Fatigue life enhancement of dovetail connector slots and noncircular openings

A method of forming fatigue life enhanced dovetail connector slots in a peripheral portion of a rotor for receiving blade roots, comprising:

• drilling a pair of spaced-apart openings in the peripheral portion of the rotor at each blade root location, substantially equal distances inwardly from the peripheral edge of the rotor;
• cold-expanding the rotor material immediately surrounding the openings by passing a cold-expansion mandrel through each opening;
• cutting the rotor along lines extending inwardly from the edge of the rotor to central regions of the cold-expanded openings;
• removing the regions of the rotor material which are circumferentially between the two openings and the two cuts at each blade location;
• and
• machining edge portions of the material in the vicinity of the cuts and the openings to a final desired size and shape but retaining the cold-expanded round regions bounding the slots.

A method of forming a noncircular opening in a workpiece which is immediately bounded by material which includes residual compressive stresses for fatigue life enhancement, said method comprising:

• drilling a plurality of at least two spaced-apart openings in the workpiece;
• cold-expanding the workpiece material immediately surrounding each opening by passing a cold-expansion mandrel through each opening;
• cutting the workpiece along lines intersecting the openings and removing a region of the workpiece material which is between the openings;
• and
• leaving circular portions of the cold-expanded drilled openings so that the noncircular opening which results is partially bounded by the circular region.