Gm Global Technolgoy Operations, Inc.

Thomas B Bartholomew

Chi-Mou Ni

Tehui Peng

A hydroformed tubular structure includes at least two hydroformed members connected at a joint. At least one of said members includes a flattened portion having opposite sides in engagement. One of the sides engages and is secured to a mating portion of another of the members and a hydroformed conjugate portion is formed in the one side adjacent the flattened portion and is secured in a recess of the other member. A hydroformed structural portion extends from the conjugate portion in a direction away from the flattened portion. A method of making the structure includes the steps of placing a tubular member in a hydroforming die, filling the tubular member with hydroforming liquid, flattening at least one portion of the tubular member intermediate its ends by forcing opposite sides of the member into engagement upon closing of the die, the liquid in the member acting to prevent collapse of other portions of the tubular member than the flattened portions, hydroforming the member into a predetermined configuration including expanded conjugate portions adjacent the flattened portions, trimming the flattened portions of the member to form a plurality of separate hydroformed parts each having at least one flattened end portion with an adjacent expanded conjugate portion, and securing the flattened portion of a first one of the parts to a second part having a recess receiving the conjugate portion of the first part to form a secure joint connecting the first and second parts.

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Metamora, MI, United States of America

Thomas B Bartholomew