The Combined Influence of Helix Angle and Total Contact Ratio on the p-FEM Calculated Tooth Root Stress in Cylindrical Gears

Abstract

Abstract Many parametrical studies about the effect of the helix angle on the maximum tooth root stress on cylindrical gears were conducted by means of a p-FEM (polynomial Finite Element Method) analysis, using models that comprehend all the contacting teeth and the adjacent ones. The studies were conducted in a way that the helix angle was varied from 0 to 35 degrees, keeping the transverse section constant (i.e. twisting the gears). Many non-HCR existing spur and helical gearsets, with different transverse contact ratio εα, transmission ratio, pressure angle, correction factor, and facewidth to module ratio were examined. Neither profile modification, nor crowning were considered. For each gearset the maximum p-FEM-calculated tooth root stress in both pinion and gear drops considerably when the total contact ratio εγ reaches the value of 2, with a minimum noticed around εγ = 2.1 ÷ 2.4; then the stress rises monotonically except for a non-remarkable drop when εγ reaches the value of 3. The p-FEM results were also compared with those based on ISO 6336-3 method B and AGMA 2001, showing noticeable differences.