and durable design purposes. The principal goal of this paper is to suggest a procedure to evaluate the variations of tensile and fatigue properties before and after a hydroforming process. A miniature specimen, which is 0.2 ㎜ thick and 2.3 ㎜ wide, is devised and tested to measure local mechanical properties. The effects of specimen size, defects, surface roughness, and hydro forming on the tensile and fatigue behaviors are discussed.
