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The main operations for the manufacturing of auto parts are the cutting of the flange and the stamping. In order to perform accurate fatigue calculation it is necessary to have the material properties for each point of the structure. Usually, only the fatigue curve obtained on the flat sheet with polished edges is used because it represents the basic metal behaviour. The real edge quality decreases the fatigue limit while the hardening induced by the stamping increases it. To take these effects into account allows a better fatigue calculation of the structural part.

This paper proposes a rolling machine that forms fine corrugated section patterns for thin sheets. A prototype of the machine was made and the performance of the machine was tested. As compared with press forming, rolling has the advantages of the high forming limit, the low forming reaction force, the easy control of the thin sheet's curve and high productivity. We confirmed these four advantages by using finite element analyses and the prototype rolling machine. Stainless steel sheets and titanium sheets, which were one of the materials with a low forming limit, were used. Firstly, the rolling showed a 1.3-times higher forming limit than the press forming in the case that a fine corrugated section pattern was formed in a stainless steel sheet of 22-mm square sizes. Secondly, the forming reaction force of the rolling was about one-twentieth of the press forming without coining, and the experimental results agreed with the finite element simulation.