Yaw pad engagement features

1. A yaw brake apparatus, comprising:

a first surface disposed on an end of a yaw piston for a wind turbine, the first surface comprising a first pattern of concentric circles formed by one or more of a plurality of first recesses and a plurality of first protrusions; and

a yaw pad comprising a second surface structurally configured to engage with the first surface and a third surface opposite the second surface that is structurally configured to engage with a slew ring of the wind turbine, the second surface comprising a second pattern of concentric circles formed by one or more of a plurality of second recesses and a plurality of second protrusions corresponding to one or more of the plurality of first recesses and the plurality of first protrusions on the first pattern such that the first pattern and second pattern fit together when aligned in a predetermined orientation, the alignment of the first pattern and the second pattern providing resistance to shear forces exerted on the yaw pad by rotation of a nacelle.

2. The yaw brake apparatus of claim 1 , where the first surface is integral with the yaw piston.

3. A yaw pad, comprising:

a metal backer plate having a first pattern of concentric circles on at least one recessed area and at least one protruding area in a surface thereof;

a friction pad having a second pattern of concentric circles on at least one recessed area and at least one protruding area in a surface thereof;

the first pattern and the second pattern being mating patterns such that the at least one recessed area of the first pattern receives the at least one protruding area of the second pattern, and the at least one recessed area of the second pattern receives the at least one protruding area of the first pattern, the first pattern and second pattern fit together when aligned in a predetermined orientation, the alignment of the first pattern and the second pattern providing resistance to shear forces exerted on the yaw pad by rotation of a nacelle; and

an adhesive that bonds the first pattern with the second pattern.

4. The yaw pad of claim 3 , where each of the first pattern and the second pattern comprise a set of concentric, substantially circular grooves.

5. The yaw pad of claim 4 , where one or more grooves in the set of concentric, substantially circular grooves comprises a rounded triangular cross-sectional shape.

6. The yaw pad of claim 3 , where the adhesive forms an adhesive layer between the first pattern and the second pattern with the adhesive layer being less than about 0.10 inches in thickness at any point.

7. The yaw pad of claim 3 , where at least one of the first pattern and the second pattern incorporates an arrangement of eight concentric, substantially circular grooves.

8. The yaw pad of claim 3 , where the first pattern and the second pattern provide an increase in surface area of the mating patterns over an unpatterned surface of at least 10%.

9. The yaw pad of claim 8 , where the first pattern and the second pattern provide an increase in surface area of the mating patterns over an unpatterned surface of at least about 15%.

10. The yaw pad of claim 3 , where the first pattern exhibits no pointed features that are approximately parallel to an unpatterned surface of the metal backer plate.

11. The yaw pad of claim 3 , where the adhesive comprises a two-part epoxy.

12. The yaw pad of claim 3 , where the friction pad is comprised of resin impregnated woven polyester.

13. The yaw pad of claim 3 , where the friction pad is non-metallic.

14. The yaw pad of claim 3 , where the friction pad incorporates metallic particles.

15. The yaw pad of claim 3 , where the recessed areas of the first pattern and the second pattern have a cross-section shaped as one or more of a rectangle, a rectangle having chamfered corners, a rectangle having curved corners, a triangle, a polygon, or a smooth curve.

16. A method of manufacturing a yaw pad, comprising:

obtaining a piece of backer material of a predetermined diameter and thickness;

obtaining a piece of a friction pad material of a predetermined diameter and thickness;

forming a first pattern of concentric circles into a bottom surface of the piece of backer material to form a backer plate;

forming a second pattern of concentric circles into a top surface of the friction pad material, where the second pattern is structurally configured to mechanically key with the first pattern;

applying an adhesive to at least one of the bottom surface and the top surface;

mating the bottom surface and the top surface by mechanically keying the first pattern with the second pattern thereby forming the yaw pad, where the first pattern and second pattern fit together when aligned in a predetermined orientation, the alignment of the first pattern and the second pattern providing resistance to shear forces exerted on the yaw pad by rotation of a nacelle;

applying pressure to the yaw pad; and

curing the adhesive.

17. The method of claim 16 , where the obtaining a piece of backer material comprises one or more of cutting a slice from a bar of metal, and cutting or punching a sheet of metal.

18. The method of claim 16 , where forming one or more of the first pattern and the second pattern is carried out using a lathe.