Tongji University , colloquially known as Tongji , located in Shanghai, has more than 50,000 students and 8,000 staff members . It offers degree programs at both undergraduate and postgraduate levels. Established in 1907 by the German government together with German physicians in Shanghai, Tongji is one of the oldest and most prestigious universities in China. Among its various departments it is especially highly ranked in engineering, among which its architecture, urban planning and civil engineering departments have consistently ranked first in China for decades, and its automotive engineering, oceanography, environmental science, software engineering, German language departments are also ones of the best domestically. Wikipedia.
Chen C.,Tongji University |
Hao L.,Tongji University |
Xu C.,Tongji University
AIP Conference Proceedings | Year: 2017
An accurate used car price evaluation is a catalyst for the healthy development of used car market. Data mining has been applied to predict used car price in several articles. However, little is studied on the comparison of using different algorithms in used car price estimation. This paper collects more than 100,000 used car dealing records throughout China to do empirical analysis on a thorough comparison of two algorithms: linear regression and random forest. These two algorithms are used to predict used car price in three different models: model for a certain car make, model for a certain car series and universal model. Results show that random forest has a stable but not ideal effect in price evaluation model for a certain car make, but it shows great advantage in the universal model compared with linear regression. This indicates that random forest is an optimal algorithm when handling complex models with a large number of variables and samples, yet it shows no obvious advantage when coping with simple models with less variables. © 2017 Author(s).
Deng G.,Tongji University |
Wu X.,Tongji University |
Shao J.,Tongji University |
Wang C.,Tongji University
Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future | Year: 2016
As the car drives at high speeds, wind noise becomes the main noise and can propagate into the vehicle interior cavity through the slits or channels on the automotive body surface. With good insulation performance, the automotive door sealing system can reduce the vehicle interior wind noise so as to improve the interior speech intelligibility. In this paper, a 3D (3-dimensional) finite element model of the automotive door sealing system, which includes the channel between the automotive door and body frame, is built to simulate its nonlinear contact and compression. And then a hybrid FE-SEA (Finite Element - Statistic Energy Analysis) model is used to predict the transmission loss (TL) of the door sealing system. The different boundary conditions, i.e. the fixed boundary condition without compression effect and the frictional boundary condition with the compression effect are then verified to have an influence on the TL of the sealing system. Taking the frictional boundary condition with the compression effect into consideration, three different uniaxial tensile test data of the hyper-elastic sealing strips are used to evaluate the effect of the elastic modulus on the TL and the effect of the thickness for the seal rubber on the TL is also studied. Consequently seals with improved TL of the automotive sealing system could be obtained. © 2016, German Acoustical Society (DEGA). All rights reserved.
Document Keywords (matching the query): automobile bodies, statistic energy analysis, automobile manufacture, automotive sealing systems.
Lu H.-M.,Yancheng Institute of Technology |
Zhang L.-J.,Tongji University |
Yu Z.-P.,Tongji University
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2011
Disc brake squeal is one of the most difficult quality issues concerned by automotive manufacturers and researchers. It is of critical importance to study squeal generation mechanism, predict brake squeal performance and propose suppressing measures in product development phase for decreasing noise pollution, satisfying customers' requirements, accelerating new product development to improve automobile competitiveness. The recent research advances were reviewed in the aspects of squeal generation mechanisms, analysis methods, influence factors and new technologies. Latest developments showed that disc brake squeal is caused with complicated mechanisms and influenced with many factors; utilizing modern design methods of complex eigenvalue analysis and transient dynamics analysis combined with on-road and bench tests is an important way to analyze brake vibration characteristics and develop disc brakes with lower squeal propensity. The existing problems and the further study needed in the future were finally discussed.
Document Keywords (matching the query): vibration analysis.
Gao Y.,Tongji University |
Li C.,Tongji University |
Cui L.,Shandong Transport Vocational College |
Gao D.,Tongji University
Qiche Gongcheng/Automotive Engineering | Year: 2010
Road excitation load is generated and its characteristics are tested using Matlab, and by combining with vehicle multi-body dynamics model, the excitation load for vehicle body fatigue analysis is obtained. The dynamic stresses of vehicle body are calculated by transient time domain approach and the fatigue locations of fuel cell bus body are identified with their fatigue life predicted by utilizing software MSC/Fatigue. The analysis provides references for structure design and modification.
Document Keywords (matching the query): automobile parts and equipment, automobile bodies, dynamic analysis, simulation analysis, stress analysis, dynamic stress analysis, fatigue analysis.
Zhang L.,Tongji University |
Zheng P.,Tongji University |
Meng D.,Tongji University |
Deng H.,Tongji University
Qiche Gongcheng/Automotive Engineering | Year: 2013
In view of the problem of severe longitudinal flutter occurred during vehicle starting with motor-drive mode in a newly developed hybrid electric car, the vibration source and control scheme are investigated in this paper. Firstly, road test of real vehicle is carried out. The vehicle starts and slowly accelerates with constant torque, the vehicle speed, the rotation speed and current of motor as well as the vibration acceleration of motor housing and seat guide are measured realtime and the frequency feature of flutter is determined with time-frequency analysis. Then based on the measured data of three-phase currents and by using finite element method, the motor torque in experiment condition is predicted and the time-frequency analysis is performed on torque ripple. The results show that it is the forced excitation caused by motor torque ripple at low-speed low-load condition, which leads to longitudinal flutter. Finally measures are taken to suppress the phase current of motor and control its torque ripple, the ride comfort at accelerated starting phase is significantly improved.
Document Keywords (matching the query): time frequency analysis, finite element analysis.
Du A.M.,Tongji University |
Wei N.,Tongji University |
Shao J.W.,Tongji University
Applied Mechanics and Materials | Year: 2014
The design of automotive trim configurations has become increasingly driven to maximize the acoustic performance benefit while minimizing material weight. Statistical energy analysis (SEA) can serve as a useful tool to predict the high frequency acoustic response on both a component and full vehicle level. This paper focuses on the automotive dash panel, using VAOne software to establish the SEA model. The method of orthogonal test is applied to optimize the sound package design to satisfy maximum high-frequency transmission loss (TL) and minimum weight by modifying the acoustic material, thickness, surface density and coverage of sound package. © (2014) Trans Tech Publications, Switzerland.
Document Keywords (matching the query): statistical energy analysis.
Gao Y.,Tongji University |
Xu C.,Tongji University |
Fang J.,Tongji University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2014
A compiled method of programed load spectrum is presented, which can simplify and accelerate the body fatigue bench test. Random load spectrum of the interface points between chassis and body, which is obtained accurately by road load spectrum collected on the proving ground, is simplified to torsion load spectrum. Based on rain-flow counting method and statistical theory, the distributions of amplitude and mean are found to confirm with normal distribution and Weibull distribution respectively. Following that, the programed load spectrum is compiled and simplified. The fatigue life of the body is predicted using finite element method (FEM) and fatigue analysis theory, and the critical regions are analyzed in terms of fatigue time and driving distance. Through comparative study of the simulation result of random load spectrum and programed load spectrum, the damage distribution and fatigue life are found to agree well with each other, which demonstrate the effectiveness of the presented method. The compiled method of programed load spectrum can help other vehicles to improve the performance. © 2014 Journal of Mechanical Engineering.
Document Keywords (matching the query): automobile bodies, fatigue analysis.
Wang Y.,Chongqing Changan Automobile Co. |
Wang Y.,State Key Laboratory of Vehicle NVH and Safety Technology |
Fang J.,Tongji University |
Wang J.,Tongji University |
Tian L.,Tongji University
Qiche Gongcheng/Automotive Engineering | Year: 2012
The mesh morphing technology is applied to the retrofit design of a baseline car model in this paper. Specifically, according to the morphing scheme worked out, the geometric dimension of FE model for its body-in-white is changed to build the FE model for new car model efficiently, with its performance predicted by finite element analysis. The results indicate that with mesh morphing technology, the dependency of design on detailed CAE data and the time-consuming preparation activities for simulation can be avoided, with the lead time for car model development shortened and the development cost reduced, truly embodying the vision of 'CAE leads design'.
Document Keywords (matching the query): car bodies, car body, model automobiles, railroad cars, car models.
Diao K.,Tongji University |
Zhang L.,Tongji University |
Meng D.,Tongji University
SAE Technical Papers | Year: 2014
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. The simulation results show that the time-varying characteristics of frictional squeal are influenced by the frictional contact characteristics of the friction pair, including tangential contact stiffness, normal contact stiffness and friction coefficient. And the disc surface run-out (SRO) is the main cause of the time-varying frictional contact characteristics. The uncertainty of sound pressure of frictional squeal derives from the uncertainty of the surface roughness, which is caused by the frictional wear and makes the occurrence of frictional squeal much easier. Copyright © 2014 SAE International.
Document Keywords (matching the query): automotive industry, transient response analysis, system stability analysis.
Li Y.,Tongji University |
Luo Y.,Tongji University |
Han S.,Tongji University
Journal of Biobased Materials and Bioenergy | Year: 2010
Natural fibres are promising reinforcements for use in composite materials due to the low cost, high specific strength and modulus, easy availability, especially the renewability and environmental friendly characteristics. In this paper, multi-scale structures of different natural fibres were clearly revealed with the aid of optical microscopy (OM) and environmental scanning electron microscopy (ESEM). Based on the observed microstructures, a model of the multi-scale structures of natural fibres was assumed and the mechanical properties of natural fibre were predicted, which showed good agreement with the statistical analysis results of the experimental data obtained by single fibre tensile test. Some recent work on the acoustic properties and thermal insulation properties of natural fibre reinforced composites (NFRCs) were reported and their potential applications in making automobiles parts were also investigated. Copyright © 2010 American Scientific Publishers All rights reserved.
Document Keywords (matching the query): automobiles, automobile parts, statistical analysis.