China Mechanical Engineering

Review on Management at Mechanical Engineering Discipline of National Natural Science Foundation of China in 2017

LAI Yinan;CAO Zhengcai;YE Xin;LIU Lei

2018, 29(06): 631-638.

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The applications, evaluations and funding of projects in the mechanical engineering discipline of National Natural Science Foundation of China (NSFC) in 2017 were reviewed. The research progresses of undertaking programs and the achievements of finished programs in 2016 were summarized. Problems occurred in the program implementation were summarized. The management measures of Division II of Engineering Sciences of NSFC on academic exchange and cooperation, talent cultivation, academic team construction, and project arrangement were introduced. The latest progresses and typical achievements obtained in the fields of mechanical engineering supported by NSFC in 2017 were listed.

Frequency-band-selecting Pulsed Eddy Current Testing Method for Detection of Defects under a Certain Depth Range

ZHAO Ying;XIE Shejuan;TIAN Mingming;TONG Zongfei;LI Yong;CHEN Zhenmao

2018, 29(06): 639-644.

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To further improve the detectability of local wall thinning defects under certain depth ranges, a FSPECT method was proposed. The principles of FSPECT method were introduced. The way of selecting the excitation signals of FSPECT was described in detail. The detection sensitivities of local wall thinning defects under certain depth ranges of the traditional square wave PECT and FSPECT were compared. The lift-off intersection point of FSPECT was investigated. The numerical experimental results show that the sensitivity of FSPECT is higher than that of the traditional PECT for testing local wall thinning defects under certain depth ranges. The lift-off intersection point of FSPECT may reflect the depth of local wall thinning defects.

Coupling Stiffness of Double Outer Generator Swing Rod Movable Teeth Transmissions

YI Yali;DOU Linrui;GUO Hui;JIN Herong

2018, 29(06): 644-649.

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Movable tooth coupling stiffness was proposed based on structures of double outer generator swing rod movable tooth transmission mechanisms. A coordinate fixed on movable tooth frame was established. Tooth profiles and pressure angles of double outer generator and central wheels were presented. System radial forces and time-varying coupling stiffnesses were investigated according to deformation compatibility conditions and Palmgren formula. The effects of structure parameters on coupling stiffness coefficients were analyzed.

Wind Turbine Gearbox Operation State Analysis Based on Data Mining

JIA Ziwen;GU Yujiong

2018, 29(06): 650-658.

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Aiming at the problems of wind turbine gearbox operation conditions which were difficult to be identified, a correlation mechanism between turbine parameters and operating status was established by an improved NSEM, which was on the concept of data mining. Using factor analysis method, the sample data space was reduced and the interpret ability of sample data was improved. By the actual operation characteristics of the unit, sliding window and exception rate method were used to analyse predictive residual, which ensured the accuracy and credibility of the final analysis results. Combined with actual case analysis, the method may be more timely and accurately than traditional one to find out abnormal states of wind turbine gearboxes.

Research on Backlash Regularity and Finite Element Simulation of Harmonic Gears

YANG Pengpeng1,2;CHEN Xiaoxia1,2;XING Jingzhong1,2;YAO Yunpeng1,2

2018, 29(06): 659-666.

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In order to reflect the backlash distributions of harmonic gears more accurately, the tooth root positioning methods of flexspline were improved in the backlash algorithm, and the tooth profile equations under the coordinate transformation was established instead of the tooth thickness equations in the original backlash algorithm. Both of the methods for calculating the backlashs based on circumferential displacement positioning and arc length positioning were proposed. The finite element model of planar tooth rings with involute tooth profile was established, and the backlash distributions under no-load conditions was obtained. Comparing the theoretical backlashs with that from the finite element model, their consistency is excellent. In order to reveal the causes of the backlash deviations, the radial displacement, the circumferential displacements and the normal rotation angles of the flexspline neutral layers in the finite element model were obtained, and the circumferential polar angles were solved to compare with the theoretical algorithm. The circumferential displacements of the flexspline teeth are the major factor of the backlash deviations.

Tribological Performance of Resin-based Brake Friction Materials Modified with La₂O₃

ZHENG Kaikui1,2;GAO Chenghui1;HE Fushan1;LIN Youxi1;JIANG Liangxuan

2018, 29(06): 666-673.

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By using constant speed friction test, CHASE friction test and morphology observation of worn surface, the effects of La₂O₃ on the friction and wear performance, fade and recovery behavior of resin-based brake materials modified with La₂O₃ were investigated. The constant speed friction test results show that the additions of La₂O₃ in brake materials effectively improve the friction coefficient and decrease the wear rate, and increase the stability of friction coefficients. In this study, the braking samples with 20% La₂O₃show optimum tribological performance. CHASE friction test results show that the additions of La₂O₃ improve the fade and recovery performance of the composites.

Study on Sand Collisions and Erosion Characteristics of Two Phase Flow in Contraction Pipes

YAO Liming1; LIU Jubao1;ZHANG Hongyan2;ZHANG Xiaochuan2;YUE Qianbei1

2018, 29(06): 674-681,704.

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As the shortcomings of current modeling method in describing the sand erosions in two phase flow, CFD-DEM was used to build contraction pipe two phase flow in fracturing condition, the accuracy of simulation model was testified by experiments and the force laws of particle collisions and contraction areas in contraction pipes were analyzed. The results show that the erosion depth of contraction areas increases by sand ratios, and the erosion depth increment decreases and approaches the maximum during the same period when the sand ratio is over 40%. The erosion depth of contraction area decreases with the viscosity increments and the influences of fluid viscosity on contraction area outer margin are bigger than inner edge.

Decoupling Motion Analysis of Wind Tunnel 6-DOF Mechanisms

SUN Qi;XIE Zhijiang;WU Jingwei;LI Sheng;SONG Ningce

2018, 29(06): 682-687.

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To improve reliability of high speed wind tunnel tests, a wind tunnel 6-DOF mechanisms were designed， and an attitude angle compensation method was put forward when support stings were transformed. In two cases of the model centroid and the mechanism rotation center with or without coincidence, the kinematics formula was proposed based on POE of the serial robots. And then without coincidence, the compensation rate of the model decoupling attitude angles was given.The laser tracker calibration experiments prove the feasibility of the compensation method and provide theoretical basis for trajectory planning and real time control.

Wavelet Characteristic Parameter Method of a Planar Four-bar Mechanism Motion Generation Synthesis

SUN Jianwei1;WANG Peng1;LIU Wenrui1;CHU Jinkui2

2018, 29(06): 688-695.

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Aiming at the problems that the Fourier series theory could not be used to synthesize the non-integral periodic rigid body guidance problems, a method was presented to solve the problems based on Haar wavelet series, which extend the early methods solving the problems of planar four-bar path synthesis to motion generation synthesis. The wavelet coefficients between the rigid body rotation angles(RBRA) and the connecting rod rotation angles(CRRA) of its corresponding basic dimensional types were analyzed, the internal relationships were determined. Based on this finding, an output feature parameters database of planar four-bar motion generation including 101 408 sets of the basic dimensional types was established. The motion generation position output problems were transformed into a planar four-bar mechanism path synthesis problems, and the theoretical formulas were given to compute the actual size and installing position parameters of the mechanism. The non-integer-period motion generation synthesis of a planar four-bar mechanism was achieved using the established database and theoretical formulas. A four-bar mechanism for conveying workpieces on a production line was presented to illustrate the validity and practicality of the proposed theory.

Numerical Analysis and Experiments of Whirl Characteristics in Horizontal Drillstrings

WANG Baojin1;REN Fushen1;ZHU Anhe2;ZHAO Lei3

2018, 29(06): 696-704.

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The dynamics equation of drillstring in horizontal well was established based on rotor dynamics and fluid mechanics, and the influences of drillstring weight, the friction resistance of borehole wall, the flow rate of drilling fluid and the hydraulic resistance on the drillstring whirling in horizontal wells were analyzed through the numerical simulation and the experimental apparatus. Furthermore, the mechanism of the horizontal drillstring whirling and the boundary conditions were explained. The results show that there will be no whirling away from the bit, however, the whirling occurs at the drillstring bottoms in horizontal wells. With the increases of weight on bit and the rotational speed of drillstring, the amplitudes of the whirling increase, and the drillstring at the bottom has a forward whirling and backward whirling after the rotational speed exceeds the threshold. The semi-frequency whirling will occur with continuous increases of the rotational speeds. In addition, the current motion status of drillstring will not be changed by the existence of drilling fluid with different flow rates. The research results hold lessons for optimizing drilling parameters in horizontal wells.

A Kind of Multi-scale Integration Measurement System for Surface Textures

WANG Shenghuai1, 2;XU Fenghua1;CHEN Yurong1;XIE Tiebang2

2018, 29(06): 705-711,719.

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A multi-scale integration measurement system was presented. Different scale measurement methods were integrated, such as microscopic image measurement, vertical scanning white light interferometry measurement, nano-probe measurement by white light interferometry and diamond probe measurement by white light interferometry. The measurement results show that in microscopy image measurement for standard glass thread ruler of 300μm, the indication error is as -0.251μm and the standard deviation is as 0.403μm. In white light interferometry for single engraved templates of 1.26μm and 3.33μm, the mean measurements are as 1.263μm and 3.328μm, indication errors are as 0.003μm and -0.002μm，the relative change of indication are as 1.27% and 0.63% respectively. In nano-probe measurement by white light interferometry for calibration grating of (106.8±1.0)nm, the mean is as 103.1nm and the relative error is as -3.5%; in diamond probe measurement by white light interferometry for standard template of Ra=4.08μm, the measurement Ra is as 4.05μm and the relative error is as 0.74％. The introduced system may satisfy the measurement needs and realize the multi-scale integration measurement for surface textures.

Static Stiffness Analysis of 2RPU/UPR+RP 5-DOF Hybrid Manipulators

ZHANG Dongsheng1,2;XU Yundou1,2;YAO Jiantao1,2;ZHAO Yongsheng1,2

2018, 29(06): 712-719.

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In order to quickly establish the stiffness model of a 5-DOF hybrid manipulator based on the 3-DOF 2UPR/RPU PM, the configuration description was presented firstly. Secondly, the inverse position kinematics was obtained by solving the kinematics of PM and serial parts separately. Then, simplifying the structures of the 5-DOF hybrid manipulators, stiffness models of the parallel parts and the serial parts were established. After that, combining the wrench screw system and the deformation compatibility conditions of the 5-DOF hybrid manipulators, stiffness model of the entire system was obtained quickly and easily. At last, equivalent simplified 3D model of the 5-DOF hybrid manipulators was constructed. One typical orientation and position of the hybrid manipulators were chosen out, and micrometric displacements of the end effector under external forces/torques were simulated in virtue of finite element and MATLAB software. Stiffness distributions in the workspace were also given. Through the comparison analyses of two different methods, the correctness of the established stiffness model was verified.

Non-negative Matrix Factorization Based on Clustering and Its Application

LI Maolin1;LIANG Lin2;CHEN Yuanming2;XU Guanghua2;HE Kangkang2

2018, 29(06): 720-725.

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With the increasing complexity of electromechanical system state informations, traditional feature extraction and selection methods were unable to meet the needs. According to the characteristics of conventional non-negative matrix factorization(NMF) algorithm, a NMF method for monitoring and fault diagnosis was proposed based on the clustering property of NMF. By comparing classification accuracy and iteration efficiency, an improved alternating least square iterative algorithm with sparsity and correlation constraints was selected, and the low-dimensional embedded dimension and iterative initialization method were also determined. Experimental results to UCI test datasets and fault diagnosis of Tennessee-Eastman process(TEP) systems show that this approach is more effective to extract the fault features, and enhance the failure pattern capabilities.

Model Simplification Method of Visual Attention and Lightweight Assembly Technology

WANG Yongmei1;DU Baojiang2

2018, 29(06): 726-731.

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A model simplification method of visual attention and lightweight assembly technology was presented. The part model library with 6-level of details from the most detailed to the null model was established. The method of calculating the dynamic level of details of standard part models was presented based on assembling parts related visions，structures and kinematic chains, also the function of switching different detailed models was implemented in assembly design according to this level definition of details. The method was used in amphibious aircraft design and the design efficiency is obviously improved.

Trajectory Tracking Control with Disturbance Attenuation for Hull Derusting Manipulators

WANG Zhong1,2;JIAO Xiaohong1;CHENG Mingxing1,3

2018, 29(06): 731-737.

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During derusting and paint-spray periods, the luffing and telescopic cylinders of the manipulator should be managed to coordinate actions， and the internal and external uncertainties acting on the system should be overcome so as to ensure the manipulator movement as uniform speed in the vertical direction. In view of uncertain disturbances existing in the deflections while the manipulator moving and unmeasured internal state variables of proportional valve cylinder system, a reduced-order observer-based trajectory tracking controller with disturbance attenuation was designed by utilizing Lyapunov stability theory. The robustness of the designed controller to disturbance was verified by comparing with the traditional PID controllers in the simulation environments. Meanwhile, the proposed control algorithm was applied to mechanical engineerings. The results show the attenuations on the external disturbances of the manipulators.

Characteristics of Mechanical Alloying Modified FeS/Cu Alloy Powders

YIN Yanguo;ZENG Qingqin;ZHANG Guotao;LIU Jianfeng

2018, 29(06): 738-742,747.

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In order to solve the problems that the FeS/Cu-based powder metallurgy materials were agglomerated and the interfaces were poor after sintering,FeS/Cu-based materials were prepared by mechanical alloying technique.The mixing characteristics, pressing properties and mechanical properties after sintering of 6% mass fraction FeS/Cu alloy powders with different ball milling time were tested and analyzed by means of scanning electron microscopy, X-ray diffraction, metallographic microscope and so on.The results show that mechanical alloying may effectively improve the mixing of FeS particles and matrix alloy powder uniformity. After sintering the material density and hardness are improved,and the interface bonding of FeS and Cu possesses good quality. As the FeS particles were uniformly dispersed in the copper alloy matrix, the continuity of the matrix materials was separated, making the toughness and crushing strength of the composites reduce.

Loading Design of Wind Turbine Blade Fatigue Tests

FU Cheng;ZHANG Fanghui

2018, 29(06): 743-747.

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In view of the complexity of wind turbine blade cross-section shapes and laminate structures， a calculation method of load moment distributions in the blade fatigue tests were deduced to avoid the risks of blade section overloading and the checking purpose for the dangerous sections of the blades were realized. At the same time, the real parameters of the measured blades were obtained by means of the test method, which avoids the test load uncertainty caused by the parameter errors of the real blades and designed blades, and improves the reliability of the tests.

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