Patent ID: 6151940
Filing Date: 2000-11-28
Classification: B21D

Abstract:
A process for hydroforming an elongate tubular structural member in a mould die, the structural member having portions spaced along its length which have different circumferential dimensions, a first of said portions having a first cross-sectional shape defining a minimum outer circumferential dimension C.sub.1 and a second of said portions having a second cross-sectional shape defining a maximum outer circumferential dimension C.sub.2, the process including the steps of:(i) selecting a precursor tube of constant cross-sectional shape and constant outer cross-sectional dimension along its length and having an outer circumferential dimension C.sub.0 which is greater than or equal to C.sub.1 and being of a cross-sectional shape which can be located within said first cross-sectional shape and having at least two axially extending nodes, and selecting the wall thickness S.sub.0 of the precursor tube so as to fall within the range S.sub.0 .ltoreq.S.sub.1 and S.sub.0 .gtoreq.S.sub.2 wherein S.sub.1 is the average wall thickness of said first portion and S.sub.2 is the average wall thickness of said second portion, and(ii) placing the precursor tube in the mould die and hydroforming the precursor tube to produce said tubular structural member.