Metal deforming – By shot-blasting
Reexamination Certificate
2000-04-24
2001-02-20
Jones, David (Department: 3725)
Metal deforming
By shot-blasting
C029S090700
Reexamination Certificate
active
06189356
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to methods and apparatus for peening components and more particularly to a method and apparatus which prevent damage to corners of components during peening.
Metal components such as those used in gas turbine engines are peened to induce compressive surface stresses. These compressive stresses inhibit crack formation and growth in the component. Because peening inhibits crack formation and growth, peened components generally have longer fatigue lives than unpeened components. However, high intensity peening (e.g., peening to Almen intensities greater than about 0.005 A) sometimes damages corners of components resulting in lower fatigue lives. The corners which are susceptible to damage include corners surrounding holes in components. The damage occurs when the corners are smeared, curled or bent over by the force of peening media hitting the corner during high intensity peening. The bent corners form notches which concentrate stress. Further, the metal at the corners becomes brittle as it is bent. The stress concentrations and brittleness increase the likelihood of crack formation and increase the speed of crack growth in the component.
To determine if corners are damaged by peening, the corners can be inspected following peening. If a damaged corner is found, the component is scrapped or reworked to remove the damaged area. However, corners usually are not inspected for peening damage and peening damage is controlled by controlling the peening process.
SUMMARY OF THE INVENTION
Among the several features of the present invention may be noted the provision of a mask for masking a corner of a metal component during peening. The component has a first surface defining an opening in the component and a second surface intersecting the first surface of the component at the corner. The mask includes a plug sized and shaped for insertion in the opening adjacent to the corner to cover the corner during peening. Further, the mask includes a rim surrounding at least a portion of the plug sized and shaped for surrounding at least a portion of the opening to cover the corner during peening thereby preventing the corner from being peened.
In another aspect, the present invention comprises a combination including a metal component having a first surface and a second surface intersecting the first surface at an external corner and a corner mask positioned at the corner of the component. The mask is made of a material which is resistant to damage from peening. The mask is sized and shaped for covering the corner to protect the corner from damage during peening. Further, the mask is sized and shaped to permit at least a portion of the first surface and at least a portion of the second surface to be peened when the mask is positioned at the corner of the component.
In yet another aspect, the present invention includes a method of peening a metal component. The method comprises the steps of positioning a mask over the corner of the component, peening the first surface of the masked component at a first intensity and peening the second surface of the masked component at a second intensity. Further, the method includes removing the mask from the corner of the component and peening the corner of the component at a third intensity less than the first intensity and the second intensity.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.
REFERENCES:
patent: 3482423 (1969-12-01), Murray et al.
Bissett Joan E.
Karafillis Apostolos P.
Simeone Peter A.
Wilson Douglas A.
General Electric Company
Gressel Gerry S.
Hess Andrew C.
Jones David
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