The Effect Of Groove-Textured And Pit-Textured Surface On The Friction-Induced Vibration And Noise

It is known that friction-induced noise can be excited when two bodies are sliding against each other under certain conditions. The friction noise is characterized by the high frequency, strong intensity, unknown mechanism, poor reproducibility and so forth. The existence of friction noise will not only result in the severe noise pollution and accordingly affect people’s lives, but it also will reduce the friction system’s performance and service life. Therefore, it has become a challenge for the researchers to find an effective way to reduce the generation of friction induced squeal noise. Considering that the friction noise is derived-from unstable vibration of frictional interface, a large amount of work has been performed to investigate the effect of surface properties (such as:surface roughness, friction layer and wear debris etc) on the friction noise. However, the reports on the friction squeal noise and accordingly reduce it by using the way of initiative surface modifications are very limited.In the previous study, it is found that the friction squeal noise would be affected by the width and the configuration of groove-textured surfaces regardless on the reciprocating sliding system and the rotating system. However, the samples used in these studies are less diversified and the mechanism of squeal generation need to be further revealed. Therefore, the disc samples with two kinds of textured surfaces (groove-textured surfaces with different width and pit-textured surfaces with different diameter) are prepared, the corresponding friction noise experimental test are performed to compare their effect on friction noise, the final results will provide the theoretical reasons for controlling and reducing the friction-induce vibration and noise.In this study, groove-textured surfaces with three kinds of widths and pit-textured surfaces with three kinds of diameters are manufactured on compacted graphite iron materials (brake disc material). Experimental test and numerical simulation (complex eigenvalues analysis and transient dynamic analysis) are performed to investigate the influence of surface texturing on friction noise, by comparing the case of smooth surface.The main conclusions are as follow:1. These two kinds of textured surface scan significantly reduce the self-excited vibration of the friction system and correspondingly suppress the high frequency friction squeal noise. T-30°-1 and P-4-2 show the best performance in reducing the friction noise in the groove-textured surfaces and pit-textured surfaces, respectively. Moreover, it can be found that the larger fluctuation of the friction force curve indicates the better performance of texturing surface in reducing squeal noise.2. The groove-textured surfaces and pit-textured surfaces can significant improve the ploughing and peeling off of the contact surface. Moreover, the grooves/pits play a storage cavity role in trapping wear debris, and change the interface wear status, which may consequently reduce the squeal noise of the friction interface.3. Two adjacent modes (the 1st and 2nd modes) are found to merge together and consequently form an unstable complex mode at the frequency of about 1175 Hz when friction coefficient increases to 0.1 for all the three contact surfaces. The unstable frequency of 1175 Hz calculated is very close to the experimental squeal frequency of 1200 Hz. Moreover, it is noticed that the friction system shows a stronger tendency to generate unstable vibration with a further increase of friction coefficient. However, for the T-30°-1 and P-4-2 surfaces, two adjacent modal frequencies started to merge toward each other, but consequently separated with each other with the friction coefficient increasing to 0.6. This suggested that the system had a strong tendency to generate unstable vibration at first, but consequently this tendency became weakened.4. Transient dynamic analysis results indicate that the vibration accelerations of smooth surface generate strong oscillation with exponential growth over a period of time. However, for the T-30°-1 surface, six intermittent and small oscillations of vibration accelerations are observed in both directions. The number of these oscillation cycles equals the number of the grooves encountered during the rotating travel of one cycle, which indicates that the existence of grooves on the disc surface can reduce the squeal noise of interface. For the P-4-2 surface, the amplitudes of vibration accelerations are larger than that of T-30°-1, and whilst smaller than that of smooth surface, moreover, occurrence of six visible wave-fluctuations in the friction force curve can be observed in the cycle of friction process.5. The results of contact stress analysis show that homogeneous contact stress distribution with small contact stress can help stabilize the friction system. Comparing with smooth surface, the grooves and pits are found to be able to effectively interrupt and transfer the distribution of contact pressure during friction sliding. Moreover, the distribution of the highest pressure on the pad surface changes with the rotation of the disc. Therefore, the groove and pit can significant redistribute the distribution of contact pressure on the pad surface and consequently suppress the squeal generation.