Mechanical Design Engineering Handbook by Peter R. N. Childs

Author:Peter R. N. Childs [Childs, Peter R.N.]
Language: eng
Format: epub
ISBN: 9780081023686
Publisher: Elsevier Ltd.
Published: 2018-11-24T00:00:00+00:00

Fig. 9.1 Pitting damage to a helical gear tooth (Batsch, 2016).

Fig. 9.2 Scuffing gear failure on the flank of a test gear due to poor extreme-pressure (EP) gear oil properties (Michalczewski et al., 2013).

Fig. 9.3 Gear failure due to scoring.

The modelling of gear stresses has been the subject of extensive research. The analysis is complex because of the dynamic nature of the loads and the very high stresses involved for some gear designs. Whilst techniques such as finite element analysis (Barbieri et al., 2014; Chen and Tsay, 2002; Jyothirmai et al., 2014; Rao and Muthuveerappan, 1993) allow detailed modelling of a specific gear geometry, the activity can be labour intensive in terms of setting up the model and uncertainty often remains concerning the validity of boundary conditions and material properties. An alternative to finite element analysis is the use of procedural approaches such as those outlined in standards developed by the American Gear Manufacturers Association (AGMA), the British Standards Institution (BSI) and the International Organisation for Standardisation (ISO).

This chapter concentrates on analysing whether failure due to bending and contact stresses in a gear set is likely. In Section 9.2, a relatively simple relationship for contact stresses is outlined prior to the introduction of AGMA equations for bending and contact stresses in Section 9.3. The AGMA equations rely on the evaluation of a significant number of factors and geometrical parameters, which depend on the specific geometry and materials concerned. In this chapter the basic approach is outlined for 20 degree pressure angle, full depth teeth spur gears only. Some of the detailed charts and equations given in the source standards have been omitted and the reader is encouraged to view the most recent standards as necessary. A general strategy for gear design is outlined in Section 9.4.

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