Table of Content

10 December 2016, Volume 27 Issue 23

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Investigation of Waveform and Technological Parameters for Non-sinusoidal Oscillation of Mold Driven by Double Eccentric Shafts

Zhang Xingzhong, Zhou Chao, Liu Pingfei, Guan Jie

2016, 27(23):  3125-3129,3135. 

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A new type waveform function of a steel continuous casting mold non-sinusoidal oscillation was constructed and a motor driven equipment scheme realizing the non-sinusoidal oscillation was put forward. The superiorities of the waveform function and the implementation scheme were analyzed. The reasonable value ranges of the parameter α(deviation rate compared with sinusoidal waveform) were discussed. The calculation methods of technological parameters were given, such as negative slide time, negative slide rate, negative slide distance, positive slide time, the maximum relative velocity between slab and mold. The isoplethic curves of multi-parameters were given, which provide a reference for the modeling oscillation synchronization control of casting velocity and oscillation frequency, and the applications of non-sinusoidal oscillation technique. 


Study on Stiffness and Damping Parameters of Parallel Link-Manipulator's Suspension System

Yang Xiaobo, Liu Yanyan, Yang Jin, Gao Junfeng

2016, 27(23):  3130-3135. 

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In order to design a buffer device of forging manipulator's suspension system rationally to reduce the influences of inertial impacts, aiming at the parallel style forging manipulators, the model of forging manipulator was simplified, the stress states and the motion laws of rods in the suspension system under the braking conditions were analyzed. By using Newton-Eular rule with dynamic analysis of the rods, the suspension system's dynamics model under braking conditions was constructed and the method of determining parameters such as buffer device's stiffness and damping was proposed. Using a 300kN forging manipulator as an example, the dynamics differential equation of the manipulator's suspension system was solved with MATLAB to analyze the buffering stiffness and damping's influences on the hanging bar's swing angle and the motion of clamping bar's centroid position. The results indicate the feasibility and rationality of determining buffering stiffness and damping using the model constructed with Newton-Eular rule and provide theoretical basis for the stiffness and damping design of the parallel link-manipulator's suspension system.

Motion Performance Analyses of Valve Welding Robots

Xu Yong, Cheng Hao, Zhang Bing, Wang Chunyan, Wu Yongbo, Cao Yindong

2016, 27(23):  3136-3141. 

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The tangential vectors, normal vectors and auxiliary normal vectors of the discrete solder joints were solved based on Frenet-Serret's vector theory. Thus the relative positions and orientations between welding point and welding torch will be derived more easily. Based on the coupling constraint relationship between the ends of the active positioner kinematic chain and the driven robot kinematic chain, the coordinated welding kinematic model and the corresponding parameter solving process were presented for the optimum ship-welding position. On the basis of solving the working space of the welding robot, according to the geometric conditions of the singular positions for the spherical wrist 6-joint series robot, 10 independent singular positions of the welding robot were obtained. The motion simulation and field tests of the robot-positioner coordinated welding operation show that the system may smoothly and accurately complete the coordinated welding tasks of valve sealing surface. These results confirm that the proposed kinematic model and parameter solving process are correct and feasible.

Logarithmic Wavelet Spectrum Method for Computing Fractal Dimension of Machined Surface Profiles

Zhang Xueliang, Wang Yusong, Wen Shuhua, Fan Shirong, Chen Yonghui, Lan Guosheng

2016, 27(23):  3142-3148. 

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A multi-scale wavelet decomposition for surface profiles was achieved herein by the multi-scale analysis capability of wavelet; and a logarithmic wavelet spectrum method for calculating the fractal dimensions of machined surface profiles and the effective decomposition scale concept were proposed. Fractal profiles with different fractal dimensions and different sampling intervals were generated by M-B function. The fractal dimensions of simulated profiles whose dimensions were known were calculated by logarithmic wavelet spectrum method, which was compared with the calculation results of other five kinds of methods such as the power spectral density (PSD) method. The results show that logarithmic wavelet spectrum method may process multi-scale fractal features nicely, and it has the highest accuracy with errors less than 0.15% when sym4 wavelet is adopted. Finally, logarithmic wavelet spectrum method was applied to calculate the fractal dimensions of actual machined surface profiles and the results illustrate its practicability.

Parameter Optimization of Torsional Spring in Clutch Operating Mechanisms

Zhu Wenbo, Zhao Xixi, Gan Yi, Chen Long

2016, 27(23):  3149-3156. 

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In order to evaluate the performances of an automobile clutch system, a testing platform of clutch system was established. The mechanisms of clutch system, which were simulated to install on a car, were tested with this platform and then the characteristic curve of pedal and the relative experimental data were obtained. It is found that pedal max-force is too large, the pre-tightening force is too small and pedal down force is too small. To solve these problems, a mechanics model of the clutch operating mechanisms was built and the relative factors which affected the performances of the clutch were analyzed. From the view of practical engineering, optimizing structure parameters of torsional spring were proposed to change pedal mechanical characteristics and ensure performance requirements of the clutch system. Motion state of torsional spring was analyzed and its mechanics model was built. Installation angle of torsional spring was optimized based on achieving maximum power effect. According to the design constraints of the clutch and the objective function of the maximizing fatigue safety factor of torsional spring, the torsional spring's wire diameter, mean diameter, arm length and number of turns were optimized. The improved torsional spring was installed again in the pedal mechanism, and the optimization scheme was verified to be feasible and rational by the testing platform.

Analysis for Mapping Relationship among CNC Machine Dynamic Performance and S-Shaped Specimen Contour Errors

Song Zhiyong, Li Qingzhao, Jiang Zhong, Kang Wenjun, Du Li, Wang Wei

2016, 27(23):  3157-3161,3166. 

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A simulation model was established herein based on double swing five-axis CNC machine, and the accuracy was validated. Then the variation of S-shaped specimen contour errors under different CNC machine dynamic performances were found. And based on the simulation results, S-shaped specimen was divided into areas, and the mapping relationship among contour errors and areas was found. This study provides a basis for adjusting the actual machining five-axis CNC machine dynamic performance parameters and performance evaluation of CNC machine and processing error tracing and identification.

Analysis of Wire Rope Ring's Axial Misalignment in WR-CVT

Guo Wei, Xu Xiaobin, Zhang Wu, Lu Zhengxiong

2016, 27(23):  3162-3166. 

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Axial misalignment of the wire rope CVT(WR-CVT) in the processes of changing the transmission ratio would limit the CVT speed ratio ranges and bearing capacity. To solve this problem, based on the axial misalignment of the metal belt ring, a calculation model of wire rope axial misalignment was established. The results indicate that the maximum displacement is as 0.6369mm,and the maximum offset angle is as 0.23°. The value is 15.8% smaller than the maximum displacement and 0.04° smaller than the maximum offset angle respectively under the same parameters and conditions of the metal belt CVT(MB-CVT) wire rope. The bearing capacity of the wire rope ring is better than metal belt ring due to the rolling in the saddle surface arc groove of the metal.

Research on Stiffness Characteristics and Mechanics Model of Metal Rubbers

Yu Huijie, Liu Wenhui, Wang Yasu

2016, 27(23):  3167-3171. 

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The mechanism of metal rubber molding and the influence factors of static stiffness characteristics were analyzed, on the basis of the theory of helical spring stiffness metal rubber an infinitesimal spring theoretic model was established. According to the test results, the model was corrected. Through the comparison of theoretical model and experiments, the results show that the theoretical values are close to the experimental ones, which may comprehensively reflect the static stiffness characteristics of metal rubbers and provide the theoretic basis for the design of the metal rubber dampers and the determination of metal wire processing parameters.

Target Positioning of Pedestrian Based on Binocular Vision and Constraints

Yang Zhiguang, Zhang Yonglin, Xie Jingming, Chen Youping

2016, 27(23):  3171-3175. 

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When confronting the problems in pedestrian detection such as large amount of calculation, time-consuming of classifier training and unfulfilled real-time requirements, a pedestrian detection method was proposed based on binocular vision. In this method, a lot of candidate contours might be obtained by processing image, and the geometrical characteristics of contours were used as a constraint to filter candidate contours. In the meantime, binocular camera might be used to get depth informations of the candidate contours, and the depth informations were used as a constraint to filter the candidate contours. By the constraints of depth informations and geometrical informations, contours of pedestrians' heads might be identified and the pedestrians' localization might get.  The experimental results show that the method reduces the amount of calculation, and enhances the detection accuracy.

Multi-source Information Perception and Interaction Standards of Mechanical Products Assembly Process Based on Internet of Things

Ma Yongjing, Liu Mingzhou, Wen Bo, Ling Lin

2016, 27(23):  3176-3183. 

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With the heterogeneity of multiple source informations in the mechanical product assembly processes, the large amounts of multi-source informations brought great difficulties to the information interaction. On the basis of analyses of the interaction difficulties that existed in the processes of information communications and the applications of the multi-source information sensing technologies in the mechanical product assembly processes, a kind of information interaction standard was put forward， which was applicable to the mechanical product assembly processes. It focused on the interaction forms, the interaction structure and the communication process of the interaction standard in the assembly processes. Finally, an interaction standard in the applications of an automobile engine assembly process showed the interaction characteristics of the standard in the practical applications, which proves that the information interaction standard has nice applicability and feasibility.

Quantitative Diagnosis Method of Gear Cracks  Based on Noise-assisted LOD

Wu Jiateng, Peng Xiaoyan, Yang Yu, Zhang Kang, Cheng Junsheng

2016, 27(23):  3190-3196. 

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A new method of quantitative diagnosis of gear crack faults was proposed based on noise-assisted LOD which combined gear fault mechanism with fault diagnosis methods. Firstly, the feature vector matrixes were constituted by feature parameters which sensitively and independent of working conditions might be extracted from a dynamics model established to obtain the dynamics responses under different levels of cracks and input into the support vector regression(SVR),thus the mapping relationship among feature parameters and levels of gear cracks was created. Based on mapping relationship, the quantitative diagnosis of gear cracks was realized by using noise-assisted LOD extracting feature parameters from actual gear crack signals.

Vibration Behavior and Control of Roll System under Nonlinear Stiffness of a Hydraulic Cylinder

Liu Bin, Li Peng, Liu Fei, Liu Haoran, Jiang Jiahao

2016, 27(23):  3190-3196. 

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For the vibrations of rolling mill under the influences of dynamic characteristics of hydraulic system, a kind of vibration model of a roll system was established under the constraints of the nonlinear stiffness of hydraulic cylinder. Amplitude-frequency response of the vibration system was obtained by using average method, the feedback controller of the system was designed based on the Lyapunov second method. Lastly, parameters of the actual mill were used to conduct a simulation research and parameters such as nonlinear stiffness coefficient, external excitation and initial displacement of the rodless cavity were analyzed how did which to affect the amplitude-frequency response. The dynamic bifurcation characteristics of the excitation amplitude and the initial displacement of the rodless cavity were studied, results show that as the changes of the parameters, the rolling mill will cause periodic, period-doubling, chaotic motion and a series of complex movements. At the same time, the feedback control was introduced, and the effectiveness of the feedback controller was verified by comparing the time domain curves and the phase plane curves, which provides a theoretical basis to improve the stability of rolling mill rolls.

Combined Parametric and Forced Resonance of an Axially Accelerating and Current-Carrying Beam under Magnetic Field

Hu Yuda, Rong Yantian

2016, 27(23):  3197-3207. 

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Combired parametric and forced resonance of an axially accelerating and current-carrying beam which was subjected to harmonic excitation under magnetic field was investigated. The elastic mechanics theory, electromagnetic field theory and Hamilton variational principle were applied to establish the nonlinear magnetoelastic coupling vibration equation of the axially accelerating and current-carrying beam. The time variables and the space variables were firstly discretized using Galerkin integral method, then multiscale method and coordinate transformation method were utilized and the amplitude-frequency response equation was obtained. Through calculation examples, the corresponding amplitude frequency response curves with different parameters, the time history response diagrams, phase plot, poincare map and dynamic phase trajectory graph of the resonance system were acquired and the effects of axial velocity, axial tension, magnetic induction intensity, electric current density and forced excitation on primary resonance-principal parametric resonance characteristics of the system were analyzed. The results show that the system presents typical nonlinear vibration characteristics and complex dynamics behavior.

Mechanism of Surface Formation of Silicon Wafer Processed by Fixed Abrasive Polishing with Assistance of Ultrasonic Vibration and Experiments

Zeng Yifan, Yang Weiping, Wu Yongbo, Liu Manli

2016, 27(23):  3208-3214. 

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Herein, based on the characteristics of higher machining efficiency and higher surface quality of ultrasonic vibration machining, a novel ultrasonic assisted fixed abrasive CMP(UFP) technique for silicon wafer was presented. The establishment of the experimental system for composite polishing was discussed in detail. In addition, the surface morphology and the material removal mechanism were investigated based on experiments and theory. Both of the theoretical model and experimental results show that with the assistance of ultrasonic vibration, the surface quality is enhanced, the material removal rate (MRR) increases, and the quality of polished surface decreases with increases of the polishing force, but the MRR increases.

Accuracy Evaluation of CNC Machines Based on IEGF-AHP Algorithm

Yao Xiaopeng, Huang Huachuan, Yin Guofu, Li Guangming

2016, 27(23):  3215-3220. 

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According to the disadvantages of indexes were fuzzy and inaccurate during CNC machine evaluation, a new evaluation method of CNC accuracy was put forward by interval extension grey fuzzy analytic algorithm. This method built interval judgment extension matrix and calculated the corresponding weight coefficients. The comprehensive evaluation values were required by grey fuzzy evaluation method. Though detecting and evaluations repeatedly at different periods on VXC-960 type machine, evolution laws of machine tool's accuracy and main factors of affecting current accuracy were acquired, and the corresponding countermeasures were put forward. Experimental results show that the evaluation method has high effectiveness and feasibility.

Problems and Solutions of Flexible Job-shop Scheduling with Operation Lot-splitting

Xu Benzhu, Ji Jing, Fei Xiaolu

2016, 27(23):  3221-3229. 

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Considering that each operation in flexible job-shop scheduling with lot-splitting had its own appropriate lot-size, the concept of scheduling with lot-splitting was proposed based on operations, and a scheduling model with lot-splitting was established based on critical path operations. This model could dynamically update machinable sub-lot set, update available machines, determine optimal processing routes and appropriate operation lot-sizes thus makespan might be optimized and total lot quantity might be reduced. The experimental results show that, compared with lot-splitting based on workpieces, using the established scheduling model the makespan may be optimized, machine utilization may be improved, total machined lot quantity may be reduced (42%) and scheduling management complexity may be decreased.


Effect of Specimen Size at Impact Load of 6063 Aluminum Alloy and Numerical Simulation

Ye Tuo, Li Luoxing, Guo Pengcheng, Li Jian, Li Rongqi

2016, 27(23):  3229-3234. 

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Dynamic compression experiments of homogenized 6063 alloy at different impact pressures were carried out based on split Hopkinson pressure bar (SHPB) technique. The results show that the strain rate of the 6063 alloy decreases with increasing of the ratio of length to diameter and cross section at a certain impact pressure. The specimens with different sizes obtain a similar stress-strain curve when deformed under a same strain rate. It is found that φ8mm×4mm and φ8mm×5mm specimens exhibit a wide range of strain rate response. The SHPB dynamic compression was simulated by using ABAQUS software. The true stress-true strain curves were calculated by two-wave analytic method. The numerical simulation results and fitted results are basically in agreement with the experimental results.

In Situ Observation on Interfacial Damages of 304L/533B Explosive Welded Composite Steel Sheet under Tensile Loading

Liu Lili, Xuan Fuzhen

2016, 27(23):  3235-3240. 

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For 304L / 533B explosive welded composite steel sheet, in situ tensile experiments were carried out in the chamber of scanning electron microscopy (SEM). Damage evolution of the interfaces and original defects were analyzed . The results show a periodically sine-shaped interface in 304L / 533B explosive welded composite steel sheet , and three kinds of defect such as micro-voids, non-fusion and micro-inclusion around the interface are observed. A sharply increased nano-hardness in the 304L side of interface is ascribed to the refined grain, while the decreased hardness in the 533B side of interface is caused by decarburization. Under the loading conditions of parallel to the interface and perpendicular to the interface, both of interfacial voids and nonfusion is deformed along the loading direction and the cracks are initiated at the edge of micro-voids. In addition, no significant changes of inclusions are detected. But the strength of composite steel sheet is not influenced by the interfacial defects. For load direction being perpendicular to the interface, the specimen fractured in the equiaxial grains zone of 533B side comes from the sharped plastic deformation. By contrast, the specimen fractured comes from the microcrack in the fine grain zone of 304L side under the load direction being parallel to the interface. Under the shear load conditions, microcracks are initiated from the interfacial voids and nonfusion defects along the interface. The specimen failed at the 533B side comes from the main crack merged with the microcracks initiated from the interfacial defects.

Research on Preparation and Corrosion Resistance of Superhydrophobic Surfaces on Carbon Steels

Li Jing, Li Hong, Yu Huadong, Du Feng

2016, 27(23):  3241-3246. 

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Superhydrophobic surfaces on carbon steels were fabricated combining sandblasting and electro-brush plating technology without modification. The surface appearance, dynamic and static contact angles and anti-corrosions were characterized by means of scanning electron microscopy (SEM), contact angle measuring instrument and electrochemical workstation. The results show that the superhydrophobic surfaces prepared by the combination method are obtained when the diameter of grain clusters are in the range of 25~ 40μm and distributed evenly, and it has excellent superdrophobocity. When the brush plating voltage is as 14V, the contact angle is up to 152°. In addition, the surfaces of sample may keep the hydrophobic property for a long time under the conditions of natural aging. The hydrophobic surfaces prepared by the combination method have better anti-corrosion performance compared with polished substrate surfaces.

Cracking Analysis of Rear Covers and Shape Optimization of Preformed Pipes for Filling-pressing Forming Axle Housings

Wu Na, Wang Liandong, Shen Yakun, Zhang Meng

2016, 27(23):  3246-3251. 

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Aiming at the phenomenon of rear cover cracking in current production, the cracking reason was revealed by analyzing the pressing deformation of rear covers in two extreme cases. The design method of the maximum longitudinal section profile of the preformed pipes was proposed, and the definitions of the profile reference coefficient K0 and gradient coefficient K1 were given. For a 5t automobile axle-housing, the value ranged of the profile reference coefficient K0 and gradient coefficient K1 were determined through simulating the pressing forming processes of the preformed pipes with different sizes of rear covers using ABAQUS. And the results of the pressing forming test show that the optimized pipes are of good formability, the wall thinning rate of rear covers is low and there is no cracking.

Analysis Method of Reverberation-ray Matrix Stiffness Chain for Electric Vehicle Bodies

Chen Yiqiang, Liu Zijian

2016, 27(23):  3252-3258,3265. 

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Based on LifeDrive pure electric vehicle modular structures, a pure electric vehicle frame structure was obtained by topology optimization method. The reverberation-ray matrix model of frame structure was established based on the beam elements. According to the reverberation-ray matrix calculation model, the thicknesses of the frame beam elements and the forces between the body and frame were obtained, the main sectional parameters of simplified model of vehicle body was optimized with a more reasonable method. The loading degree between body and frame was calculated by finite element method. Results show that the frame and the body structures meet the requirements of the target loading degree and stiffness performance, and this method provides reference to the body and frame conceptual design of electric vehicle.

Control on AARB of Vehicle Based on Sliding Mode Variable Structure Theory

Chen Song, Xia Changgao, Sun Xu

2016, 27(23):  3259-3265. 

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In order to control the rolling of vehicle, AARB was designed. For nonlinear time-varying characteristics in the roll motions, a sliding mode controller was designed to track the ideal roll angle on the basis of the proposed AARB and the controller, steering simulations with the fishhook maneuver and double lane change maneuver were carried out to test the validity of the proposed control strategy in the aspect of roll controlling with AARB. Stimulations show that the method is effective in reducing the rolling of the vehicle and having good feedback to the driver for judging the vehicle body posture compared to the passive anti-roll bar. Therefore, the safety and comfort of the vehicle with AARB is greatly improved.