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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.

The ever increasing popularity of electric vehicles and higher requirement on safety and comfort has led heat pump air conditioning system indispensable in electric vehicle. Many studies have shown that the addition of nano particles contributes to great improvement on thermal conductivity than that of conventional refrigerants. Therefore, the application of the magnetic nanorefrigerant in heat pump air conditioning system has massive potential to heighten the heat transfer efficiency. This paper aims at studying the magnetic nanorefrigerant comprised of the magnetic nano powder Fe3O4 and refrigerant R134a. According to the relevant theoretical analyses and empirical formula, the heat transfer coefficient, density, viscosity, and other physical parameters are calculated approximately. In the heat pump air conditioning system of a certain type of electric vehicle, the special working condition parameters are selected to carry out calculation analysis with numerical analysis software.

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.

Uniaxial fatigue tests of rubber dumbbell specimens under different mean and amplitude of strain are carried out. An Extreme Learning Machine (ELM) model optimized by Dragonfly Algorithm (DA) is proposed to predict the fatigue life of rubber based on measured rubber fatigue life data. Mean and amplitude of strain and measured rubber fatigue life are taken as input variables and output variables respectively in DA-ELM model. For comparison, genetic algorithm (GA) and particle swarm optimization (PSO) are used to optimize ELM parameters, and GA-ELM and PSO-ELM models are established. The comparison results show that DA-ELM model performs better in predicting the fatigue life of rubber with least dispersion. The coefficients of determination for the training set and test set are 99.47% and 99.12%, respectively. In addition, a life prediction model equivalent strain amplitude as damage parameter is introduced to further highlight the superiority of DA-ELM model.

In order to enhance the efficiency of durability testing of automobile parts, a time-frequency domain accelerated editing method of road load time series of rubber mount on powertrain was discussed. Based on Stockwell Transform method and Accumulative Power Spectral Density, a new time-frequency domain accelerated editing method (ST-APSD) was proposed. The accumulative power spectral density was obtained by ST of the load time series signal of automobile powertrain rubber mounting force which is acquired by the real vehicle in the test field. Based on the accumulative power spectral density, the threshold value was proposed to identify and delete the small damage load fragments, and then the acceleration spectrum was obtained.

The durability road test of a vehicle is an important test to verify the reliability of vehicle components. In order to carry out the durability bench test for drive shaft systems of all-terrain vehicles, a method for acquiring time domain signals of articulation angles of the CVJ, input torque, and rotational speeds of drive shaft systems is proposed. The acquired load spectrum of drive shaft systems is preprocessed including deleting small amplitudes, de-drifting, deburring, filtering, etc. Peaks and valleys are extracted from the preprocessed load spectrum. Based on the graphic method and the estimator stabilization method, the upper and lower thresholds of the time domain extrapolation of the load spectrum are determined, and then the peaks and valleys excesses that exceed the upper and lower thresholds are extracted. The generalized pareto distribution function is used to fit the distribution of peaks and valleys excesses.

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.

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.

The elliptically shaped bearing (ESB) with a rigid, elliptical inner race and a flexible, thin-walled outer race is the most easily damaged core component of harmonic drive. The ESB rotates under cycle load of alternating stress due to its special elliptic structure. Hence, the fault features of ESB such as fatigue spalling and pitting are apt to be concealed by the excitation of impulses caused by alternating between major axis and minor axis. In order to diagnose the fault on raceway surfaces of ESB, a new method of CMWT-FH based on Continuous Morlet Wavelet Transform (CMWT) and FFT-based Hilbert (FH) spectrum analysis is proposed to extract the fault feature.

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.

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.

As the power of electric vehicles (EVs), lithium-ion batteries (LIBs) are subjected to a variety of mechanical loads during electrochemical operation. Under this operating environment, lithium-ion batteries are at risk of internal short circuit, thermal runaway and even fire, threatening the safety of electric vehicles. The purpose of this paper is to investigate the mechanical behaviors and failure mechanisms of the battery separator to improve the safety of lithium-ion batteries under mechanical loads. In this study, uniaxial tensile, through-thickness compression and biaxial punch tests were performed to characterize two types of separators, dry-processed polypropylene (PP) separators and wet-processed ceramic-coated separators, and to analyze and compare their mechanical properties and failure modes. The comprehensive mechanical tests show that the failure modes of the different separator types are different, with the more anisotropic separator having more complex failure modes.

Automobile rubber isolator was subjected to random load cycle for a long time in the service process, and its main rubber material for vibration isolation was prone to fatigue failure. Since the traditional Miner damage theory overlooked the load randomness, it had a prediction error problem. In order to improve the prediction accuracy of rubber fatigue life, the traditional Miner damage theory was modified by random uncertainty theory to predict the rubber fatigue life under random load. Firstly, the rubber dumbbell-shaped test column, which was vulcanized from rubber materials commonly used in vibration isolators, was taken as the research object. The uniaxial fatigue test of rubber under different strain amplitudes and strain mean values was carried out. Then the fatigue characteristic curve of rubber with equivalent strain amplitude as the damage parameter was 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.

Rubber isolators are widely used under random vibrations. In order to predict their fatigue life, a study on the fatigue analysis methodology for rubber isolators is carried out in this paper. Firstly, taking a mount used for isolating air conditioning compressor vibrations as studying example, accelerations versus time of rubber isolator at both sides are acquired for a car under different running conditions. The acceleration in time domain is transformed to frequency domain using the Fourier transform, and the acceleration power spectral density (PSD) is the obtained. Using the PSD as input, fatigue test is carried for the rubber isolator in different temperature and constant humidity conditions. A finite element model of the rubber isolator using ABAQUS is established for estimating fatigue life, and model validity is verified through static characteristic testing. Dynamic responses of the rubber isolator at frequency domain are calculated if a unit load is applied.

The fatigue prediction model of an air spring based on the crack initiation method is established in this study. Taking a rolling lobe air spring with an aluminum casing as the studying example, a finite element model for analyzing force versus displacement is developed. The static stiffness and dimensional parameters of limit positions are calculated and analyzed. The influence of different modeling methods of air springs bellow are compared and analyzed. Static stiffness measurement of an air spring is conducted, and the calculation results and the measured results of the static stiffness are compared. It is shown that the relative error of the measured stiffness and calculated stiffness is within 1%. The Abaqus post-processing stage is redeveloped in Python language.

The ball joint with cross groove offers both angular and plunging motion. When transmitting the same torque, the cross groove ball joint is lighter than other plunging Constant Velocity Joints (CVJs). It is crucial for the design of the joint and enhancing the contact fatigue life of the raceway to accurately estimate component loads of the ball joints with cross groove. In this study, the transmission efficiency of the joint and the peak value of contact force between ball and the track are used as evaluation indexes for characterizing dynamic performance of the joint. A multibody dynamic model of the joint is established to calculate its dynamic performance. In the model, the contact properties and friction characteristics of the internal structures were modeled, and a nonlinear equivalent spring and damping model was adopted for estimating the contact force. The transmission efficiency loss of the cross groove joint was measured and compared with the calculated values.