An extremely wide selection of different plastic materials is currently available on the market. A major limitation, however, is a huge gap in gear-specific material data on these materials, which is a problem that has been persisting for decades now. Providing a step towards a solution is the German guideline VDI 2736, which proposes design rating methods (Ref. 2) along with testing procedures (Ref. 3) to be followed to generate reliable data required in the gear rating process. This paper delves into the current state of the art in plastic gear testing, providing a comprehensive overview of employed testing methods, supplemented with case studies.

This paper deals with the residual stress depth profiles in case-carburized gears, their effects on the fatigue behavior as well as the enhancement of ISO/TS 6336-4 to include the consideration of tensile residual stresses in the tooth core area. For this purpose, an equation is also presented with which these tensile residual stresses can be estimated so that they can be used in the enhanced evaluation of TFF risk.

This month's issue of Gear Technology covers a subject engineers love to learn about from others but hate to learn about through firsthand experience: gear failure. In a broad sense, all engineering is concerned with failure. Eventually, all parts fail, so engineers need to determine the limits of their design and ensure that it will meet the requirements of the particular application.