Calculation model of the stressed state of the tooth contact zone of surface-hardened gears

Abstract

Stress state of the surface layer in the contact zone of mating teeth of cylindrical gears has been studied. It is established that stressed state of contact surfaces in the meshing pole of mating teeth is characterized not only by surface contact stresses, but also by deep equivalent stresses. It is shown that under contact loading the stressed state of surface layer is heterogeneous and changes with distance from the surface. Analysis and substantiation of calculation model for stressed state of diffusion layer in contact zone of mating teeth of surface-hardened gears are performed. Value of coefficient, which takes into account influence of normal stresses on efficiency of tangential ones, is specified. Reliability and validity of model of calculation of stressed condition of surface layer in contact zone of mating teeth of surface-hardened gears were estimated according to results of full-scale bench tests of the gears made of cemented steel 20ХГНР. The values of contact stresses in tooth meshing pole were corrected considering the load concentration across the width of cogged ring gear. Spalling depth of damaged teeth was determined by measuring impressions taken from the teeth of each examined gear with methacrylic resin. It is established that the nucleation zone of deep contact pitting for gears with 6.5 mm module is on the depth of occurrence of calculated maximum equivalent shear stresses. The consistency of the calculation results with the experimental data shows the validity of the calculated stress-strain model for involute gears.