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Abstract
High-energy clutch works in a severe condition, the power which passes the cluth can reach two or three hundred kilowatts, whether the friction disk can work normally directly related to the working performance and working reliability of the clutch. The research object of the papers is a certain type of high-energy density clutch, and dynamics analysis of combination process of the cluth is done, and the mechanical model of the combination process of wet cluth is established. By using ADAMS software, the simulation model of high-energy is established, change of contact force and distribution law of contact force is analyzed and summarized. By analyzing the change of contact force, the vibration law of cluth is studied. The results show that: the total combination time is about 0.26 seconds; the distribution law of pressure on the disk is decided to time and location. the pressure of four point which is mutual 90 degrees on the disk is analyzed, there exists apparent pressure cyclical fluctuations at each four point; by analyzing the contact force, the peak value of contact force can reach 25 kN, and the peak value appears at the time of 0.05, 0.1, 0.15, 0.22, 0.25 seconds, the cluth librates in the axial direction by the cycle of 0.05 seconds. The results provides boundary conditions for a further analysis of the temperature field, flow field of the clutch.
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A numerical treatment of fretting-wear under vibratory loading is proposed. The method is based on the Dynamic Lagrangian Frequency Time method. It models unilateral contact by using Coulomb’s friction law. The basic idea is to separate time into two scales, a slow scale for tribological phenomena and a fast scale for dynamics. For a given number of vibration periods, a steady state is assumed and the variables are decomposed into Fourier series. An Alternating Frequency Time procedure is performed to calculate the non-linear forces. Then, a hybrid Powell solver is used. Numerical investigations on a beam with friction contact interfaces illustrate the performances of this method and show the coupling between dynamic and tribological phenomena.
Based on engagement process characteristics of wet clutch, average Reynolds equation and elastic contact model of two rough surfaces were applied to establishment of an efficient mathematical model for wet clutch engagement process. Runge-Kutta method was used to calculate the model. Rules of influences of friction-lining permeability, lubricant viscosity, engagement pressure and characteristics of static and sliding friction coefficient on torque response, peak value of viscous torque, lock-up torque peak value and engagement time were studied. The correctness and effectiveness of the model were verified by experiment. The simulated and experimental results indicate that increase of the permeability of friction lining or engagement pressure can accelerate the torque response and shorten engagement time; increase of lubricant viscosity can retard the torque response and shorten engagement time; reduce of the difference of static and sliding friction coefficient of friction pairs can decrease torque peak value at lock-up.
To study the clutch engagement judder and its influence factors, a four-degree-of-freedom (4-DOF) powertrain dynamic model was established. The analysis was performed on the mechanism of self-excited vibrations and the stability under the variation in the friction coefficient during clutch engagement. With the numerical simulations for the shifting process in a vehicle, the effects of many kinds of influence factors on clutch judder were discussed. The result showed that the negative slope of friction coefficient and oscillation of clamp pressure would cause or aggravate the clutch judder, and the judder could be reduced effectively by increasing the static coefficient of friction component, the damping ratio and the stiffness of transmission shaft, which could benefit the design and control of clutches.
Ventilated disc brakes are widely used for reducing velocity due to their braking stability, controllability and ability to
prove a wide-ranging brake torque. During braking, the kinetic energy and potential energies of a moving vehicle are converted
into thermal energy through friction heating between the brake disc and the pads. The object of the present study is to investigate
the temperature and thermal stress in the ventilated disc-pad brake during single brake. The brake disc is decelerated at
the initial speed with constant acceleration, until the disc comes to a stop. The ventilated pad-disc brake assembly is built
by a 3D model with a thermo-mechanical coupling boundary condition and multi-body model technique. To verify the simulation
results, an experimental investigation is carried out.
KeywordsVentilated disc brake-Temperature field-Thermal stress-Thermo-mechanical couple-Multi-body model
The problem of obtaining smooth gear changing whilst maintaining long life of wet clutches in automatic transmissions demands more knowledge about their behaviour. Experimental and theoretical studies on the engagement of a wet clutch have been carried out. A wet clutch test rig which can apply a drive torque during engagement was developed. The apparatus could also vary the sliding velocity, inertia, force rate, and lubrication. Measured output data included normal force, brake torque, sliding velocity and temperature over time. The input parameters and output characteristics obtained were similar to those in automatic transmissions used in cars. The friction characteristics as well as power and temperature were investigated. A simple model was developed to estimate the engagement performance which gave a good approximation of the performance measured in the tests. The friction is high in the beginning and end of the engagement cycle and lower inbetween. There is a torque peak just before the clutch stops owing to friction characteristics. The maximum developed power occurs at about half of the engagement time, while the maximum temperature is just before clutch stop.