Gear tooth impact testing

It is very difficult, if not impossible, to estimate the impact resistance of gear teeth from standard impact test data. This is because of the in-homogenous nature of most gear teeth, with a high-Carbon case and a low-Carbon core, and its complex geometry. While gears are subject to impact loading in "real life" and current research efforts are significantly focused on developing alternate materials for gears, in a variety of applications, a need to characterize the impact resistance of a gear tooth under varying strain rates has consequently arisen. In order to meet this need an existing drop tower has been modified and instrumented to test gear teeth under varying strain rates to induce various modes of fracture. This paper describes the analytical model developed to represent the drop tower and the gear holding fixture, which was utilized to evaluate various design alternatives to design a system where strain rates could be varied. Based on the results of the model, a system was implemented and a preliminary set of impact tests conducted. While some dynamic problems were encountered, these tests show that the system is performing largely as required. The source of the dynamic problems encountered was also examined and changes to the system to overcome these problems are planned. Data obtained in the impact tests conducted will also be presented to demonstrate the capability of the system.