Study of the Correlation Between Theoretical and Actual Gear Fatigue Test Data on a Polyamide

摘要

Printed with permission of the copyright holder, the American Gear Manufacturers Association, 500 Montgomery Street, Suite 350, Alexandria, Virginia 22314-1560. Statements presented in this paper are those of the authors and may not represent the position or opinion of the American Gear Manufacturers Association. DSM Engineering Plastics is a producer of nylon plastic materials used for gear manufacture. In the past two years, the company has been conducting fatigue tests on actual molded gears in order to provide design data. The experiment used spur gears that are fully lubricated and temperature-controlled. Testing for the materials has been done at DSM Research, while the gear tests are being conducted at the University of Berlin. The purpose of the testing is to see if there is a good correlation between fatigue data generated on test bars vs. the actual fatigue performance in a gear. In order to do this, the theories of gear calculations to get root stresses were also examined. Advanced finite analysis (FEA) showed that there are corrections needed to account for high loading or high temperatures in plastic gears, which corroborates other work within the industry. With proper corrections to get accurate root stresses, there can be shown good correlation between tensile bar fatigue and actual spur gear fatigue. Also, high crystalline nylon has been found which is an excellent material for gears in demanding applications, and can withstand both high torques and high operating temperatures.