Table of Content

25 October 2019, Volume 30 Issue 20

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Experimental Research on Controllable Vibration Assisted ECM of Deep Narrow Grooves of Titanium Alloy

WANG Feng1,2;ZHAO Jianshe1;LIU Dingming1;FAN Yantao1;TIAN Zongjun1

2019, 30(20):  2395-2402. 

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To improve the ECM accuracy of deep narrow grooves of TB6 titanium alloy,the distributions of current densities and electrochemical dissolution rates of deep narrow groove side-walls in different machining modes were studied based on electric field simulation.Then,a comparative study of 3 kinds of machining modes including continuous feed,vibrating feed,coupling of pulse and vibration were carried out by experiments.The experimental results show that,when the vibration frequency and the continuous feed rate are fixed,the standard deviation of the groove widths may be significantly reduced by increasing the vibration amplitude,and further the machining consistency of the deep narrow grooves is improved; when the continuous feed rates are the same,the average groove widths and standard deviation of groove widths are both smaller by adopting the coupling of pulse and vibration mode,and the machining accuracy is higher.Moreover,the average entrance groove widths of 2.62 mm,the average groove widths along the depth direction of 2.73 mm,the entrance groove width standard deviation of 0.05 mm,and the groove width standard deviation along the depth direction of 0.03 mm may be obtained by using the coupling of pulse and vibration mode.

Dynamic Performance of Mould Table Vibration Systems Considering the Influencing Factors of Joint Surface

YI Yali1;XIANG Jian1;LIU Da1;ZHEN Hongwei2;JIN Herong1

2019, 30(20):  2403-2411. 

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In order to improve the vibration compactness and uniformity of concretes, focusing on the current vibration system design of the vibrating table in the production line, the influence factors of the joint surface was introduced to analyze the motion trend among the vibration subsystems. The mold vibration system was discretized into a four-degree-of-freedom series vibration system based on Simulink, and the theoretical response model was established. The variation of displacement response amplitudes with surface pressure of vibration subsystems was analyzed, and the adjacent amplitude differences rates of 36 groups of vibration subsystems were summarized. The harmonic response analysis of vibration subsystems based on Workbench, the maximum error between theoretical and simulation results is as 13.3%. Three groups of prefabricated components produced under the joint pressures of the adjacent vibrating subsystems were selected with the small amplitude difference adjacent and meet the limit amplitude, did the dimensional measurement and load tests, the performance of the production meet the acceptance criteria of the industry，which provides a reference for setting reasonable working condition parameters for prefabricated concrete production.

Analyses on Internal Gear Skiving Accuracy Influenced by Shaft Angle Error

WU Zhenyu1;WANG Siming1;ZHAO Daxing1;LI Tuopu2;DENG Yingcheng2

2019, 30(20):  2412-2423. 

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During the internal gear skiving, because the existence of shaft angle error, there would be some deviation in gear precision after machining. For improving the machining accuracy of the gear skiving machine, First，the kinematics model between the cutting tool and the workpiece was established under the three motion mode of non-feed, tool feed and workpiece feed. Second, the relative motion relationship between tool and workpiece was analyzed under different shaft angle error directions. And the mechanism of machining error of internal gear profile was studied. Then, through the establishment of multi-factor coupling model, the influence of different shaft angle error directions on gear skiving error were compared and analyzed, and the optimal axial feeding mode and shaft angle error direction were obtained. Finally, the validity of the theoretical analysis was verified by trial machining experiment of the prototype. And the workpiece after machining met level 6 precision requirement.

Modeling of DN63 Displacement-follower Ultra High Pressure Proportional Cartridge Valves

ZHANG Jin1,2,3;XUE Xiongwei1;KOU Chenghao1;YAO Jing1,3;KONG Xiangdong1,3;LI Hao4

2019, 30(20):  2424-2430,2438. 

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Taking the DN63 displacement-follower ultra-high pressure proportional cartridge valve as the research object, considering the friction forces and the flows of the valve mouth, the mechanism of the leading part of the displacement servo valves and the main valve parts was modeled respectively. Density and viscosity changing rules of oil caused by ultra-high pressure and temperature changes were analyzed, and the mechanism model parameters were modified to improve the accuracy of the model. The model was simulated by Simulink and was tested by experiments. The results of simulations and tests show that both of them are nearly the same, which verifies the correctness of the model.

Tribological Behaviors of GLC Films with Different Dopants under Starved-oil Conditions

LI Yingchun1,2;ZOU Chunsheng1;QIU Ming1;PANG Xiaoxu1;CHENG Bei1

2019, 30(20):  2431-2438. 

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GLC film,Cr-doped graphite-like carbon(GLC/Cr) film and WC-doped graphite-like carbon(GLC/WC) film were prepared by magnetron sputtering technique to investigate the effects of dopants on micro-structure of the films and the tribological properties in an starved-oil environment.The results show that the doping of Cr or WC increases the contents of sp2 bonds in GLC films,enhances the graphitization and reduces the hardness and elastic modulus of GLC films.In starved-oil environments,the three films have approximately the same friction coefficient but different wear resistances,and their wear life from high to low is as GLC/Cr ,GLC,GLC/WC.The results provide theoretical and experimental bases for improving the life and reliability of aero-engine main shaft bearings under extraordinary operating conditions.

Discharge Erosion of VHF Resonant Micro EDM Pulse Generators

WANG Feng;ZHANG Yongbin;LIU Guangmin;WANG Qing;YUAN Weiran;HU Bo

2019, 30(20):  2439-2446. 

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Aiming at the problems of low discharge frequency, large pulse width, and high-efficiency erosion ability at the nanoscale difficult to meet the increasing demands which were common in traditional micro-EDM pulse generators, a VHF micro energy pulse generator was designed based on principle of circuit resonance. The open circuit voltage waveform with a discharge frequency of 55 MHz and a peak voltage of 220 V was generated by the VHF resonant pulse generator, and the voltage pulse width was compressed to 9.1ns. Discharge experiments under different open circuit voltages were carried out, and the discharge waveforms under various experimental conditions were obtained. The experimental results show that the VHF resonant pulse generator has good processing performance.

Investigation on Improving Fretting Wears of Aeroengine Involute Spline Couplings Based on Tooth Profile Modification

XUE Xiangzhen1;HUO Qinxin1;ZHENG Jiahong1;CHEN Xi2;QIN Liyun2

2019, 30(20):  2447-2455,2479. 

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The distribution law of the axial loads of involute spline couplings was analyzed. The fretting wear prediction process of involute spline couplings was established. A method for modifying the involute spline couplings' profile was presented. The research results show that the axial loads of involute spline couplings increase along the axial direction, while the different torsional stiffness, the different shear modulus, the different torsion modulus, and the different meshing length. The fretting wears of the spline with or without modification increase with the number of cyclic loads. After modification, the maximum fretting wear amounts of the involute spline couplings at the shaft end are as 51 μm, the maximum fretting wear amounts of the involute spline couplings at the middle position are as 96 μm, the maximum fretting wear amounts of the involute spline couplings at shaft end are as 78 μm.

Impulse Fault Signature Extraction Based on Multi-dictionary Resonance-based Sparse Signal Decomposition

WANG Xiao1，2;XIE Ping1;GUO Yuangeng1;WU Xin1;JIANG Guoqian1;HE Qun1

2019, 30(20):  2456-2462,2472. 

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RBSSD method often suffered from incomplete decompositions when dealing with low signal-to-ratio signals due to the single dictionary property, and has some limitations especially in practical applications due to the difficulty in parameter selection. To address this issue, a new multi-dictionary RBSSD (MD-RBSSD) method was proposed herein. Instead of using single dictionary, the proposed MD-RBSSD method introduced symlet8 wavelet dictionary and sine dictionary on the basis of the tunable-Q dictionary used in RBSSD. Thus, the low-resonance components obtained using RBSSD is further decomposed to extract fault impulse signatures. Furthermore, the correlated kurtosis was introduced to provide a quantitative evaluation for the decomposition results. Simulations, experiments and engineering case study were used to verify the effectiveness of the proposed method. The results show that compared with the traditional RBSSD method, the proposed MD-RBSSD method may extract fault impulse components more accurately and efficiently, reduce the parameter selection difficulty of RBSSD, and improve the applicability of RBSSD in engineering applications.

Fault Prediction Model of Ship Unloader Based on Improved Association Rules

YE Yongwei;CHENG Yifei;LAI Jianren;REN Shedong

2019, 30(20):  2463-2472. 

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In order to ensure the safe and stable operation of the bridge grab ship unloaders, problems such as low utilization ratio of monitoring data and not timely failure diagnosis were put forward. To address these problems, a new ship unloader equipment fault prediction model method was proposed based on the improved interest association rule analysis method. The sensor monitoring method and time domain analysis method were used to obtain the operating parameter spaces of the ship unloaders. By using the clustering discrete algorithm, the monitoring data were divided into nonlinear clustering intervals according to their attribute ranges, and the association rule group of ship unloaders was obtained, and the directional feature constraint function of the state monitoring data association rules was constructed to extract the weight coefficients of state data of correlation dimensions, and fault prediction was realized through the association rule changes in the prediction model. The experimental results show that this method may effectively reflect the associated internal feature informations of the ship unloader running state monitoring, and realize the prediction of the ship unloader fault categories, and it is of realistic significance to reduce the frequency of faults.

Island Hole Repairing Based on Multi-directional Advancing Method

LI Song;MA Congcong;LU Fan;CAO Jingjing;ZHOU Yong

2019, 30(20):  2473-2479. 

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Aimed at the poor repairing effectiveness of the existing hole repairing algorithms for complex holes, a multi-directional advancing method was proposed. Firstly, the boundaries of the holes and islands were identified and adopted as the advancing front with multi-directional advancing method,and the holes were inserted with the vertices and triangular surfaces. Then, the rationality tests of new vertices and new triangles were carried out. Finally, the new vertices were adjusted according to the normal vector and the curvature so as to fit the original surface features. The results validate the effectiveness and superior performance of the proposed method.

Dynamic Load Distribution Optimization for Humanoid Wrist Joints

LI Yanbiao1,2;WANG Lin1,2;LUO Yiqin1,2;XU Mengru1,2;ZHENG Hang1,2

2019, 30(20):  2480-2488. 

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A dynamic load coordination distribution optimization method was proposed for humanoid wrist joint mechanisms. Firstly, based on Lagrange method and principle of virtual work, the dynamics model of the humanoid wrist joint mechanisms was established, and the dynamic performance evaluation indexes and force mapping performance evaluation indexes were derived. Secondly the comprehensive performance evaluation index was defined by a weighted summation method. An optimal performance trajectory was obtained by Dijkstra algorithm. Then, considering time, energy consumption, and stationarity, optimal generalized time was obtained by genetic algorithm. Finally, the feasibility of this optimization method was verified by numerical examples.

Path Planning of Mobile Robots Based on A* Algorithm and Artificial Potential Field Algorithm

WANG Hongbin1;HAO Ce1;ZHANG Ping1;ZHANG Mingquan1;YIN Pengheng1;ZHANG Yongshun2

2019, 30(20):  2489-2496. 

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A hybrid algorithm was introduced based on the global and local path planning for the mobile robot navigations and collision avoidances under complex and unstructured environments. Firstly, this paper makes effective improvement on the traditional A* method. The new A* algorithm can complete the robot's path planning task. The optimized path point was obtained by using the quadratic A* search method, and the traveling path of mobile robot was shortened. Furthermore, dynamic tangential point method could effectively smooth the planned path. Secondly, considering the path and environment, the improved artificial potential field method was adopted to carry out the local path planning for the mobile robot. The problem of local minimum value was solved by adding virtual subtargets. The adaptive step size adjustment algorithm was used to dynamically optimize the step size of the mobile robot. Finally, according to different scenarios, the proposed algorithm was compared with the traditional algorithm by numerical simulation, and the results show that the proposed algorithm has some advantages in the path planning under different environments.

An Integrated Optimization Method for Setups Planning and Line Balancing of Mixed Model Transfer Lines

ZHANG Heng;LI Aiping;FU Xiang;SHAO Huan;LIU Xuemei

2019, 30(20):  2497-2504. 

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In order to solve a class of line setups planning and line balancing problems for mixed model transfer lines with the production of family box-type parts, an integrated optimization method was proposed. Considering the transfer line constraints and precedence relations among operations, cycle time, number of fixture types, balancing ratios, and line smoothing coefficient were taken as optimal objectives. Product proportion coefficient was introduced to the model based on the analysis of the production index of each part with different combinations of setups. Then an improved genetic algorithm was used to optimize the model. Finally, a mixed-model transfer line producing two cylinders was used to demonstrate the validity and efficiency of the proposed method.

Wind Resistance Experiment and Cooling Fan Design of Aeronautic Generators

ZHAO Yanchen1;WANG Yangang1;LIU Hanru1;QIN Jiangping2;ZHANG Rongrong2

2019, 30(20):  2505-2511,2519. 

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In order to study the practical method of aeronautic generator cooling fan matching design, the wind resistance of an aeronautic generator was measured by the relevant experimental equipment. Through one forced air ventilating experiment, wind resistance, flow rate, and temperature rise of the generator under different working conditions were measured. According to the experimental results and design requirements of the generator, the orthogonal design method was employed to obtain a cooling axial-flow fan with wide chord, big turning angle, and high pitch ratio. Meanwhile, a specially expanding hub was  designed to further enhance the cooling performance. The test of generator installed with fan shows that the designed fan meets the demands of aeronautic generator cooling system which is suitable for the high pressure rise and small flow rate working conditions.

Structure Improvement on Two-stage CNG Pressure Regulators Based on Method of DOE

PENG Yuhui1;WU Zhizhou1;HUANG Yupeng1;LEI Xiangyu2

2019, 30(20):  2512-2519. 

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Through constructing the digital model of a two-stage CNG regulator to simulate the working performances, 8 factors possibly affecting the pressure stability of regulator's outlet were deliberately drawn out. Then, by the method of DOE, sensitivity of the parameters were analyzed, and the most sensitive 3 parameters were figured out to make improvements of the regulator. Consequently, comparative experiments for the 4 different regulators were conducted based on professional test platform. The experimental results reveal that the flow stability for the regulators with improvements is increased by 25% and 50% respectively under low flow conditions and high flow conditions, and the pressure stability of outlet is increased by respectively 80% and 77.8% simultaneously.