Abstract
The true root stresses of internal spur gears with various numbers of teeth and addendum modification coefficients are calculated by means of 2-dimensional elasticity theory and mapping function, and the position of the critical section on the compressive side of the internal spur gear tooth is indicated. The stress concentration factors at the position of the critical section are calculated under different loading conditions. A practical formula for the compressive true root stress of the internal spur gear tooth is derived on the basis of these calculated results. Furthermore, the root stresses calculated by this practical formula are compared with those calculated by the theory of elasticity and FEM, and with measured stresses, and the validity of the practical formula is thereby confirmed.
