Table of Content

25 August 2017, Volume 28 Issue 16

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Identification of Axial Distribution Joint Parameters of Interfaces among Spindle-Holder-Tool Based on Frequency Response Function Analysis

ZHU Jianmin;HE Dandan

2017, 28(16):  1891-1898. 

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In allusion to identify the joint parameters for axial distribution interfaces among spindle-holder-tool accurately, a method of surface modeling and parameter identification of spindle-holder and holder-tool was proposed based on frequency response function analysis. According to the connectionrelationships among the various parts of spindle system, the bearing-spindle interfaces were simplifiedas some elastic supports and a discrete distribution model of interfaces among spindle-holder-tool was built on axial, and the corresponding contact parameters were identified through Cuckoo search algorithm, so as to explore their distributions. A four fluted milling cutter was used as an example,a spindle system's dynamics model was established in ANSYS based on parameters identified,and the calculated tool point frequency response function in ANSYS was compared with the measuredones. Experimental results show a non-linear distribution of joint parameters for interfaces among spindle-holder-tool on axial, and the relative errors between the calculated tool point frequencyresponse function and the measured ones are within 4%, which reaches a high prediction precision.

Dynamic Analysis of Locking Processes of Loader Hydraulic Torque Converters

HUI Jizhuang;CHENG Shunpeng;WU Linlin;ZHANG Jinlong

2017, 28(16):  1899-1905,1913. 

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In order to reduce the influences of vibration shocks caused by the locking processes of a hydraulic torque converter on the service life of the parts and to improve the locking quality, according to the working principles of loader locking clutchs of the torque converters, the lock up processes and binding parameters were analyzed, the locking oil filling hydraulic control system and oil filling control curve were designed, and the loader drive systems were simplified. Simultaneously, a mathematical model of the lock up processes was established. Based on the model, the simulations were carried out by using Simulink, the effects of locking filling time and filling pressures on dynamic locking processes were analyzed respectively. Results show that the blocking effectiveness is the best when the oil filling time is as 0.2s, and the filling pressure is as 1.2MPa. The correctness of designed oil filling control curves is proved and it achieves the purpose of reducing the dynamic loads during the locking processes and improving the vehicle motion stability, providing a reference for dynamic analysis of locking processes of other engineering vehicles.

Study on Surface Integrity Modeling and Cutting Parameter Optimization of Superalloy in High-speed Finish Milling

SUN Tao1,2;LIANG Jin1;LI Dengwan2;WEI Bin1;GUO Nan1

2017, 28(16):  1906-1913. 

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A high-speed finish milling experimental program contained qualitative factor hybrid levels was projected by uniform design method. The finish milling multiple quadratic regression model of superalloys was established, and cutting force, cutting temperature and surface integrity were taken as objective functions in it. This model shows a good regression effects. Meanwhile, the influence laws of cutting conditions on the surface integrity were analyzed emphatically. Based on the regression models, a multi-objective optimizing model of high-temperature alloy's parameters in high-speed finish milling was built, and the test results show a high predictive accuracy. The conclusions provide a directional significance for cutting parameter selections and quality controls of superalloys under a long bearing life at high temperature.

Design and Analysis of Non-circular Gear Slider-Crank Mechanisms Used as Driver for Pulsating Blood Flow Generators

TAO Dehua1;WANG Ying1;CHEN Jianneng2;RONG Quansheng1;ZHOU Xian1;SHU Xuedao1

2017, 28(16):  1914-1920,1927. 

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A novel non-circular gear slider-crank mechanism was proposed to make pulsating blood flow generators produce stable pulsations of blood flows. The blood flow pulsations were realized by the combination of non-circular gears and slider-crank mechanisms. In order to make the designed mechanism run smoothly, the acceleration curves of the output components of the mechanism were fitted by the 2 sections of cubic Hermite interpolation polynomials under the preconditions of satisfying the law of human body blood flow pulsations, and then the equations of velocity, displacement and jerk of the output components were deduced according to the equations of the acceleration curves and the boundary conditions. The non-circular gears section curve reverse model was obtained by the output component kinematics curves equations. The 3D solid model of this mechanism was established based on mechanism parameters obtained from instance analysis and the virtual prototype test was performed after modeling. The comparison between the results of virtual simulation experiments and theoretical analyses shows that the designed mechanism may realize the pulsating blood flows according to the laws of expected, and the mechanism has fine kinematics characteristics, also verifies the correctness of the equation of kinematics curves and the kinematic analysis model.

Design and Verification of Angular Momentum Balancing Mechanism of Remote Sensing Camera Posture Control Axis

LIU Bingyou1,2;ZHU Chang'an2;GUO Jie2;JIN Yi2

2017, 28(16):  1921-1927. 

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In the occasion that more than one remote sensing cameras were installed on one remote sensing satellite, reaction and angular momentum would be produced by adjusting certain remote sensing camera. This reaction and angular momentum would change the posture of remote sensing satellite, and then influence the posture of other remote sensing cameras. An angular momentum balancing mechanism was designed to balance the angular momentum in posture control axis of remote sensing camera. This angular momentum balancing mechanism was composed of a motor, a principal axis, a gear system, a gear speeder and an angular momentum balance wheel. In the mechanism, the principal axis was driven by the motor rotor, the principal axis drives the posture control axis of remote sensing camera, meanwhile, the reaction of the motor stator drives the gear system and rotates the angular momentum balance wheel via the gear speeder. The angular momentum could be calculated by adjusting the quality amplification coefficient of the angular momentum balance wheel or the speed increasing ratio of the gear speeder. Thus, the angular momentum internal self-balancing can be realized. Then, the correctness of mechanism design was proved by the principle of angular momentum conservation and the basic principles of theoretical mechanics. Finally, a three-dimensional dynamic simulation model of the mechanism was established and the simulation parameters of the mechanism were set according to the actual parameters of the mechanism. Simulations were carried out with given load and results are analyzed. The feasibility of the mechanism design is further validated.

Research on a Novel MRF-MDMF

LI Bin;LI Hua;YAO Jin

2017, 28(16):  1928-1936. 

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Aiming at the key problems of the stiffness mutations and smaller damping torque in a magnetorheological fluid dual mass flywheel, a novel MRF-MDMF was proposed to obtain good multistage nonlinear torsional stiffnesses. Through the theoretical analyses of magnetic induction intensity and damping torques of MRF-MDMF, and the optimization of its structure, the magnetic induction intensity distribution of optimized structure and the maximum of damping torques were conducted. Then，the calculated values of magnetic induction and damping torques were compared with the simulation values. Finally, the natural characteristics and the forced vibration were analyzed. The results show that MRF-MDMF is conducive to the improvements of damping effects of powertrain, the matching input currents are used to achieve the best damping effect in different conditions, and its damping torques are far greater than that of the ordinary magnetorheological fluid dual mass flywheel. The results provide a precious theoretical reference for the design of MRF-MDMF.

New Stick Structures of Large Hydraulic Excavators Using Topology Optimization Method

NING Xiaobin1;LIU Yaran1;LI Jie2;LI Guang3;LI Jialin3

2017, 28(16):  1936-1942. 

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Based on the structural strengths of the sticks, a new stick structure of the working devices of large shovel hydraulic excavators was designed by the method of structure optimization. Mine rock model was build by using the discrete element method, and the digging resistances of the bucket were obtained. The rigid-flexible coupling model of the working devices of the large shovel hydraulic excavators was established by using the multi-body dynamics method, the dynamic loads of the sticks during the stick digging were obtained, and the dynamic structural strengths of the sticks were analyzed. The topology optimization design of the stick structures in finite element was carried out by using the variable density topology optimization method of SIMP interpolating function, and the new stick structures of the working devices of large shovel hydraulic excavators were obtained. The dynamic structure strengths of the new stick structures were analyzed, the strengths of the new stick structures maintained the original level. The results indicate that the new stick structure has the same strength as the analogy designed, while the weights of the sticks are reduced.

Work Roll Horizontal-Vertical Nonlinear Vibration Characteristics and Suppression of Hot Strip Tandem Mills

LING Qihui;ZHAO Qiancheng;WANG Xian;KANG Yuhua

2017, 28(16):  1943-1950,2007. 

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Work roll vertical-horizontal system's nonlinear vibration model of a hot strip tandem mill was established based on the rolling interface horizontal-vertical direction friction mechanics model and the dynamic rolling force model, with the influences of mill structures and the frictions between work roll bearing seats and memorial arch pillars considered. The amplitude-frequency characteristics equation of the system was obtained by using average method, and the characteristics of amplitude-frequency were analyzed under the effects of the factors such as the extraneous forces and nonlinear parameters, which provided theoretical guidance for the suppression of work roll system vertical-horizontal vibrations. Different vibration states such as periods, doubling periods, chaos were exhibited along with the extraneous force amplitude changes when analyzing the system Lyapunov index and displacement bifurcation diagram. Finally, a method of inhibition of horizontal vibrations and vertical vibrations was presented based on the influences of scaleboard gaps on system vibrations and the analyses of amplitude-frequency characteristics under circumstances whether there were scaleboard gap or not between work roll bearing block and arch column. The results of simulation and practice show the effectiveness of the method.

Finite Element Numerical Simulation of Forming Forces and Metal Deformations in Cold Roll-beating Forming Processes

LI Long;LI Yan;CUI Limu;HUANG Geng;YANG Mingshun

2017, 28(16):  1951-1959. 

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To get an accurate and efficient numerical simulation method of forming forces and the overall metal plastic deformations of the external tooth cold roll-beating forming, based upon the basic principles of cold rolling forming, a typical finite element model was established to characterize external tooth cold roll-beating forming, and the example was calculated according to the experimental conditions. The culculation results compared with the experimental ones, it is shown that this calculation model and method may describe the main forming force average peaks in stable forming. Meanwhile the calculation results of metal plastic deformations may effectively reflect tooth formations of cold rolling forming, predict and explain the occurrences of the flashes on the edges and the bow defects. Then, the method was investigated to improve the efficiency of the numerical calculation, the higher computational efficiency may be obtained when the mass scaling factor is as 60 000 and the minimum element length is as 0.25mm.

Chained Form Conversion and Motion Planning Method for a Nonholonomic Manipulator

LI Liang1;LIU Yifang2;TAN Yuegang3

2017, 28(16):  1959-1964. 

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A motion planning algorithm was proposed to avoid the inverse chained form conversion singularity of nonholonomic three-joint manipulators. Free variables of generalized coordinates were separated according to the structural features of nonholonomic manipulators. Then the boundary values of variables acted as undetermined coefficients of control inputs. Inequality constraints were proposed to make sure that a trajectory in chained form spaces might be mapped into joint spaces for singularity of inverse chained form conversion. Additional constraints were used to avoid singular configuration of the inverse chained form conversion. Results of simulations and experiments prove the feasibility and effectiveness of this motion planning algorithm.

A Coordination Control Method for Wearable Robots and Its Motion Assist Mechanism

ZHANG Xia1;QIAN Lei1;LUO Tianhong1;CHEN Renxiang1;HASHIMOTO Minoru2

2017, 28(16):  1965-1971. 

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In order to improve flexibility in human-robot interaction (HRI) of a wearable robot, a novel notion of coordination control method was proposed using CPG. CPGs autonomous behavior and its outer-interaction mechanism were utilized to generate active/passive motion patterns of robot joints. Therefore, the inverse kinematics and inverse dynamics computations were avoided. Computer simulation analysis and physical experiments were carried out to explore the motion assist mechanism, stop and restart flexible movement generation mechanism. Results demonstrate that the coordination control method has motion assist effect, and active/passive motion patterns may be obtained due to CPGs autonomous behavior and its outer-interaction characteristics. CPGs attenuation features are able to generate stop and restart flexible motions, and thus improve robot flexibility in HRI environments.

Dynamics Property Analyses of a Novel PURU+RR+S Spherical Parallel Humanoid Robotic Ankle Mechanisms

XU Yiliu1;YANG Long2,3;YANG Zhongyuan2;XIAO Chao2;ZHOU Yulin2

2017, 28(16):  1971-1976. 

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A novel PURU+RR+S spherical parallel humanoid robotic ankle mechanism was proposed herein, the kinematic models including poses, velocities of all components were established according to geometric constraint relations and velocity composition theorem of this mechanism. Based on this, the influences of inertia forces of each components were considered, dynamics model of this mechanism was established based on the principles of virtual work and Lagrange equation. A group of kinematic data of human ankles were obtained by experimental measurements, position and orientation functions of human ankles were derived using Fourier formula. The position function was used as outputs of the theoretical model and the virtual prototype of ankle mechanisms respectively. Numerical solutions and simulation data of the inputs of ankle mechanisms were obtained, and then the correctnesses of kinematic and dynamic models were confirmed. The research provides a theoretical basis of dynamics for structure design and applications of the humanoid robotic ankle mechanisms in engineering.

Research on Tele-operation Systems for Installation of Aerial Curtain Walls Based on Force Feedbacks

YAN Han;DONG Yuewei;LI Tiejun

2017, 28(16):  1977-1986,1993. 

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A tele-operation system was established in the field of aerial curtain wall installations. To improve the handling ability and stability of the robots, this system contained the force feedback and visual feedback, allowing the operator to get a good telepresence. According to the asymmetric structures of the master-slave robot systems, the workspace mapping relation and the workspace conversion relation were established. The trajectory planning algorithms of the robots were established and simulated by MATLAB. A fuzzy PID controller was designed to adjust the tracks of the moving processes of the curtain walls. The design of remote operating system was completed, and the functions of the system were carried out. Experimental results show that the remote operating systems may ensure the positional accuracy of the installations, and reduce the risk of collision according the force feedbacks from the slave robots.

Lightening Technological Implementation of Model-based Definition Product Information on Mobile Web

JIAN Chengfeng;SUN Chang

2017, 28(16):  1987-1993. 

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Based on the STEP AP242 protocol, which supported product model definition exchanges, a multi-view semantic model was proposed to classify and keep the non-geometric informations. With the model, semantic ontology was implemented to unify the product geometry and non-geometric semantic informations. Then a boundary-based lightening algorithm was proposed to match the performance of mobile terminals, which might cut product model with the product non-geometric information kept. Finally the experimental data was given to prove the feasibility.

Modeling and Path Planning for Complex FGM Mold Fabrication Using Plasma Deposition Manufacturing

WANG Xiangping1;ZHANG Haiou1;WANG Guilan2

2017, 28(16):  1994-1999. 

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In response to the requirements for design and fabrication of FGM mold with complex geometry and irregular material variations, a novel method made up of voxel modeling with nonuniform graded source and path planning was proposed based on dual data model. In the dual data model, the standard tesselation language(STL) model was used to design graded source and create geometric path, and the voxel model latter was used to design material distributions and create FGM representations. Deposition path was finally generated by geometric path discretization and material composition retrieving and blending. The new method may simultaneously represent multiple local reference features with complicated shapes, and making deposition path superior in terms of precision and efficiency for geometric portion and complex distributions for material portions. An example of automobile front fender mold shows its capability and validity.

Corrosion Behavior of High Strength Aluminum Alloy under Different Corrosion Environments

ZHOU Song;XU Liang;HUI Li;WANG Lei;MA Shaohua;HAN Fang

2017, 28(16):  2000-2007. 

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Aiming at the corrosive material problems caused by harsh environment during the service of aviation aluminum alloy materials, research on the corrosion behavior and mechanism of 2xxx aviation aluminum alloys servicing in different corrosive environments(3.5% NaCl solution, water in fuel tank and wet air) was conducted based on the analyses about the corrosion morphology, openning areas, depths and quantity of the pits, pH values and corrosion products. Results show that corrosion products are mainly found in the first 24 hrs for specimens in 3.5% NaCl solution with the biggest pit depth about 45μm, with the increase of the corrosion time between 72~120 hrs, the increase of pit depths and quantities are not obvious. The corrosion behavior for specimens in water in fuel tank was similar to that in NaCl solution, but the pit openning areas and quantities decrease dramatically. The corrosion extents for specimens in the wet air decrease compaired with the other two corrosive environments with the least pit quantity, the deepest pit depth is lower than 20μm and the biggest pit openning area is around 5000μm², the differences among pit depths decrease with the increase of corrosion time.

Applications of Pressurized Internal Cooling Method in Superalloy Grinding Processes

PENG Ruitao1;LI Zhongping1;HUANG Xiaofang1;TANG Xinzi1;HU Yunbo2

2017, 28(16):  2008-2015. 

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In view of the cooling problems of much grinding heats generated in the grinding processes of nickel-based superalloy, a cooling method that combined pressurized internal cooling and intermittent grinding was proposed to actively control the high temperatures of grinding arc areas effectively. The pressurized internal cooling wheel with abrasive orderly was designed and fabricated. The temperature field model of GH4169 superalloy grinding processes was established in Fluent software. The effects of wheel speeds and coolant pressures on the cooling performance of the grinding wheels were simulated and analyzed. The grinding experiments of GH4169 using press-internal cooling wheel was conducted, the grinding temperature, machined surface roughness and surface topography were compared and studied. The results show that: under the same grinding parameters, compared with external cooling, internal cooling method may obtain more excellent machining surface quality, the grinding temperatures and surface roughnesses are significantly lower; when other grinding parameters are the same, the greater coolant pressure, the lower grinding temperatures and surface roughnesses, meanwhile with better and more regular surface morphology.