Jean-Pierre de Vaujany

A wear model for worm gear

This paper presents a numerical model to predict the wear of worm gear. This last is based on well-known Archard’s wear formulation. The influence of lubrication is taken into account with a local wear coefficient, depending on the ratio between the minimum lubricant film thickness and the amplitude of the surface roughness. When material on a wheel flank is worn, it is then necessary to update the surface profile, consequently the contact pressure calculations. To compute the quasi-static load sharing and thus the contact pressures required for the wear model, the equation of displacement compatibility is solved, using the influence coefficient method, which allows a fast and accurate computing. The bending deflections of the worm and wheel, and the local contact deformations of mating surfaces are included. The Boussinesq theory is applied for calculating the local contact deformations. The bending is determined by the combination of only one standard finite element method computation and interpolation functions. This method allows taking into account the environment of the gear meshing, such as the actual shafts, rim, web, bearing locations, which affect the quasi-static results and thus the wear. In addition, the model allows to obtain numerous results, such as load sharing, contact pressures distribution, transmission error, stiffness, wear distribution, etc. A comparison between theoretical wear predictions and experimental results, issued from the literature, are also presented.

Designing and Manufacturing Spiral Bevel Gears Using 5-Axis CNC Milling Machines

The design of spiral bevel gears still remains complex since tooth geometry and the resulting kinematics performance stem directly from the manufacturing process. Spiral bevel gear manufacture owes most to the works of Gleason and Klingelnberg. However, recent advances in milling machine technology and CAM (Computer Aided Manufacturing) make it possible to manufacture good quality spiral bevel gears on a standard 5-axis milling machine. This paper describes the CAD definition and manufacturing of spiral bevel gear tooth surfaces. Process performance is assessed by comparing the resulting surfaces after machining with the pre-defined CAD surfaces. Using this manufacturing process allows to propose new type of geometry. This one is more theoretical and, in some respects, easier to design than the standard spiral bevel gear as it enables simpler mesh optimization. The latter can be achieved by using the model of meshing under load recalled in this paper.Copyright

Design and analysis of a spiral bevel gear

Spiral Bevel gears are used in power transmission systems with two crossed shafts. The topic of the paper is a model for helping the spiral bevel gear design, depending on meshing parameters. The global parameters of the gear are calculated with the standard ISO 23509 equations. A prediction of the profile modifications has also been performed to center the load pattern on the flank and to minimize the maximum contact pressure. A numerical simulation is achieved with the ASLAN software, developed by LaMCoS laboratory for calculating the quasi-static load sharing of spiral bevel gears.