Table of Content

25 March 2019, Volume 30 Issue 06

Previous Issue    Next Issue

Locomotive Bearing Fault Diagnosis Using an Improved Empirical Wavelet Transform

DUAN Chendong;ZHANG Rong

2019, 30(06):  631-637. 

Asbtract ( )   HTML   PDF (757KB) ( )  

References | Related Articles | Metrics

Locomotive bearings worked in the background of loud noise, it was difficult to extract the fault characteristics effectively. To solve this problem, an EWT was proposed. In order to overcome the problem of noise component interference sub-band divisions in EWT method, an approach was proposed, which used local minimum on a kind of time-frequency kurtosis spectrum of analyzed signals to make the frequency-band partitions, and orthogonal wavelet filter group was constructed based on the sub-bands to perform EWT decomposition. Simulation experiments and engineering applications show that the improved EWT may better overcome the interference of noise components on sub-band divisions, and effectively extract the defect features of locomotive bearings.

Numerical Simulation of Hydrodynamic Suspension Polishing Processes and Optimization of Polishing Tool Structures

ZHENG Zijun;LI Panxing;CAI Donghai;WEN Donghui

2019, 30(06):  638-643. 

Asbtract ( )   HTML   PDF (717KB) ( )  

References | Related Articles | Metrics

Aim to optimize structure parameters of hydrodynamic polishing tools, firstly, significant influences of size and uniformity of hydrodynamic pressures in machining areas affected by polishing tool disc structural parameters were analyzed with variance analysis method by orthogonal experiment and CFD numerical simulation. Then a multivariate non-linear regression method and a genetic algorithm were used to optimize the sample data of orthogonal experiments, and the optimal structure parameters were obtained. Numerical simulation results show that the mean of dynamic pressure and the uniformity of the dynamic pressure generated by the optimized polishing tools improve 30% comparing with that of the polishing tool disks before optimization.

Improved Dynamic Stall Model of Vertical Axis Wind Turbine Blades

ZHANG Lijun;ZHAO Xinhui;MA Dongchen;MI Yuxia;WANG Hanxiang;Jiang Hao

2019, 30(06):  638-643. 

Asbtract ( )   HTML   PDF (680KB) ( )  

References | Related Articles | Metrics

In order to calculate the aerodynamic performance of vertical axis wind turbine blades under dynamic stall, 2 dynamic stall models, B-L model and MIT model, were modified in detail based on actual working conditions of the wind turbines. Taking a vertical axis wind turbine with a height of 17 meters in Sandia laboratory as an example, dynamic tangential force coefficient and dynamic normal force coefficient of the blade were calculated based on the 2 models above when the blades tip speed ratio was as 2.33 and 3.09 respectively. The research results show that the MIT correction model has higher prediction accuracy for the tangential force coefficient in windward areas and the normal force coefficient in the leeward areas, and the B-L correction model has higher prediction accuracy for the normal force coefficient in the windward areas and the tangential force coefficient in the leeward areas.

Evaluation of Wear and Failure of Gate Bottom Pivot Friction Pairs under Grease Lubrication

QIN Hongling1,2;GUO Wentao1;XU Xiang1,2;YUAN Zekun1;ZHAO Xinze1,2

2019, 30(06):  650-657. 

Asbtract ( )   HTML   PDF (952KB) ( )  

References | Related Articles | Metrics

Friction and wear testing machine was used to obtain tribological properties of QAL9-4/40Cr and ZCuAl8Mn13Fe3/40Cr under different contact stresses under conditions of grease lubrication. Grey system theory GM(1,1) model which evaluated allowable wear amounts of wear failure was applied. When actual contact stresses of the two copper-based friction pairs are below allowable stresses under low-speed and heavy-load conditions, wear patterns are mainly plough-cut; wear amount increases and friction coefficient decreases, when the contact stresses increase. On the contrary, the wear patterns are mainly sticky, and the wear rate and friction coefficient increase sharply. Under low-speed and heavy-load, QAL9-4/40Cr has better wear resistance when two copper base friction pairs are subjected to the same contact stresses. Coincidence of the theoretical predicts and the test results attend 95%.

Design and Kinematics of 3-translation Parallel Mechanisms with Zero Coupling Degree

SHEN Huiping;WU Chengqi;XU Ke;ZHAO Yingchun;YANG Tingli

2019, 30(06):  658-664. 

Asbtract ( )   HTML   PDF (735KB) ( )  

References | Related Articles | Metrics

According to the topology design theory based on position and orientation characteristic（POC）equations, a new asymmetric 3T PM (RPa‖3R)2R+RPa with zero coupling degree and decoupled motions was designed. The main topological characteristics such as POC, degree of freedom, and coupling degree were calculated. Workspace and singularity of the PM were analyzed based on inverse position solutions of the PM. Velocity and acceleration of the center of mass of the PM were obtained by Jacobian matrix, and simulation curves of velocity and acceleration was put forword.

Design and Mechanics Performance Analysis of a Concrete Pipe End Grinding Robot

CUI Guohua1;LIU Jian1;MA Liang2;CUI Kangkang1

2019, 30(06):  665-671. 

Asbtract ( )   HTML   PDF (851KB) ( )  

References | Related Articles | Metrics

In order to improve the accuracy and efficiency of grinding prestress concrete cylinder pipe ends, a novel self-propelled pipe end grinding robot was designed.Configuration and structure of this robot were designed based on configurational evolution method, and the mechanics model of the robot was established. Taking the jack end grinding robot applied to the 4 m diameter pipe as an example, ultimate load of the robot in the operations was obtained, and the finite element simulation analysis was carried out. Analysis results show that the strength and stiffness of the robot meet the requirements of fields in running processes. And the field test proves that the robot has higher grinding efficiency and reliability.

Study on Oscillation Heat Transfer Characteristics and Position of  Cooling Gallery

WEN Jun1,2;WANG Dongfang1;LEI Jilin1;LI Zhekun1;WEN Zhigao2;DAI Yunhui3;XIN Qianfan1

2019, 30(06):  672-679. 

Asbtract ( )   HTML   PDF (844KB) ( )  

References | Related Articles | Metrics

An aluminum alloy piston of non-road high pressure common rail diesel engine was invoked as the research object. A numerical simulation model of piston-internal cooling chamber heat transfer was established based on the experimental results. The accuracy of the simulation model was verified by comparing the simulated temperature field of the piston with the test results. Transient heat transfer characteristics of piston oil cooling gallery in engine working cycle processes were studied. Influences of the gallery positions on piston temperature fields and piston thermal stress fields were analyzed. The results reveal that the instantaneous heat transfer coefficient of the gallery inner wall is periodically changed with the gallery oil distribution in engine working cycle processes. The piston maximum temperature and the first ring temperature may be significantly reduced when the gallery positions are close to the piston top surfaces and the bottoms of the ring groove.Thus, the gallery positions should be as close as possible to the piston top surfaces and the bottoms of the ring groove within the allowable ranges of structural strength. But, when the gallery is positioned too close to the piston walls, a greater local thermal stress will be generated at the areas of third ring groove and inner cavity top surfaces of the pistons.

General Class Size Synthesis Tasks of Disc Cam Mechanisms with Roller Follower Moving in Planar General Motions

LIN Mengjie;LI Yanping;CHANG Yong

2019, 30(06):  679-683. 

Asbtract ( )   HTML   PDF (639KB) ( )  

References | Related Articles | Metrics

The roller center C(u,v) was selected as a variable, and the possibilities of instantaneous area set Γ*(x,y)/boundary Γ*(x,y) were systematically analyzed and discussed. By introducing the concepts of simple ergodic region Σ[2] and Σ[0], and the approach of discrete-grid, the concepts and solutions of union of solution area Ω*[2/0](u,v)/Γ*[2/0](x,y) were proposed innovatively. Coordinate system Ouvr**0min was constructed, three-dimensional surface S** was generated, and the characteristics of state-edge of regression J**and bottom point P** were extracted to reveal the existence of the most compact mechanism size solution and the solution method, which solved the general class size synthesis tasks of disc cam mechanisms with roller follower moving in planar general motions.

Distribution Detection Method of Film Thickness in Mechanical Seal Based on Ultrasonic Principle

WANG Jianlei1;WANG Xiaohu1;ZHANG Chen 1;JIA Qian2;CHEN Runlin1;LIU Kai1

2019, 30(06):  684-689. 

Asbtract ( )   HTML   PDF (678KB) ( )  

References | Related Articles | Metrics

Aiming at the problems of distribution detection of mechanical seal lubricating films, a multi-point measurement model of mechanical seal lubrication film distribution by ultrasonic principles was established herein. A lubrication film distribution measurement system  was constructed, which was composed of modules for signal generation, ultrasonic transmission-reception, data acquisition, and data storage-display and equipped with an analog measurement device. Lubrication films with thicknesses of 5 μm, 10 μm and 20 μm were tested on an analog measuring device. The results show that the ultrasonic film principle may be used to accurately measure the distribution of the lubrication films, the single point measurement error ranges are 0.2~1.1 μm, and the detection accuracy is the highest when the film thickness is as 5 μm.

Real-time Flexible Acceleration and Deceleration Control Algorithm Based onAdaptive Look-ahead and Predictor-corrector Method

LI Hao1,2;WU Wenjiang2,3;HAN Wenye2,3;GUO An1,2

2019, 30(06):  690-699. 

Asbtract ( )   HTML  

References | Related Articles | Metrics

To improve high-speed and high-quality machining of continuous line segments, a novel real-time flexible acceleration and deceleration control algorithm was proposed. This algorithm contained three parts: the acceleration-deceleration feasibility and real-time forward-looking function were guaranteed in look-ahead processes with acc-dec feasibility conditions; the velocity planning module calculated next feedrate with smooth velocity and acceleration curves; in order to respond to changes of machining parameters immediately, adjusting current velocity planning results was carried out in dynamic override module. The experimental results reveal that the proposed algorithm may realize real-time flexible acceleration/deceleration control, support dynamic override and implement high-quality processing.

A Cable Path Planning Method Based on Improved A* Algorithm

JIANG Kang;MA Shiji

2019, 30(06):  699-708. 

Asbtract ( )   HTML   PDF (923KB) ( )  

References | Related Articles | Metrics

Aiming at the path planning problems of virtual cable routing in complex wiring space environments, the evaluation function of traditional A* algorithm was improved herein, and an additional value factor was introduced to select the appropriate path nodes. Moreover, rigid factor which was used to evaluate the cable paths in continuous bending was applied, and location factor of cable routing was incorporated into the algorithm to adjust the positions of optimal cable paths. Path planning in 2D grid map and wiring results in 3D model show that the improved A* algorithm may generate a reasonable routing paths.

A New Model of Spray Robot Electrostatic Rotating Cups

LIU Yang;ZHAO Chen;WANG Xuhao;ZHANG Jiajun

2019, 30(06):  709-715. 

Asbtract ( )   HTML   PDF (747KB) ( )  

References | Related Articles | Metrics

The cumulative rate model and paint projection model were the important basis for off-line programming of spray robots. For the cumulative rate model, a double offset β model was established. The model might represent both of the full moon model and the locally asymmetric ring type model. Based on this analysis, the uniform velocity spray thickness model of the new model was analyzed, which was prepared for the trajectory planning of off-line programming. For the paint projection model, the functional relationship between accumulation rate of a point on workpiece surfaces and accumulation rate of corresponding point was deduced when the coating projection model was arbitrary function model. Then combined with the experimental data, a curve projection model was proposed based on normal distribution. The experiments prove that this model is more consistent with the actual situations.

Applications of Wireless Positioning Technology in Mobile Cranes

LI Jieren1;XU Li1;XU Qingshan1;WANG Jianmin2

2019, 30(06):  716-721. 

Asbtract ( )   HTML   PDF (574KB) ( )  

References | Related Articles | Metrics

In order to solve the problems that crane could not be positioned accurately and dynamically, a wireless positioning algorithm for cranes was proposed based on ultra-wideband positioning principle. Wireless positioning algorithm model, hardware framework and control system were studied and designed, and the simulation analyses and the whole machine test were carried out. Test results show that the wireless positioning system meets the set performance parameters' requirements.

Design and Slow Tool Servo Turning of Progressive-addition Lenses

NIU Hengtai1;KANG Min1,2;WANG Xingsheng1; YANG Jun1

2019, 30(06):  722-727. 

Asbtract ( )   HTML   PDF (689KB) ( )  

References | Related Articles | Metrics

The design and processing of non-rotationally symmetric or aspherical spectacle lenses had many difficulties nowadays. A parametric design method of progressive-addition lenses (PAL) was proposed herein. This method avoided complex mathematical calculations by controlling the surface curvatures to control the optical powers and astigmatism distribution. Distribution of surface astigmatism and surface power were calculated and evaluated. A method for generation of cutting contact points was proposed for discrete surfaces. The slow tool servo turning technology was used in machining of the PAL. Experimental results show that the design method and cutting contact points generation method are successful.

Optimization Design of Blunt Trailing-edge Airfoil under Conditions of Rough Blades

ZHANG Xu1,2;ZHANG Mengjie1;WANG Gege1;LI Wei2,3;RUAN Jiangtao1

2019, 30(06):  728-734. 

Asbtract ( )   HTML   PDF (894KB) ( )  

References | Related Articles | Metrics

Optimization design of blunt trailing-edge airfoil profiles was carried out by using particle swarm optimization algorithm coupling with the software XFOIL. A lug boss with the height of 0.015c (c is chord) and the width of 0.04c was added on the optimized airfoils through translating the suction surface coordinates on the position of 0.1c away from the leading-edge, and the blunt trailing-edge modification of rough airfoils was obtained. Lift and drag coefficients, lift-drag ratios, pressure coefficients, and flow characteristics before and after blunt trailing-edge optimization were investigated numerically. The results indicate that after blunt trailing-edge optimization of rough S812 airfoil, the trailing-edge thickness is as 0.039 8c, and the thickness distribution ratio is as 1∶13.16. The lift coefficient within calculating angle and lift-drag ratio before the attack angle  of 17.2° increase remarkably, and the maximum lift-drag ratio is significantly increased. The vertex at airfoil’s blunt trailing-edge causes the downwash effects on the airflow of suction surfaces.

Stacker Scheduling of Layouts for Automatic Warehouses with Double Ended

CAI Anjiang1;XUE Xiaofei1;GUO Shihong2;CAI Yao1;GUO Zongxiang1;ZHAO Xiangli3

2019, 30(06):  735-741. 

Asbtract ( )   HTML   PDF (629KB) ( )  

References | Related Articles | Metrics

The allocation method of double ended automatic warehouse tasks and the scheduling paths of stacking machines were studied. Taking stacker running time of completing the I/O tasks for the storage efficiency evaluation standard, and considering the problem of I/O counter allocation, the stacker scheduling model was established based on both single command operation mode and composite command operation mode. A vortex search algorithm was used to optimize scheduling paths of the stackers. The optimal solution of stacker scheduling model was obtained, and its storage efficiency was optimized. The simulation results show that the research may effectively allocate the I/O counter allocation of the goods, optimize the scheduling paths of the stackers, and improve the storage efficiencies of the automated warehouses.

Control Method of Weld Line for Tailor-welded Blank Parts with Different Thicknesses

GONG Zhihui1;ZHAO Shuwu2

2019, 30(06):  742-747. 

Asbtract ( )   HTML   PDF (706KB) ( )  

References | Related Articles | Metrics

Deviations between the design weld lines and the formed weld lines were inevitable in the stamping processes of TWB with different thicknesses due to the plastic deformations, so a method to shrink the deviations by adjusting the weld lines on the blanks in advance was put forward. Firstly, design weld lines were transformed into a integrated curves by extending to the binder or the filled holes according to the process supplement surfaces, then the integrated ones were discretized into a series of points to establish the position relationship of each discrete point between the three of the designed weld lines, the blank lines and the formed lines, then the deviations of each corresponding points between the formed weld line and the design lines were calculated through stamping simulations, the ideal weld curve on blank could be acquired through adjusting the blank discrete point according to the deviations calculated before. Based on these, the weld curves of blanks would be transformed into a straight line, which would be rotated and moved properly according to stamping simulation results to further shrink the deviations between the formed weld line and the design lines. The stamping test results show that the method is effective and reveals the main sources of deviations are coming from straight weld lines of the blank.

Damage Evolution and Life Prediction of Low Cycle Fatigue for Magnesium Alloys under Asymmetrical Stress Loading

CHEN Ling1, 2;ZHANG Xianming1;LIU Fei2;OUYANG Ping1;JIA Yanyan3

2019, 30(06):  748-755. 

Asbtract ( )   HTML   PDF (836KB) ( )  

References | Related Articles | Metrics

Low cycle fatigue damage evolution of magnesium alloys under asymmetrical stress loading was analyzed， where the changes of elastic modulus, equivalent modulus, total strain energy density, and mean strain were selected as damage variables. And then, a corresponding life prediction models was developed. Results show that the low cycle fatigue damage evolution of the magnesium alloys under asymmetrical stress loading may be described by the changes of total strain energy density or mean strain as damage variables, and the corresponding life prediction models have good effectiveness. Damage curve of the mean strain changes, as the damage variable, has better representation in comparison.