Device and method for the autofrettage of a workpiece

Patent metadata

Field	Value
Publication number	US-11298737-B2
Application number	US-201816472366-A
Country	US
Kind code	B2
Filing date	Jan 5, 2018
Priority date	Jan 20, 2017
Publication date	Apr 12, 2022
Grant date	Apr 12, 2022

Abstract

A method for the autofrettage of a workpiece may involve arranging the workpiece between a first securing means and a second securing means, and applying high-pressure fluid to an internal volume of the workpiece that is formed between the first and second securing means. A die or ram may be driven into the internal volume through an inlet in the first securing means. Consequently, as a result of the ram being advanced, not only is a fluid pressure generated in the internal volume, but also the workpiece is mechanically autofrettaged by way of the ram. A device may be employed to perform such hydromechanical autofrettage of the workpiece.

First claim

What is claimed is:

1. A method of autofrettage comprising:
positioning a workpiece between a first securing means and a second securing means;
applying fluid to an internal volume of the workpiece formed between the first securing means and the second securing means;
driving a die into the internal volume through an opening in the first securing means, wherein the die is driven into the internal volume such that fluid is pressed between a head of the die and the workpiece and flows along the die in a direction of the first securing means; and
by movement of the die, generating a fluid pressure in the internal volume and mechanically autofrettaging the workpiece.

2. The method of claim 1 wherein the die is driven until the die enters a recess in the second securing means.

3. The method of claim 1 comprising filling the internal volume with fluid before the die is driven into the internal volume.

4. The method of claim 1 wherein a fluid pressure for hydraulic autofrettage is generated by way of the die, wherein the workpiece is mechanically autofrettaged by way of a head of the die that is oversized relative to an internal dimension of the workpiece.

5. A method of autofrettage comprising:
positioning a workpiece between a first securing means and a second securing means;
applying fluid to an internal volume of the workpiece formed between the first securing means and the second securing means;
driving a die into the internal volume through an opening in the first securing means; and
by movement of the die, generating a fluid pressure in the internal volume and mechanically autofrettaging the workpiece,
wherein a pressure-induced widening of the workpiece that results from the movement of the die depends on a size of the die, wherein the pressure-induced widening of the workpiece is independent of a rate at which the die is driven.

6. The method of claim 5 comprising controlling the movement of the die such that a strain of the workpiece causes fluid to flow from the internal volume past a head of the die.

7. The method of claim 5 comprising at least one of:
building up the fluid pressure in the internal volume after introducing the die into the workpiece; or
adjusting the fluid pressure in the internal volume to a defined value, which is below a pressure level that results due to the movement of the die, by way of a pressure limiter connected to the second securing means.

8. An autofrettage tool apparatus for autofrettage of a workpiece, the autofrettage tool apparatus comprising:
a first securing means that includes an opening;
a second securing means, wherein an internal volume of the workpiece is positionable between the first securing means and the second securing means, wherein the internal volume of the workpiece is configured to receive fluid; and
a die configured for mechanical autofrettage of the workpiece, wherein the die is configured to be positioned in the opening of the first securing means,
wherein the autofrettage tool apparatus is configured for hydromechanical autofrettage of the workpiece by way of fluid and the die,
wherein at least one of:
a head is detachably fastened on the die or is mounted on an end side in front of the die; or
a head of the die comprises a front-side chamfer and a rear-side chamfer, wherein between the front-side chamfer and the rear-side chamfer a lateral surface that is cylindrical or becomes conically wider toward the rear-side chamfer is formed.

9. The autofrettage tool apparatus of claim 8 wherein at least one of:
the opening of the first securing means is flush with a longitudinal axis of the workpiece; or
the second securing means comprises a recess that is flush with a longitudinal axis of the workpiece, the recess being configured as a recess for fluid or for a head of the die.

10. The autofrettage tool apparatus of claim 8 wherein the second securing means is solid or wherein the second securing means comprises a lower side configured to support the autofrettage tool apparatus and for transmission of die forces.

11. The autofrettage tool apparatus of claim 8 comprising an intermediate element disposed geometrically with respect to the die in the first securing means.

12. The autofrettage tool apparatus of claim 8 wherein the die comprises a head that is oversized relative to an internal dimension of the workpiece, the head being configured for mechanical autofrettage of the workpiece.

Assignees

• Uhde High Pressure Tech Gmbh
• Thyssenkrupp Ag

Inventors

• Knauf Wilfried
• Uhlig Klaus

Classifications

• B23P9/025

  to inner walls of holes by using axially moving tools · CPC title

• B23P9/00 Primary

  Treating or finishing surfaces mechanically, with or without calibrating, primarily to resist wear or impact, e.g. smoothing or roughening turbine blades or bearings (treatment covered by a single other subclass, see the relevant subclass, e.g. B24C, C21D7/00, C22F1/00); Features of such surfaces not otherwise provided for, their treatment being unspecified · CPC title

• C21D7/12

  by expanding tubular bodies · CPC title

• B21D26/033 Primary

  Deforming tubular bodies (corrugating tubes by applying fluid pressure B21D15/03, B21D15/10) · CPC title