Improvement in Surface Fatigue Life of Hardened Gears by High-Intensity Shot Peening
Abstract
Two groups of carburized, hardened, and ground spur gears that were manufactured from the same heat of vacuum-induction-melted-vacuum-arc-remelted (VIM-VAR) AISI 9-310 steel were endurance tested for surface fatigue. Both groups were manufactured with a standard ground 16-rms surface finish. One group was subjected to a shot-peening intensity of 7 to 9A, and the second group was subjected to a shot-peening intensity of 15 to 17A. All gears were honed after shot peening to a surface finish of 16 rms. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a gear temperature of 350 K (170 deg F), and a speed of 10 000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The following results were obtained: The 10-percent surface fatigue (pitting) life of the high-intensity (15 to 17A) shot-peened gears was 2.15 times that of the medium-intensity (7 to 9A) shot-peened gears, the same as that calculated from measured residual stress at a depth of 127 microns (5 mil). The measured residual stress for the high-intensity-shot-peened gears was 57 percent higher than that for the medium-intensity-shot-peened gears at a depth of 127 micro (5 mi) and 540 percent higher at a depth of 51 micro (2 mil).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1992
- Accession Number
- ADA251522
Entities
People
- Dennis P. Townsend
Organizations
- National Aeronautics and Space Administration