Experimental Study On The Exciting Effect Of Hammering Inpulses On Friction-Induced Vibration And Squealing Noise

Friction-induced vibration and squealing noise of mechanical systems are very common natural phenomena and very elusive nowadays, In most conditions, friction-induced vibrations are highly undesirable. In the past several decades, researchers have made many endeavors to understand the origin of the friction noise, and proposed different explanations of squeal origin. Though a number of researchers in the world have dedicated to work in this area over the years, the study on friction-induced squeal is still a hard work. The main difficulty encountered in studying friction-induced vibration and squeal is the high complexity of the friction system.This paper presents a series of experimental test results. It is clear from the test results that the hammering pulse forces applied on friction system can lead to friction squealing noise. A series of analyses are performed on this kind of hammering-induced friction squealing noise. The analysis results clearly demonstrate that the hammering-excited friction squeal and self-excited friction squeal have a number of common characteristics. In addition, further test studies are carried out for understanding the origin of hammering-excited squealing noise. The study leads to the following conclusions:(1) In some conditions of friction motion, the hammering pulse forces applied on friction system can lead to friction squealing noise. The hammering-excited friction squeal and the self-excited friction squeal have the same time-frequency characteristics. It is considered that both the hammering-excited squeal and the self-excited friction squeal may be generated by the same mechanism. Mode coupling of the friction system may be the origin of both the hammering-excited squeal and self-excited friction squeal.(2) The generation of self-excited friction squeal is dependent on wear debris. When the wear debris on the contact surface is removed, self-excited friction squeal will disappear immediately.(3) When self-excited friction squeal of friction system does not occur, the occurrence tendency of self-excited friction squeal will be more obvious after hammering pulse forces are applied on the friction system.(4) The hammering pulse forces applied on friction system will significantly increase the amount of debris in friction sliding processes.(5) The generation mechanism of hammering-excited friction squeal is considered to be: A hammering pulse force applied on friction system will cause the system to vibrate. Although the duration of the vibration is very short, it will aggravate the friction and wear. Thus, the wear debris will generate more rapidly, and a large amount of debris is generated. Self-excited vibration is activated with the effect of the debris. Therefore, the friction squeal occurs.