Method and apparatus to propagate crack growth in a workpiece

Patent metadata

Field	Value
Publication number	US-9573284-B2
Application number	US-201414156057-A
Country	US
Kind code	B2
Filing date	Jan 15, 2014
Priority date	Jan 15, 2014
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

A method and apparatus for forming a starter notch along the length of a work-piece for subsequent fatigue testing. The starter notch is formed with a cutting wire such that it will promote fatigue-cracking in the work-piece in one defined direction and avoids cracking in directions other than the length direction of the starter notch. Improved fatigue-testing analysis may therefore be realized.

First claim

What is claimed is:

1. A method for forming a starter notch in a work-piece comprising:
providing a cutting wire;
supplying said work-piece having a thickness and engaging said work-piece with said cutting wire and forming a starter notch at least partially along the thickness and into said work-piece to define a penetration length direction of said starter notch;
providing a wire cutting apparatus, including said cutting wire having a first end portion and a second end portion, wherein a weight is coupled with the first end portion of the cutting wire;
a housing, wherein the housing includes a work-piece receiving opening and a plurality of pulleys arranged in series, wherein the plurality of pulleys comprise a first guide pulley, a second guide pulley and a third guide pulley;
introducing the cutting wire onto said first guide pulley;
routing the cutting wire from the first guide pulley through a fully enclosed hole formed in the work-piece and onto said second guide pulley;
routing the cutting wire from the second guide pulley onto a third guide pulley;
arranging the third pulley such that the weight coupled with the first end portion of the cutting wire is suspended from the third guide pulley;
arranging at least one of the first guide pulley and the second guide pulley such that the cutting wire is positioned to cut said starter notch in the fully enclosed thru-hole of the work-piece;
moving at least a portion of a length of the cutting wire through the thru-hole and simultaneously cutting said starter notch in the thru-hole which extends outward from the thru-hole; and
wherein said starter notch is configured to promote fatigue-cracking in said work-piece from said notch in a direction extending along said penetration length within a region of +/−5 degrees of said penetration length direction of said starter notch, without said fatigue-cracking within a region of greater than 5 degrees to 90 degrees of said penetration length direction of said starter notch.

2. The method of claim 1 wherein said thru-hole has an inner surface and said cutting wire forms said starter notch on said inner surface.

3. The method of claim 1 wherein said cutting wire has a diameter of 100 microns to 500 microns.

4. The method of claim 1 wherein said starter notch penetrates into said work-piece to provide a penetration length of up to 0.009 inches.

5. The method of claim 1 wherein said work-piece has a thickness of 0.3 inches to 0.7 inches.

6. The method of claim 1 wherein said work-piece has a length of up to 20 inches.

7. The method of claim 1 wherein said work-piece has a width of up to 4 inches.

8. The method of claim 1 wherein:
moving at least a portion of the length of the cutting wire through the thru-hole is performed by pulling the cutting wire through the thru-hole with the weight falling under gravity.

9. The method of claim 1 wherein:
moving at least a portion of the length of the cutting wire through the thru-hole and simultaneously cutting a notch in the thru-hole which extends outward from the thru-hole is performed by moving the cutting wire through the thru-hole in alternating opposing directions.

10. A method of propagating crack growth in a work-piece comprising:
providing a cutting wire;
supplying said work-piece having a thickness and a thru-hole;
engaging said work-piece in said thru-hole with said cutting wire;
forming a starter notch at least partially along the thickness and into said work-piece to define a penetration length direction of said starter notch;
forming a fatigue-crack in the work piece which extends from the starter notch;
enlargening the thru-hole in the work-piece such that the notch is removed from the work-piece while at least a portion of the fatigue-crack remains in the work-piece.

11. The method of claim 10 further comprising:
reviewing the fatigue-crack in the work-piece with one or more fatigue-crack detection technologies.

12. The method of claim 10 wherein said fatigue-crack is formed in said work-piece in a direction extending along said penetration length within a region of +/−5 degrees of said penetration length direction of said starter notch.

13. The method of claim 12 wherein said fatigue-cracking is not formed within a region of greater than 5 degrees to 90 degrees of said penetration length direction of said starter notch.

14. The method of claim 10 wherein said thru-hole is a fully enclosed thru-hole having an inner surface and said cutting wire forms said starter notch on said inner surface.

15. The method of claim 10 wherein said cutting wire has a diameter of 100 microns to 500 microns.

16. The method of claim 10 wherein said starter notch penetrates into said work-piece to provide a penetration length of up to 0.009 inches.

17. The method of claim 10 wherein said work-piece has a thickness of 0.3 inches to 0.7 inches.

18. The method of claim 10 wherein said work-piece has a length of up to 20 inches.

19. The method of claim 10 wherein said work-piece has a width of up to 4 inches.

20. The method of claim 10 further comprising:
providing a wire cutting apparatus, including said cutting wire having a first end portion and a second end portion, wherein a weight is coupled with the first end portion of the cutting wire;
a housing, wherein the housing includes a work-piece receiving opening and a plurality of pulleys arranged in series, wherein the plurality of pulleys comprise a first guide pulley, a second guide pulley and a third guide pulley;
introducing the cutting wire onto said first guide pulley;
routing the cutting wire from the first guide pulley through a fully enclosed hole formed in the work-piece and onto said second guide pulley;
routing the cutting wire from the second guide pulley onto a third guide pulley;
arranging the third pulley such that the weight coupled with the first end portion of the cutting wire is suspended from the third guide pulley;
arranging at least one of the first guide pulley and the second guide pulley such that the cutting wire is positioned to cut said starter notch in the fully enclosed thru-hole of the work-piece; and
moving at least a portion of a length of the cutting wire through the thru-hole and simultaneously cutting said starter notch in the thru-hole which extends outward from the thru-hole.

21. The method of claim 20 wherein:
moving at least a portion of the length of the cutting wire through the thru-hole is performed by pulling the cutting wire through the thru-hole with the weight falling under gravity.

22. The method of claim 20 wherein:
moving at least a portion of the length of the cutting wire through the thru-hole and simultaneously cutting a notch in the thru-hole which extends outward from the thru-hole is performed by moving the cutting wire through the thru-hole in alternating opposing directions.

Assignees

• Southwest Res Inst

Inventors

• Thwing Clinton J
• Mahoney Don E

Classifications

• Y10T83/0304

  Grooving · CPC title

• B26D3/14 Primary

  Forming notches in marginal portion of work by cutting (by punching B26F1/12) · CPC title

• B23D57/003

  Sawing machines or sawing devices working with saw wires, characterised only by constructional features of particular parts (constructional features of these parts per se B23Q) · CPC title

• B26D1/547

  having a wire-like cutting member (endless wire B26D1/46; severing using a heated wire B26F3/12) · CPC title

• B23D57/0007

  using saw wires · CPC title