Considering the effect of teeth surface sliding friction, free vibration of two-stage planetary gears (TPG) is studied theoretically for the first time. The lateral-torsional coupling dynamic model and equation are established with three degrees of freedom: two translations and one rotation. The change rule of natural frequency is discussed with the case of first stage planetary gear’s number 4 and second stage planetary gear’s number 3, 4 and 5. Afterwards three vibration modes are summarized by calculating the free vibration. In order to understand the behavior of friction, the effect of friction on natural frequencies is analyzed for the case of considering friction and not considering friction. Furthermore, the ‘self-coupling’ phenomenon is obtained from the vibration of center component of TPG Meanwhile, the ‘mutual coupling’ is obtained between the first-stage planetary gear (FPG) and the second-stage planetary gear (SPG).

Brake squeal is a ubiquitous disturbance in automotive systems. Facing the complexity and the cost of experimental tests, simulations of brake squeal have become essential as well as to provide a predictive numerical method. Two major approaches exist in the numerical analysis of this phenomenon, the transient analysis and the complex eigenvalue analysis. In this study, the Constrained Harmonic Balance Method is applied on an industrial finite element system in order to estimate the nonlinear stationary responses due to friction induced vibration. This paper aims at explaining how a finite element system was adapted to the CHBM and at analyzing the results. First of all, the method used to reduce a finite element brake system is examined and the contact issue is particularly emphasized. Then, a brief summary of the CHBM is made. Finally, limit cycles are obtained close to the Hopf bifurcation.

This study develops the forward-backward processing method to deal with a huge number of data collected from a long test duration at a low sampling rate. Applications of this method, in addition to the proper choice of the ratio of the frequencies of the reciprocating motion and the sampling rate and the choice of the optimum subdivision number in a cycle, are able to obtain a smooth reborn profile with a high degree of accuracy from the huge number of sampling data. This reborn profile is obtained by averaging the data mapped into every subdivision of this cycle. In order to identify the qualified cycles in the reciprocating motions, which are able to map all the sampling data in these cycles into a cycle, the starting-point criterion is also developed. This present method has been proven to be really effective when applied to the experimental results of friction coefficient and electrical contact resistance collected in a dry wear test.

A Coulomb friction damper, consisting of a case-hardened roll-threaded collar resting against a reverse taper segment of drill rod, is studied for its noise-reduction potential. Axial impact causes the drill rod to be excited in many transverse bending modes of vibration, along with longitudinal and torsional resonances. Due to the inertia of the collar, simultaneous axial and rotational self-tightening motion occurs on the rolled thread. The collar consequently presses on the case-hardened tapered surface of the drill rod, inducing interfacial frictional rubbing, resulting in 5–45 dB of attenuation in peak acceleration of the modes of vibration, and reduction in decay time on the order of 10 seconds.

Predictive models of friction-induced vibration have proved elusive despite decades of research. There are many mechanisms that can cause brake squeal; friction coupled systems can be highly sensitive to small perturbations; and the dynamic properties of friction at the contact zone seem to be poorly understood. This paper describes experimental and theoretical work aimed at identifying the key ingredients of a predictive model. A large-scale experiment was carried out to identify squeal initiations using a pin-on-disc test rig: approximately 30,000 squeal initiations were recorded, covering a very wide range of frequencies. The theoretical model allows for completely general linear systems coupled at a single sliding point by friction: squeal is predicted using a linearised stability analysis. Results will be presented that show that almost all observed squeal events can be predicted within this model framework, but that some subsets require innovative friction modelling: predictions are highly dependent on the particular choice of friction model and its associated parameters.