Multicriteria optimization model for polymer gears
Izr. prof. dr. Jože Tavčar, univ. dipl. inž., dr. Borut Černe, mag. inž., prof. dr. Jože Duhovnik, univ. dipl. inž., dr. Damijan Zorko, mag. inž., vsi Univerza v Ljubljani, Fakulteta za strojništvo
The design of polymer gears is a demanding process due to the multitude of interconnected material, geometric and operational parameters, which together form a very complex system for analytical treatment. Polymer gears fail due to various forms of damage mechanisms such as wear, breakage due to fatigue, damage caused by elevated temperature, and flank damage due to pitting. The type of damage mechanism that will occur during gear running depends on the operating conditions. At high torque loads, the gear pair will e.g. be damaged due to excessive temperature load, at lower load due to wear, in case of lubrication the tooth breakage will in general occur due to fatigue of the material. Due to the wide range of mechanical properties, thermal characteristics and tribological conditions, the failure behaviour of polymer gears is very diverse. The main contribution of this article is a multi-criteria model that allows simultaneous consideration of different criteria such as: root and flank stress, gear temperature at the root, temperature in tooth contact, wear, deformation, cost and volume. The optimization model is presented on a test case of a selected helical gear pair. The authors developed a multi-criteria model into the computer program OptiTooth intended for the calculation and optimization of cylindrical gears. In the first step, the algorithm allows to vary the geometry according to different criteria: number of teeth (z1, z2), gear width (b), helix angle (β) and normal modulus (mn). Subsequently, the engineer has an overview of a large number of possible solutions and also of the influence of various design parameters on the target criteria and the overall value of the multicriteria function. In a few computational iterations and changes in design parameters, the optimized geometry of the gear pair can be obtained.
polymer gears, failure type, wear, temperature, multi-criteria function