Apparatus and method for selective bonding to form hollow components

1. An apparatus comprising:

means for peripherally welding a hollow cavity-back blade and a cover of the cavity-back blade to form a 3-dimensional hollow blade assembly;

a first die half and a second die half for receiving the 3-dimensional hollow blade assembly, the first die half or the second die half including a plurality of protrusions;

a plurality of bellows, each including a hollow portion configured to be engaged by corresponding ones of the plurality of protrusions, each bellows contained in one or both of the first and second die halves, and disposed around or inward of the peripherally welded interface of the cover and the blade; and

a recessed catenary supported above each of one or more of the plurality of bellows between ones of the plurality of protrusions and the corresponding one or more of the plurality of bellows;

wherein at least a portion of the plurality of bellows are arranged in a manner to provide pressure to the cover at approximately a 90 degree angle to each of a plurality of nodes, each node defined by an intersection of two or more ribs in the cavity-back blade.

2. The apparatus of claim 1 , further comprising a bellows retainer disposed annularly outward of ones of the plurality of protrusions and the corresponding hollow portion of one or more of the plurality of bellows.

3. The apparatus of claim 2 , wherein the bellows retainer includes at least one knife-edge seal for engaging a bellows flange against a mating knife edge machined into a recessed flat surface where the bellows flange resides.

4. The apparatus of claim 1 , further comprising means for generating localized heating at a plurality of interfaces between the blade cover and the plurality of nodes, the heating means sufficient to elevate a temperature of the first and second die halves for diffusion bonding, brazing, stress-relieving, and/or creep-forming a combination of the cavity-back blade and the cover.

5. The apparatus of claim 4 , wherein the heating means are sufficient to locally elevate the temperature of a titanium workpiece to a range of 1300° F. to 1600° F.

6. The apparatus of claim 5 , wherein the means for generating localized heating comprises a circular heating element adjacent to one of the plurality of interfaces, the circular heating element in electrical communication through one of the first die half and the second die half.

7. The apparatus of claim 6 , wherein the means for generating localized heating further comprises at least one of a quartz heater and a light emitting diode in electrical communication through one of the first die half and the second die half.

8. The apparatus of claim 1 , wherein the first and second die halves are shaped to maintain a twist of about 20° to about 40° relative to a chordwise direction of the combination of the cavity-back blade and the cover, and the plurality of bellows are positioned and operative to diffusion bond the cavity-back blade and the cover atop or around a plurality of circular ribs at the plurality of nodes.

9. A method for making a hollow metal blade, the method comprising:

peripherally welding a hollow cavity-back blade and a cover around an interface therebetween, the cover adapted to engage an opening in the hollow cavity-back blade combining the blade and the cover to form a 3-dimensional hollow blade assembly;

placing the 3-dimensional hollow blade assembly in a die having a first die half and a second die half to maintain the 3-dimensional twist of the hollow blade, the first die half or the second die half including a plurality of protrusions; and

positioning a plurality of bellows in one or both of the first and second die halves, each including a hollow portion configured to be engaged by corresponding ones of the plurality of protrusions,

positioning a retainer annularly between ones of plurality of protrusions and the corresponding hollow portion of one or more of the plurality of bellows, the retainer including at least one knife-edge seal for engaging a bellows flange against a mating knife edge machined into a recessed flat where the bellows flange resides;

positioning a recessed catenary disposed above each of the bellows between ones of the plurality of protrusions and the corresponding one or more of the plurality of bellows; and

operating the plurality of bellows to selectively and locally press the hollow blade and cover together around or inward of the peripherally welded interface of the cover and the cavity-back blade;

wherein at least a portion of the plurality of bellows are arranged in a manner to provide pressure to the cover at approximately a 90 degree angle to each of a plurality of nodes, each node defined by an intersection of two or more ribs in the cavity-back blade.

10. The method of claim 9 , wherein the plurality of bellows provide localized pressure at each node with a load sufficient to create a low temperature diffusion bond around each node.

11. The method of claim 10 , wherein the peripherally welded interface is stress relieved and the blade is minimally creep-formed into a final 3-dimensional configuration corresponding to the first and second die halves.

12. The method of claim 10 , wherein the combination of the cavity-back blade and the cover are titanium alloys, and the heating means are sufficient to elevate the temperature to a range of 1300° F. to 1600° F. in the areas to be diffusion bonded.

13. The method of claim 9 , wherein localized heating is provided by a circular heating element adjacent to one of the plurality of nodes, the circular heating element aligned with a corresponding circular rib in the hollow blade assembly.

14. The method of claim 9 , wherein the first die half and/or the second die half maintain a twist of about 20° to about 40° relative to a chordwise direction of the combination of the cavity-back blade and the cover.