Method and apparatus for improving the fatigue life of components and structures
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
B21D-028/26
B21D-028/24
B21D-031/00
출원번호
US-0066408
(2002-01-30)
발명자
/ 주소
Easterbrook,Eric T.
출원인 / 주소
Stresswave, Inc.
인용정보
피인용 횟수 :
3인용 특허 :
26
초록▼
Metal cold-working tooling and a method of employing such tooling. The tooling is used to produce deformation in a workpiece, to provide a selected beneficial residual stress profile in the workpiece, in order to provide high fatigue life structures in a minimum number of manufacturing steps. An ind
Metal cold-working tooling and a method of employing such tooling. The tooling is used to produce deformation in a workpiece, to provide a selected beneficial residual stress profile in the workpiece, in order to provide high fatigue life structures in a minimum number of manufacturing steps. An indenter is used to coldwork a workpiece, causing dimples in the workpiece. Preferably, the dimples are provided with a shape formed by application of a uniform pressure profile to the workpiece surface. As optimized, a relatively uniform beneficial residual stress profile is provided at both the surface and at the midplane apertures in a workpiece, so as to improve overall fatigue life. Also, an improved indenter tool profile shape is described, having a smoothly curved indenter surface portion. And, the use of consumable lamina wafers provides the benefit of easy application of uniform stress profile to a workpiece.
대표청구항▼
The invention claimed is: 1. Tooling for working a structure to improve the fatigue strength at a selected location in said structure, said structure comprising a first surface, a second surface, and a body therebetween, said tooling comprising: a first indenter, said first indenter comprising a co
The invention claimed is: 1. Tooling for working a structure to improve the fatigue strength at a selected location in said structure, said structure comprising a first surface, a second surface, and a body therebetween, said tooling comprising: a first indenter, said first indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said first surface of said structure to impart a residual stress profile in said body of said structure, and wherein said contacting end of said first indenter comprises a shaped surface profile substantially conforming to a dimple shape in said first surface of said structure produced by the application of a substantially uniform pressure profile on said pre-selected portion of said first surface of said structure, and wherein said contacting end of said first indenter further comprises a surface shape defined by the equation: wherein uz=normal displacement of a selected surface location of said contacting end of said indenter above a flat reference plane, v=Poisson's Ratio of the material comprising said workpiece; E=Elastic Modulus of the material comprising said workpiece; Pm=contact pressure distribution that yields said workpiece; a=radius of the contacting end of said indenter; and θ, r=polar coordinates of a selected surface location on said contacting end of said indenter. C=a constant ranging from 1 to 110. 2. Tooling as set forth in claim 1, further comprising a second indenter, said second indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said second surface of said structure to impart a residual stress profile in said body of said structure, and wherein said contacting end of said second indenter comprises a surface shape substantially conforming to a dimple shape in said second surface of said structure produced by the application of a substantially uniform profile on said pre-selected portion of said second surface of said structure, wherein said contacting end of said second indenter further comprises a surface shape defined by the equation: wherein uz=normal displacement of a selected surface location of said contacting end of said indenter above a flat reference plane; v=Poisson's Ratio of the material comprising said workpiece; E=Elastic Modulus of the material comprising said workpiece; Pm=contact pressure distribution that yields said workpiece; a=radius of the contacting end of said indenter; θ, r=polar coordinates of a selected surface location on said contacting end of said indenter, and C=a constant from about 1 to about 110. 3. Tooling as set forth in claim 1, wherein said first indenter further comprises a downwardly projecting centering punch portion. 4. Tooling as set forth in claim 2, wherein said second indenter further comprises a downwardly projecting centering punch portion. 5. Tooling as set forth in claim 1, wherein said first indenter comprises a dynamic indenter, said dynamic indenter adapted for engagement of said shaped surface of said contacting end against said first surface of said structure. 6. Tooling as set forth in claim 2, wherein said second indenter comprises a second dynamic indenter, said second dynamic indenter adapted for engagement of said shaped surface of said contacting end against said second surface of said structure. 7. An apparatus for treating material bounding the location selected for creation of an opening in a workpiece, in order to provide beneficial residual stress in material bounding said opening, to thereby improve fatigue life of said workpiece, said apparatus comprising: a support structure, said support structure adapted to securely support a workpiece; a shaped indenter having a contacting end; and a dynamic indenter driver, said dynamic indenter driver adapted to drive said contacting end of said shaped indenter into a pre-selected surface portion of said workpiece at a velocity sufficient to cause formation of a stress wave in said workpiece in reaction to the action of said contacting end of said shaped indenter; and wherein said contacting end of said shaped indenter further comprises a surface shape defined by the equation: wherein uz=normal displacement of a selected surface location of said contacting end of said indenter above a flat reference plane; v=Poisson's Ratio of the material comprising said workpiece; E=Elastic Modulus of the material comprising said workpiece; Pm=contact pressure distribution that yields said workpiece; a=radius of the contacting end of said indenter; θ,r=polar coordinates of a selected surface location on said contacting end of said indenter, and C=a constant from about 1 to about 110. 8. The apparatus as set forth in claim 7, further comprising an anvil, said anvil positioned in a firm backing relationship with said workpiece, said workpiece comprising an obverse and a reverse side, so that when said indenter acts on said obverse side of said workpiece, said reverse side of said workpiece is substantially supported by said anvil against movement in the direction of impact of said indenter. 9. The apparatus as set forth in claim 7, further comprising a second indenter and a second indenter driver, and an indenter driver controller, and wherein said first indenter driver and said second indenter driver are responsive to said indenter driver controller to simultaneously impact an obverse side and a reverse side of said workpiece, respectively. 10. The apparatus as set forth in claim 9, wherein said first indenter further comprises a pilot alignment guide, and wherein said second indenter further comprises a pilot alignment guide receiving portion, said pilot guide disposed through said workpiece for close interfitting engagement with said pilot guide receiving portion of said second indenter, so that during impact of said workpiece by said first indenter and said second indenter, said pilot alignment guide is received by said pilot guide alignment receiving portion. 11. The apparatus as set forth in claim 8, wherein said anvil further comprises a pilot alignment guide, and wherein said first indenter further comprises a pilot alignment guide receiving portion, said pilot guide disposed through said workpiece for close interfitting engagement with said pilot guide receiving portion of said first indenter, so that during impact of said workpiece by said first indenter, said pilot alignment guide is received by said pilot alignment guide receiving portion. 12. The apparatus as set forth in claim 7, further comprising at least one a deformable, consumable lamina disposed between said first indenter and said pre-selected surface portion of said workpiece, and wherein said consumable lamina comprises an obverse side and a reverse side, and wherein said obverse side is acted upon by said first indenter. 13. The apparatus as set forth in claim 9, further comprising a second deformable, consumable lamina disposed between said second indenter and a second pre-selected surface portion of said workpiece, and wherein said consumable lamina comprises an obverse side and a reverse side, and wherein said obverse side is acted upon by said second indenter. 14. The apparatus as set forth in claim 12 or in claim 13, wherein said obverse side of said consumable lamina further comprises a lubricant, said lubricant adapted to decrease friction between said first or said second indenter and said obverse side of said lamina. 15. The apparatus as set forth in claim 14, wherein said lubricant comprises a dry film lubricant. 16. The apparatus as set forth in claim 1, or in claim 7, wherein said indenter comprises a lubricant coated surface, said lubricant coated surface adapted to decrease friction between said indenter and workpiece. 17. The apparatus as set forth in claim 16, wherein said lubricant comprises a dry film lubricant. 18. A method of manufacturing a joint which includes overlapping at least first and second structural members, said method comprising: (a) contacting a preselected portion of said first structural member with an indenter having a contacting end at a pressure greater than the yield point of the composition of said first structural member to deform a portion of said first structural member in a manner so as to impart a pre-selected residual stress at a location at or near a selected location for a first fastener aperture through said first structural member, and wherein said residual compressive stress is substantially uniform along the entire length of sidewall portions of said first fastener aperture and wherein said contacting end of said indenter comprises a shaped surface profile substantially conforming to a dimple shape in said pre-selected portion of said first structural member produced by the application of a pressure profile that provides an effective amount of beneficial residual compressive stress in said pre-selected portion of said first structural member; (b) machining said first structural member to define said first fastener aperture via sidewall portions resulting from said machining; (c) providing in said second structural member, a second fastener aperture defined by second sidewall portion; and (d) inserting a fastener through said first and said second fastener apertures. 19. The method of claim 18, further comprising the step of applying force to said fastener to seat said fastener within said first and said second fastener apertures. 20. The method of claim 19, wherein the step of seating said fastener further comprises deforming an end portion of said fastener in order to secure and retain said fastener against said first structural member. 21. Tooling for working a structure to improve the fatigue strength at a selected location in said structure, said structure comprising a first surface, a second surface, and a body therebetween, said tooling comprising: a first indenter, said first indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said first surface and said body of said structure to impart a preselected beneficial residual stress profile in said surface and in said body of said structure, wherein said contacting end of said first indenter comprises a curved portion and or a slanted portion and has a pre-selected shaped surface profile for imparting a pre-selected dimple shape in said first surface and said body of said structure, said preselected shaped surface profile resulting in a dimple shape in said first surface which does not appreciably increase the thickness of said structure when said contacting end is engaged with said first surface, and wherein when a hole having a sidewall is installed between said first surface and said second surface of said structure, results in a substantially uniform residual compressive stress profile along said sidewall. 22. Tooling as set forth in claim 21, further comprising a second indenter, said second indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said second surface of said body of said structure to impart a pre-selected residual stress profile in said surface and in said body of said structure, and wherein said contacting end of said second indenter comprises a pre-selected shaped surface profile for imparting a pre-selected dimple shape in said second surface and said body of said structure, said preselected shaped surface profile resulting in a dimple shape in said first surface which does not appreciably increase the thickness of said structure when said contacting end is engaged with said first surface, and wherein when a hole having a sidewall is installed between said first surface and said second surface of said structure, results in a substantially uniform residual compressive stress profile along said sidewall. 23. Tooling as set forth in claim 21, wherein said first indenter further comprises a downwardly projecting centering punch portion for creating a centering feature in said first surface. 24. Tooling as set forth in claim 22, wherein said second indenter further comprises a downwardly projecting centering punch portion for creating a centering feature in said second surface. 25. Tooling as set forth in claim 21, wherein said first indenter comprises a dynamic indenter, said dynamic indenter adapted for engagement of said shaped surface of said contacting end against said first surface of said structure. 26. Tooling as set forth in claim 22, wherein said second indenter comprises a second dynamic indenter, said second dynamic indenter adapted for engagement of said shaped surface of said contacting end against said second surface of said structure. 27. Tooling for working a structure to improve the fatigue strength at a selected location in said structure, said structure comprising a first surface, a second surface, and a body therebetween, said tooling comprising: a first indenter, said first indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said first surface of said structure to impart a residual stress profile in said body of said structure, and wherein said contacting end of said first indenter comprises a shaped surface profile substantially conforming to a dimple shape in said first surface of said structure produced by the application of a substantially uniform pressure profile on said pre-selected portion of said first surface of said structure, and wherein said first indenter comprises a dynamic indenter, said dynamic indenter adapted for engagement of said shaped surface of said contacting end against said first surface of said structure. 28. Tooling as set forth in claim 27, further comprising a backing anvil, said backing anvil adapted to firmly support said structure when said structure is subjected to engagement by said indenter, so that movement of said structure is substantially prevented in the direction of action on said structure by said dynamic indenter. 29. Tooling, as set forth in claim 27, further comprising a second indenter, said second indenter comprising a contacting end for engagement with and deformation of a pre-selected portion of said second surface of said structure to impart a residual stress profile in said body of said structure, and wherein said contacting end of said second indenter comprises a surface shape substantially conforming to a dimple shape in said second surface of said structure produced by the application of a substantially uniform pressure profile on said pre-selected portion of said second surface of said structure, and wherein said second indenter comprises a second dynamic indenter, said second dynamic indenter adapted for engagement of said shaped surface of said contacting end against said second surface of said structure. 30. A method for working a bounding portion of material in a structure, said structure comprising two or more workpieces, said bounding portion adjacent a pre-selected location for an opening in said structure, in order to provide residual compressive stresses in said bounding portion for improving the fatigue life of said structure, said method comprising: providing an indenter, said indenter comprising a contacting surface portion, said contacting surface portion comprising a curved portion and or a slanted portion and adapted to impact said structure at pre-selected surface locations adjacent said pre-selected location for said opening in said structure; indenting said pre-selected surface location of said structure to provide a pre-selected amount of residual stress in said structure within said bounding portion of material. 31. The method as set forth in claim 30, further comprising removal of a selected portion of material from said structure, said selected portion of material removed from said structure having an outer border portion, said outer border portion located at or adjacent to said pre-selected surface location on said structure having been impacted by said shaped surface portion of said indenter. 32. The method as set forth in claim 30, wherein said indenter comprises a dynamic indenter. 33. The method as set forth in claim 30, wherein said opening comprises an elongated recessed portion. 34. The method as set forth in claim 31, wherein said opening comprises a through passageway. 35. The method as set forth in claim 33, wherein said elongated recessed portion further comprises a closed end portion. 36. The method as set forth in claim 31, wherein said indenter comprises a shaped indenter surface portion, said shaped indenter surface portion providing, when impacted on said workpiece at a pre-selected velocity, a pre-selected amount of permanent deformation in said workpiece sufficient to produce a shaped surface portion in said workpiece corresponding to that shape formed by indenting said pre-selected location in such workpiece material with a uniform pressure profile, and wherein said uniform pressure profile over said pre-selected location is at least as large as the yield stress pressure in said material. 37. The method as set forth in claim 31, wherein said surface portion comprises a flat surface portion. 38. A method for working a bounding portion of material adjacent a preselected location for an opening in the body of a workpiece, to create beneficial residual compressive stress in said bounding portion for improving the fatigue life of said workpiece, said method comprising: providing an indenter, said indenter comprising a surface portion, said surface portion adapted to impact said workpiece at pre-selected surface locations adjacent said pre-selected location for said opening in said workpiece; indenting the body of said workpiece at said pre-selected surface location of said workpiece with said indenter to provide an effective amount of beneficial residual compressive stress in said structure substantially uniformly along the bounding portion of material in said body of said workpiece; removing from said body of said workpiece a selected portion of material, said selected portion of material removed to define a bounding portion adjacent an opening created by removal of said material, said material removed comprising at least a portion of said workpiece having been impacted by said shaped surface portion of said indenter, so that at least a portion of said bounding portion of said body of said workpiece material expands toward said opening. 39. The method as set forth in claim 38, wherein said opening comprises an elongated recessed portion. 40. The method as set forth in claim 39, wherein said elongated recessed portion further comprises a closed end portion. 41. The method as set forth in claim 38, wherein said opening comprises a through passageway. 42. The method as set forth in claim 38, wherein preselected surface location portion comprises a flat surface location. 43. The method as set forth in claim 38, wherein said workpiece comprises a section of non-uniform thickness. 44. The method as set forth in claim 38, wherein said workpiece is of uniform thickness in cross-section. 45. The method as set forth in claim 38, further comprising the step of providing an external support behind said workpiece prior to the step of indenting said workpiece, said external support positioned in a firm backing relationship with said workpiece, so that when said indenter acts on said workpiece, said workpiece is substantially supported by said external support against movement in a direction normal to the direction of impact of said indenter. 46. The method as set forth in claim 38, wherein said workpiece comprises an interior through passageway defined by an interior edge wall, and wherein the method further comprises the step of providing an internal support adjacent said interior edge wall to resist deformation of said workpiece during the step of indenting said workpiece. 47. The method as set forth in claim 38, wherein said workpiece comprises an interior through passageway defined by an interior edge wall, and wherein after the step of indenting said workpiece, the method further comprises the step of trimming a portion of said workpiece adjacent said interior edge wall. 48. The method as set forth in claim 38, wherein said workpiece comprises a plurality of locations at which openings are to be placed, and wherein the step of indenting said workpiece is performed at said each of said locations simultaneously. 49. The method as set forth in claim 38, wherein said workpiece comprises a plurality of locations at which openings are to be placed, and wherein the step of indenting said workpiece is performed at said each of said locations sequentially. 50. The method as set forth in claim 38, wherein the step of indenting and the step of removing material from said workpiece are each performed two or more times. 51. The method as set forth in claim 50, further comprising a subsequent step of removing sufficient material from said workpiece to form a finished passageway defined by a finished wall edge portion. 52. The method as set forth in claim 48, wherein said step of simultaneously indenting said workpiece comprising acting on an obverse and on a reverse side of said workpiece. 53. The method as set forth in claim 50, wherein the first removal step comprising removing material to form a first hole portion having a dead end portion in said workpiece a first diameter, and wherein a subsequent indentation step comprising acting said indenter against said dead end portion of said first hole portion. 54. The method as set forth in claim 53, further comprising, after the step of acting said indenter against said dead end hole the step of removing material to form a second hole portion in said workpiece, said second hole portion of a second diameter, wherein said second diameter is smaller than said first diameter of said first hole portion. 55. A method for working a bounding portion of material in a structure, said structure comprising two or more workpieces, said bounding portion adjacent a pre-selected location for an opening in said structure, in order to provide residual compressive stresses in said bounding portion for improving the fatigue life of said structure, said method comprising: providing an indenter, said indenter comprising a shaped surface portion, said shaped surface portion adapted to impact said structure at pre-selected surface locations adjacent said pre-selected location for said opening in said structure, said shaped surface portion having at least in part a shaped surface profile effectively approximating to a dimple shape in a first surface of said structure produced by the application of a substantially uniform pressure profile on at least one pre-selected location of said first surface of said structure; indenting said pre-selected surface location of said structure to provide a pre-selected amount of residual stress in said structure toward said bounding portion of material; removing a selected portion of material from said structure, said selected portion of material removed from said structure having an outer border portion, said outer border portion located at or adjacent to said pre-selected surface location on said structure having been impacted by said shaped surface portion of said indenter, so that said bounding portion of material expands transversely to said outer border portion of said selected portion of material removed from said structure. 56. The method as set forth in claim 55, wherein said opening comprises a through passageway.
연구과제 타임라인
LOADING...
LOADING...
LOADING...
LOADING...
LOADING...
이 특허에 인용된 특허 (26)
Champoux Louis A. (Seattle WA), Apparatus and method for prestressing a countersunk fastener hole.
Simonetto Charles M. (Le Perreux FRX), Method of deforming two opposite edges of a single workpiece by machining, and apparatus for implementing the method.
Burris Kenneth W. ; Clements Thomas E., Process for improving fatigue resistance of a component by tailoring compressive residual stress profile, and article.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.