Patent ID: 6766678
Filing Date: 2004-07-27
Classification: B21D

Abstract:
A process for deforming a piece of a thin-walled metal tube, comprising the steps of:bending the piece of tube with respect to an original longitudinal axis of the piece of tube, and then hydroforming the piece of tube at least at the location where the piece of tube has been bent, compressing the piece of tube prior to the bending step at the location where the piece of tube will exhibit the bend as a result of the bending step so as to form a wrinkle comprising a longitudinal indentation, which runs substantially parallel to the longitudinal axis of the tube on the outside of the bend to be formed, wherein in the compression step prior to the bending step at least one said longitudinal wrinkle is formed at the outside of the bend and at least one said longitudinal wrinkle is formed at the inside of the bend on either side of a neutral plane of bending stresses of the bend, thereby moving wall material on both sides of the neutral plane closer to the neutral plane, wherein the tube prior to bending defines a transverse perimeter of a cross-section of the tube, the transverse perimeter is transverse to the longitudinal axis of the tube and passes through the longitudinal wrinkles, wherein the transverse perimeter has at least one indented portion formed respectively by said at least one wrinkle formed at the outside of the bend and at least one indented portion formed respectively by said at least one wrinkle formed at the inside of the bend, such that at least one indented portion is located on either side of the neutral plane of bending stresses of the bend, wherein prior to said bending some points of said transverse perimeter are further from the longitudinal axis of the tube than other points of the transverse perimeter, wherein the neutral plane passes perpendicularly through the transverse cross section prior to the bending; wherein the transverse perimeter after forming the longitudinal wrinkles, but prior to bending, includes portions which overlap a second transverse perimeter of a portion of the tube which is not compressed.