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Disc brake squeal has always been a great challenge to the automotive industry. Based on the pin-on-disc system, a series of frictional squeal bench tests are carried out, which show significant time-varying characteristics on occurrence, sound pressure and frequency of frictional squeal. To investigate the generation mechanism of time-varying characteristics of frictional squeal, a four-degree-of-freedom (4DOF) lumped parameter model considering the time-varying tangential contact stiffness, the normal contact stiffness and the friction coefficient is established in this paper. Through both the system stability analysis and the transient response analysis, the time-varying frictional squeal is predicted successfully, and the generation mechanism and the key impact factors are also investigated in depth.

To accurately and efficiently predict the temperature fields inside a lithium-ion battery is key technology for the enhancement of battery thermal management and the improvement of battery performances. The dimensional analysis method is applied to derive similarity criterions and the similarity coefficients of battery interior temperature fields, based on the governing partial differential equations describing the three dimensional transient temperature field. To verify the correctness of similarity criterions and the similarity coefficients, 3D finite element models of battery temperature field are established with a prototype and scale model, on the assumption that the battery cell has single-layer structure and multi-layers structure separately. The simulation results show that the similarity criterions and the similarity coefficients are correct.

Brake squeal shows a significant uncertainty characteristic. In this paper, a series of bench tests were carried out to study the uncertainty of brake squeal on a multi-function brake inertia dynamometer test bench. Then based on time-frequency analysis results, a creative squeal confirmation and determination method was presented, which can show the squeal variations in the domains of time, frequency and amplitude together. An uncertainty analysis method was also established, in which the statistical parameters of squeal frequency and sound pressure level (SPL), and probability density evaluation of frequency based on Quantile-Quantile Plot (QQ plot) were given. And a judgment method of the frequency doubling was devised based on numerical multiple and occurrence concurrence, as well as the uncertainty statistical analysis method considering frequency doubling. All the methods established were applied to the uncertainty analysis of brake squeal.

A pin-on-disc system was established to study the generation mechanism and key impact factors of relationship between dynamic contact force and frictional squeal. Through the frictional squeal rig test, both intermittent and continuous squeals were produced repetitively. During the rig test frictional squeal, contact forces and acceleration of the pin end were sampled under various speed and loading force conditions, and the wavelet analysis, time-frequency analysis and feed-in energy calculation methods were used to investigate the relationship between dynamic contact force and frictional squeal. It was found that the frictional squeal would not appear unless the normal force was large enough, and the intermittent squeal would turn to continuous squeal with the quasi static part of normal force increasing to a limiting value, and vice versa. The mode coupling characteristic was discovered obviously when the frictional squeal appeared.

Contact pressure distribution is one of the key influence factors and the essential causes of brake squeal. In this study, a drum brake finite element model is established using ABAQUS. The contact pressure distribution is simulated and the brake squeal instability is predicted based on the complex eigenvalue analysis method. Different contact pressure distributions are obtained by changing the structure and material parameters of the drum brake as well as altering the friction coefficient and the brake pressure. Then, the effect of contact pressure distribution on brake squeal is investigated, and the mechanism of the key contributing factors of brake squeal is studied. The innovation of the study is that it correlates squeal properties directly to the contact pressure distribution characteristics, which is considered as the essential influence mechanism of brake squeal.