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An analysis of the vehicle braking, combining with the linear relation between wear and frictional work already investigated, was used to establish a wear equation. Initial braking velocity, the number of brakings per 1 km and pad thickness loss per 1000 km were determined by using taxis with identical car types and identical pad qualities. Based on the averaged experimental results and some normal braking conditions, the calculated average apparent specific wear rate through the equation was unexpectedly found to decrease firstly and then increase with the increase of average initial braking velocity. The pad friction properties relevant to the equation analysis were tested by using a dynamometer, followed by measuring wear as a function of temperature at three different initial velocities that equal the average initial braking velocities respectively.

Electric vehicle motors have the characteristics of fast torque response, large amplitude, and braking feedback torque. Therefore, the excitation of the electric vehicle powertrain has obvious transient impact characteristics, which put forward new requirements for the design of the mounting system. This article carried out the real vehicle test of rapid acceleration and rapid deceleration. A 12-degree-of-freedom nonlinear dynamic model of the electric vehicle mounting system is established. The model is used to calculate the vibration acceleration of the active side and the passive side of the mount, and compared with the test value to verify the correctness of the simulation model. The impact degree, the maximum pitch angle of the powertrain, and the longitudinal acceleration of the powertrain centroid are used as evaluation indicators to analyze the transient response of the electric vehicle mounting system under rapid acceleration and rapid deceleration conditions.

Multi-body dynamics simulation is widely used in the dynamic research of constant velocity joints (CVJ). Useful kinematic and dynamic conclusions can be obtained from simulations to replace part of the test process and reduce test costs. In this paper, multi-body dynamics parameterized (MBDP) models of the high-efficiency constant velocity joints are proposed in the software of ADAMS. A friction model and Hertz contact theory are applied to describe the contact status. And the torque transmission efficiency of the kind of high-efficiency CVJ is calculated through the MBDP model. Bench tests of torque transmission efficiency are carried out on the CVJ to verify the calculation accuracy of the multi-body dynamics model. And the test result of high-efficiency joint shows an excellent behavior for efficiency when compared with BJ.

The influence of the channels of a liquid-cooled plate on the heat dissipation performance of battery module is investigated in this paper. A topology optimization method for obtaining channel configurations of the liquid cooled plate is presented. Firstly, the battery pack cooling system test platform is built to test the flow resistance of the liquid-cooled plate under different flow rates and the maximum temperature and temperature difference of the battery under different working conditions. Secondly, the geometric model of the battery pack is established, and CFD software is used to simulate according to the test conditions. The test results validate the correctness of the model. Then, taking the average surface temperature of the liquid-cooled plate as the optimization objective, the topology optimization structure of the liquid-cooled plate is obtained by variable density method.

The breaking torque is an essential property that identifies the strength of driveshafts under high torque loads. In the breaking torsion test, the constant velocity joint of the driveshafts is usually loaded slowly at a very slow rotating speed under a specific joint angle until it breaks. Under different joint angles, the Rzeppa type constant velocity joint, namely ball joints (BJ), will break at different positions and with different torques. Common results of fracture position include the shaft of the outer race, the shell of the outer race, and the cage column. Simultaneously, the plastic deformation caused by compressive stress occurs at the specific position of the ball track and the cage. In order to analyze the failure reason of the ball joint under a larger joint angle, the quasi-static finite element simulations and test methods are used to analyze the damage caused by stress distribution based on material properties.

The influence of engine cooling fan on the working state of engine cooling system under different driving forms and control strategy is studied, and a simulation model of engine thermal management system of a commercial vehicle is established. The model takes into account the measured performance parameters of the cooling system components, the gear shift logic of the transmission, the effect of vehicle speed on the airflow rate of the radiator, and proposes a modeling method for different cooling fan driving forms. The performance parameters such as engine outlet coolant temperature and corresponding cooling fan speed under different vehicle speeds and engine loads are calculated and analyzed by using the established model. The road measurement test of the engine thermal management system under the same working condition was carried out to read the relevant data from the engine ECU and confirm the reliability of the data.

An Inline 4-cylinder engine is equipped with second-order balance shafts.When the engine is running under full load in 5000rpm,the engine generated severe structural radiation noise.The bench test analysis shows that the main reason is the resonance of the engine near 800Hz and 1500Hz. In this paper, a method for modeling and analyzing the vibration of the engine structure is proposed, and the sound quality of the engine is evaluated and imporved by the Moore–Glasberg loudness method. Firstly, the finite element model of the engine was established, and the experimental modes of the engine casing assembly, crankshaft and balance shaft were measured. The natural frequencies and modal shapes obtained by calculation and experiment were compared, which validates the established finite element model.Secondly, a flexible multi-body dynamic model of the engine was established.

Design of powertrain mounting bracket is always challenging in achieving good NVH characteristics, sound durability and simultaneously reduced weight. Structural optimization is an effective tool to obtain an optimum design. Depending on the design status, different schemes, i.e. size, topology and shape optimization, are applied. In this paper, a case study of application of structural optimization in the design of a mount bracket has been presented. Firstly, both test and FEA (Finite Element Analysis) results expose problems of the initial design. Therefore, it is necessary to redesign the bracket. With sufficient design freedom and time in topology optimization, design space and optimization parameters are defined. Die direction and other manufacturability considerations for the casting components are vital. Shape optimization is then conducted to further decrease the weight and refine local weakness.

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.

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.

Aiming at the problem of middle and low frequency noise absorption, a combined sound-absorbing structure is designed based on porous material and a coiled-up cavity resonance structure. Combined with the sound absorption principle of porous materials and coiled-up cavities, a theoretical analytical model was established. By the finite element method, the sound absorption coefficient curve of the combined structure in a frequency range of 500-2000Hz is calculated, and the correctness of the analytical calculation and the finite element simulation calculation was verified in the impedance tube experiment. The results show that the combined structure has good sound absorption performance in the 500Hz-2000Hz frequency band, and the sound absorption peak appears near the 1108Hz frequency, reaching nearly perfect sound absorption. Compared with a single porous material, the sound absorption performance of the combined structure is better.

During the operation of the ball joint, its service life and transmission efficiency are affected by the internal friction. Taking the ball joint as the research object, based on fractal theory, the friction between the steel ball and the raceway inside the ball joint of an automotive drive shaft system is studied in this paper. During the analysis, the friction between the steel ball and the arc raceway is regarded as the friction between a sphere and an arc raceway surface. In order to describe the friction state more accurately, this paper proposes a correction coefficient to modify the distribution function of contact asperities in the plane, and obtains the distribution function of contact asperities between the sphere and the arc raceway surface. The correction coefficient is related to the load, the size parameters and the material parameters of the steel ball and the raceway.

The amplitude-sensitive nonlinear mathematical model of the hydraulic engine mount (HEM) with a free-floating decoupler is deduced through the theory of fluid dynamics. The model considers the amplitude-sensitive characteristics, such as local pressure loss of the inertial track and the decoupler, the amplitude-sensitive dynamic stiffness of main rubber, and the switch mechanism of the decoupler. A new model of decoupler’s switching mechanism is established, which makes parameter identification simpler comparing to the existing analogous models. The finite element method is used to identify parameters of the lumped-parameter model, such as the contact force between the decoupler plate and the cage, the stiffness of the main rubber, the equivalent piston area, the chambers’ compliances, etc. The lumped parameters of fluid track are obtained by fluid mechanics formula.

When the automotive engine cooling fan is actually working, there is a process of interaction and coupling between the fluid and solid domains on the blades. In order to study the influence of the "fluid structure coupling" effect on the aerodynamic and structural performance of fans during operation, a fan performance calculation model was established with and without considering the fluid structure coupling effect of fans. We conducted aerodynamic performance tests on fans, tested the relationship between fan flow rate, static pressure, transmission efficiency and fan speed, and compared and analyzed the calculated fan performance. The aerodynamic performance and structural deformation of the fan were calculated under different flow rates, rotational speeds and environmental temperatures, with and without considering the coupling of fan blades and airflow. The calculation results were compared and analyzed.

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.

To characterize the stress flow behavior of engineering plastic glass fiber reinforced polypropylene (PPGF) commonly used in automotive interior and exterior components, mechanical property is measured using a universal material testing machine and a servo-hydraulic tensile testing machine under quasi-static, high temperature, and high strain rate conditions. Stress versus strain curves of materials under different conditions are obtained. Based on the measured results, a new parameter identification method of the Johnson-Cook (J-C) constitutive model is proposed by considering the adiabatic temperature rise effect. Firstly, a material-level experiment method is carried out for glass fiber reinforced polypropylene (PPGF) materials, and the influence of wide strain rate range, and large temperature span on the material properties is studied from a macroscopic perspective.

To enhance the transient vibration performance of the vehicle at key on and key off, a method for optimizing mount parameters of a powertrain mounting system (PMS) is proposed. Uncertainties of mount parameters widely exist in a PMS, so a method for optimizing mount parameters of a PMS, which treats the mount parameters of a PMS as uncertain, is also proposed in this paper. Firstly, a 13 degrees of freedom (DOFs) model including car body with 3 DOFs, a PMS with 6 DOFs and unsprung mass with 4 DOFs is established, and the acceleration of the active side of mounts is calculated. An experiment is carried out to measure the accelerations located at active and passive sides of each mount and the accelerations of seat track. A comparison is made between the measured and estimated accelerations, and the proposed model is validated. Two optimization methods for the PMS are proposed based on the developed 13 DOFs model.

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.

To study the heat dissipation performance of the multi-fan cooling module composed of multiple fans and a radiator, numerical models of the radiator and the multi-fan cooling module were established, and heat dissipation performance prediction analysis and application analysis were conducted. In modeling, the Effectiveness-Number of Transfer Units (ε − NTU) method is used to predict the heat dissipation performance of the radiator. The aerodynamic performance of the fan at any speed is obtained by the similarity theorem using the data obtained from the tests at a certain speed. The influence between the fan and the radiator was established by using the flow addition scheme. To validate the established model, heat dissipation performance using 36 radiators and 11 multi-fan cooling modules is measured, and the measured data are compared with the calculations.