Overload capacity of a Wolfrom type planetary system

Abstract

Purpose

The purpose of this paper is to introduce an alternative approach to the FE modelling and simulation of complex gear trains, such as the Wolfrom planetary system, in order to study their overload capacity. This is a challenging task because of the following: first, multiple contacts occur between complex geometric parts. Second, the model has to be solved for many instances in order to determine the relative position of the planetary system members at which the maximum bending stress and surface pressure occur. Third, the maximum allowable overloading torque has to be determined iteratively.

Design/methodology/approach

A Wolfrom planetary system with transmission ratio 19.2 is modelled and simulated using the finite element method. The optimum element size is selected by modelling and solving key areas of the system. Then, a complete model is built using balanced element length at the flanks and roots, with respect to low solution time and result accuracy. A single loading torque is applied at the input shaft and the load distribution results from the solution when equilibrium is achieved. The input torque is increased until the maximum allowable stress or pressure is reached.

Findings

Combining the load distribution derived from a mixed density mesh with Hertzian pressure calculations, improves the accuracy of the results and decreases the total evaluation time of overload conditions. Furthermore, meshing disturbances due to the elastic deformation of the matting tooth pairs can be identified. It is shown that in the Wolfrom reducer analysed, the limiting mode of failure is the tooth breakage, which occurs when the input torque is increased by a factor of 3.8.

Research limitations/implications

The balanced element length meshing requires individually meshed key areas and additional workflow steps. In this way, the complexity is increased but the solution time minimised. Automation tools can improve the simulation process.

Originality/value

The balanced element length model and the result evaluation provides an improved approach of the overload capacity estimation where analytical methodologies cannot be applied.

Citation

Mihailidis, A., Nerantzis, I. and Athanasopoulos, E. (2015), "Overload capacity of a Wolfrom type planetary system", International Journal of Structural Integrity, Vol. 6 No. 5, pp. 636-648. https://doi.org/10.1108/IJSI-11-2013-0043