High Strength Gears by Powder Metallurgical Manufacturing Processes

摘要

To increase the bearing capacity of powder metallurgically produced gears, the highly stressed surface is densified, whereby good results are obtained in tooth flank bearing capacity; a wider spread use of PM gears is inhibited by the lower bearing capacity of the tooth root. Accordingly, the objective of this research project is to increase the bearing capacity of the tooth root by optimizing the local distribution of density and to aim for bearing capacities of full-density gears. The fatigue strength of the material is provided as a function of density, to make the density gradient - caused by the surface densification - available for optimization. In addition, the size effect of the fatigue strength has been taken into account. After modifying the density gradient, the resulting changes in the stress distributions are analyzed; for this purpose, the Finite Element Analysis (FEA) has been extended by the inclusion of a density dependent Young's modulus. Using the new gained insights, a first prediction is made for the fatigue behavior of a surface densified PM-gear.