WO2013085967A1

WO2013085967A1 - Apparatus and method for linear friction welding repairs

Info

Publication number: WO2013085967A1
Application number: PCT/US2012/067899
Authority: WO
Inventors: Stephen A. Johnson
Original assignee: Apci, Llc
Priority date: 2011-12-05
Filing date: 2012-12-05
Publication date: 2013-06-13

Abstract

The apparatus and repair method allows new material to be welded to damaged component pieces using linear friction welding. The method involves, first cutting or machining the damaged portion of the work pieces to form a repair area. The repair area is machined to have a uniform concave repair weld surface. Next, a mating repair block or plug is produced or machined, which will provide the new material to replace the damaged material removed from the damaged work piece. The repair plug is formed or machined to have a convex weld surface, which mates to the concave weld surface of the work piece. A linear friction weld machine bonds the repair plug to the work piece within the repair area by vibrating the repair plug against the work piece under an initial weld pressure, which plasticizes the weld surfaces.

Description

APPARATUS AND METHOD FOR LINEAR FRICTION WELDING REPAIRS

This application claims the benefit of U.S. Provisional Patent Application, Serial No. 61/630,131 filed December 5, 2011, the entirety of which is incorporated by reference herein.

This invention relates to an apparatus and method for making repairs using linear friction welding.

Background and Summary of the Invention

All metal components subject to mechanical stress can fatigue, fracture and fail. In many instances, metal components having machined facets or structural members that fracture or fail cannot be repaired using conventional welding methods. In addition, it is often cheaper to discard than to repair certain metal components.

Repairing metal components typically involves welding new material to the damaged component that will then be machined into a refurbished component. Welding the new material to the damaged component is accomplished using arc, gas and resistance welding processes and equipment; however, these welding methods and equipment generally do not produce weld interfaces of the same strength and structural integrity as the original virgin material. The strength and structural integrity of the repair component is critical in many applications, such as those found in the aerospace industry.

Linear friction welding (LFW) is a process of joining two components which may be made from the same or different materials. The LFW process typically involves pressing the two components together under a large amount of force and rapidly vibrating the components with respect to one another to generate friction at the interface between the two components. The pressure and movement generate sufficient heat to cause the material at the interface to plasticize. Once the material at the interface begins to plasticize, the vibration is stopped and an increased force is applied. As the plasticized material of both components cools in this static condition, the components are bonded together and a weld is formed. While LFW is suitable in many applications, heretofore, LFW has not been practical for repair welds.

The apparatus and method of this invention allows new material to be welded to damaged component pieces using linear friction welding. The new material can then be machined to refurbish the component piece. The method involves, first cutting or machining the damaged portion of the work pieces to form a repair area. The repair area is machined to have a uniform concave repair weld surface. Next, a mating repair block or plug is produced or machined, which will provide the new material to replace the damaged material removed from the damaged work piece. The repair plug is formed or machined to have a convex weld surface, which mates to the concave weld surface of the work piece. Once the work piece and the repair plug are prepared, both are secured to mounting fixtures of a linear friction welding (LFW) machine, such as the ones available from APCI, Inc. of South Bend, Indiana. The LFW machine vibrates the repair plug against the work piece while pressing them together under an initial load or "weld pressure." Friction causes the material at the weld surfaces to plasticize. The vibration is then stopped and the work piece and the repair plug are pressed together under a final load or forging pressure, which forms the weld interface bonding the material of the repair plug to the material of the work piece. Once the weld interface is formed, the work piece can be removed from the LFW machine and the new material from the repair plug can be further machined as necessary to finish the refurbished work piece.

The apparatus and method of the present invention may take form in various systems and components, as well as the arrangement of those systems and components. The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. The drawings are only for purposes of illustrating exemplary embodiments and are not to be construed as limiting the invention.

Brief Description of the Drawings

The drawings illustrate the present invention, in which:

Fig. 1 is a partial perspective view of a portion of a damaged extruded work piece;

Fig. 2 is another partial perspective view of the work piece of Fig. 1;

Fig. 3 is a partial perspective view of the repair plug and the work piece of Fig. 1, showing the damaged portion of the work piece machined away;

Fig. 4 is another partial perspective view of the repair plug and the work piece of Fig. 1, showing the damaged portion of the work piece machined away;

Fig. 5 is a partial end view of the linear friction welding machine with the work piece and repair plug of Figs. 3 and 4 seated within its mounting fixtures;

Fig. 6 is a partial side view of the linear friction welding machine of Fig. 5 with the work piece and repair plug of Figs. 3 and 4 seated within its mounting fixtures;

Fig. 7 is another partial end view of the linear friction welding machine with the work piece and repair plug of Figs. 3 and 4 seated within its mounting fixtures;

Fig. 8 is another partial side view of the linear friction welding machine of Fig. 5 with the work piece and repair plug of Figs. 3 and 4 seated within its mounting fixtures;

Fig. 9 is partial end sectional view of the repair plug and work piece seated within the fixtures of the linear friction welding machine of Fig. 6;

Fig. 10 is partial side sectional view of the repair plug and work piece seated within the fixtures of the linear friction welding machine of Fig. 6;

Description of the Preferred Embodiment

Referring now to the drawings, Figs. 1-10 illustrate an embodiment of the apparatus and the method for repairing a damaged work piece 10 using linear friction welding (LFW) machine 100. As shown in Figs. 1 and 2, damaged work piece 10 is an extruded aluminum member having a number of fractures and chips 11 in one of the L-shaped flanges 12. The LFW repair method of this invention is illustrated in the drawing and explained hereinafter by way of example in the repair of an extruded aluminum component, although, those skilled in the art may readily adapt and apply the teaching of this invention to other applications. In addition, the linear friction welding (LFW) repair method of this invention can be used to repair ferrous work pieces regardless of configuration or metal composition.

Work Piece & Repair Key Preparation

The LFW repair method of this invention begins with preparing the damaged work pieces 10. First, the damaged portion of the work pieces 10 is machined or cut way to form a repair area 21 leaving a uniform concave repair weld surface 22, using any suitable mechanism or method (Figs. 3 and 4). The size and arc of the weld surface 22 is selected and determined dependent on the extent of the damage to work piece 10. Generally, only the damaged area of the work piece is removed, although the amount of material removed to facilitate the repair may vary with any particular damaged work piece.

Next, a mating repair block or plug 30 is produced (Figs. 3 and 4). The repair plug 30 is formed or machined from the same material as work piece 10 or a compatible material for bonding to the work piece. Repair plug 30 will provide new material to the work piece when bonded together to restore the damaged work piece to its original shape and configuration or allow the newly bonded material to be machined or finished to restore the work piece to its original shape and configuration. Consequently, repair plug 30 is formed or machined to have a similar profile to match that of the damaged work piece 10. Repair plug 20 is also formed or machined to have a convex weld surface 32, which mates uniformly to the weld surface 22 of work piece 10. Once, the repair plug is machined to mate with the repair area 21 of work piece 10, the repair plug can be welded to the work piece.

LFW Machine & Fixtures

While the method of this invention may employ the use of any linear friction welding (LFW) equipment, machine or apparatus, the method is best employed using linear friction welding (LFW) apparatus, fixtures and machines, such as the ones developed by APCI, Inc. in South Bend, Indiana and described in U.S. Patent Application Serial Number 12/868,623 filed August 25, 2010, which issued as U.S. Patent Number 8,070,039 on December 6, 2011. The LFW apparatus, fixtures and machines from APCI are ideal for the repair process of this invention because of their ability to control the amplitude, frequency and termination of the weld vibration, as well as the weld and force pressures during the weld process. The teachings of the above identified U.S. Patent Number 8,070,039 are incorporated herein by reference. For simplicity of illustration and explanation, the LFW machine 100 is only partially illustrated.

As shown in Figs. 5-8, LFW machine 100 generally includes a press assembly 110 (only partially illustrated) and a vibration assembly 120 (only partially illustrated). Press assembly 110 includes a hydraulic press 112, which provides the weld and forge pressures for the welding process and a fixture 118 that securely holds work piece 10 to a press assembly. Vibration assembly 120 includes a carriage 122 suspended by a pair of rocker arms 124 and an oscillator mechanism, which provides a controlled reciprocation of the carriage. Carriage 122 supports a second fixture 128 that securely holds repair plug 30. The oscillator mechanism includes a ram that is connected to carriage 122 and is driven by various motors, linkages, gears and cam assemblies. As shown, the oscillator mechanism drives ram 126 to move carriage 122 to reciprocate back and forth along a weld axis that is perpendicular to the longitudinal axis of both work piece 10 and repair plug 30 when held in fixtures 118 and 128.

Forming the Repair Bond

Once both work pieces 10 are properly secured within fixtures 118 and 128, LFW machine 100 vibrates repair plug 30 against work piece 10 while pressing them together under an initial load or "weld pressure" (Figs. 6, 8 and 9). Friction causes the material at the weld surfaces 22 and 32 to plasticize. The vibration is then stopped and work piece 10 and repair plug 30 are pressed together under a final load or forging pressure, which forms the weld interface (Fig. 10) bonding the material of repair plug 30 to the material of work piece 10. Once the weld interface is formed, work piece 10 can be removed from LFW machine 100 and the new material from the repair plug can be further machined as necessary to finish the refurbished work piece.

The embodiment of the present invention herein described and illustrated is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is presented to explain the invention so that others skilled in the art might utilize its teachings. The embodiment of the present invention may be modified within the scope of the following claims.

Claims

I claim:

Claim 1. A method for repairing a work piece using linear friction welding, the method comprising:

a. machining a cavity from the work piece such that the cavity has a uniform concave surface;

b. providing a repair piece having a uniform convex surface dimensioned to mate with the concave surface of the work piece cavity;

c. seating the repair piece within the work piece cavity;

d. pressing the repair piece into the work piece cavity under a first load; e. rapidly vibrating the repair piece relative to the work piece whereby the friction between the repair piece and the work piece plasticizes the material of the repair piece and the work piece; and

e. pressing the repair piece against the work piece under a second load to form a weld interface between the repair piece and the work piece.

Claim 2. A linear friction welding apparatus comprising:

a first fixture for holding a work piece having a cavity formed therein such that the cavity has a uniform concave surface;

a second fixture for holding a repair piece having a uniform convex surface dimensioned to mate with the concave surface of the work piece cavity;

a pressing assembly operatively connected to one of the first fixture and second fixtures for pressing the repair piece against the work piece under selective loads; a vibrating assembly for vibrating the second fixture relative to the first fixture so that the repair piece moves against the work piece to generate friction between the repair piece and the work piece.