Effect of Tooth Profile Modification In Asymmetric Spur Gear Tooth Bending Stress By Finite Element Analysis

摘要

Gearing is one of the most critical components in a mechanical power transmission system, and in most industrial rotating machinery. It is possible that gears will predominate as the most effective means of transmitting power in future machines due to their high degree of reliability and compactness. In addition, the rapid shift in the industry from heavy industries such as shipbuilding to industries such as automobile manufacture and office automation tools will necessitate a refined application of gear. Presently gears are suffered by backlash, undercut and interference. These defects can be eliminated by increasing the pressure angle and increasing addendum of mating gears. An additional alteration that is very rarely used is to make the gears asymmetric with different pressure angles for each side of the tooth. This is because two profiles of a gear tooth are functionally different for most of the gear drives. The workload on one side of profile is significantly higher than the other side of the gear. An asymmetric spur gear drive means that larger and smaller pressure angles are applied for the driving and coast sides. Interference is a serious defect in the involute system of gearing and should be avoided by undercutting the tooth, when the number of teeth is less than the minimum required number of teeth. Apart from the fact that interference hampers the conjugate action when the involute portion of a tooth mates with the non involute portion of the mating tooth, the two meshing gears will not have free rotation. Rather, the gear causing interference will have a tendency to jam on the flank of the pinion unless, of course, the pinion tooth-root has already been undercut making room to provide free movement of the gear tooth. Besides, due to interference and in the absence of undercut, the mating gear will try to scoop out metal from the interfering portion. Therefore, the teeth become damaged and it will have an overall detrimental effect on the gearing system. The main objective of this paper is to study the effect of bending stress at the critical section for different pressure angles on the drive side along with the profile shift. Comparison has been made for symmetric and asymmetric spur gear tooth using Lewis equation and Finite element analysis software.