Abstract
In applications requiring high load carrying capacity, conforming contacting pairs with a relatively large contact footprint are used. These include circular arc, Novikov, and Wildhaber gears found, for example, in helicopter rotors. Closely conforming contacts also occur in many natural endo-articular joints, such as hips, or their replacement arthroplasty. The main determining factors in contact fatigue are the sub-surface shear stresses. For highly loaded contacts, classical Hertzian contact mechanics is used for many gears, bearings, and joints. However, the theory is essentially for concentrated counterforming contacts, where the problem is reduced to a rigid ellipsoidal solid penetrating an equivalent semi-infinite elastic half-space. Applicability is limited though, and the theory is often used inappropriately for contacts of varying degrees of conformity. This paper presents a generic contact mechanics approach for the determination of sub-surface stresses, which is applicable to both highly conforming as well as concentrated counterforming contacts. It is shown that sub-surface shear stresses alter in magnitude and disposition according to contact conformity, and lead to the different modes of fatigue failure noted in practice.
Highlights
Conforming gear pairs are used in highly loaded applications, for example, the Novikov gears of the final drive of helicopter gearboxes and some turboprops [1,2]
The same can be true of some counterformal gear teeth pairs, where Hertzian contact mechanics is often erroneously used in literature
This paper provides a 2D solution for sub-surface stresses in contacts of varying degrees of conformity
Summary
Conforming gear pairs are used in highly loaded applications, for example, the Novikov gears of the final drive of helicopter gearboxes and some turboprops [1,2]. The of onset determines useful gearing [9–11], so an maximum accurate prediction sub-surface shear stresses is the main aim.life. For hard and brittle surfaces, maximum shear shear stress is the most important according to the Tresca failure criterion, whereas for ductile solids, The onset of fatigue spalling determines the useful life of gearing pairs [9–11], so an accurate prediction of sub‐surface shear stresses is the main aim. It is analytical and applicable to a range of contacting elastic solids, such as discs, circular arc, and Novikov gears, as well as counterformal semi-infinite solids where the Hertzian pressure distribution is used
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