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Highlights • A new model of a vibration system with double layer structure is established. • The system vibration modes can be changed from period-doubling bifurcation to chaos. • The parameters are optimized to improve system stability and shrink chaotic vibration. Abstract This study establishes a dynamic model of a new brake system with two-layer structure to explore the mechanism of vibration and noise reduction of a brake pad with new structure. The model is used to analyze the effects of parameters of the double-layer pad on the stability and stick-slip vibration characteristics of the brake system. The stability of the brake system is optimized by brake parameters with respect to the stability diagram of brake pressure under a relatively wide range. System vibration modes can be changed from period-doubling bifurcation to chaos based on the variation of brake pressure and the parameters of double-layer pad via numerical analysis. The chaotic vibration region is optimized in this study using the correlation coefficient, which consists of friction-layer pad mass m b2 and connection stiffness k 2. Results show that the range of chaotic vibration region can be reduced when the friction-layer pad mass and connection stiffness are large. [ABSTRACT FROM AUTHOR]

The multi-clearances of breaking type steering trapezoidal mechanism joints influences vehicle steering stability. Hence, to ascertain the influence of clearance value on steering stability, this paper takes the steering mechanism of a certain vehicle type as a prototype that can be simplified into a planar six-bar linkage, then establishes the system dynamic differential equations after considering the two clearances of tie rods and the steering knuckle arms. The influence of the clearance parameters on the movement stability of the steering mechanism is studied using a numerical computation method. Results show that when the two clearances are equal, the planar movement of the tie rods changes from period-doubling to chaos as the clearances increase. When the two clearances are 0.25 mm and 1.5 mm respectively, the planar movements of the two side tie rods come into chaos, causing the steering stability to deteriorate. Moreover, with the increase of clearances, turning moment fluctuates more intensively and the peak value increases. [ABSTRACT FROM AUTHOR]

This study proposes a new dynamic model of a brake system that combines pad tangential motion and disk torsional motion to reduce the vibration and noise of the brake system. The stability analysis of this system with a smoothed Stribeck friction model verified its instability, which is caused by Hopf bifurcation. Moreover, numerical simulation showed several phenomena of the system vibration changing with angular velocity: (1) the system vibration maintains in the stable limit cycle after Hopf bifurcation within a relatively wide range of low angular velocity and (2) period-doubling bifurcation and chaos will occur only by decreasing the angular velocity. This study further discusses the effects of friction parameter on stick–slip vibration within a common range of brake pressure under “low” and “lower” angular velocities; the result shows that a decrease of both μ s − μ k and decay factor can effectively reduce the range of chaotic vibration region. [ABSTRACT FROM AUTHOR]

• A calculation method for the thermal turbulent fluid-film pressure in the FRB is proposed. • A transient tribo-dynamic model for the turbocharger rotor-FRB system is developed. • A combined numerical analysis of lubrication with nonlinear dynamics is presented. • A proper unbalance provides a stable region of synchronous vibration in medium-high speeds. • By adjusting the unbalance and bearing clearance, the stable region transfers to different speeds. The rotor-bearing system of small size and light weight used in automotive turbochargers can reach the speeds between 100,000 to 300,000 rpm, but the undesirable sub-synchronous whirl, whip, bifurcation and chaos probably appear in the response of self-excited unbalance and unsteady fluid-film forces with the high shear rate and low viscosity lubricant. From the perspective of coupling tribology and dynamics, the transient acting pressures in the double fluid-film lubricated bearing are computed by employing the turbulent lubrication theory and finite difference method at various high temperature conditions. Then a nonlinear dynamic model for the floating-ring bearing supported turbocharger rotor is developed through D'Alembert's principle and transfer matrix method in this paper. Comparative analysis of the trajectory, Poincare mapping, frequency-domain response and bifurcation behavior are conducted to investigate how to avoid fluid-induced instabilities via the rotor unbalance effect. The results show that an increase in unbalance can effectively suppress the sub-synchronous oil whirl at relatively low rotor speeds. At high speeds, the effect can also prevent the rotor from entering chaos by the path of quasi-periodic bifurcation, but an excessive unbalance will induce oil whip accompanied by frequency locking. A stable "interval region" of medium-high speeds characterized by the synchronous single-period small-amplitude vibration emerges only with the proper unbalance, which is available to guarantee the healthy operation of a turbocharger rotor. [ABSTRACT FROM AUTHOR]