The Effect Of Sandingblasting Sur-Face On Friction-induced Vibration And Noise

Friction-induced noise is kind of unstable voice, which is resulted from the energy spreading out through the surrounding medium when the system is excited by friction be-haviors between the contact surfaces. Friction-induced vibration and noise will seriously af-fect the friction system precision, reliability and normal operation, and lead to serious noise pollution. Friction-induced noise is mainly caused by the friction behaviors between the contact surfaces, and the interface characteristics play a key role in affecting the noise prop-erties. However, there are few reports on the correlation between frictional interface and friction-induced noise. Moreover, our knowledge about the key factors of controlling the triggering and evolution of squeal is still scarce, considering the complexity and randomness of interface wear features. Therefore, it is significant to study the effect of sandblasting sur-faces with different roughness on friction-induced vibration and noise properties. The study will help to further understand the key factors of affecting squeal and reveal the mechanism of squeal generation, and provide an efficient way to suppress and reduce squeal by using sandblasting surface treatment.In this work, experimental study of the friction-induced noise properties of smooth and sandblasting surfaces was performed by using two experimental setups with different struc-ture and system stiffness. The squeal characteristics of sandblasting surfaces in the two dif-ferent test setups, and the effect mechanism of sandblasting surfaces on the generation and evolution of squeal was investigated. The main conclusions can be drawn as following:(1) Sandblasting surfaces had significant influence on both the generation and intensity of squeal. Although the results from the two test setups with different system structure and stiffness showed some difference in friction-induced noise properties, a consistent law sill could be obtained from the tests:the generation of squeal would be postponed and the inten-sity of squeal would be reduced with the increase of surface roughness of sandblasting sur-faces. Therefore, the surface roughness of sandblasting surfaces was found to play a key role in the triggering and evolution of squeal, by performing experimental tests excluding from the influences of system structure and stiffness.(2) All the friction force curves of the smooth and sandblasting surfaces exhibited sig-nificant fluctuations during the generation of noise, which were corresponding to the self-excited vibration of friction system. The dominant frequencies of friction force, vibra-tion acceleration and noise were the same which were closed to the natural frequency of the friction system. The coherence analysis results showed that the correlation coefficients be- tween friction force and vibration accelerations and sound pressure at the dominant frequen-cy were very high. Squeal was found to originate from the unstable vibratory response due to friction-induced vibration corresponding to mainly one natural frequency of the tri-bo-system.(3) The generation of squeal was mainly attributed to self-excited vibration of friction system resulted from severe fluctuation of friction force, which was caused by some inter-face factors, such as the accumulation of wear debris, detachment and ploughing. For the smooth surface, the "irregularities" characteristics resulted from the accumulation of wear debris and detachment on worn surface would easily cause high-frequency wave-fluctuations of friction force and thus the generation of high-intensity squeal. In contrast, for the sand-blasting surfaces, the real contact areas generated by the wear of asperities existed as’con-tact plateau’, which were distributed discontinuously. The worn surfaces on the’contact plateau’were mainly characterized by ploughing, which showed relatively smaller contribu-tion to the high-frequency wave-fluctuations of friction force. Therefore, the generation of squeal was later and the intensity of squeal was lower for the sandblasting surfaces compared to the case of smooth surface.(4) The effect mechanism of the sandblasting surfaces on friction-induced vibration and noise can be described as following:with the increase of surface roughness of the sandblast-ing surfaces, the dispersion of asperities increased and the real contact area became smaller and more dispersed during the process of wear, which would suppress the high-frequency wave-fluctuations of friction force and thus the generation of squeal. For the sandblasting surfaces the worn surfaces on the’contact plateau’ were mainly characterized by ploughing, which showed relatively smaller contribution to the high-frequency wave-fluctuations of friction force and thus later squeal generation and lower squeal intensity, compared to the others "irregularities" characteristics resulted from the accumulation of wear debris and de-tachment. In summary, sandblasting surfaces could help to reduce the irregularities and con-sequently the squeal tendencies compared to the smooth surface, this would suppress the generation of high-frequency fluctuations of the friction force, and consequently significant-ly reduce squeal.