General Electric Company

John C Clark

Alexander H Nahm

Thomas E Schubert

Eric N Bamberger

A rolling element bearing member designed for use in a preselected bearing operation, such as a gas turbine engine, which develops a predetermined operating hoop tensile stress in the member includes a hardened layer contiguous with a ductile core having a hardness less than 50 Rockwell C. For example, the hardened layer is a carburized layer of high hardness in the range of 58-66 Rockwell C. The hardened layer has improved resistance to crack initiation and propagation as a result of providing the layer with compressive residual stress in an amount greater than the predetermined operating hoop tensile stress, for example in the range of about 10-60 ksi to a depth up to about 0.06 inch. Such a member is made by providing a member of a metal alloy having the capability of developing such a hardened layer, and then processing the member to develop the layer in the amount of compression.

Rolling element bearing member

The rotor that carries the target in a rotating anode x-ray tube is carried on a shaft that is journaled in axially spaced apart ball bearings. The outer and inner races of the bearings have curved grooves presented toward each other and there are a plurality of balls in the grooves. A preloaded spring is interposed between corresponding races of the bearings for applying oppositely directed axial forces to them. The grooves are so shaped and the clearance between the balls and groove surfaces is such that when the axial force is applied, one race shifts axially relative to the other in which case each ball has two points of contact, one point at which the ball contacts the surface of the groove in the outer race on one side of a plane transverse to the shaft axis and another point where the ball contacts the surface of the groove in the inner race on the other side of the plane. The chosen axial preload force is in a range of forces that compels many balls to share the radial load of the rotor and target to minimize contact stress on each ball and the races and the preload spring force range begins just above the force that would result in one or a few of the balls carrying the radial load.

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Oxford, OH, United States of America

John C Clark