Abstract: A method for simultaneously shot peening and smoothing includes use of relatively large, smooth, hard, spherical steel shot having a substantially uniform diameter in the range 1-2.5 mm. Titanium workpieces are provided in one step with a compressive stress layer of the order of 0.13 mm and a surface finish of better than 15.times.10.sup.-6 inch AA, compared to conventional peened finishes of the order of 40.times.10.sup.-6 inch AA. Surface finish and peening intensity are inter-related and dependent on shot diameter, mass, velocity, and energy within relatively small limits. The shot diameter is uniform within .+-.0.05 mm; the shot impact velocity is uniform within .+-.4 percent or less, in the range 1.4-12 m/s.

Abstract: In apparatus for shot peening, gravity is used to accelerate uniform sized steel shot, and thereby impart a combination of good surface finish and uniform compressive stresses to workpieces. It is especially useful for finishing gas turbine airfoils. Shot is introduced into the peening enclosure (28) through a gate (40) at near zero velocity. It is then accelerated along a streamline (31) toward the workpiece (18) with uniform velocity. The workpiece, positioned along the streamline, can be manipulated in three rotational modes: oscillatory rotation to uniformly peen contoured surfaces of a workpiece, periodic incremental rotation to peen different sides of a workpiece; and, tilting motion to enable peening of shoulders (22). The apparatus is especially suited to peening fragile workpieces such as gas turbine airfoils (18). A diverter plate (44) intercepts the shot stream at times when repositioning of a fragile workpiece is undertaken.

Abstract: Disclosed is a two step process of peening for workpieces having small radii fillets or fragile edges, such as gas turbine airfoils have. In the first step, relatively small size shot of less than 1 mm dia is used to impart a first peening intensity to a workpiece. This results in a first relatively rough surface finish. In the second step, shot of substantially uniform diameter in the range 1-2.5 mm is impacted with uniform velocity to provide a surface finish smoother than 30AA (10.sup.-6 inch). When fillets are peened, improved fatigue life results from the duplex process. When used on edges, where direct edge impact is avoided in the second step, deformed edges are avoided by the process. Yet the workpiece is substantially smooth and the edges have the requisite residual stress distribution.

Abstract: Shot peening of thin edges of workpieces which are subject to deformation damage by direct impacts is accomplished by rotating the workpiece edge near centerline through a particular angle measured from the normal to the shot streamline. The angle is sufficient to cause oblique blows on the centerline of the edge, but insufficient to cause direct impacts. Compressive stresses by the oblique blows provide residual compressive stresses along the centerline to the desired depth. The angle is calcuable from the edge radius, the depth of stressing desired at the centerline, and the depth of stressing produced by shot at a reference location. Oscillatory rotation is preferably used to obtain even peening.

Abstract: Disclosed is apparatus and method for electrochemically finishing the edges of airfoils and other thin edged objects. When the edge on an airfoil varies in thickness along its length, a tapered electrode is provided which has both a decreased diameter and increased spacing distance, providing a means for obtaining an edge with a radius proportioned to the thickness. Generally, in the system having an electrode with a unit surface area A, and with an electrode-workpiece surface spacing distance S, both A and S are changed so that the ratio A/S is lowered for electrode portions proximate to edge portions having lowered thickness.

Abstract: Disclosed is apparatus and method for electrochemically finishing the edges of airfoils and other thin edged objects. When the edge on an airfoil varies in thickness along its length, a tapered electrode is provided which has both a decreased diameter and increased spacing distance, providing a means for obtaining an edge with a radius proportioned to the thickness. Generally, in the system having an electrode with a unit surface area A, and with an electrode-workpiece surface spacing distance S, both A and S are changed so that the ratio A/S is lowered for electrode portions proximate to edge portions having lowered thickness.