Table of Content

25 January 2016, Volume 27 Issue 02

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Wear Analysis on Intermittent  Mechanism  Systems  Inclulding  Flexible Bar

Deng Peisheng, Yuan Daning, Liu Hongzhao, Wang Gengxiang

2016, 27(02):  143-149. 

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A slider-crank mechanism with multi-clearance was established based on the mechanical system dynamics analytical software ADAMS. In the process, the impact function theory was used to simulate contact and collision occurring in the clearance joints. The dynamic effects of flexible members and clearance joints on mechanical systems were studied in detail, and the Archard wear model was  employed to predict the wear of clearance joint.A finite element model of linkage was  established through ANSYS considering the linkage was flexible, and the first five modes of the linkage were exported into ADAMS to set up a rigid-flexible coupling model of slider crank mechanism with multi-clearance.The  simulation results show that the dynamic behavior of the slider-crank mechanism with clearances and flexible linkage is very close to the ideal mechanism.In the process that the crank moves for one cycle, the impact force in the clearance joint occurs in some special locations, the pin and bushing still keep a continuous contact in a large range of crank angle, and the wear result predicted is reduced.

Assembly Accuracy Allocation Method Based on JSS Matrix

Lü Cheng, Liu Zijian

2016, 27(02):  143-149. 

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Joint surface error was described by SDT,typical joint surface error transfer properties were analyzed. Information integrated expression symbols of joint surfaces were defined, combined with the polychromatic sets theory,JSS matrix,was established,that could describe assembly relationship,joint surface type and error transfer properties,and  then assembly error transfer path search method was proposed,critical error distribution that affected  the precision of assembly was identified. Assembly error model was established based on the multibody kinematics principles,and  combined with assembly accuracy requirements,the accuracy allocation of joint surface and the relevant geometric element were implemented, then the basis was provided for tolerance design and accuracy control during assembly process.At last, the feasibility and practicability of the proposed  method was verified by example analyses.

A Simple and  Convenient Method to Obtain Strain Modal Shape

Wu Jiaquan, Ye Fei, Li Hongyan, Zhang Xinyu, Ma Kun

2016, 27(02):  156-160. 

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Based  on strain modal analysis theory,a new strain modal shape factor was defined.The principles and methods to obtain structure strain modal shape from FRF were  derived.Meanwhile,the method was validated by a simply supported beam experiment.The results show that the method does not need to  measure the displacement mode,and  can quickly obtain the strain modal shape by  using strain gage to measure strain FRF information.  This method simplifies the process of strain modal experimental testing in structural damage identification.

Feature Extraction Method Based on High Order Cumulant Faced to Running Stability  Deterioration  of  Rotating  Machinery

Jiang Zhanglei, Xu Xiaoli

2016, 27(02):  160-167. 

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This paper focused  on  feature extraction method based on high order cumulant like 1.5-dimension spectrum and fourth-order cumulant diagonal slice spectrum,and also its  performance on running stability deterioration.Experimental data of varying degrees of deterioration under various types of deterioration were collected,and  sensitivity  property,trend property,difference property,and consistency property were proposed to evaluate  different methods.It can provide theoretical basis for selecting feature extraction method for fault diagnosis  and trend prediction of running stability deterioration.

Nipped Configuration of Unconfined Particle Beds under Falling Ball Impact Test

Mao Yalang, Sun Yi, Ji Shiming, Shan Jihong, Jin Xiaohang

2016, 27(02):  168-172. 

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In order to establish the impact breakage model of unconfined particle beds and improve the grinding efficiencies in ball mill, a study of nipped configuration of unconfined particle beds was carried out on the basis of the falling ball impact test. The influence of bed height, impact energy, impact velocity, ball size, and particle size on nipped configuration were analyzed by the falling ball impact test. Experimental results show that on the conditions of sufficient impact energy, the bed height of the nipped particles is the stack height with 2 layers particles. The nipped range has a significant relationship with the falling ball size and the nipped angle. Finally, a mathematical model was built to analyze the relationship among nipped range radius, ball size and angle of repose.

Layout Optimization on  Dual-robot Machining  Center  Based  on  Genetic  Algorithm

Wang Jun, Cao Chunping, Ding Wuxue, Sun Yu

2016, 27(02):  173-178. 

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First,a dual-robot operation processing unit for large dashboard was established.Under the premise of ensuring the robot and the workpiece working without collision, in order to maximize the sharing  working space rate of two robots,a method to optimize the layout of the double robotic workcell  was procesd based on genetic algorithm with MATLAB software simulation analysis.Besides,the sharing working space rate and the processing cycle were compared.The results show that:relative to the company's existing state,the sharing working space rate is increased by 14.6 percent,and  the cycle time is  reduced by 1.2min,which  demonstrates the effectiveness and feasibility of the method.

Study  on Friction  of  Precision Ball  Screws  Based on Creep Force Models

Chen Yongjiang, Tang Wencheng, Gan Weimin, Meng Haodong

2016, 27(02):  178-186. 

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After establishing a  proper friction force model to define the slip component between the ball and raceways,instead of assuming that all balls in the ball screw were equally loaded and run at the same speed,a multi degree of freedom dynamic model of the double  nut preload ball screw was developed.The impact frequency of balls on the cover of the returning tube was obtained by using with the EMD and envelope method.Through  theoretically  calculated values with the experimental measured values  of ball impact frequency the correctness of the established dynamics model was verified.The effects of  screw rotational speeds,axial loads,pitch and curvature ratio on the friction of ball screws were investigated.

Multiply  Separated  Position  Synthesis  of  Function  Generation  Mechanism   Based  on  Monad  Vectors

Wang Chengzhi, Zhang Quanming, Wang Shuke, Zhou Qiu, Dai Ting

2016, 27(02):  187-194,229. 

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The   relative  motion differences of the monads were presented to model the  systems  of  equations  for kinematic function synthesis of planar linkages.The  uniform  formulae  of  the  relative motion  differences with 0-order to higher-order  derivatives  were  constructed firstly,and  then  the  new  variables  and  corresponding  special  auxiliary equations of  the  monad  vectors  were  used to eliminate trigonometric  function,the angular unknowns and  even  their  higher  order angular unknowns.The  monad vectors and their corresponding auxiliary  equations could  be directly used to construct synthesis systems for finitely, infinitesimally and multiply separated precision positions, and the systems were polynomial equations with smaller  values of  the total degrees.Applying  the formulae to   five and four multiply separated positions of function synthesis for pin-jointed four-bar planar  linkages was  discussed.Some  cases  of  the  multiply  separated  positions  were  exemplified  and  their  differences between   the  generated y-value  and  required y-value  were calculated  and  charted.The  results show that the positions at finitely and infinitesimally separated positions  were passed through exactly according  to  the required function.However,the  y-values  generated  by  the mechanism with the higher-order  functional  requirements  may  be no more close to the required y-value  than  those  generated  by the mechanism with the lower-order functional requirements  at all 0-order positions in the required range.The  procedure is simpler and the formulae of monad have the better modularity than the dyad  and triad,and  can  be   easily  adapted  to  automatic modeling and solving the equations  in   a computer.

Video Stabilization Method Based on Subzone Gray Projection in  Applications  of  Satellite Assembly

Bai Feng, Zhang Xiaojun, Zhang Minglu, Sun Lingyu

2016, 27(02):  195-200. 

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Aiming to solve the problem that traditional electronic image stabilization algorithm could not eliminate video random jitters  quickly and efficiently, based on subzone gray projection a  video stabilization method  was used to ensure the robot system outputting satellite assembly pictures stably and coherently. Two frames were divided and subregions of low contrast were deleted. The interval projection and cross-correlation algorithm were used to get local motion component. The global motion vector was solved by the rest local motion component after iterative steps based on the average error threshold. An average filter would be used in global motion vector of multiple frames if image had low frequency scanning component. Experimental  results show that using the stabilization method based on subzone gray projection's  image the  stabilizing precision  increases 119.1%  in natural scene images and 55.8% in simulation  assembly images of low contrast compared with traditional gray projection method, meanwhile the execution time is only 0.5% of block matching algorithm. It proves that the method can eliminate random jitters effectively, output stable coherent video images rapidly, and guarantee the satellite installation of robot system.

Shearer's Coal-rock Recognition System Based on Fuzzy Neural Network Information Fusion

Zhang Qiang, Wang Haijian, Jing Wang, Mao Jun, Yuan Zhi, Hu Denggao

2016, 27(02):  201-208. 

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Aiming at the low accuracy and reliability problems when using single signals  to recognize the coal-rock interface for controlling and adjusting the height of shearer roller, a multi-sensor information fusion coal-rock recognition method was put forward based on fuzzy neural network. The sample characteristics of vibration, current and sound power spectrum signals  were obtained through the acquisition and analyses of experimental data during cutting the section with different proportions of  coal-rock, and the coal-rock recognition signals' fuzzy membership function was found according to the minimum fuzzy optimization model.The controlled measurement of roller's height with highly reliability and accuracy  was obtained through multi-dimensional fuzzy neural network，which was built by adaptive neuro-fuzzy inference system. Laboratory cutting experiments and the scene cutting experiments of random coal-rock trajectory were  carried  out,the results show that the cutting trajectory of shearer's roller is basically the same as the random trajectory of coal-rock specimen, the results confirm the effectiveness and reliability of the system.

Monitoring  Method  of   Cylindrical Plunge Grinding Wheel Wear  Based on Time Constant

Chi Yulun, Li Haolin

2016, 27(02):  209-214. 

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Based on cylindrical plunge grinding force model,a new algorithm of time constant was proposed by using power signals,and the time constant was used to identify grinding wheel wear status. In order to improve calculation accuracy,grinding power signals in  the infeed stage and dwell stage  were selected to calculate the time constant.At last,through experiments of  different grinding process parameters and different dressing parameters,the validity of monitoring method was proved.

Structural Optimization of Cartridge Proportional Throttle Valve Based on Multi Objective Genetic  Algorithm

Zhao Jinsong , Zhu Hanyin, Ren Xuhui , Yao Jing ,

2016, 27(02):  215-221. 

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This paper presented  optimization design method of cartridge proportional throttle valves pilot structure parameters. The influences  of  the pilot structural parameters on the dynamic characteristics of the whole valve was studied by simulation based on  nonlinear mathematical model of the cartridge proportional throttle valve. In order to improve the design efficiency，the constraints of the parameters in the optimization process were considered.Based on multiobjective genetic algorithm the structure optimization method  was proposed to improve the dynamic characteristics of the whole valve. And the dynamic characteristics before and after optimization were verified by experiments. The research results show that the dynamic characteristics of the whole valve based on the optimization design method are improved  significantly.

Bonding Behavior and Tribological Property for Self-lubricating Spherical  Plain  Bearings  with  PTFE/Kevlar  Woven Liners

Li Yingchun, Qiu Ming, Miao Yanwei

2016, 27(02):  222-229. 

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The  liners of hybrid PTFE/Kevlar  fabrics were modified with two different methods(ultrasonic wave treated and rare earth CeO2 treated).The peeling strength was measured using Instron5944 electronic universal material testing machine and hign frequency pendular friction wear testing machine,the  tribological  property was investigated using  the spherical plain bearing tester with high swaying frequency,and  worn surfaces observed by scanning electron microscope(SEM).The effects  of pretreatment methods on the bonding property and tribological property of spherical plain bearings and  the  relation  of thetribological property and film-forming behavior would be investigated.The results show that the bonding behavior of the modified bearings is  improved,and its tribological property  is improved as well.There is a correlation between the tribological property and film-forming behavior.When more smooth and continuous PTFE  transfer  film  is  formed in short time,
its tribological property is also better.

A Shape Matching Method for Train Dust Collector  Based  on  Geometrical Features

Sun Guodong, Yang Linjie, Mei Shuzheng, Zhao Daxing

2016, 27(02):  230-234,257. 

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Due to the problem of inaccurate positioning of the train dust collector,a shape matching method  was proposed based on geometric features.Firstly,the contour points were  sampled and initial location of critical points and mapping relations of point sets were determined  based  on  polar radius and local curvature.Then taking centroid as a benchmark,dual descriptors  with geometric features of angles and scales were generated and processed by  standard quantification.Finally, the similarity of the descriptors was calculated with modified Manhattan distance.The experimental results show  that the proposed shape matching method  is  harldy influenced by geometric transformation such as scale, rotation,and translation, which demonstrates its adaptability and robust.

Dispersant Performance on TC4 in Small Hole EDM

Tang Haofeng, Cao Mingrang, Yang Shengqiang, Li Wenhui, Li Weidong

2016, 27(02):  235-239. 

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There existed many problems in the small hole EDM process which conducted on TC4, and the chip removal and the relative loss of electrode were especially prominent. In order to solve the problems, a certain concentration of sodium polyacrylate(PAAS)  was used as working solution of small hole EDM.Studies were  done on  many ways such as the particle size of processing scrap and surface tension of working liquid, and simulation analyses was  completed  about the effects  of  flow field on processing scarp using  software FLUENT. Experiments were processed on the basis of the analyses,therefore, the optimal working fluid ratios in small hole EDM on TC4 was obtained. After the improvements, the maximum material removal rate can be increased by 97.56%, and  the  depth to diameter ratio is increased by 56.94%.The research results have  reference values  on making appropriate working liquid in the small hole EDM.

Electro-hydraulic Servo  Position and Pressure Hybrid Control Method of Forepoling System on Tunnelling

Xie Miao, Liu Zhixiang, Chi Cheng, Mao Jun

2016, 27(02):  239-245. 

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Taking into account the operational principles  of forepoling equipment,and as the target to  improve  support efficiency and to reduce  the disturbance on the roof in the process of supporting, a kind of speed and pressure composition control method was proposed.The control method adopted  fuzzy switching controller to complete the conversion of electro hydraulic position and electro hydraulic pressure control. Theoretical analysis and experimental results show that, compared with the traditional speed and pressure control method, the control method herein  can reduce concussion on the roof in the process of switching from speed control to pressure control, and can improve support efficiency. Research fruits can provide a theoretical basis for the research and control strategy of forepoling equipment.

Spectral  Derivation  of  Resultant  Milling  Force  and  Eccentric Estimation  of Tool  Based on  Trigonometric Series Expansion

Liu Can, Wu Jingquan, Liu Huanlao, Tan Guangyu

2016, 27(02):  246-250,272. 

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The  cutting  force  was  discomposed  into  nominal  and  eccentric  component  forces  based  on unary cutting force  model,the trigonometric series of periodic signals  was  applied to expand these two component forces，and then the  amplitude and phase expressions of their harmonics were obtained. Based on these expressions,it  is  deduced  that  the even-harmonics amplitudes of the eccentric force for even-tooth milling  cutter are  zero,the tooth-frequency amplitude of the eccentric force for  3 teeth  milling  cutters is zero too, and a new estimation method of eccentric distance and angle for milling  cutters was presented, which uses  the harmonics of resultant  cutting force in spindle and tooth frequencies, the estimated eccentric values are close to that measured in experiments.It testifies  in theory that there  are no even harmonics in the eccentric component force of even-tooth  milling cutters, the presented method needs only one set of equation and one  cutting test, and its numerical calculation is rather easy for even-tooth milling  cutters. The research  fruits can be used to  identify eccentricity and wear, and estimate  eccentricity in process for even-tooth milling  cutters.

A  Direct  Integral Method  to   Solve Stress  and   Strain  of Conical Parts in  Deep Drawing  Process

Qin Siji, Deng Chao, Yang Li, Kong Xiaohua, Wang Yaohua

2016, 27(02):  251-257. 

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Under  the  conditions  of  plane  stress  and proportional  loading,differential  equations of strain  and stress in deformation zone of conical part in deep drawing were obtained by  the method of parametric equation. After solving the differential equations under the corresponding boundary conditions in the regions of flange, die corner and conical wall  of the conical part the stresses and strains  might  be obtained respectively in every regions by the direct integral method. The applications  of the direct integral method were  extended from solving the in-plane axisymmetic sheet metal forming problems to analyze  conical part deep drawing process.The conical angles were equal to zero and  a certain value in flange region and conical wall respectively. The die arc regions might  be divided into several small segments and each of them  could  be taken as a conical part with constant conical angle. This method was  applied to solve conical part deep drawing problems and   to analyze the forming problem of axisymmetric curved parts with given profile shape. As the substitute of iteration method, the direct integral method was applied to solve nonlinear equations and the solving process  could  be simplified  greatly.The experiments  of  conical part deep drawing were  carried out by using 0.87mm-thick ST16 sheet and  the strain distributions in flange,die arc and conical wall regions were measured.It shows  that the analytical solutions by the direct integral method are accordant with experimental results.

Working Load Prediction and Stiffness Analysis of Large Friction Welding Machine Tools

Wang Jiaxing, Ni Yanbing, Dong Na, Wu Nan

2016, 27(02):  258-264. 

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With  the  FSW machine  development, based on the basic principle of fluid mechanics, a kind of prediction model of the force of the mixing head was presented  herein.Using Pro/E and ANSYS, a  finite element model of the  welding equipment was established. And the machine rigidity and deformation were analyzed through simulating the processing conditions by static force, then determine the maximum deformation of the welding equipment parts and overall stress concentration points. Checking the welding machine and its components stiffness,provide the basis for the welding machine building is  provided.

Research on  Energy Saving  of  Pressure and Displacement Compound  Control  Strategy for Fast  Forging System

Yao Jing, Cao Xiaoming, Li Bin, Kong Xiangdong, Zhou Fang

2016, 27(02):  265-272. 

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According to the problems of constant pressure output,return cylinder's  large pressure and low transmission efficiency in fast forging process of forging hydraulic press's  ordinary electro-hydraulic proportional valve system,this paper proposed  a pressure and  displacement compound control strategy, and  took  pressure control for the return cylinder's back-pressure cavity and load sensitive control for the pump's inlet pressure under the premise of ensuring the control precision.The energy-saving mechanism was studied and the two important factors-the return cylinder's   back-pressure cavity pressure pb  and the pressure difference Δp  between pump outlet and the working cavity - that influenced the effect  inveness  of energy saving were analyzed through establishing the complete mathematical model for hydraulic press's  pressure and  displacement compound control. Experimental results show  that  the position error for loading can limit 1.5mm based on the fast forging hydraulic press's pressure  and  displacement compound control system, and installed power reduced to 52.3% compared to the traditional electro-hydraulic proportional valve control system, meanwhile power consumption is reduced to 49.2% compared to ordinary proportional valve system.

Study on Reliability Evaluation  and Maintenance Policy of Auto Body  Multi-station  Assembly  System

Liu Yinhua, Ji Feixiang, Ye Xialiang

2016, 27(02):  273-277. 

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For the degradation process of fixture components in the multi-station assembly system,the reliability evaluation model integrated with  the effects of  fixture element wear,variations of incoming parts and mating tolerances of locating elements was proposed herein.Furthermore,under the condittion of a given  BIW deviation fluctuation threshold,a dynamic maintenance policy for the multi-station fixture components was presented based on the reliability model.At last,a 4-station sheet metal assembly case was used to illustrate the proposed method, which provides an effective tool for the fixture maintenance and dimension quality assurance.

Crashworthiness  Optimal Design  of  Automotive  Side  Door  under  Pole  Side  Impact

Tang Tao, Zhang Weigang, Chen Ding, Zhang Wenqiang

2016, 27(02):  278-283. 

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In order to improve the crashworthiness of  pole to vehicle side impact,topology optimization method was introduced to design the side door beam based on SIMP theory,and  the optimized material distribution was obtained.Then,appropriate section was chosen to construct  the door beam and a Y-shape beam structure was formed.Multi-objective optimization was conducted by using response surface  method combined with NSGA-Ⅱ algorithm.Compared to initial design,the crashworthiness of optimized door beam was  improved greatly with the pole impact intrusion reduced by 22.5%,while the door stiffness still meets the regulation requirements.