Table of Content

10 February 2018, Volume 29 Issue 03

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Development of a 3-DOF Parallel Manipulator

RONG Yu1,2,3;LIU Shuangyong3;WANG Hongbin1;HAN Yong3

2018, 29(03):  253-261. 

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A new type of 3-DOF manipulators based on (U+UPS)P+UPS mechanisms was proposed. Firstly, the inverse position equation was presented, the velocity transmission model and the statics transmission equation were established respectively. Also, the 3D maps of the workspaces and the 3D maps of condition number of Jacobian matrix in the workspaces were drawn by searching method. Then, a set of kinematics performance evaluation indexes were defined, and the relationship curves among structure parameters and the kinematics performance evaluation indexes were drawn. A set of statics performance evaluation indexes were defined, and the relationship curves among structural parameters and the statics performance evaluation indexes were drawn. The structural parameters were analyzed by Monte Carlo method. An excellent set of structural parameters is found: the distance between two universal joint's rotation center points of the fixed platform is as 240 mm, the distance between spherical joint's rotation center point and UP branch's connect point of the moving platform is as 80 mm, the distance between middle connecting rod's spherical joint's rotation center point and UP branch's center line is as 90mm, the distance between middle connecting rod and UP branch's universal joint's rotation center points is as 600mm. Finally, the prototype was made. The statics calibration experiments of the manipulator were carried out, and the manipulator structure was proved to be reasonable.

Analysis and Experimental Research of Contact States of Single Metal Seal under Drilling Conditions

ZHANG Yi1;CHANG Xueping1;FU Yukun2;WU Qian1

2018, 29(03):  262-266. 

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Combined with high temperature and high pressure working conditions in the drilling fields, the finite element analysis of assembly processes and bilateral compressions of single metal seal were completed, the dynamic sealing surface contact pressure gradient distributions were obtained,and a new method to calculate the dynamic seal leakages was presented based on the MATLAB. Then, the rotary seal test rig was established, and the distributions of the contact pressures and the seal leakages of the dynamic seals were measured. The test results and the simulation results show that the seal surfaces are convergent under low pressures, which are conducive to the formations of the lubricating film, and the high pressures are divergent. The contact pressures on the inner sides of the seal surfaces are gradually decreased with the increases of the pressure differences between the lubrication and the drilling fluid, while the outside gradually increased. Meanwhile, the leakage rate increases with the speed increases of the seals, while decreases with the increases of the axial compressions of the dynamic seals.

Checking Calculation Method of Three-row Roller Slewing Bearings

LI Yunfeng1,2;ZHANG Pengyue1,2

2018, 29(03):  267-272. 

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For the three failure modes of slewing bearings (i.e. raceway plastic deformation, raceway fatigue spalling and ring fracture) appeared in engineering applications nowadays, a method for checking the three-row roller slewing bearings under combined loads was established systemically by using the numerical analysis model and the finite element analysis model of the slewing bearings. Numerical analysis model solved the statically indeterminate solving problems of rolling element load distributions with the help of the deformation coordination conditions and the force balance conditions. The rollers was simplified as spring unit based on finite element analysis model, while the rings still adopted entity unit, which avoided a great quantity nonlinear numerical solving calculation of the contacts between the entity rollers and the entity raceways. Safety factors of resisting to plastic deformation of the raceway, fatigue life of the raceway and structural strength safety factors of the rings were calculated by using the established checking method, which provides the basis to determine the degrees of the bearing satisfying the requirements of the working conditions of given applications.

Study on Micro-hole Polishing Mechanism and Experiments Based on Laser-induced Cavitation Bubbles

CHEN Tieniu;GUO Zhongning;ZENG Baiwen;YIN Sihua

2018, 29(03):  273-278,285. 

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A novel micro-hole polishing method was introduced, this method applied the laser plasma shock waves, cavitation bubble shock waves of bubble collaps and jet to push the abrasive particles to polish the micro-holes. A high-speed camera and a silicon piezoresistive high-frequency dynamic pressure sensor were utilized to research the mechanism of the micro-hole polishing. Then the experiments of 304 stainless steel pipe polishing  were carried out based on different laser energy, different laser pulse number and different laser pulse frequencies, which were found that the surface roughnesses were improved with the increasing of laser energy(from 7mJ to 21.6mJ ) and laser pulses number(from 0 to 7000), but the different laser pulse frequencies(from 1Hz to 10Hz ) might not improve the surfaces roughnesses of the micro-holes. Finally, the polishing effectivenesses of different positions along the stainless steel pipes were studied, it is found that the polishing effectivenesses at the entrance of the pipes about 1~1.5mm are better than the middles and ends of the pipes. Through the experiments of micro-hole polishing mechanism and experiments based on laser-induced cavitation bubbles, it is pointed out that the plasma shock wave, the cavitation collapse shock wave and jet work together during the micro-hole polishing, and the general rules of micro-hole polish are obtained based on laser-induced cavitation bubbles.

Research on Reliability of Key Parts of Locomotive and Rolling Stocks Based on Optimized ABC Algorithm

SHEN Guoqiang1;HE Deqiang1;TAN Wenju2;MIAO Jian1

2018, 29(03):  279-285. 

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According to the over-maintenance problems and inadequate maintenance problems in the operations and maintenances of locomotive and rolling stocks based on graphical method and ABC algorithm for the models of reliability of key parts of locomotive and rolling stocks, a new fitting method was proposed to established the three-parameter Weibull model by estimating the three parameters of Weibull distribution. Firstly, the initial estimates of the three-parameter Weibull parameters and the search spaces of the ABC algorithm were determined by the graphical method. Then the ABC algorithm was used to obtain the optimal parameter estimation. Finally, a new fitting method was compared with the least squares method and method of probability weighted moments. The results show that this method may obtain the parameter estimation values and build the reliability analysis model of the key parts of the locomotive and rolling stocks accurately. The Weibull model may be used in determining the optimal maintenance periods and improve the maintenance procedures of locomotive and rolling stocks for maintenance personnels.

Dimensional Synthesis of Equal-span Cam Mechanisms with Floating Roller Pushrods Based on Technology of Forward-inverse Mapping Intersection

FAN Wu1;LIN Mengjie1;LI Yanping1;CHANG Yong1,2

2018, 29(03):  286-291. 

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A new concept and configuration of equal-span cam mechanisms was put forward herein, which originated from the constant yoke radial cam mechanisms but jumped off and broke through the traditional restrictions of “three points collinear cam axis and main/auxiliary roller center”. The remarkable unique morphological characteristics were revealed and the angles of go and return travels, kinematics sizes, distances, initial position parameters and return movement laws were explored into the solving. By introducting new concept of “merger search belt-area” and putting forward “forward-inverse mapping intersection”, “whole choice area” of main/auxiliary roller and optimal mechanism solutions are obtained under the conditions of α≤[α] and equal-span, thereby enabling dimensional sythesis tasks for equal-span cam mechanisms with floating roller pushrods. The object spaces and solution set spaces of the mechanisms were expanded significantly because of the development of the equal-span cam mechanisms. Through a mathematical example of mechanism synthesis, the paper demonstrates that the equal-span cam mechanisms have significant superiorities compared with yoke radial cam mechanisms.

Hexahedron Mesh Generation Method Based on Sub-domain Decomposition

WANG Pan;ZHANG Jianming;HAN Lei;JU Chuanming;CHI Baotao

2018, 29(03):  295-300. 

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A new hexahedron mesh generation method was proposed herein. First, the feature edges of the domain were extracted and the appropriate decomposition face was generated according to the feature edges. Then, the complex geometry was decomposed into multiple sub-domains by the decomposition face and the structured hexahedron meshes were generated by the method of transfinite mapping in the sub-domains. Finally, the mesh of target domain was obtained by combining the meshes of all sub-domains. The method was capable of preserving transfinite mapping’s advantages of the briefness in algorithm, high efficiency and high quality of the meshes, at the same time, could overcome transfinite mapping’s shortcomings of bad geometric adaptability, which might only used to regular geometric shapes. Numerical experiments were presented to demonstrate that the new method may generate high-quality hexahedron meshes for complex geometries automatically which may not generate hexahedron meshes by commercial softwares directly.

Compensation Control of Vibration Displacement Systems for Continuous Casting Molds Driven by Servo Motor with Time-varying Load Torque

MA Zhuang1,3;FANG Yiming1,2;LI Jianxiong1;LIU Le1

2018, 29(03):  295-300. 

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In order to handle time-varying load torques and the problems of multiple inverse solutions between the vibration displacements and the rotating angles in the control systems of continuous casting mold vibrations, a robust backstepping controller was presented based on piecewise mapping function method. Firstly, the mathematical model of control system was developed according to analyze the device characteristics and system control processes, at same time the piecewise mapping function method was designed in order to convert the errors of vibration displacements into the angular displacement errors. Then, extended state observer was used to estimate varying load disturbances, which were introduced into the controller to reject disturbances and theoretical analyses proved that the system was global asymptotic stability. Finally, simulation results verify the effectiveness of the designed controller.

Analyses and Experiments for Mechanical Bulging Processes of Truck Drive Axle Housings

LUO Jianguo;LI Pan

2018, 29(03):  308-314. 

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The mechanical bulging technology with axial auxiliary thrust was proposed which was suitable for manufacturing the drive axle housings of medium-sized trucks. The mathematic expressions of the corresponding limit expansion coefficients below the recrystallization temperature were derived, the influences of the matching of each force parameters in the forming processes on the limit forming coefficients were analyzed, and the ranges of axial auxiliary loads in radial bulging processes were given. Based on the derived theory, a 5 ton truck drive axle housing was taken as the research object, DEFORM-3D software was used to simulate the key forming processes, the rules of metal flow state, stress-strain distributions and the variations of wall thickness were obtained, and the forms and locations of the defects in the expansion processes of the axle housings were predicted. Relevant physical experiments were carried out on the extrusion equipment, the experimental results show that the axial auxiliary loads are necessary to prevent cracking during bulging processes. The shape and wall thickness distributions of the qualified samples in the experiments are measured. The experiment results coincide with that of simufation. The feasibility of mechanical bulging forming technology for the drive axle housings of medium trucks is verified both in theoretical and practical areas.

Robustness Optimization of Powertrain Mounting Systems Based on Chebyshev Interval Method

CHEN Jian;LI Shiai;LIU Ce;DENG Zhiqiang;SHU Hongchao

2018, 29(03):  314-319. 

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Automotive powertrain mounting systems were one of the main vibration isolation systems of vehicles, which had great influences on its performances for the vehicle noise, vibration and harshness(NVH) experiences. Considering the powertrain mounting stiffness existed a certain degree of errors or volatilities, Chebyshev interval method was applied to calculate the natural frequencies and decoupling rates of powertrain mounting systems varied with the extents of element stiffness change intervals, and the calculation accuracy was determined based on examples. To improve frequencies of the mounting systems and robustness of decoupling rates, robustness optimizations were conducted according to the interval optimization models of frequencies and decoupling rates of automotive mounting systems. Results show that the optimization method may obtain better energy decoupling rates, high robustness and reduce the vibration transmissibility from mounting systems.

Analysis of Ellipse and Similar Ellipse Tooth Profile Modification Scheme of Rotor Oil Pump

HUO Pengguang1;GONG Jinke1;CAI Hao2

2018, 29(03):  320-325,332. 

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A new kind of similar elliptic rotor tooth profile was designed to solve the problems of current oil pumps with elliptical profile rotor, including the inner rotor and outer rotor meshing with each other. At the same time, the flow performance analysis, liquid moment analysis and multibody dynamics analysis were compared with elliptic profile and similar elliptic profile. Applications of oil pump with similar elliptical may reduce the costs of modifications without changing the original design of the pump bodies. It also may reduce torques generated by oil on inner rotors on the basis of improving the oil pump flows at low speeds. The similar elliptic profile improves the rotor pump flow performance and reduces abrasion and saves energy.

Improved ECMS Energy Management Control of HEVs Based on DP Algorithm

DENG Tao;HAN Haishuo;LUO Junlin

2018, 29(03):  326-332. 

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In order to improve the fuel economy of HEVs, the torques of the coupler sides were taken as the research objects, and the optimization of the torque distributions was taken as the objective. The working states of the hybrid powertrain under the global optimum of the parallel HEVs were obtained by using the DP method. Based on these as the inputs and the equivalent factors were obtained, an improved ECMS was proposed. The virtual equivalent engine fuel consumption processes were equivalent to the processes of virtual battery charges and discharges. The instantaneous equivalent fuel consumption minimum control model was established and simulated, and then compared with the power following strategy and traditional ECMS. The results show that for the improved ECMS, the state of charge(SOC) is reduced by 3.36% and the fuel economy is increased by 10.95% compared with the power following strategy. Compared with the traditional ECMS, SOC is improved by 1.48% and the fuel economy is increased by 3.20% .

Thermal Cycling Test and Life Prediction of Aviation Electrical Connectors

LUO Yanyan1;MA Xuan1;LI Xiaoning2;WANG Zhen3

2018, 29(03):  333-339. 

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Through the accelerated life tests and analyses, the reliability and life prediction method of aviation electrical connectors was studied under thermal cycling conditions. A thermal cycling accelerated test scheme for simulating diurnal temperature differences was proposed, including experiments and circuit designs. The strains of jacks in the period of stable high temperature during the tests were used as the main monitoring parameters indicating the performance degradation processes of aviation electrical connectors. The accelerated thermal cycling tests were carried out and the performance degradation laws of aviation electrical connectors induced by stress relaxation were analyzed. The critical strain values for the failure of aviation electrical connectors were derived theoretically. And the gray model, time series model and neural network based time series model were adopted in the life prediction of aviation electrical connectors under thermal cycling conditions. The results show that the strain decreases with the increases of the numbers of thermal cycles. And the larger the temperature differences, the more the strain reduction is, the more obviously the stress relaxation phenomenon shows, the faster the performance degrades and the shorter the service life is. The thermal cycling life is approximately exponential attenuation with the increases of temperature differences.

Research on Evolutionary Game Strategy of Promoting Development of Remanufacturing Industries by Government

ZHENG Handong1, 2;CHEN Yi1;LI Enzhong2;SANG Fan2;SHI Peijing2;XU Binshi2

2018, 29(03):  340-347. 

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For the problems of lack of emphasis on remanufacturing by OEM at the present stage, an evolutionary game model was constructed to study the development of remanufacturing promoted by OEM and government. Combined with current situations of China remanufacturing industries, the costs and profits of different strategies for government and OEM were analyzed. The replicator dynamics equations of government and OEMs were established based on evolutionary game theory and the dynamic evolution processes of decisions were analyzed. The influences of parameter variations on the evolution results were demonstrated by numerical simulations. The results show that whether OEMs do remanufacturing is related to the proportions of remanufacturing enterprise and incentive powers. A higher remanufacturing investment cost and (or) the lower profit will be prevented OEM from carrying out remanufacturing. Local government will offer incentives to support OEM remanufacturing when extraneous income from remanufacturing industrial investment is up to a point. Finally, initial proportion of strategies for both OEMs and local government, remanufacturing investment costs and benefits, incentive costs and additional benefits were analyzed through the numerical simulations. It is benefit for OEMs and local government to take appropriate measures for the development of remanufacturing.

Modeling and Simulation of Fillet Weld Tracking for Robots Based on Rotating Arcs

LI Yi1，2，3;CHEN Jiayang1;HU Shengxian1;DENG Xin1;ZHANG Fengtao1;XIE Xiaoxue1

2018, 29(03):  348-352. 

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The six degrees welding robot kinematics model, rotating arc sensor welding seam deviation information collection and curve characteristics of fillet weld were studied, the robot transformation matrix after rectifying flange coordinate system relative to the base coordinate system was deduced，and the robot reverse kinematics was calculated. Then, the complex fillet seam tracking and posture welding torch adjustment models were established. The given height and lateral deviation signals were input into the MATLAB platform, and the simulation tests of robot welding seam tracking model were carried out. The simulation results prove that this model is effective and accurate. This paper provides theoretical references for using the rotating arc sensors in the welding robots. The research fruits provide the theory basis for seam tracking system designs.

Interfacial Microstructure of Diamond Vacuum Brazed with Cu-based Composite Filler Metals Adding Ni-Cr-B-Si Alloy

LU Jinbin1,2;LI Hua1,2;LIU Wei1,2;ZHONG Sujuan3;MA Jia3

2018, 29(03):  353-358,365. 

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In order to reduce the heat damages of the diamonds and to adjust the properties of the filler metals, Cu-based composite filler metals adding Ni-Cr-B-Si were used to carry out the vacuum brazing experiments on diamond abrasives. The morphology and microstructure of the diamonds and the brazing filler metals were analyzed by scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD) respectively. The results show that the composite filler metals of CuSn powder adding Ni-Cr-B-Si at 20% is suitable for brazing the diamonds, which may realize the chemical metallurgical bonding with the diamonds. The thermal damage of diamonds is obviousty reduced, the morphology of the diamonds is intact, the surfaces are smooth and there are different carbides with specific morphology formed on the different crystal faces of the diamonds. In the solidification processes of the filler metals, α-Cu dendrites separate out firstly, then through the peritectic and eutectoid transformations, α-Cu dendrites, Cu5.6Sn, Cu3Sn, Ni3Sn and α-Cu are finally formed. With the content of Ni-Cr-B-Si increasing, the hardness of the brazing filler metals improves, which can reach 360-400 HV when the content of Ni-Cr-B-Si is as 20%.

Finite Element Modeling and Application Analyses of Ultrasonic Spot Welding Quality Inspections

HE Zhicheng1;JI Yanjun1;CHENG Aiguo1;HE Daocong2

2018, 29(03):  359-365. 

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This paper described the finite element modeling method which might be used in two layer welding spots: using destructive crystalline phase experiments, the external size parameters of finite element model were obtained, while using ultrasound echo attenuation theory and the ultrasonic detection signal characteristics, the damping coefficients were obtained. The finite element model of two layer welding spot materials was established for the BLD, then, the model accuracy was verified by means of comparisons with equipment inspection, finally the ultrasonic probe's angle positioning sensitivity was analyzed in the body surface detection conditions, and verified by experiments. The results show that when the spot welding of body surface quality inspection, the spot welding detection results will be less affected when the probe angle deviated from the welding spot normal within 10°, sometimes even may be ignored.