A new wear prediction method of tooth surfaces of involute gears based on a real tooth surface model and a modified fractal method is developed. The real tooth surface model of an involute gear pair is introduced, and microgeometry feature detection of tooth surfaces is achieved by monitoring variations of normal vectors of each discrete data point of the real tooth surface model. To predict wear progression of tooth surfaces of a gear pair, an abrasive wear analysis model and the modified fractal method are used to analyze contact performance and its changes with accumulation of surface wear. The abrasive wear analysis model can analyze wear depths of gear tooth surfaces with sliding distances, local contact pressure, and directions of wear progression based on Archard's model. The modified fractal method is proposed to calculate instantaneous contact stiffness and estimate elastic and plastic deformation regions based on an asperity contact model. Microgeometry features of tooth surface asperities can be described as the basis of an asperity contact model and allow tooth contact analysis of real tooth surface models with their local microgeometry feature changes due to plastic deformations. Feasibility and effectiveness of this wear prediction method were verified by comparing predicted results of gear surface wear progression with gear wear test results.

An elastic transmission error (TE) compensation method for a rotary vector (RV) speed reducer is proposed to improve its transmission accuracy based on error sensitivity analysis. Elastic and geometric TEs of the RV speed reducer can be compensated by tooth surface modification of cycloidal gears. Error coefficients of the TE of the RV speed reducer are derived to determine error factors with positive effects on TEs based on error sensitivity analysis. A total TE, including the elastic TE, is obtained by using Adams. The elastic TE compensation method is developed to calculate modification values of error factors with positive effects on the TE to decrease the elastic TE of the RV speed reducer. TE simulation results show that the elastic TE accounts for 25.28% of the total TE, and calculation results show that the maximum contact force and normal deformation of the modified prototype are obviously improved. The feasibility and accuracy of the proposed elastic TE compensation method for RV speed reducers were verified by TE experiments. TE experiment results showed that the TE of the modified RV speed reducer is 47.22% less than that of the initial RV speed reducer.

Accurately and rapidly evaluated error sensitivity of actual tooth surfaces of hypoid gears can be a significant foundation for a variety of dynamic preference analysis and machine tool setting readjustments. Due to the complexity of local geometric features as well as the limitations of the data measurement on tooth surfaces of hypoid gears, automated error-sensitivity analysis for actual tooth surfaces still presents many substantial challenges. This paper presents a novel methodology for the error-sensitivity analysis of real tooth surfaces of hypoid gears. The methodology combines an error-sensitivity analysis model with a numerical analytical real tooth contact analysis (RTCA) model. The real tooth surfaces, describing local micro-geometry features on actual tooth surfaces, have been produced by 3D discrete data points reconstruction. In this method, the discrete data points on actual tooth surfaces are measured by using a coordinate measure machine (CMM). The location, size, and shape of contact patterns are determined from the predicted interference areas distribution by numerical analysis. In addition, the error-sensitivity analysis model is established for evaluation of the sensitivity of hypoid gears with real tooth surfaces that corresponds to misalignments. The results of experiment show that the proposed method can obtain actual contact properties that significantly improve the basic design performances significantly.

A new active ease-off topography modification approach is proposed to improve the meshing performance of hypoid gears based on a fourth-order predesigned transmission error (PTE) model and a modified error sensitivity analysis method. Ease-off topography modifications that describe local deviations of pinion tooth surfaces can be conducted by converting the fourth-order PTE into equivalent deviations of pinion tooth surfaces. The modified error sensitivity analysis method is developed to investigate the effects of misalignments on the moving velocity of a contact point of a hypoid gear pair. The moving velocity of the contact point can describe transmission error (TE) curve shapes of ease-off tooth surfaces. The ease-off topography modification approach can achieve TE precontrol and modification curvature adjustment of the pinion for stable meshing performance of the hypoid gear pair. Moreover, pinion ease-off tooth surfaces are finished by a five-axis computer numerical control swarf-cutting machine tool. Swarf-cutting tests and TE measurement tests are conducted on hypoid gear pair specimens to demonstrate the feasibility and effectiveness of the proposed methodology.