Accession Number : ADA309177

Title :   Detecting Gear Tooth Fatigue Cracks in Advance of Complete Fracture.

Descriptive Note : Technical memorandum,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Zakrajsek, James J. ; Lewicki, David G.

PDF Url : ADA309177

Report Date : JAN 1996

Pagination or Media Count : 15

Abstract : Results of using vibration based methods to detect gear tooth fatigue cracks are presented. An experimental test rig was used to fail a number of spur gear specimens through bending fatigue. The gear tooth fatigue crack in each test was initiated through a small notch in the fillet area of a tooth on the gear. The primary purpose of these tests was to verify analytical predictions of fatigue crack propagation direction and rate as a function of gear rim thickness. The vibration signal from a total of three tests was monitored and recorded for gear fault detection research. The damage consisted of complete rim fracture on the two thin rim gears and single tooth fracture on the standard full rim test gear. Vibration-based fault detection methods were applied to the vibration signal both on-line and after the tests were completed. The objectives of this effort were to identify methods capable of detecting the fatigue crack, and determine how far in advance of total failure positive detection was given. Results showed that the fault detection methods failed to respond to the fatigue crack prior to complete rim fracture in the thin rim gear tests. In the standard full rim gear test all of the methods responded to the fatigue crack in advance of tooth fracture; however, only three of the methods responded to the fatigue crack in the early stages of crack propagation.

Descriptors :   *COMMERCIAL AIRCRAFT, *HELICOPTERS, *FATIGUE(MECHANICS), *GEAR TEETH, VIBRATION, BENDING, FRACTURE(MECHANICS), CRACK PROPAGATION, DEFECTS(MATERIALS), DRIVES, FAILURE(MECHANICS), GEARS, TRANSMISSION GEARS.

Subject Categories : Helicopters
      Civilian Aircraft
      Machinery and Tools

Distribution Statement : APPROVED FOR PUBLIC RELEASE