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A road test on semi-trailers is carried out, and accelerations of some characteristic points on the braking system,axles,and truck body is measured,also brake pressure and noise around the support frame is acquired.The measured data was analyzed to determine the causes of the brake noise, and the mechanism of the noise of the drum brake of semi-trailers during low-speed braking was investigated. The following conclusions are obtained: (1) Brake noise of the drum brake of the semi-trailer at low-frequency is generated from vibrations of the brake shoes, axle, and body, and the vibration frequency is close to 2nd natural frequency of the axle. (2) Brake noise is generated from stick-slip motion between the brake shoes and the brake drum, where the relative motion between the brake drum and the brake shoes is changed alternately with sliding and sticking, resulting in sudden changes in acceleration and shock vibration.

An experiment is carried out to measure creep groan of a drum brake located in a trailer axle of a truck. The noise nearby the drum brake and accelerations on brake shoes, axle and trailer frame are collected to analyze the occurring conditions and characteristics of the creep groan. A multi-body dynamics model with 1/4 trailer chassis structures is established for analyzing brake component vibrations that generates the creep groan. In the model, the contact force between brake cam and brake shoes, the contact friction characteristics between brake linings and inner circular surface of brake drum, and the properties of chassis structure are included. Dynamic responses of brake shoes, axle and trailer frame during the braking process are estimated using the established model and the responses are compared with the measured results, which validate the model.

An Inline 4-cylinder engine is equipped with second-order balance shafts. When the engine is running under no-load acceleration conditions, the gear system of the balance shaft generated whine noise. In this paper, an analysis and experiment method for reducing the whine noise is presented. First, a flexible multi-body dynamic model of the engine is established, which includes shaft and casing deformation, micro-modification of the gears. Taking the measured cylinder pressure as input, the load on each gear of balance shaft gear system is calculated. In addition, the influence of tooth surface micro-modification on the meshed noise was analyzed. The results show that the dynamic meshing force between the crank gear and the shim gear is large under the original tooth surface micro-modification parameters, which is the main reason of the whine noise.

Tortuosity, viscous characteristic length and thermal characteristic length are three important parameters for estimating the acoustic performance of porous materials, and it is usually measured by ultrasonic measurement technology, which is costly. In this paper, a method for identifying the tortuosity, viscous characteristic length and thermal characteristic length for the porous fiber materials mixed with kapok fiber and two kinds of other fiber materials is proposed. The tortuosity is calculated by using the porosity and high-frequency normal sound absorption coefficient of porous materials. According to the normal sound absorption coefficient curve of porous materials under plane wave incidence, viscous characteristic length and thermal characteristic length are identified through the Johnson-Champoux-Allard-Lafarge (JCAL) model and genetic algorithm by using the measured parameters, the calculated tortuosity and static thermal permeability.

To reduce the noise in the frequency range of 100Hz~1000Hz, a metamaterial structure composed of lightweight frame, hard membrane-like material and added mass is proposed in this paper. The advantage of this structure is that it is lightweight and the membrane-like material does not need to be stressed in advance. Finite element method (FEM) and experiment are used to investigate the sound transmission loss (STL) performance of the metamaterial structure. The results show that the peak STL is caused by the local resonance of the added mass and the membrane-like material. The valley versus frequency results from the resonance frequencies of metamaterial structure, and it is divided into three resonance frequencies: resonance frequencies from added mass, membrane-like material and frame.

In this paper, the influence of the decoupler-cage structure on the hitting noise of the hydraulic mount is studied, the abnormal noise of the hydraulic mount is mainly caused by the collision impact between the decoupler and the cage, the hitting noise was simulated and evaluated using calculation and experiment. a finite element model of the collision impact between the decoupler and the cage is developed, and an explicit finite element analysis is performed to obtain the time history of the vibration acceleration of the model, which is used as the boundary condition of the noise analysis. The acoustic boundary element method is used to analyze the impact noise of the decoupler-cage, and the frequency domain distribution characteristics of the impact sound pressure are obtained. The influence of different decoupler structure on the hitting noise is studied, and the recommended values for each parameter for a structure are given.

As an important vibration damping element in automobile, the rubber mount can effectively reduce the vibration transmitted from the engine to the frame. In this study, a method of parameters identification of Mooney-Rivlin model by using surrogate model was proposed to more accurately describe the mechanical behavior of mount. Firstly, taking the rubber mount as the research object, the stiffness measurement was carried out. And then the calculation model of the rubber mount was established with Mooney-Rivlin model. Latin hypercube sampling was used to obtain the force and displacement calculation data in different directions. Then, the parameters of the Mooney-Rivlin model were taken as the design variables. And the error of the measured force-displacement curve and the calculated force-displacement curve was taken as the system response. Two surrogate models, the response surface model and the back-propagation neural network, were established.

As an important vibration damping element in automobile industries, the vibration transmitted from the engine to the frame can be reduced effectively because of rubber mount. The influence of preload on the static characteristics of rubber mount and the constitutive parameters identification of Mooney-Rivlin model under preload were studied. Firstly, a test rig for stiffness measurement of rubber mount under preload was designed and the influence of preload on the force versus displacement of mount was studied. Then, the model for estimating force versus displacement of rubber mount was established. The response surface model for parameters identification was established. And the identification method for estimating parameters of Mooney-Rivlin model of rubber mount was proposed with the crow search algorithm. Taking the rubber mount as the research object and taking the parameters of Mooney-Rivlin model as the variables.

If a car is braked frequently or at high speed, the thermal decay of brake system performance appears, which reduces the braking performance of the car. To compensate brake moment reduction during braking at thermal decay of brake system, a compensation strategy of brake moment is designed by using “feedforward +PID feedback” to pressure at wheel braking cylinder. The trigger and exit conditions of the strategy for the wheel cylinder pressure are proposed based on the threshold. A vehicle model consisting braking system is established if a vehicle runs at straight line, and the braking distance and braking acceleration are estimated, the results shown that the thermal decay compensation control strategy proposed in this paper can reduce the braking distance and braking time.

Taking a closed airbag suspension system as studying objects, the nonlinear dynamic model of the reservoir, compressor, solenoid valve, pipeline and air spring is established. The compressor exhaust volume, solenoid valve flow rate and air spring charging and discharging rate are calculated and compared with experiment to validate the model. Taking pressure difference and height adjustment rate under different working conditions of an airbag suspension as control measures, a control strategy is developed based on the established nonlinear dynamic model. The result indicates that when the vehicle is in curb weight, design weight and GVW (gross vehicle weight), the working time of the compressor can be reduced by 13.6%, 15.1% and 46.5%, respectively, compared with the conventional mode, during a height adjustment cycle. Then a state observer is proposed to estimate the steady-height for reducing the disturbance of measured height from road excitation.

In the manufacturing of battery boxes using the aluminum extruded process, poor consistency of products and a short life of the die for making aluminum structural sections are usually observed. A new method of producing battery boxes is proposed that combines steel stamped and aluminum extruded process. This paper first describes the design requirements for a battery box using a new process, and several important issues such as weld seam arrangement and error proofing in the manufacturing process are discussed. To address the issue of weld seam arrangement, the following three principles should be considered in the design: These principles include that the profile lap angle should be above 90°, three or more beams should not be lapped too closely together, and multiple brackets in close proximity should be designed as one unit.

The identification of vehicle noise is the basis for studying the acoustic characteristics of vehicles. In this paper, both excitation of noise sources and response of interior noise were identified. Firstly, a transfer path analysis (TPA) model was established to identify the excitation of noise sources, which includes vehicle main noise sources, such as engine, tire, exhaust pipe and muffler. Based on the operational signals and transfer function which were tested in the vehicle semi-anechoic room, the excitation of noise sources was identified using inverse matrix method. Identify result indicated that tires have higher excitation amplitude than engine in high frequency band. Therefore, the transfer path between the tire and the cabin, such as carpet and windshield, should be taken as the focus of acoustic performance improvement. By improving the acoustic material on the transfer path, the loss of sound in the transfer path will be increase.

Electromagnetic semi-active hydraulic engine mount (HEM) with double inertia tracks can realize the opening and closing of the inertia tracks through the control of electromagnetic actuator, so as to meet the needs of vibration isolation in different working conditions, but the cost is high. In this paper, without using electromagnetic actuator, a mechanical semi-active HEM with double inertia tracks is designed and manufactured with simple structure and low cost. In this study, the feature of mechanical semi-active HEM with double inertia tracks is that a baffle-current limiting column structure is added in the inertia track. Under different excitation amplitudes, the baffle-current limiting column structure can open and close the inertia track passively. Several mechanical semi-active HEM with double-inertia tracks samples and conventional inertia tracks HEM samples are manufactured and the dynamic characteristics of these samples under low frequency excitation are tested.

The application of turbochargers in fuel vehicles brings high-frequency noise, which seriously affects the vehicle's ride comfort. The hiss noise of a turbocharged car is improved in this paper. Firstly, under different operating conditions and whether the air intake system is wrapped, the noise in the vehicle cabin and the driver's right ear is tested, and the noise sources and noise characteristics are identified. Then, the acoustic calculation model of the muffler is established, and the transmission loss (TL) of the original muffler behind the turbocharger (MBT) is calculated. The TL of the muffler is measured by the double-load impedance tube method. The finite element calculation model is verified by comparing the TL of muffler calculated with tested. Thirdly, the MBT is redesigned. The improved muffler significantly improves the performance of eliminating high-frequency noise, and its TL beyond 20 dB is expanded to the band of 1600 ~ 3500 Hz.

The vehicle will produce certain shock and vibration during the braking process, which will affect the driving experience of the driver. Aiming at the problems of pitch vibration, longitudinal vibration and shock during the braking process, this paper proposes a planning and following control method for target longitudinal acceleration in post-braking phase, and designs control trigger strategies. Target longitudinal acceleration planning takes minimizing longitudinal shock as the design goal. The following control takes the brake pressure as the control object, and adopts the “feedforward +PID feedback” method to follow the target longitudinal acceleration. Besides, considering the safety of braking process, the trigger condition of control is designed which utilizes BP neural network method to judge whether the control has to be triggered. Based on Simulink software, the simulation model of straight-line braking is established.

Turbulence caused by the blade tip of engine cooling fan is one of important noise generating factors. Existing theoretical researches show that the bionic serrated designs applied at the front and rear edges of fan blades can effectively improve the airflow characteristics and reduce the aerodynamic noise. However, the effect of its application at the blade tip needs to be explored and verified. In this research, vehicle engine fans whose tips are designed and remodeled with different size of triangular serrated edge have been tested on airduct, to explore the fan static pressure and noise that caused by changing of period and amplitude size. The large eddy simulation (LES) and FW-H acoustic analogy method are adopted to calculate the transient noise of each designed fan.

In the field of low-frequency noise control, the acoustic metamaterials have received extensive attention from researchers. However, the existing work mainly focuses on small structures with fixed boundaries, which is quite different from engineering applications. Based on the membrane-type acoustic metamaterials, this paper uses a rigid thin plate to replace the tensioned membrane, design and manufacture of two new types of local resonance structure and studies their sound insulation properties. First, the metamaterial samples with a small size of 100mm in diameter and a large-size square with a side length of 506mm were produced, and the sound TL of the two was tested through the impedance tube and the reverberation chamber-anechoic chamber, respectively. The results show that the new structure can form an obvious sound insulation frequency band at low frequencies. Based on the finite element method, a metamaterial acoustic transmission loss calculation model is established.

The tensioner of the engine front end accessory drive system was taken as a study object, and the mechanical structure and working principle of the automatic tensioner were analyzed. The hysteresis behavior test of tensioner torque-angular displacement was carried out, and the effects of different excitation frequencies and excitation amplitudes on the hysteresis behavior of the tensioner were analyzed. According to the modified Dahl hysteresis model, the model parameters of the tensioner was identified. Based on the identified model parameters, the hysteresis behavior of the tensioner was calculated, and the calculation model accuracy was verified with the tested results. The influence of the hysteresis curve transition area exponent on the tensioner behavior was studied. The dynamic behavior of the engine front end accessory drive system was simulated using the simulation software.

As one of the key components of the heat pump system, the electronic expansion valve mainly plays the role of throttling and reducing pressure in the heat pump system. The refrigerant flowing through the orifice will produce complex phase change. It is of great significance to study the internal flow field by means of CFD calculations. Firstly, a three-dimensional fluid model is established and the mesh is divided. Secondly, the phase change model is selected, the material is defined and the boundary conditions are determined. According to the principle of the fluid passing through thin-walled small holes, the flow characteristics of electronic expansion valve are theoretically analyzed. Then the flow characteristics of expansion valve are numerically calculated, and a bench for testing mass flow rate of the expansion valve is built. Then the theoretical value, CFD value and experimental value are compared to verify the correctness of the established three-dimensional fluid model.

The decoupling brake-by-wire system controls the key components of the flow path and liquid flow of the whole brake system through the solenoid valve of the bottom control unit. The reference cross-sectional area value at the valve inlet is obtained by calculation, and the valve body structure model is established. The flow channel structure is extracted, and the porous media model is used to replace the fluid area of the filter screen at the entrance of the solenoid valve. The Fluent software is used to analyze the influence on the flow characteristics of the solenoid valve with or without a filter. The accuracy of the model is verified by the experimental results, which also show that the porous medium can effectively and accurately reflect the characteristics of the solenoid valve end filter.