Effects of groove orientation on transmission characteristics of hydro-viscous film in the parallel-disk system

The disk groove can greatly influence the hydrodynamic behaviors of the rotating film, especially on the cooling performance and the transmission efficiency. In the present work, the effects of groove orientation on the hydro-viscous transmission of the parallel-disk system are investigated. The Reynolds equation and thermal equation, considering tangential Coriolis effect and temperature–viscosity dependency, are derived and solved. The effects of the groove orientation on the shear stress, load-carrying capacity, viscous torque, and transmission efficiency are analyzed. The results reveal that the Coriolis resisting torque can be restrained but the load-carrying capacity declines if the groove orientation is consistent with the rotating direction, and the variation of the transmission efficiency can even be inverted at the turning point of the groove orientation. Therefore, the effects of groove orientation must be paid more attention in the hydro-viscous transmission.

Measurement of temperature-dependent mechanical properties of magnetorheological fluids using a parallel disk shear stress testing device

Mechanical properties are critical to the working performance of magnetorheological fluids (MRFs), especially in high temperature situations. This paper presents an experimental investigation to analyze the effects of temperature on mechanical properties of MRFs. First, a parallel disk method was implemented for the shear stress measurement of MRFs and the measurement principle was theoretically illustrated. Then, a detailed introduction to the MRF sample preparation and the testing device development was performed as well. In the study, five kinds of MRF samples with different material parameters were prepared and a shear stress testing device which possesses the temperature control function was developed and evaluated. After these, a series of measurements were conducted on the viscosity–temperature characteristic, shear stress–temperature characteristic and thermal stability of MRF samples. Measuring results indicated that the mechanical properties of MRFs were obviously dependent on temperature. The phenomenon mainly embodied in the reduction of off-field viscosity and shear stress with increasing temperature, as well as the performance degradation after undergoing a low–high–low temperature cycle or a high temperature treatment of more than 150 ℃.

PARALLEL DISK CONTINUOUSLY VARIABLE TRANSMISSION (PDCVT):PROTOTYPE DEVELOPMENT AND PERFORMANCE TESTING

In this paper, a typical Parallel Disk Continuously Variable Transmission System (PDCVT) is developed in the spirit and approach of Kazerounian and Furu-Szekely. In situations where a speed ratio is required to be changed frequently, continuously variable transmission is one of the desirable solutions. The PDCVT system is one such solution which offers the advantages such as high power to weight ratio and reliability in operation. First of all, the development and manufacturing details of the developed PDCVT system are discussed and experimental and theoretical values of transmission ratios have been determined with different ball diameters and materials. Also, the theoretical and experimental evaluation of transmission torque has been carried out. Experiments have been carried out to determine the system parameters: the stiffness of the spring for preloading mechanism of the system and the area of contact between the balls and rotating disks to determine the coefficient of friction.