Wouter Ost

The tribological behaviour of paper friction plates for wet clutch application investigated on SAE#II and pin-on-disk test rigs

Abstract The friction behaviour of wet clutches for automatic transmission applications strongly influences the dynamic behaviour of the entire machine or vehicle including the transmission. The wear, but also the friction curve, determines the lifetime of the clutch. The role of wear is obvious. The friction coefficient of the material couple friction plate/separator plate decreases with number of engagement cycles. As a result, the possible torque of the transmission decreases with time. Under a certain threshold, the clutch has to be revised. But because manufacturers tend to oversize their clutches the decrease in friction coefficient does not yield a limitation to the lifetime of the clutch. In this paper, both SAE#II and pin-on-disk tests are used to investigate the wear and friction characteristics of the friction material. Although the pin-on-disk tests fail in correctly reproducing the wear rate of the SAE#II tests, they can be used for a qualitative analysis of the influence of material parameters and operating conditions on both friction coefficients and wear rate.

Resonant Bending Fatigue Test Setup for Pipes With Optical Displacement Measuring System

Pipes and tubular members are used in offshore applications as structural elements, such as columns or in transport pipelines, risers, etc. When subjected to dynamic loads, weld defects or geometrical stress raisers can initiate fatigue cracks, causing the columns or pipelines to fail prematurely. In order to investigate the fatigue behavior of pipe joints, a resonant bending fatigue setup was designed, suitable for testing pipes within a diameter range from 6 in. to 20 in. In this setup, the pipe, filled with water, is subjected to a dynamic excitation force with a frequency close to the natural frequency of the filled pipe. The force is applied using a unique drive unit with excentric masses. The pipe is supported in the nodes of its natural wave-form, so that no dynamic forces are transmitted to the setup. The deformation of the pipe is measured at discrete locations using an optical 3D dynamic measuring system. Through-thickness fatigue cracks can be detected by pressurizing the water in the pipe and applying a pressure gauge. In this paper, some unique aspects of the design of the resonant bending fatigue setup are discussed by presenting the results of a semianalytical model used for calculating the deformation and bending stress in the excitated pipe and by comparing these results to the deformation measurements made by the dynamic measuring system. The working principles of the setup are illustrated by showing the preliminary test results for a 12 in. diameter X65 steel pipe with a wall thickness of 12.7 mm. It is demonstrated that the model predicts the behavior of the pipe in the setup very accurately.

Testing the Friction Characteristics of Industrial Drum Brake Linings

In the present study a new brake setup was developed to test drum brake linings on an industrial brake with drum diameter of 30″. During the tests performed on the setup, the brake undergoes a series of cycles in which the drum is slowed down from service speed to standstill. In each cycle the same amount of energy is dissipated as during a realistic safety stop. This was obtained by adding a flywheel in the setup so that the system’s kinetic energy at service speed matches the energy of the hoisting system dissipated during an emergency stop. Two different brake lining materials were characterized. Both materials were subjected to two test series to study the changes in coefficient of friction over a number of cycles. It was observed that the coefficient of friction of both linings was dependent on the drum temperature. The coefficient of friction of the first material decreased with increasing drum temperature, while the latter had the opposite behaviour.

THE FRICTIONAL STABILITY OF WET CLUTCH FRICTION MATERIALS INVESTIGATED ON A SMALL SCALE TEST-RIG

The work presented in this paper is part of a European project (COST 532, project E2) to study clutch shudder and its influences, together with wear testing of clutch materials. The relation between the friction force and the relative velocity, and the dynamics thereof are investigated for typical wet clutch materials (oil lubricated paper/steel contact) on a small scale test rig, using a ground and polished steel ring onto which a coupon from a friction clutch plate was slid. The results clearly show that although momentarily the relative velocity of the sliders vs. the rotating ring reaches zero, no stick episode ensues. The mechanical parameters (stiffness, damping and normal load) of the test-rig were varied and the influence thereupon on the friction during sliding was investigated.© 2005 ASME