Reinforcement of friction plug welds

1. A method of filling a hole in a metal workpiece, comprising:

friction welding a plug in the hole to form a friction weld, wherein the friction weld consists of only the plug and the workpiece metal; and

forming a weld land on a root side of the workpiece during the friction weld, said weld land comprising plug material and workpiece material, wherein the weld land extends a predetermined height above a surface of the root side of said workpiece, wherein the weld land has a predetermined width, and wherein forming the weld land is performed by:

placing an anvil against the workpiece and around the hole, the anvil comprising a first cavity having a bottom surface facing the workpiece, the first cavity configured to receive the plug, the anvil further comprising a second cavity substantially surrounding the first cavity, wherein the second cavity is larger in diameter and smaller in depth relative to the first cavity, wherein the second cavity comprises a tapered recess surrounding the first cavity, wherein the tapered recess is angled downwardly toward the first cavity relative to a depth of the first cavity; and

urging a portion of the workpiece into the first cavity, and thereafter into the second cavity.

2. The method of claim 1 , wherein the friction welding is performed by:

rotating the plug, and

forcing the rotating plug into the hole, the first cavity, and the second cavity.

3. The method of claim 1 , further comprising:

removing portions of the plug that extend beyond the workpiece after the plug has been friction welded in the hole.

4. The method of claim 1 , wherein the first cavity is defined by sidewalls inclined at a first angle relative to a second angle defined by a slope of the tapered recess, and wherein the first angle is greater than the second angle.

5. The method of claim 1 , wherein the weld land is left as welded.

6. The method of claim 1 , wherein the weld land is machined down by an amount.

7. The method of claim 6 , wherein the amount is sufficient to leave the weld land extending past the surface.

8. The method of claim 6 , wherein the amount is sufficient to remove the weld land.

9. A method of friction plug welding a workpiece, comprising:

rotating a plug;

plasticizing a portion of the plug and filling a hole in the workpiece by forcing the rotating plug through the hole and against an anvil to friction weld said plug in said hole, wherein the anvil comprises a first cavity having a bottom surface facing the workpiece, the first cavity configured to receive the plug, the anvil further comprising a second cavity substantially surrounding the first cavity, wherein the second cavity is larger in diameter and smaller in depth relative to the first cavity, wherein the second cavity comprises a tapered recess surrounding the first cavity, wherein the tapered recess is angled downwardly toward the first cavity relative to a depth of the first cavity;

during plasticizing, also substancially filling the first cavity and the second cavity with the plug; and,

forming a weld land on the workpiece, wherein the weld land consists of only workpiece material and plug material, wherein the weld land extends a predetermined height above a surface of a root side of said workpiece, and wherein the weld land has a predetermined width.

10. The method of claim 9 , wherein the first cavity is defined by sidewalls inclined at a first angle relative to a second angle defined by a slope of the tapered recess, and wherein the first angle is greater than the second angle.

11. A method of friction plug welding a metal workpiece, comprising:

rotating a plug;

forcing the rotating plug into one end of a hole passing through the workpiece;

plasticizing a first portion of the plug and a second portion of the workpiece using heat generated by frictional engagement between the rotating plug and the workpiece;

placing an anvil against the workpiece;

forge welding the plug to the workpiece, including forcing the plug against the anvil;

reinforcing the weld by urging the first portion into a first cavity in the anvil, the first Cavity having a botton surface and reinforcing the weld also including urging the second portion into a second cavity in the anvil, wherein the second cavity substantially surrounds the first cavity, wherein the second cavity has a larger diameter and a smaller depth relative to the first cavity, wherein the second cavity comprises a tapered recess surrounding the first cavity, wherein the tapered recess is angled downwardly toward the first cavity relative to a depth of the first cavity, and wherein urging the first portion and the second portion forms a weld land on the workpiece, wherein the weld land extends a predetermined height above a surface of a root side of said workpiece and wherein the weld land has a predetermined width.

12. The method of claim 11 , wherein the first cavity is defined by sidewalls inclined at a first angle relative to a second angle defined by a slope of the tapered recess, and wherein the first angle is greater than the second angle.