A comparison with tensile fatigue data

Intent of the study

Designing gears requires a fair amount of expertise and experience. For metals these standards are well developed and documented. For plastics this know-how is less well developed and many new concepts are based on successes from the past.

To understand the differences between metal and plastic gears, fundamental research, using finite element analysis and analytical methods, was conducted. This revealed the important effects of tooth bending which changes to operation of and stresses within gears considerably.
Next to this experimental programs were run to assess the lifetime of various grades Stanyl gears at high temperatures under various loading conditions.

Combining this expertise and experience gives insight in the performance of plastic gears and resulted in data and guidelines which can be used by designers to make a sound gear design in plastic. 

Summary

The paper shows an experimental study on the fatigue lifetime of high-heat polyamide (Stanyl) gears running in oil at 140°C. Based on previous works ('Zahnverrformungseffektei bei Kunststoffstirnrädern', Antriebtstechnik 2008and'Tooth-Bending Effects in Plastic Spur Gears' Gear Technology 2007  ), an analysis is made correcting for tooth bending and calculating actual root stresses. A comparison with tensile bar fatigue data for the same materials at 140°C shows that a good correlation exists between gear fatigue data and tensile bar fatigue data. This insight provides a solid basis for gear designers to design plastic gears using actual material data.