Bending strength of oil-lubricated cylindrical plastic gears

Oil-lubricated plastic gears enable significantly higher power transmission compared to dry-running gears. One of the most relevant damage mechanisms herein is tooth root breakage. Due to the high elasticity of thermoplastics, load-induced deflections strongly affect the tooth root stresses. In this work, a modified method for calculating the tooth root stresses is used to increase the accuracy of the bending strength calculation of plastic gears. Experimental results with steel-plastic spur gear pairings prove that load-induced deflections and dynamic tooth forces are not yet adequately considered in VDI 2736. In doing so, it was to some extent possible to validate and confirm the POM fatigue strength data in accordance with VDI 2736.