Grumman Aerospace Corporation

Northrop Grumman Systems Corporation

James R Kennedy

Edmund Y Ting

John M Papazian

Edwin Gerard Haas

David J Larson, Sr

Alan Levy

Alvin Levy

A gauge for measuring an out-of-plane surface displacement profile around a cold-worked fastener hole in relation to the distribution of residual compressive stresses around the hole and related fatigue life. The gauge has a deformable strain sensor positionable to be deformed in accord with the out-of-plane surface of the structural material circumferentially surrounding the cold-worked hole. A measurement reporting readout device is in communication with the strain sensor and relates three-dimensional surface-profile measurement data in accord with strain sensor deformation to determine or verify the cold expansion magnitude, uniformity and consequent fatigue life through three-dimensional elastoplastic finite element comparative analyses and/or experimental measurements for a hole in any material of given thickness.

Surface displacement measurement gauge

A method for inspecting a cold expanded fastener hole in a structural part to confirm that the hole has been expanded by a desired amount involves determining the degree to which the hole has been expanded as a function of the out-of-plane deformation in material surrounding an entrance or exit of the hole formed as a result of the cold expansion process. Out-of-plane deformation at either of the entrance or exit is compared to a model constructed from an array of experimentally or analytically determined out-of-plane deformation profiles for a hole with the same, or substantially the same, dimensions subjected to varying degrees of cold expansion. The degree of expansion of the hole is derived based on this comparison.

Method for quantitative inspection of cold-expanded fastener holes

Fatigue lifetime enhancement of the holes formed in structural members occurs by introducing a cold working tool or interference fit fasteners fabricated from shape memory alloy materials. The tool may be employed to expand the wall of a hole while the tool material is raised above the critical transitional temperature. Then, upon lowering the tool material below the critical transitional material, it contracts permitting it to be withdrawn. Bushings and interference fit fasteners may be installed in holes formed in structural members when a shape alloy material bushing or fastener is heated above the critical transitional temperature so that an interference fit results and the hole is cold worked. If the alloy material is not cooled below the critical transitional temperature, the interference fit may be permanently maintained, thereby further enhancing the fatigue life of the members.

Method of cold working holes using a shape memory alloy tool

Diffusion bonding of aluminum alloy objects of different sizes and shapes may be greatly improved when the surface of the object is exposed to a mechanical deformation cycle which forms a cold-worked surface microstructure, followed by a heat treatment cycle to produce recrystallization of the surface layer. The method of the invention results in the formation of finer grains at the surface which enhances the strength of a diffusion bond.

Method for diffusion bonding of metals and alloys using mechanical

Diffusion bonding of aluminum alloy objects of different sizes and shapes may be greatly improved when the surface of the object is exposed to a thermal spray source which deposits fine metal particles on the surface. Rapid quenching of solidification occurs at the surface. Such treatment results in the formation of finer grains at the surface which enhances the strength of a diffusion bond.

Method for diffusion bonding of metals and alloys using thermal spray

Diffusion bonding of aluminum alloy objects of different sizes and shapes are greatly improved when the surface of the object is exposed to a high energy source which causes a heat treatment or melting and rapid quenching or solidification at the surface. Such treatment results in the formation of finer grains at the surface which enhances the strength of a diffusion bond.

Method for diffusion of metals and alloys using high energy source

Diffusion bonding of surface layers of an alloy, such as an aluminum alloy, having surface oxides of low solubility in the alloy includes treating the surface layers to be bonded to remove existing surface oxide coatings, and diffusion bonding the surface layers to one another by placing the alloy to be bonded under sufficient pressure to cause disruption of the oxide coatings by localized surface deformation of the alloy, enhanced by a superplastic microstructure, without substantial deformation of the alloy, i.e., macroscopic deformation approaching zero percent, while heating the alloy in a non-oxidizing atmosphere for a time sufficient for diffusion bonding to occur. The alloy may be treated so that at least the surface layers thereof have a fine grain structure of the type associated with superplastic forming properties. Components may be formed by diffusion bonding and superplastic forming.

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Huntington, NY, United States of America

James R Kennedy