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Table of Content

    25 December 2014, Volume 25 Issue 24
    Modeling, Simulation and Experimental Research of Hydraulic Pressure System in Battery Pole Piece Rolling Mill
    Zhang Wei, Yuan Conglin, Liu Guangkuo
    2014, 25(24):  3267-3271. 
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    To improve the pole piece mill rolling efficiency and rolled sheet quality, this paper analyzed hydraulic pressure system, getting the load characteristic equation of battery pole piece and dynamic simulation model of the hydraulic system. The experimental and simulation with constant rolling force and roll gap was also analyzed and contrasted. The simulation results are basically identical with the experimental ones, shows that the established simulation model has practical reference values and provides an important basis for the hydraulic control system parameter optimization and setting reasonable pressing process.

    Flexible Assembly Method of Ribs Based on Coordinate Holes
    Guo Feiyan, Wang Zhongqi, Kang Yonggang, Li Xining, Zhang Xiukun, Zeng Tian
    2014, 25(24):  3271-3277. 
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    To ensure the assembly accuracy of the wing-like parts, a new positioning method was studied based on coordinating holes at the internal location assembly pattern. By comparing the traditional positioning method based on the profile of the card  board, due to the superiority of the coordinating holes at the coordinating process of the wing-like parts according to the  coordination routine of the shape and the dimensions of the aircraft parts, a new flexible coordinate method of the ribs was proposed. The locater unit was designed to meet all of  the ribs of a certain aircraft by checking the locating process under  the DELMIA environment. By analyzing the coordinate principles and calculating the coordinating errors of the skin, the  theoretical results show that the assembly accuracy is improved. Flexible assembly examples show that the flexible  positioning unit has a simple structure and correspending low cost. The experimental measured results also reveal the new flexible coordinating method can fully satisfy the assembly precision of the skin.

    Study on Static Stiffness Model of Long Circumferential Spring Dual Mass Flywheel
    Hu Wei, Jiang Zhengfeng, Zeng Rong, Chen Lei, Wang Liwei
    2014, 25(24):  3278-3281,3288. 
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    The static stiffness model of circumferential arc spring dual mass flywheel (DMF-CS) was established based on the feature of changeable helix angle of arc spring. Based on the theoretical equations of the spring curve, according to periodical changing characteristics of the helix angle, the relation between transferred torque and total deformation of the arc spring was figured out using related mechanics theory. Applying the static stiffness test bench of DMF-CS, the experimental study was carried out. The theoretical and experimental results were compared, which validated the feasibility and accuracy of the established model. Meanwhile, the established model was compared with other theoretical models, which show that this model improves the precision of the static stiffness calculation.

    Optimization for Key Parameters of Heat Dissipation Structure in Heat-pipe Milling Cutter
    Liu Zhijun, Quan Yanming
    2014, 25(24):  3282-3288. 
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    In order to set reasonable structural parameters after optimization to heat pipe cutter, the heat-flow in the radiating process of heat pipe cutter was discussed, and the unclear relationships among structural parameters and radiating increments were analysed and experimented to evaluate. An experimental platform was designed for evalutating the relationships among structural parameters and radiating increments in heat pipe cutter. Then, the relationships among experimental factors and radiating increments, and its optimal values were obtained through a series of orthogonal tests. Finally, the heat pipe cutter produced based on experimental optimal values was used in cutting temperature experiments to verify the conclusions of the orthogonal tests. Comparing with common heat pipe cutter, it is founded that the temperature of structural optimization heat pipe cutter on cutting zone can reduce  50℃.

    An Inner Spiral In-pipe Robot
    Liang Liang, Jiang Hua, Tang Yong, Chen Bai, Duan Xiangping
    2014, 25(24):  3289-3294. 
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    A novel inner spiral in-pipe robot was proposed. The structure of the robot was designed, and the dynamics equations of the robot were established. When the robot run in the pipe filled with liquid, the pressure to the pipe wall, the robotic axial thrust force and the robotic circumferential resisting moment  were  analyzed numerically. The results show that the robot  is driven by the external magnetic field, the robotic axial thrust force and the robotic circumferential resisting moment all increase and the damage to the pipe wall is  also aggravated. In order to optimize the robotic axial thrust force and the robot energy efficiency index, the orthogonal experimental optimization method was used, and the optimal inner spiral geometric parametrical combination was obtained. According to the working principles of the inner spiral robot, an inner spiral driving device was designed and fabricated, and the running experiments in the pipe full of 201 methyl silicone oil proved the feasibility of the proposed robot. The proposed inner spiral robot has smooth surfaces and can be suspended to run. As the damage to the pipe is small, the robot can be used in tiny human pipes.

    Formation Control System Based on Virtual Force for Multi-robot System
    Lou Xiaochun, Xie Yu
    2014, 25(24):  3294-3297,3302. 
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    Aiming at multi-robot self-organizing collaboration control problem and using Zigbee wireless communication systems this  paper presented a black board communication mode based on local information stored. Combined the leader-follower and  the artificial potential field approach, a virtual force was defined based on distance and velocity vector. The problems of the paralyzed deadlock and decision conflicton for multi-robot self-organizing collaboration were solved by introducing a random generating function and variable repulsive force feedback control algorithm. And the small mobile intelligent physical implementation of the three two-wheel differential platform was built. Simulation results and mobile robots entity test demonstrate the validity and practicability of the proposed method.

    Bayesian Reliability Qualification Experiments for Exponential Products Based on Expected Net Gain from Sampling
    Wang Yanfei, Yang Muhua
    2014, 25(24):  3298-3302. 
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    The reliability qualification experimental design about failure rate for exponential products was made based on Bayesian  decision theory. Considering the relation between the actual economic loss and the failure rate, the decision loss function was constructed so as to quantify loss. According to the posterior risk criteria, the loss caused by producer's risk and  consumer's risk were constrained. The maximum sample size and the failure number were determined in order to get the maximum expected net gain from sampling in type Ⅱ censoring way. The qualified determination time according with the product identification was deduced by posterior loss criteria. In all, the consumer can obtain the more rational and effective qualification scheme than only considering the decision risk. At last, an example was given to illustrate the validity and practicability.

    Damage Detection Method Based on Strain Modal and Trust Region Optimization Algorithm
    Li Shilong, Ma Liyuan, Dong Bin, Wang Tianhui
    2014, 25(24):  3303-3307. 
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    By combining strain mode with trust region optimization algorithm, a least-squares objective function was defined based on strain mode, then the detection problem was transformed into an optimization problem. Because the traditional modal strain index included both of damage location and damage degree information, there likely existed miscarriage of justice when the objective function was minimized, so the objective function based on strain mode was improved here. The improved optimization was carried out in two steps, the damage degree could be detected after it was located in the first step.Two numerical simulation experimental results show that the improved damage detection method is more desirable, and it provides a new idea for the applications of strain mode in practical engineering.

    Pattern Recognition Method Based on Embedded SRVPMCD
    Pan Haiyang, Yang Yu, Ma Li, Cheng Junsheng
    2014, 25(24):  3308-3313. 
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    Targeting the inherent defects of the variable predictive model based class discriminate(VPMCD) and the problems of how to choose the features of those mechanical faults, which was the effects on timeliness due to the excessive characteristic dimensions and feature selection needed o introduce the subjective factors, a new embedded SRVPMCD method was put forward herein. Introducing variable and calculating the significant level by stepwise regression, establishing a prediction model that only contained significant characteristic values, achieving the function of embedded feature selection and modeling simultaneously, and then using the established prediction model to predict the characteristic values of those unclassified signals samples, the prediction results would be recognized by the model as accordance to classify. The analysis results for roller bearing fault signals show that compared to the original VPMCD and combined methods, the pattern recognition method based on embedded SRVPMCD can realize the double functions of feature selection and classification, and identify the working states and fault types of roller bearing quickly.

    Feature Extraction Based on Compressed Sensing Weak Matching Pursuit Algorithm
    Li Xinbin, Ma Yang, Qiu Jiankun, Zhang Shuqing
    2014, 25(24):  3314-3320. 
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    A new feature extraction method was proposed to solve the feature extraction problem in rolling bearing fault diagnosis, which was based on compressed sensing weak matching pursuit algorithm. A joint dictionary which was made up of Fourier dictionary and impulse time  frequency atom was built as complete redundant atom library of weak matching pursuit algrithom. And then a improved simplified particle swarm optimization algorithm was presented for searching the atom which can match mostly the bearing fault signal characteristics to realize the sparse decomposition process quickly and efficiently. A improved threshold denoising method was introduced to solve the problem of bad signal consecutiveness and  low degree of approximating the real signals. The simulation results of using standard bearing fault signals of CWRU(Case Western Reserve University) and the measured signals of a certain steel company demonstrate the proposed new method is of advantages.

    Equivalent Transformation Algorithm for Motion Time Periodization of Acceleration and Deceleration before Interpolation
    Yin Juan, Luo Fuyuan
    2014, 25(24):  3320-3325. 
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    To solve the problem that the motion time calculated from acceleration and deceleration control before interpolation control in CNC system, on the basis of continuous time velocity profiles and the principles of displacement equivalent transformation, an algorithm for the generation of periodic discrete velocity profiles was proposed, whose motion time fited into an integral number of interpolation periods. The feedrate computational formulae for each interpolation period of different acceleration and deceleration phases were deduced in detail in cases where both start speed and end speed were any desired positive real number. The proposed method did not need variant interpolation periods and it was easy to apply in traditional servo motion control system. The interpolation instance shows it is able to generate such velocity profile that the constant speed is strictly equal to instruction speed and guarantees the velocity at the segment terminal to be the specified speed. In addition, it has high motion efficiency and interpolation accuracy.

    Analyses on Tilted Oil Film Dynamical Characteristics of Hydrostatic Rotary Tables
    Xiong Wanli, Fu Mali, Wang Shaoli, Lü Lang
    2014, 25(24):  3326-3333. 
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    The disadvantages of the CFD(computational fluid dynamics) numerical simulation such as long period of modeling and poor efficiency of calculation were displayed. An analytical method for studying tilted bearing characteristics of hydrostatic rotary tables was proposed based on equivalent oil film thickness of each pocket margin. The formulae of load capacity, moment  and stiffness for tilted oil film bearings were derived and computational efficiency was improved. Numerical simulation for oil film was also conducted by CFD software Fluent. The results show that tilted oil film bearing load capacity error between the analytical method and CFD remains at 6% or less. Furthermore, the moment error between two methods is kept at 8% or less. The reliability of the analytical method was verified. The effects of tilted displacement rate, supply pressure, throttle aperture, rotation speed on the oil film basic performance parameters were studied by the analytical method.

    Optimization of Draw-die Entrance Curve in Sheet Metal Stamping
    Wang Jinwei, Guo Shuijun, Yang Xujing, Zheng Juan
    2014, 25(24):  3333-3337. 
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    During the sheet metal stamping, the shape of the draw-die entrance has an important influence on the friction between the sheet metal and die surfaces, the quality of the sheet metal surface and the life of tool. To get an optimal the draw-die entrance curves, a new method of using cubic spline curve as the draw-die profile was adopted. This paper investigated the effects of draw-die entrance curves on the sheet metal tool wear distribution over the entrance of the die. With the forming quality requirements, searching for an optimal die profile was based upon response surface methodology and design of experiments. The results demonstrate that the tool wear is reduced significantly and well distributed over the entrance of the draw-die using the optimized cubic spline curve profile. As a result, the occurrence of surface defects is reduced, the quality of the sheet metal surface is increased, and the life of the tool can be extended.

    An Adaptive Adjustment Technique of Multi-parameters in Microimaging System
    Wang Hongwei, Chen Guo, Li Ai, Chen Libo
    2014, 25(24):  3338-3342. 
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    Image quality was a key link to ensure the analysis for wear particle in the wear fault diagnosis system which was based on micro-image processing.However, the micro-image quality of wear particle was related to camera parameters and light source parameters. Herein GA was used to adjust 6 parameters of camera and light source automatically. A fitness function was constructed to describe the difference between the standard image and the image under certain parameters. A group of optimal parameters of the camera and light source were obtained by means of the GA method  operational procedure, such as real coding, roulette wheel selection, arithmetic crossover and uniform mutation operation. Finally, the new method was verified through the experiments, and the results show that the GA method is very effective for adaptive adjustment of multi-parameters in micro-imaging system.

    Weak Signal Detection Based on Cascaded Piecewise-linear Stochastic Resonance
    Sun Huer, Wang Zhiwu
    2014, 25(24):  3343-3347. 
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    Aiming at the detection problem of the weak signal under noise background, a method enhanced weak signal detection was proposed based on cascaded piecewise-linear stochastic resonance. In this method, a new model of piecewise-linear stochastic resonance was applied, that avoided the saturation phenomenon in classical bistable system when detecting a weak signal, and thus the cascaded piecewise-linear stochastic resonance were selected, which could remove high frequency noise efficiently and enhanced the energy of low frequency signals. Simulation signals and bearing inner-race defective signals were analyzed, the results show that the proposed method is effective for raising the signal-to-noise ratio. Compared with cascaded bistable system, it is more convenient to adjust less correlated parameters, and possesses a good prospect of engineering applications.

    Inverse Kinematic Analysis for 6-PUS Parallel Mechanism Based on Influence Coefficient
    Xie Zhijiang, Wang Chengfei, Shi Haoming, Wang Junjie, You Shimao
    2014, 25(24):  3348-3352. 
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    Inverse kinematics and influence coefficient matrix were received based on the characteristics of a 6-PUS parallel mechanism, and correct kinematics equations were obtained. Then, in order to obtain the corresponding kinematics performance atlas, theoretical analysis and simulation of kinematics performance index were calculated with MATLAB software. A specific example was introduced to verify kinematics performance atlas can provide theoretical proof for the mechanism design and optimization and the choice of control strategy.

    A Method to Find Critical Parts Structure of 3D Structural Model Based on Formal Concept Analysis
    Wu Qiang, Xie Liping, Dong Yan
    2014, 25(24):  3352-3358. 
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    Existing part's coding method based on the assembly structural model was to search all structural codes and compare all codes in part retrieval. It reduced the retrieval efficiency. To solve this problem, a method to find critical structures of the parts based on formal concept analysis was proposed. By mapping relationships among the part functional surfaces and the positions to the binary formal context, a concept lattice of 3D parts structural model was built. Weights were designed by the information entropy, the important attributes and the intents were found, then the formal concepts were sorted. The users can set thresholds as well as the deviation with the central weights to determine critical structure of the parts. It  lays the basis for the efficient parts query using structure coding.

    Experimental Investigation and Safety Analysis on Cold Stretching for Austenitic Stainless Steel Pressure Vessels
    Han Yu, Wang Kesheng, Chen Xiaoping, Zhang Zhu
    2014, 25(24):  3359-3364. 
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    The allowable stress of ASS was determined according to the cold stretching of ASS pressure vessels from European Standard EN 13458-2:2002. An experimental vessel of ASS was designed and manufactured. The welding process was reasonably made and favourable welds quality was proved with classⅠ of radiographic and penetrant testing. The technique of cold stretching was implemented by a self-developed precise automatic pressure device. The circumference variation was measured to calculate the permanent deformation of the stretched vessel. The experimental results show good agreement with the theoretical values. Bursting pressure test for the cold stretched vessel was conducted to define its burst pressure and location, also plastic reservation was examined by measuring the variation of the circumference and wall thickness of the crack initiation site. Ultimate load-carrying capacity and bursting safety factor were investigated to discuss the safety of the cold stretched experimental ASS pressure vessel.

    Analysis of Metal Flow and Process of Back Gear with Double Boss in Warm Forging
    Li Heng, Chen Wenlin, Zhou Rui, Shi Weibing, Wu Yucheng
    2014, 25(24):  3364-3367,3390. 
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    Based on the geometric features of back gear with double boss, a new two-step warm forging process before finishing was put forward to reduce the number of cold forging process. Empty corners in the bottom of profile of all teeth were found when using the above process. In order to solve the problem, a rigid plastic FE model was built to simulate the warm forging process. The velocity, stress and strain field were investigated, and the metal flow rules were discussed with the experimental results. Then a qualified gear was achieved through expanding the radial wave shape by means of an indentation established in die. The measured results show that the new process can satisfy a high level precision of forging. The work presented herein may be used as basic data for the design of the precision forging processes.

    Analysis of Remanufacturing Process and Residual Stress of Axis Parts Based on Thermal Spraying
    Cao Huajun, Tong Shaofei, Chen Haifeng, Shu Linsen
    2014, 25(24):  3368-3372. 
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    As one of the key supporting technologies of remanufacturing engineering, thermal spraying was an important technical means to achieve surface size recovered rapidly, to improve performance significantly and to extend service life of the damaged parts. But the excessive residual stresses in the coating system had an important influence on the quality and reliability of remanufactured parts. A case of used hobbing machine spindle was analyzed, and air plasma spraying was adopted to remanufacture the abraded outer taper surface. The residual stresses generated in coating/substrate system during the cooling process and also the distribution were simulated by using finite element method, and X-ray diffraction  method was applied to verify the rationality of the established model and the credibility of the simulation results. Simulation results have good consistency with the test ones.

    A Study  of  Fatigue  Crack Growth Behavior of U75V Rail Steels under  Different  R-ratios
    Lü Bin1,2;Din Zhenyu1,2;Gao Zengliang1,2
    2014, 25(24):  3373-3377. 
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    The fatigue crack growth threshold values of  U75V  rail steels under different stress ratios were measured and the fatigue crack propagation tests were  carried out.It is shown that R-ratio has significant effects on the crack propagation behavior.The fatigue crack growth threshold values acquired by the stepped unloading method decrease with increasing the stress ratio,while the crack growth rates increase with increasing stress  ratio.The fracture surface morphologies are carefully studied after the experiments.It is  found that ridges cover the fracture surface.Transgranular fracture occurring in crystallographic plane is observed around the near-threshold regions;the lower growth rate regime appears to be parallel arrays of ridges, orientated at the contours of the pearlite lamellae; curving and fragmental ridges accompanied with cleavage fracture as well as secondary cracks are found in the higher growth rate regime.

    Study on Influence of Prior Austenite Size on Critical Point between Stable and Near-Threshold Fatigue Crack Propagation in Weld Metal of a Nuclear Turbine Rotor
    Sun Lingen, Cai Zhipeng, Pan Jiluan, Liu Xia, Xu Xiaojin, Ding Yuming
    2014, 25(24):  3378-3384. 
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    The fatigue crack growth properties were important to the welded rotor in nuclear turbine. The fitting relations between the fatigue crack growth rate and stress intensity factor range for submerged arc weld metal of 25Cr2Ni2MoV simulating product of nuclear power low pressure turbine rotors were researched. The critical points between stable and near-threshold fatigue crack propagation were different in different specimens and their locations were determined by the method of backward inference. After the observation of the microstructure around the critical points, a good correspondence between the size of prior austenite and the maximum size of monotonic plastic zone on the crack tip was confirmed. The differences of the critical points between different specimens are caused by the heterogeneous microstructures in the multi-pass and multi-layer weld metal, and become an important reason for the dispersion of the experimental threshold values.

    Control and Optimization of Vehicle Based on Genetic Algorithm Method for Encountering an Emergency Collision Avoidance
    Wang Wei, Zhao Youqun, Bei Shaoyi, Liu Wenting, Xu Jianxiong
    2014, 25(24):  3385-3390. 
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    In consideration of the nonlinear tire lateral deviation, a nonlinear two DOF model was established in MATLAB/Simulink, using for emergency avoidance steering. The correctness of the model was verified through real vehicle test. Based on vehicle handling stability evaluation and single neuron self-adaptive PID control theory, a control algorithm to make vehicle moving along the given single route was proposed, with different speeds.And the experimental results were good. Next, taking advantages of multi-island genetic algorithm, an optimal control system was achieved to optimize the control parameters. The same experiment was carried out again with the optimized system. The results show that the optimized control algorithm is more accurate than before ones.And it also has good robustness and adaptability.

    Effects of Fluid-structure Interaction on Aerodynamic Noise of Automobile's Side Window
    Xie Chao, Gu Zhengqi, Zong Yiqi, Luo Zemin, Jiang Caimao
    2014, 25(24):  3391-3396. 
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    Aerodynamic noise is the main noise source when automobile runs at high speed. The aerodynamic noise around automobiles was dominated by dipole source which depends on fluctuating pressure around automobiles. Flow field  calculation was carried out using CFX software and structure calculation was carried out using ANSYS software, respectively. Based on MFX-ANSYS/CFX data coupling platform, two-way synchronization solution method was used to compute the flow field and the response of automobile's side window structure. The results show that, fluid-structure interaction enhances the flow field pressure pulsation, as the speed increases, the effects of fluid-structure interaction on aerodynamic noise become more intense. Compared with non-coupled numerical calculations, the coupling calculation results are closer to experimental values,and has a higher accuracy.

    Research on Steering Characteristics in New-energy Mining Car Based on Bekker Theory
    Liu Xiang, Liu Bo, Long Zizhao, Gao Yu
    2014, 25(24):  3397-3402. 
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    Because the mining car did not swerve flexibly and turning radius was too large, the hydraulic system needed to be improved. According to the Bekker terramechanics theory, the dynamics and kinematics model of steering characteristics were established. By ADAMS and AMESim, the co-simulation model of dynamics and the hydraulic system was built. Through the contrast analysis of simulation results and field experimental data, it proves that the hydraulic system can form stable speed difference between inside wheel and outside wheel, which realizes steering function smoothly.

    Reduction Fuel Consumption Method for a Commercial Vehicle
    Jiang Jian, Xiao Hui, Wu Zhaohui, Wu Bing
    2014, 25(24):  3403-3407. 
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    In order to reduce fuel consumption, this paper introduced to several methods such as air resistance optimization, lightweight of automobile, optimization of the rolling resistance and the transmission ratio. Firstly, the methods of CFD data simulation were adopted to optimize the shape for a commercial vehicle, then integrated with the clay model wind tunnel test the effects for the optimization of air resistance were validated. Secondly, in order to optimize the rolling resistance lightweight of automobile, lower-rolling resistance coefficient of tyre were applied. At last, in order to the commercial vehicle working in the economic area the transmission system ratio was optimized.