Surface Durability (pitting) and Wear The test strategy is to find loads that have an average life-to- failure durability of three- to six-million cycles for high loads and 12- to 15-million cycles for low loads. Six tests are conducted at each of these load levels with the specimen gear running at 900 rpm and the mating gear at 540 rpm. A Weibull statistical analysis of the results establishes the service life of 10%, 50%, and 90% failures with 50% and 90% confidence levels.

Low Speed Bending The test strategy is to use a standard 18-tooth specimen gear and a 30-tooth mating gear that have a life-to-bending failure of 250,000 to 500,000 cycles.

Scuffing The test strategy is to run the gear set at a low load and speed using a cold/room temperature lubricant for half an hour. Measurements for surface finish occur in 0.5-hour increments after each step, starting with a moderately high load, speed, and lubricant temperature. The load and/or lubricant temperature is increased with each step. The test concludes when surface roughness significantly increases and visible tears (scuff marks) occur at the tip of the driven gear.

Single-Tooth Bending Fatigue The test strategy is to identify a load that will cause a failure by using a single-tooth fatigue fixture with cycles of 50,000 to 100,000 and 250,000 to 500,000 cycles. Six tests are performed at each of these load levels.

Rolling/Sliding Contact Fatigue The test strategy is to determine the loads by a gear operating speed of 1330 rpm, using three- to six-million cycles for high loads and 12- to 15-million cycles for low loads.

Low overhead and accessibility enable the ARL Penn State to operate its gear test capabilities at a lower cost than industry. As a result, excellent gear and gear materials testing services are now available to manufacturers who cannot afford an in-house gear test facility.

For more information see the Point of Contact for this survey.