摘要 |
A preform having edges overlapped and jointed, two outer members for forming outer surfaces of a hydroformed product, and reinforcement members for forming reinforcement ribs that divide a hollow cross section of the hydroformed product, including a joint formed by, when more than three sheet materials for forming the outer members and the reinforcement members are overlapped together, welding a first sheet material on a surface of the overlapped sheet materials to a second sheet material positioned inside the first sheet material, and a space disposed and aligned with a joint plane between the second sheet material and a third sheet material located inside the second sheet material during the welding process.
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