Compressive hydroforming

Details Compressive hydroforming Compressive hydroforming

1999-12-15

2001-07-10

Jones, David (Department: 3725)

Metal deforming

By application of fluent medium, or energy field

With actuated tool engaging work

C072S058000, C072S055000

Reexamination Certificate

active

06257035

ABSTRACT:

The present invention relates to a method for hydroforming a tubular workpiece. Currently, hydroforming is used on a large scale for manufacture of frame components for road vehicles. The hydroforming process has application in other manufacturing and industrial processes where a tubular product formed to very precise dimensions and possessing properties of strength and lightness is desired, for example in the aerospace industry and furniture manufacturing.
In the course of hydroforming, a tubular workpiece is confined within a die cavity formed by dies within a press, and the workpiece is pressurized internally, usually with a pressurized liquid, for example, water. For example, the pressurization may be about 28 to 250 MPa, depending on the nature of the part that is being hydroformed. The internal pressurization causes the tube workpiece to conform to the interior of the die cavity. Advantageously, the tubular workpiece is pre-pressurized, typically to about 3 to 20 MPa depending on the part, before the press is operated to close the dies together and completely confine the workpiece in the die cavity. Pre-pressurization allows the workpiece to be confined in a die cavity that is not excessively large in comparison to the external dimensions of the tubular workpiece without pinching of the blank occurring when the die sections are closed together. Commonly assigned U.S. Pat. No. Re. 33990 (Cudini) dated Jul. 14, 1992, for example, discloses hydroforming within a cavity the circumference of which is the same as or somewhat greater than the tubular workpiece such that forming the workpiece to the shape of the die cavity causes zero expansion or expansion of the circumference of the workpiece by no more than about 5%. The procedure of expanding the tube workpiece 0 to 5% has numerous advantages over procedures in which higher expansion ratios are employed. For example, punching of holes through the side wall of the hydroformed workpiece while pressurized within the forming die is facilitated. Further, dimensional stability, that is, part to part repeatability of dimensions is improved, and products with sharper corners, having a smaller ratio of the radius of cross-sectional curvature to the wall thickness are possible. Moreover, the yield strength of the product is improved to some extent.
Nevertheless, with known procedures, problems of leakage of the pressurized liquid during the course of hole punching may still occur, especially when holes of large width are formed. Further, the dimensional stability, yield strength and the cross-sectional sharpness of the corners that can be created are still not as great as may be considered desirable.
The present invention provides a method of forming a tubular workpiece wherein fluid pressure is applied to the interior of the workpiece before enclosing the pressurized workpiece in a die that has a die cavity having an internal periphery that is smaller than the external periphery of the workpiece, whereby the workpiece is subjected to compressive forming. The die is then opened and the compressively formed workpiece is removed.
In the present method, by making the cavity smaller than the tube workpiece, and effecting compressive forming of the workpiece, the material of the tube wall is pushed against the punch during procedures of piercing the wall of the workpiece, and this avoids problems of leakage when large width holes are punched in the workpiece while confined in the die. Further, the compressive force that is applied to the tube wall of the workpiece produces a very high degree of dimensional stability, provides improved yield strength, and allows very sharp cross-sectional corners to be formed. The compression forces acting on the material of the tube wall push the material of the tube wall into areas, such as very sharp corners, into which it would not normally flow.


REFERENCES:
patent: Re. 33990 (1992-07-01), Cudini
patent: 5070717 (1991-12-01), Boyd et al.
patent: 5974846 (1999-11-01), Ash
patent: 385146 (1965-03-01), None
patent: 45-1344 (1970-01-01), None
patent: 153909 (1963-01-01), None

Affiliated with

Also associated with

Rating

Compressive hydroforming does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Compressive hydroforming, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compressive hydroforming will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2558773