Papers by Author: Ji Xin Wang

Abstract: Power Spilt Device (PSD) is the key power component of Hybrid Electric Vehicle (HEV). It is very important to simulate and analyze the temperature field and stress field of PSD gear train. The thermal-mechanical coupling analysis is difficult, as it involves the interaction between temperature field and stress field. This paper presents the process of the thermal-mechanical coupling simulation in ABAQUS, and tooth surface temperature and contact stress are obtained and analyzed.

Abstract: For a typical Full-hybrid electric vehicle (HEV) layout, such as Toyota Prius, the power-slit device (PSD) is a key component. Determination of volume or weight of a PSD is an important issue in preliminary design of power transmission applications. The purpose of this paper is to preliminary design of PSD gear drives by minimizing volume of gear trains. A stochastic approach Genetic Algorithm (GA) was applied to a differential-based coupling PSD design problem. Static and dynamic penalty functions were introduced to the objective function for handling the design constraints. The calculation of quadratic mean deviation and dynamic bounding parameter values such as determination of crossover and mutation parameter values were adopted to ensure the convergence of the fitness function. The optimized design method based on GA produced quite well results, which promptly supplied preliminary design parameters of gear drives for differential-based coupling PSD design.

Abstract: Modeling for complex spiral wire rope structures, on which the mechanical performances largely depend, are paramount to finite element analysis application. Three mathematical modeling thoughts were brought out to create the geometric models of wire rope strands. The first one was presented based on the centerline times of the helical structures, as the centerline times can be decreased through transitional coordinate system. For the second, the centerlines of the wire rope were formed by the helical movement of predefined point. In the third one, a local coordinate system which can be transformed into the world coordinate system by their relationship was employed. The above three ideas were implemented by different kinds of derivation. The geometric parameter equations were presented to express the accurate wire rope models. These approaches are beneficial for parametric modeling and analysis of wire rope strands.

Abstract: To realize the structural light weighting design of the transmission components of engineering vehicles on the basis of life in control, this paper took wheel loader as an example, collected the time-domain load signals of the transmission system in typical working conditions, provided processing steps for load spectrum synthesis by a certain percentage, and generated the program load spectrum which consisted of various amplitudes and means. The load spectrum can be used for fatigue loading at the output flange of gearbox. Then, the finite element model of the flange was established, and the stress analysis was carried out in the stress concentration location such as fillet. The prediction method of fatigue life on the base of program load spectrum was given. After the fatigue life prediction based on the compiled load spectrum and the theory of cumulative fatigue damage, the fatigue life of outside fillet of the flange, where is of maximum stress, is obtained. It was possible to obtain adequately fatigue prediction results in engineering vehicle design, using load spectrum, finite element analysis, and a stress-life approach to fatigue damage calculations.

Abstract: The load time history signal of engineering vehicle is usually polluted by various nonstationary and stationary noises in the field test. An approach based on wavelet transform (WT) and fractal dimension (FD) is proposed in order to improve the adaptability and efficiency of denoising. This method initially decomposes the original signal into detail and approximation space in the WT domain by WT-based multiresolution decomposition. The short-time fractal dimension of detail coefficient is calculated at each scale. After the application of the binary processing to the short-time fractal dimensions, the locations where the thresholding of the detail coefficients has to be executed are ensured. The desired load signal is provided by applying WT-based multiresolution reconstruction to the processed detail coefficients and the unprocessed approximation coefficients. The proposed method is applied to an actual load time history signal of engineering vehicle. And the performance of this method is compared with that of the WT-based hard thresholding denoising method. The results show that this method is an alternative way to process the load time history signal of engineering vehicle.

Abstract: Fatigue failure of gears carrying heavy loads is the leading cause of gearbox breakdown in the large-scale earthmoving machinery. The fatigue life of gear is mainly determined by loads distribution. Taking the Wheel Loader as an example, this paper introduced an indirect test system of gear load under the loose soil conditions. Then the load data in time, amplitude and frequency field were respectively analyzed. The results show that the indirect measurement method proved workable, and the load data of gear is characterized by bi-modal. Therefore, to decrease statistical errors, mixture model must be adopted to fit these bi-modal signals.

Abstract: A continuous non-stationary load spectrum of wheel loader transmission was obtained from field testing by a special test system, including time-history of torque, speed, oil pressure and gears. During the data processing, each work cycle was divided into six steps: no-load forward, shoveling, heavy-load back, heavy-load forward, unloading and no-load back with considering the characteristic of gears, torque and oil pressure signals. Discretization, Butterworth filter and the singularity rejecting were adopted to analyze the load data of each step, from which the non-stationary random signals were translated into the pure stationary load signals. The time-history load testing method and data processing of random load spectrum of transmission was presented.

Abstract: Signal processing is an important work of load spectrum generation, while wavelet denoise method is regarded as one of the best method in engineering signal processing. So on the purpose of obtaining a good load spectrum of engineering vehicles, db3 wavelet is selected as the mother wavelet. Then the denoise layer number was determined by some comparisons, as well as a proper threshold and threshold function algorithm. Finally a whole process in denoise of the load spectrum of a wheel loader, which is from the selection of the mother wavelet to the determination of the denoise layer number to the selection of the threshold algorithm and the threshold function algorithm, is depicted in this paper. A new coefficient is introduced and a satisfactory result is got. It is safe to conclude that wavelet denoise method is the relative best selection for load spectrum analysis of engineering vehicles.

Abstract: The structural durability of wheel loader are required to estimate on the basis of design loading spectrum, which is a spectrum combination of various operating and loading conditions. To generate the load spectrum of transmission system, an actual operational loads of wheel loader under the driving cycle was investigated. A signal collection system was applied to get time-history voltage signals and then torque loads were obtained according to the conversion coefficient between voltage and torque. After zeroing and filtering, the mean, the amplitude and number of load cycles were gained with the rain-flow counting method. The mean and amplitude were tested by Nominal distribution and Weibull distribution respectively. Test results show that they are independent. The two-dimensional joint probability density function of amplitude and mean was gained. After extrapolation, the load spectrum of the spacerflange under whole-life cycle is gained and the process of compiling load spectrum is also provided.

Abstract: According to the structural characteristic and the test requirement of tow-post ROPS, a nonlinear finite element model of ROPS based on large-strain shell element was established, and the influence of elastic-plastic deformation of ROPS was taken into consideration. Then the computer simulation of ROPS was performed in lateral loading case, which obtained the deformation mode and the distribution law of equivalent plastic stress of ROPS followed by the discussion of deformation mechanism of ROPS. The simulation results accorded with test results. This paper can provide theoretical basis for the structural design of two-post ROPS.