Table of Content

10 November 2016, Volume 27 Issue 21

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Roll Flower Design and Forming Mechanism of Rectangular Tubes in Cold Roll Forming Processes

Du Fengshan, Fu Zhiqiang, Yu Hui

2016, 27(21):  2841-2845. 

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In terms of multi-pass groove rolling characteristics of rectangular tubes in cold roll forming processes, considering the existence of topological equivalence relations between round tube billets and rectangular tubes, a centroid mapping mathematic model was established between them to realize the roll flower design of rectangular tubes in cold roll forming processes. The cold roll forming experiments were carried out on the test mill, and rolled products may meet the GB/T 6728-2002 standard. A simulation model for cold roll forming of rectangular tubes was established based on an elastic-plastic finite element method. The regularities of metal flow and longitudinal elongation were researched to analyze the formation cause of displacement neutral plane in corners and edges of the tube ends. The distributions of residual stresses of rectangular tubes were researched to determine the easy cracking positions. The results may be expected to provide theoretical basis for the design model of roll flower and forming technology of cold roll forming processes.

Wear Prediction Analysis of Mining Dump Truck Body Based on Degradation Processes

Shen Yanhua, Wei Fulin, Shi Boqiang

2016, 27(21):  2846-2850,2854. 

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The dumping processes of a dump truck were simulated by coupling the discrete element method and the finite element method. The abrasive wear time series of each grid on the bottom floor was obtained by the co-simulation results. Wear height variation of bottom floor was regarded as the stochastic dynamic process, and the geometric Brownian motion was used to build the degradation model of body wear. The drift and diffusion coefficients of wear height on each grid were calculated by maximum likelihood estimation and Bayesian posterior method. The wear behavior evolution of the body floor may be predicted based on the degradation model.

RET of Machining Center Tool Magazine System

Cong Ming, Han Yuting, Liu Dong

2016, 27(21):  2851-2854. 

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The main failure causes were assumed after the early failures about tool magazine and manipulator of a type of machining center were analyzed. In order to accelerate the testing processes and further to validate the hypothesis, the test scheme of RET was designed. Firstly, three acceleration factors were choosen and their values were also determined, then the comprehensive stress profile of RET was determined, and the performances of three positions of the tool magazine were monitored. Finally, 6 failures of the test were analyzed, and the hypothesis of the failure causes were verified. And the improvement measures were put forward.

Design and Kinematics Analysis of a 2PRS-2PSS Parallel Mechanism

Zhang Yanbin, Ding Ding, Wu Xin, Wang Zenghui, Zhao Yifu

2016, 27(21):  2855-2861. 

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A new two-translational and two-rotational 4-DOF 2PRS-2PSS parallel mechanism was proposed. Orientation angles among axis of all actuated prismatic joints and fixed base of the parallel mechanism were variables. Firstly, the motion output characteristics were analyzed by theory of position and orientation characteristics. The kinematics of the mechanism was analyzed by using vector approach. Forward and inverse solutions of the position and orientation of the mechanism were derived. Then, the equations of velocity and acceleration were obtained. In addition, the singular configurations of the mechanism were discussed in detail based on the singularity of its Jacobian matrices. Finally, simulation results show that the theoretic analysis is correct.

Identification of Dynamics Parameters for an Electro-hydraulic 3-UPS/S Parallel Stabilized Paltform

Guo Fei, Li Yongquan, Li Yukun, Zhang Yu, Zhang Lijie,

2016, 27(21):  2862-2868,2876. 

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An electro-hydraulic parallel stabilized paltform was selected as the research object, and the inertia and friction parameters of the system were identified via the experiments. The identification model for the inertia parameters was obtained by screw equivalence principle and virtual work principle, and the exciting trajectory was designed by Fourier series which was modified by quintic polynomial and optimized. The intrinsic friction parameters were separated from the friction model, the identification model for the friction parameters was built, and the exciting trajectories were planned. The identification results were obtained by the experiments, and verified through an arbitrary trajectory.

Analyses on Dynamics Characteristics of a Quasi-zero-stiffness Vibration Isolation System Based on Euler Beam

Gao Shuang, Zhu Xiang, Shen Zongqi, Li Tianyun

2016, 27(21):  2869-2876. 

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Combining the Euler beam under axial pressures with a positive stiffness spring, a quasi-zero-stiffness vibration isolation system was obtained, which had high static stiffness and low dynamic stiffness characteristics. The requirements of the quasi-zero-stiffness system were achieved through the static characteristic analyses. The harmonic balance method was used to solve the dynamic differential equations. The steady state and amplitude frequency response of the system were also analysed. The influences of parameters such as damping and exciting forces on the force transmissibility of the system were discussed. At last, the jumping frequencies of the system were analysed. The results show that the increase of the exciting force and the initial offset make the effects of vibration isolation of system worse, therefore the amplitude of the exciting force should be controlled, and the overload should be avoided. To choose the proper damping ratio, the vibration isolation effect at high frequencies and the effective isolation frequency range should be considered comprehensively.

Characteristics of Cutting Tool Wear during LAM Processes for Ti-6Al-4V Alloy

Gao Yanfeng, Xiao Jianhua

2016, 27(21):  2877-2883. 

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Cutting forces, chip morphology, and tool wear mechanism during LAM processes for Ti-6Al-4V alloy were investigated experimentally herein. The results show that, under the LAM conditions, the tangential cutting forces of the cutting tool decrease significantly, while the radial cutting forces of the cutting tool increase slightly. With the increasing of laser power, the saw-tooth chips gradually transform to the continuous chips, and the adiabatic shear bands are disappeared. Different from the break edge tool wear during the conventional milling processes, the frictional wear is the main wear pattern during LAM processes, which is beneficial to reduce the maximum wear values on the tool flank, but it may not reduce the average wear values on the tool flank. The tool life is prolonged during LAM processes. When the mean wear extent of flank in the range of 0.15~0.20mm, the wear speed of cutting tool is reduced. It manifests that the LAM may not reduce the initial wear speeds of cutting tools.

Speed Measurement of Miniature Reciprocating Refrigerant Compressor Based on Hilbert Transform

Shen Xi, Sun Zhe, Xu Ming, Gu Jiangping, Jin Huaqiang

2016, 27(21):  2884-2889. 

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In recent years for refrigeration industry, refrigeration compressor rotation speed measuring precision demands were increasing. The traditional direct measurement method of compressor destructed itself, and indirect measurement method based on shell vibration, needed high require-ments for test conditions, and the measurement errors were bigger. To improve the measurement accuracy, and to meet the demands of industries, a signal extraction method was proposed based on Hilbert transform herein, this method indirectly reflected the characteristics of the compressor rotation by the movement regularity of the piston and the induced electromotive force changes. This method is of high precision, strong anti-jamming. The errors are less than 2r/min by compared with visual compressor, which meets the requirements of engineering.


Research on Dynamic Characteristics of an Eccentric Swing Multiphase Pump

Ji Xiaoke, Liang Zheng

2016, 27(21):  2890-2894,2901. 

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Working principles and structural characteristics of a new eccentric swing multiple pump were described. Motion and dynamics mathematical model of the motion parts of the multiphase pump was established. Numerical calculation was performed for a prototype of motion and dynamics mathematical model. Finally, experiments verified this theory was feasible. The results show that drag torque which is formed by the differential pressure forces on the swing-axle is the main influence on the shaft power pump. In the import and export pressure ranges of 1.2～3MPa, the deviation of the power input tested and calculated is in the ranges of 1%～38.2%.

Automatic Neighbor r Selection for One-dimensional DFT Method in the Surface Defect Inspection of TFT-LCD

Zhang Tengda, Lu Rongsheng, Dang Xueming

2016, 27(21):  2895-2901. 

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In order to obtain neighbor r automatically, each line of a faultless surface image for TFT-LCD panel was preprocessed firstly in the detection of surface defects on TFT-LCD panel. Then thier gray level co-occurrence matrix (GLCM) was calculated, and the homogeneity property of the GLCM was extracted. Finally, the difference of homogeneity was computed, and the optimal neighbor was that level where the difference showed a maximum value. An experimental system of TFT-LCD panel detection was built. The images with various length including integer-period, non-integer-period and non-integer-period filled into integer-period were processed in the experiments. From the acquisition of r, it may be seen that the r for non-integer-period fills into integer-period is the same as it for integer-period under the same environments. And by applying the results into actual defect detection, the system may detect the defects accurately.

A Multi-objective Comprehensive Decision Method for Machine Tool Machining Process Parameters Based on Combination Weight

Deng Zhaohui, Meng Huijuan, Zhang Hua, Wan Linlin

2016, 27(21):  2902-2908. 

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Considering the complexity of machining processes, a multi-objective decision method was proposed, which took the traditional decision-making factors and environmental impact target into account. The combination weight were determined by analytic hierarchy process and criteria importance through inter-criteria correlation, and the positive and negative reference sequences were set by TOPSIS. Grey correlation and Euclidean distance were used to sort each experimental group(combination of process parameters). The groups which had a significant difference under the two methods were rejected, and the compromise optimal parameters might be obtained. Finally, the method was verified by surface grinding experiments.

Monitoring Method Analysis of Multistage Centrifugal Pump Seal Ring Wear

Ma Bo, Zhu Jun, Zhang Ming

2016, 27(21):  2909-2914. 

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A flow field model of multi-stage centrifugal pump was created to analyes the effects of multi-stage centrifugal pump seal ring gap on the flow field based on CFD theory, and a curve of centrifugal pump efficiency with the wear of the seal ring was established. A method of monitoring and assessing seal ring wear was proposed based on the centrifugal pump efficiency and the axial vibration. A multi-stage centrifugal pump test bench was established, the feasibility of the proposed method was verified with the comparison of experiments and simulations. Characteristics of ring wear, corrosion, and impeller blockage were analyzed by experiments. The method was improved by excluding the effects of impeller corrosion and blockage on seal ring wear monitor.

Position Servo System Based on Adaptive Tracking-differentiator Controller

Lu Hao, Hu Jianhua, Wang Yunkuan, Zheng Jun, Qin Xiaofei

2016, 27(21):  2915-2919. 

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The general control strategies were often unable to meet the fast response without overshoot for the position control of PMSM， to resolve these problems, on the basis of analysis of traditional tracking-differentiator, an adaptive tracking-differentiator controller was proposed herein. The designed controller would arrange transient process for position commands and use the least square method to fit the linear function of a curve of pluse step input s and filtering factor h in transient process. Furthermore, this controller might adaptively choose the optimum parameters of the transient process according to the different curves of pluse step and might achieve the fast response without overshoot for the wide range of step commands. The experimental results demonstrate the feasibility and advantages of the proposed controller.

6R PRBM of Fixed-guided Compliant Links

Liu Kai, Cao Yi, , , Ge Shuyi

2016, 27(21):  2920-2925. 

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Based on the principles of PRBM, a new fixed-guided 6R PRBM was presented to improve the calculation accuracy for the fixed-guided compliant links firstly. Secondly, the kinematics equation of the model was set up, and the optimal characteristic radius coefficients and the spring stiffness coefficients were acquired using the optimization algorithm and inverse kinematical analysis. In order to validate the calculation accuracy of the fixed-guided 6R PRBM, numerical examples were demonstrated by comparing the tip locus of the fixed-guided 6R PRBM with that of the fixed-guided 2R PRBM. Further research shows that the fixed-guided 6R PRBM may actually simulate the tip locus of the compliant links and the relative error is almost equal to zero. Finally, the accuracy of the model in actual calculation was verified by finite element analysis and engineering examples.

Narrow/Generalized ClassⅡ Synthesis of Conjugate Cam Mechanism with Floating Flat Face Pushrod

Chang Yong, Wu Qiuping, Li Yanping

2016, 27(21):  2926-2934. 

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Concepts of “rise and return travel” and “F/P type mechanism” were adopted herein. Conjugate cam mechanism was divided into main cam mechanism and assistant cam mechanism, which were studied respectively. Basic schematic diagram of instantaneous one dimensional linear area of the assistant cam and the curves of v′C1-θ1, v′C2-θ1 and u′K-θ1were offered. Then, the existence(features) of mechanism solution which met conditions of allowable pressure angles and cam contour were presented. In addition, the differences between the main cam mechanism and the assistant cam mechanism were presented. The existence of minimum spanning distance D*min was revealed as well. By several instructive important conclusions, the narrow and generalized class Ⅱ synthesis of conjugate cam mechanism with floating flat face pushrod was resolved.

Theoretical and Experimental Investigations of Particle Impact Damper with Elastic Restraints

Du Yanchen, Qin Jing

2016, 27(21):  2934-2938. 

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In order to study the vibration reduction effects of particle impact damper with elastic restraints on cantilever beam, a dynamics model of the damper was proposed, and its damping performance was simulated by numerical calculations. At the same time, the damping effects of 5 different stiffnesses of the particle impact damper with elastic restraints were studied experimentally. The results show that the calculated results are in good agreement with the experimental ones, indicating that the dynamics model established is reliable. And in the particle impact damper system with elastic restraints, the damping effects of spring stiffness ratio are nonlinear, and the spring stiffness has effects on the resonance point of the collision system.

Design and Evaluation of Non-dimensionalised Automotive Suspension Parameters

Chai Tian, Han Xu, Ding Fei, Lei Fei

2016, 27(21):  2939-2943,2981. 

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A method for evaluating and designing suspension parameters was presented herein. A quarter vehicle model was employed to develop the transfer function of the suspension vibration system, and then a non-dimensionalised expression for the suspension responses was presented in terms of non-dimensionalised factors. Based on the obtained expressions, the effects of non-dimensionalised factors on the sprung mass acceleration, rattle space, and tire deflection were investigated. Considering the nonlinearity of the suspension stiffness and damping, and the uncertainty of sprung mass, the performances of different parameter combinations were evaluated with radar chart, in order to obtain some parameter combinations corresponding to better compromised performances. The obtained results indicate that the non-dimensionalised parameter design method may effectively evaluate the performances of the suspension system with nonlinear stiffness and damping, as well as uncertainty of sprung mass.

Analysis of Power Efficiency for Dry Milling Machines Based on Response Surface of Machining Parameters

Zhao Gang, Wang Qiang, Ruan Dan, Zhang Xuehao

2016, 27(21):  2944-2948. 

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The power in dry machining processes was consumed more than the amount used in the wet machining. Through collecting the power data from the dry NC milling processes in real time, the RSM was used to establish the quadratic regressive equations of the total energy and unit energy of machine tools with respect to the impact factors of processes. Unit cutting energy consumption, and response surface and dimensional reduction surface of per machine energy consumption were analyzed by processing parameters. The results show that the increases of process parameters and material removal rate are of positive for enhancing machine tool energy efficiency. In addition, decreases of foundation energy consumption ratio and increases of cutting energy consumption are beneficial for improving energy efficiency of dry cutting machine tools.

Finite Element Model Updating Based on Inversion Method of Identification

Chen Yongliang, Liu Deshuai, Liu Yukun, Peng Tao

2016, 27(21):  2949-2955. 

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In dynamic analysis, a method to identify parameters of contact surfaces was put forward. The finite element model of mechanical structure was set up, and its key contact surface was replaced by spring-damper elements. Then the modality calculation was carried out. The objective function was built by combining the calculation results with the experimental results. Finally, the optimal parameters were obtained by the fitting of BP neural network and parameter optimization of genetic algorithm. The method was applied to the vertical grinder to obtain the parameters of contact surface. The results show that the method of identifying the parameters of contact surfaces is feasible.

Simulation and Experiments for Isothermal Free Forging Processes of 20CrMnSiNi2MoA Drilling Steel

Pan Guangyong, Yu Xinping, Ma Xiujin

2016, 27(21):  2956-2961. 

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The stress-strain curves of 20CrMnSiNi2MoA steel was calculated by JMatPro simulation software. And then the material flow stress constitutive equation was calculated based on stress-strain curves. The material of forging method of asymmetrical V-type die(FMV) isothermal free forging compression was simulated based on finite element software DEFORM-3D.The prediction of microstructure simulation results shows that the original austenitic grain size decreases as the amounts of compression are refined due to the occurrence of dynamic recrystallization. And the average grain size is smaller with the increases of deformation rate at a certain temperature. Through the FMV free of isothermal and heat treatment the bit products were obtained. And their mechanical properties compared with similar foreign product materials.

Drill Bit Cold Heading Parametric Modeling and Forming Process Optimization

Zhou Hongming, Zhang Heng, Zhang Xianglei, Peng Jiaojiao, Zhang Xiangxiang

2016, 27(21):  2962-2966. 

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Aiming at problems of high rejection rate and pre-heat treatment in cold heading of 40Cr drill bit, a cold heading forming method was put forward. The method optimized parameters of cold heading and reduced the treatment processes. Through the analyses of the influence parameters of cold heading processes, a cold heading parameter mathematical model was established. Numerical analysis of mathematical model got the optimization of parameters of cold upsetting. Using finite element simulation and experimental method, cold upsetting parameters were verified herein. The results show that, in the cold heading process that was guided by optimized cold heading parameters, materials without heat treatment may be used to produce cold heading drill bit with requirements.

Modeling and Simulation of ABS HCU

Zhang Jin, Kong Xiangdong, Yao Jing, Wang Juan, Chang Liying

2016, 27(21):  2967-2974. 

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The ABS HCU had a direct effect on the security of the automobile. The mathematical models of the hydraulic components were established based on the working principles and structures, including the master cylinder, wheel cylinder, increasing pressure valve, reducing pressure valve, accumulator, motor and pump. The unknown parameters of the models were obtained based on MATLAB/Simulink combined with the electromagnetic field, flow field and experimental identification, the accurate simulation models were established. A parameterized model of HCU was built. The HCU system simulation model was verified to be accurate through the comparison of the experiments and simulations, the results lay the foundation for the further studies of ABS virtual prototype.

Li-ion Battery SOH Prediction Based on PSO-RBF Neural Network

Zhang Ren, Xu Fang, Chen Jiaoliao, Pan Guobing

2016, 27(21):  2975-2981. 

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Key Laboratory of E&M, Ministry of Education & Zhejiang Province，Zhejiang University of Technology，Hangzhou，310014
For the traditional method to hardly estimate the internal parameters of Li-ion battery SOH, a PSO algorithm based on RBF neural network for SOH prediction of Li-ion batteries was proposed. Based on the Li-ion battery equivalent model, several key parameters which affected the SOH characteristics of the battery were determined by experimental data of the charged and discharged processes. The test data were input simulation model for network training and verification. Simulation results show that, compared to the BP neural network and the general RBF neural network, the algorithm may increase 20% of prediction accuracy, save more than 66.7% of the optimization time.