Method and apparatus to propagate crack growth in a workpiece

摘要

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.

主权项

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.