Investigation Of Shot Peening As A Forming Process For Aircraft Wing Skins

Author:  Kulkarni, Schey, Badger,
Source:  J. Applied Metalworking, Vol. 1, No. 4
Doc ID:  1981038
Year of Publication:  1981
Abstract:  
The technique of generating curvatures in thin sheets by shot peening is well established for forming airplane wing skins to controlled contours. Success used to depend on the peening machine operator's skills; therefore, a systematic experimental investigation was conducted into the effects of workpiece geometry and process variables on resulting curvatures. Most of the tests were conducted on 152 x 610 mm 2024-T3 and 7075-T6 A1 alloy sheets of up to 12.7 mm thickness. Shot of 0.6-1.7 mm dia. was used in a wheel-type machine at speeds up to 80 m/s. The radius of curvature R of a peened specimen can be expressed as R = A + B/S where S is the shot density (weight/unit area) and A and B are parameters which are functions of other process variables. Specimens with a length-to-width ratio of L/W = 1 have equal stiffness in the L and W directions but developed a predominant curvature, the direction of which was affected by secondary variables such as the rolling direction in the sheet. However, transverse and longitudinal radii of curvature were almost identical in thicker specimens of L/W = 1/4 and could be used to predict the transverse curvatures of long workpieces peened under production conditions, as confirmed by production-scale experiments. Descriptors: Aluminum base alloys-- Metal working; Wings (aircraft)-- Metal working; Sheet metal-- Metal working; Contouring; Shot peening; Forming