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Table of Content

    10 May 2016, Volume 27 Issue 09
    Elastodynamics Analysis of a 5-UPS/PRPU Redundantly Actuated Parallel Machine Tool
    Zhou Xin, Xu Yundou, Yao Jiantao, Zheng Kuijing, Zhao Yongsheng,
    2016, 27(09):  1137-1142,1149. 
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    An elastodynamics model of the 5-UPS/PRPU redundantly actuated PMT was derived by combining the finite element model and substructure synthesis techniques herein. Firstly, the overall system was divided into different substructures. According to the theory of spatial beam element, the dynamics equation of the spatial beam element was derived, and then assembling into different driving limbs; according to the dynamic constraints and kinematic constraints among the moving platform and each driving limbs, the dynamics equation of the overall system might be obtained by assembling the dynamics equation of the driving limbs. The 5-UPS/PRPU redundantly actuated PMT was set as an example to illustrate the derivation of the dynamic response of the moving platform. At last, by comparing the dynamic response of the redundantly actuated PMT and its non-redundant PMT, it can be concluded that: the elastodynamics performance of the PMT may be improved by the actuation redundancy, so that the errors caused by the driving limb deformations can be reduced as well. The research provides a theoretical reference of the structure design and optimization for the designers.
    Stiffener Layout Optimization of Thin Plate Structures Based on Sensitivity Number
    Li Lei, Zhang Bao, Li Quanchao, Tan Songnian
    2016, 27(09):  1143-1149. 
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    A heuristic design method for stiffener layout of thin plate structures was proposed herein. Starting from some prescribed initial nodes, the stiffeners grew and branched off towards the direction that the structural performance would be optimized. And the stiffeners with the minimum effectiveness on the structural performance were deleted simultaneously. During the design process, the relative density of each element was treated as the design variable. The growth and degeneration of the stiffeners were determined by the elemental sensitivity numbers. The design algorithm was programmed in Python and integrated with ABAQUS software which was used as the FEA preprocessor and solver. To validate the effectiveness of the proposed method, it was applied to design the stiffener layouts of some typical structures with the objective of maximizing the overall stiffness, and the obtained results were compared with the results in existing literatures.
    Gravity Balance and Steering and Obstacle-crossing of Three-arm Inspection Robots
    Tao Guanghong, Fang Lijin
    2016, 27(09):  1150-1157,1164. 
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    A novel three-arm inspection robot for power transmission line was proposed, which was composed of four serial parallelogram mechanisms. The robot mechanism possessed the ability to meet the gravity balance requirements when steering and crossing obstacles by adjusting the robot pose. The obstacle-crossing flows were presented, the pivotal step of steering obstacle-crossing was analyzed, the binary approximating principles were applied to search the robot obstacle-crossing pose satisfing the balance constraints.The solution method satisfing the balance constraints of the robot inverse kinematics was proposed,the robot steering and crossing obstacles under gravity balance conditions was realized. The research results show that the novel three-arm inspection robot has steering and obstacle-crossing capacity.
    Groove-Textured and Pit-Textured Surfaces to Suppress Friction-Induced Squeal Noise
    Hu Lihong, Mo Jiliang, Wang Dongwei, Yang Jiangzhou, Chen Guangxiong, Zhu Minhao
    2016, 27(09):  1158-1164. 
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    Groove-textured surface with different widths and pit-textured surface with different diameters were manufactured on brake disc materials of the trains. Experimental test and numerical simulation were performed to investigate the influences of textured surface on friction noise by comparing the case of smooth surface, and consequently revealed the mechanism of the effects of textured surface on the friction vibration and noise. The results show that high-frequency squeal will be significantly suppressed by the two textured surfaces, and the groove-textured surfaces with specific dimensional distribution show good potential in reducing and suppressing squeal. Numerical analysis might be used to reveal the mechanism of the effects of textured surface on interfacial friction noise. A impulse force between the specimens is generated when friction material sliding across the edges of the grooves or pits, which plays a key role in friction noise active control at interface and suppresses the generation of some specific high-frequency squeal.
    Experiments and Simulation of Ejection Seat Impact Dynamics
    Han Bing, Liu Geng, Wu Liyan, Zhou Hao
    2016, 27(09):  1165-1168. 
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    An experiment of ejection seat was built by studying aircraft ejection escape device, the responding curves of the ejection seat and the displacements of the impact were measured. The model of experimental work conditions of ejection escape were simulated by the nonlinear finite element software DYTRAN. The numerical simulation was carried out for ejection seat impact dynamics, and the impact load response rules were analyzed. The simulation results of response rules have perfect corresponding with the experimental data.
    Mechanism Design and Analysis of a Novel Hydraulic Driving Heavy Load Forging Robot
    Li Geqiang, Wang Shuai, Deng Xiaozhong, Zhou Bin
    2016, 27(09):  1168-1175. 
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    This paper put forward a new mechanism project aiming at the characteristics of large load, fast moving speed and high positioning precision of a hydraulic driving heavy load forging robot. The scheme might realize 5-DOF motion, which contained body walking, body rotation, clamp expansion, clamp lifting, clamp rotation and clamp gripping. The main body of the movement was a kind of hybrid mechanism, which was composed of three groups of parallelogram mechanism, it was driven by three groups of hydraulic cylinders in parallel. This scheme might increase the working space of the robot effectively, making the load allocation reasonable and be easy to control. Kinematics and dynamics model were established, the motion planning of the robot clamp was based on sine curve, the change curves of displacement and driving force of each hydraulic cylinder were obtained in MATLAB. The correctness of the model and the rationality of the mechanism were verified, the scheme provides a solution for the design of heavy load forging robot mechanism.
    Abrasion Properties of Composite Sliding Guideways for Gear Hobbing Machines
    Li Xianguang, Yang Yong
    2016, 27(09):  1175-1183. 
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    In order to master the abrasion properties of composite sliding guideways of gear hobbing machines, based on the principle of crawl of vibration theory, Reynolds theory, and the working condition parameter of composite sliding guideway, a model of the stable attrition phase was established to calculate the attrition depth of changing with time, the experimental project for test the attrition depth of composite sliding guideway of the gear hobbing machine was proposed, and the corresponding experimental apparatus were developed successfully. The attrition depth were tested with the sample parts of composite sliding guideway of gear hobbing machine, the theoretical calculations were compared with the experimental values.It is shown that the relative error of the results is lower than 5%. The above analyses indicate the effectiveness and validity of the proposed method, which has beneficial reference value and instructive significance for optimum oil groove structure, geometry parameter, and oil film load-bearing capacity design, and type selection of composite sliding guideways on gear hobbing machines.
    Impact Feature Separation Method Based on FSWT Zoom Time-frequency Spectrum De-noised by SVD
    He Zhijian, Zhou Zhixiong
    2016, 27(09):  1184-1190. 
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    In order to extract the impact features of rolling bearings effectively,an impact feature separation method was proposed based on FSWT zoom time-frequency spectrum de-noised by SVD. Firstly, the original signals were analyzed by FSWT to get their whole time-frequency distributions. Then the interesting time-frequency region could be selected according to the time-frequency energy distribution characteristics, furthermore the fault characteristics region could be separated by a zoom analysis to the interested time-frequency region with higher resolutions. So as to inhibit the influences of the noise on the accuracy of zoom time-frequency distribution maps, FSWT zoom analysis was integrated with the SVD de-noising process, the FSWT zoom analysis time-frequency distribution matrix was de-noised by the SVD singular value difference spectrum threshold de-noising method to make the impact features outstanding. Finally, the fault impulse signals were separated by applying the FSWT inverse transform to the de-noised zoom analysis time-frequency spectrum. The simulated analysis and actual fault diagnosis example results demonstrate the impact feature separation method based on FSWT zoom time-frequency de-noised by SVD may extract the periodic impact features from low SNR signals and accomplish the fault diagnosis of rolling bearings.
    Study on Rolling Bearing Fault Diagnosis Based on EEMD and MFFOA-SVM
    He Qing, Chu Dongliang, Mao Xinhua
    2016, 27(09):  1191-1197. 
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    Both of the time domain and frequency domain of the vibration signals would be changed when rolling bearing faults occured. A rolling bearing fault diagnosis method was proposed based on EEMD, MFFOA and SVM. EEMD was used to decompose the fault signals, and to calculate the root mean square value and frequency of the center of gravity, achieving the normalization processing feature vector. In order to improve the classification accuracy rate, a MFFOA-SVM model was built, and then the feature values were extracted for training and testing, so that it might recognize the faults or not and the degree of pitting corrosion failures. The actual signals were analyzed and diagnosed, and compared with genetic algorithm optimization results, it proves the validity of the method, and the improved method has a good prospect for its applications in rolling bearing diagnosis.
    Fault Diagnosis of Bearings Based on Morphological Filter and Laplace Wavelet
    Zang Huaigang, Liu Zihao, Li Yukui
    2016, 27(09):  1198-1203. 
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    Under stronger noise background,the extraction of the impulse responses appearing in fault vibration signals was usually affected by noise around. Aiming at this issue,an envelopment analysis method was proposed to diagnose localized defects in bearings based on the mathematical morphological filtering and Laplace wavelet. Firstly,to filter the complex noises in the signals with morphological filter and to enhance the impact features of signals, then,the impulse responses were extracted by Laplace wavelet correlation filtering method. At last,the envelope spectrum analysis was carried out on the correlation coefficient of impulse responses.  The advantages of morphological filter and Laplace wavelet were combined, which might accurately capture the fault pulses under strong noises. This method was applied to bearings fault diagnosis of the inner rings and outer rings. It is nice to verify the effectiveness of the proposed method by the results of the fault detection comparing with the traditional envelope spectrum analysis.
    A New Structural Damage Identification Method Based on Kriging Surrogate Model
    Guo Junlong, Ma Liyuan, Li Yongjun, Wang Tianhui
    2016, 27(09):  1198-1203. 
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    A new damage identification method was proposed based on Kriging surrogate model. The initial samples were used to construct the initial Kriging surrogate model to represent the relationship between the dynamic response and the structural damage parameters instead of  that between the dynamic response and the structural physics parameters. Reducing the finite element mesh generation and the finite element calculation during the damage identification effectively, the efficiency of damage identification was improved. Updating the Kriging surrogate model by sampling criterion, making sure the Kriging surrogate model might exactly describe the relationship between the dynamic response and the structural damage parameters. A numerical example of a tube and grider structure was given to prove the effectiveness of the method. Finally, the method was used in damage identification of a missile launch platform model. The results show that the method is effective.
    Design Methods of Constrained Damping Specimen Used in Measurement of Viscoelastic Damping Material's Mechanics Parameters
    Wang Chao, Lü Zhenhua, Gu Yeqing
    2016, 27(09):  1208-1214. 
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    The sandwich specimens with supplemental structural damping were frequently used in the measurement of mechanics parameters of viscoelastic material with low stiffness through flexural resonating cantilever beam method (FRCBM), so appropriate designed specimens might assure the accuracy of experimental results. Through sensitivity analysis, influence coefficient was proposed and used in the precision analysis of experimental results which were affected by the measurement accuracy of thickness ratio, resonance frequency ratio, density ratio and loss factor of the specimen, and some significant technical specifications were proposed to help design specimens. Finally, the applicability of the sandwich specimens used in the measurement of viscoelastic material's mechanics parameters through FRCBM was analyzed.
    Kinematics Analysis of a 3-DOF Symmetrical Rotational Parallel Mechanism without Intersecting Axes
    Chen Ziming, , Huang Kun, , Zhang Yang, , Ding Huafeng, Huang Zhen,
    2016, 27(09):  1215-1222. 
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    The traditional 3-DOF rotational PMs also called as spherical parallel mechanisms(SPMs) usually had a rotation center which was the intersecting point of multiple revolute joint axes. This strict geometric conditions were very hard to fulfill in the manufacture processes and would restrict further applications of this kind of mechanisms. Thus, a PM with three rotational DOF and no intersecting axes was designed herein. It consisted of three identical limbs distributed symmetrically without intersecting axes in or between limbs. The inverse kinematics was solved and four symmetrical assembly modes were obtained. Then the singularity of the mechanism was analyzed and classified into three types: limb singularity, platform singularity and actuation singularity. At last, its orientation workspace was studied. This mechanism can realize three dimensional rotations with large workspace and is easier for manufacturing and assembly, so it has broad application prospects.
    Optimization of Pressure Side Slider Series Four-bar Linkage Working Mechanism Used by Double-action Press
    Jia Xian, Zhao Shengdun, Fan Shuqin, Tan Shuanbin
    2016, 27(09):  1223-1228. 
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    Concerning the side-pressing effects and large displacement variations in  outer sliders conducting side-pressing action by unreasonable lengthes and angles of truss system in J45-315 closed single-point and double-acting drawing press, an optimized mathematical model of the organization was built by using step-length searching method to optimize the variations of displacement shifts. After optimization, the variations are deduced from 0.092mm to 0.015mm, which means the pressing angle adds 3.4% while the variation is decreased to 83.7% of the original. The stamping property of double-acting mechanical press can be effectively increased and it lays a foundation for the optimization of working organizations when double-acting mechanical press conducts side-pressing action driven by outer sliders.
    Vibration Assisted Milling for Bionic Surface Manufacturing#br#
    Bai Lijuan, Zhang Jianhua, Tao Guocan, Shen Xuehui, Wang Jinjun,
    2016, 27(09):  1229-1233,1242. 
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    In order to explore the feasibility of bionic surface feature manufactured by feed direction vibration assisted milling, tool and workpiece separation conditions were derived from mathematical calculation, and the tool path was simulated with reasonable analysis scheme. Then the results were compared with vibration assisted milling experimental surfaces and specific biological surfaces. It turns out that vibration assisted milling surfaces and specific biological surfaces have similarity in topography, which proves that vibration assisted milling is feasible in the field of bionic surface manufacturing.
    Structure Optimization Design of Hydrostatic-dynamic Journal Combined Finite Volume Method with Orthogonal Experimental Design Method
    Meng Shuguang, Xiong Wanli, Wang Shaoli, Lü Lang, Zheng Lianggang
    2016, 27(09):  1234-1242. 
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    Due to the problem of operating performance optimization of  hydrodynamic-static  hybrid journal with orifice restrictor, based on the calculation model  of  parallel plate diffusion  flow and the principles of flow  conservation,a interpolation function of the boundary pressure for the micro control volume was derived.A method belonged to the finite volume method was proposed to calculate the characteristics for a kind of deep-shallow recess bearing,including load capacity,bearing stiffness,flow rate and temperature ascending relationship.The method was used to study bearing characteristics with different structure parameters and working parameters,such as supply pressure,spindle speed,oil  inlet  aperture,shallow depth and initial oil film thickness.Then,the optimization ranges of the above parameters  were obtained. Under the preconditions of satisfying multi-objective optimization,the optimal combination of the structural parameters and operating parameters of the bearing was deduced, using a orthogonal experimental design method which named four factors three levels.The deep-shallow bearings with orifice restrictors were trial by the optimal parameters, and an experimental platform was established. The pressure values of oil cavity were measured with different rotational speed and supplying pressure. The results show that the trend of experimental data and numerical simulation results for spindle speed are consistent, and the error is within 11%. The reliability of the structure optimization design method for the deep-shallow bearings with orifice restrictors is verified, which combines the finite volume method with orthogonal experimental method.
    Type Synthesis of Three-rotational and One-translational Decoupling Parallel Mechanisms
    Chen Hai, Qin Youlei, Cao Yi,
    2016, 27(09):  1243-1250. 
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    Based on the screw theory and driven-chain principle, a method of structural synthesis of decoupling three-rotational and one-translational (3R1T) parallel mechanisms was proposed according to the analysis of input and output characteristics of decoupling parallel mechanism. Firstly, because of the demands that the Jacobian matrices of decoupling parallel mechanisms had to be non-zero diagonal matrices, the direct and the inverse Jacobian matrices were constructed by screw theory. Then, the effective screws, the actuated screws and the mobile un-actuated screws of each limb were established based on reciprocal screw theory and all possible topology structures fulfilling the requirements were performed in the light of different connectivities of the limbs. Finally, the decoupling 3R1T parallel mechanism was obtained by the connection of 4 limbs with the moving platform and fixed platform in terms of the parallel mechanism kinematic principles.The outputs of the synthesized parallel mechanism were provided by the independent input-driven of each chain. This decoupling parallel mechanism is compact, which can be controlled with ease and has a certain prospect.
    Structure Parameterized Design for a New Mechanical Elastic Wheel
    Yan Lele, Zhao Youqun, Fu Hongxun, Wang Qiang
    2016, 27(09):  1251-1256. 
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    It usually required repeated design when subtle changes in the structure sizes or mechanical elastic wheel structures did not meet the requirements of strength, stiffness and so on, so the cycle of design and analysis was obviously prolonged. Aiming at such problems, based on the theory of parametric design and secondary development for Pro/E, a platform for structural parametric design of mechanical elastic wheel was developed. The platform realized the strength and size check, structure size checking, automatic generation for 3D parts model and engineering graphics, virtual assembly, et al, at the same time, it avoided the complications of design data by consulting the national standard and engineering manual in the traditional design. Running examples show that the mechanical elastic wheel structure parametric design can be realized by the technology and methods presented herein.
    Global Optimization for Electric Vehicle Equipped with EMCVT Based on Shifting Energy
    Ye Ming, Ren Hong, Li Xin
    2016, 27(09):  1257-1262. 
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    Integrating motor efficiency, battery state of charge (SOC) and EMCVT efficiency, the global optimization of EV equipped with EMCVT running in new Europe driving cycle (NEDC) was carried out based on dynamic programming. In this optimization, SOC and transmission ratio were state variable and decision variable respectively. Ratio shifting model was built to estimate energy consumption during shifting. New optimal control strategies were achieved by taking shifting energy consumption into cost function. With this control strategy, shift times and fuel consumed are both reduced.
    Research Progresses of Ductile Fracture and Blanked Surface Quality in High-speed Blanking
    Chen Minghe, Hu Daochun,
    2016, 27(09):  1263-1271. 
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    The smooth edge formed by shear crack propagation in plastic zone and premature fracture initialized by void growth and coalescence in blanking process were introduced, the mechanism of blanking ductile fracture and the determination of fracture parameters were explored with meso-damage theory. The influences of the processing parameters upon the blanking quality, the effects of material softening due to the heat generated during plastic work, and the microstructure of blanked surface were critically reviewed. Then the key problems for the development of high-speed blanking were discussed, and the viewpoints of future development of ductile fracture and blanked surface quality were proposed.
    Advances in Sphericity Measurement Technology of Micro Sphere#br#
    Huang Qiangxian, Hu Xiaojuan, Bian Yakui, Mei Jian, Zhang Liansheng, Chen Lijuan
    2016, 27(09):  1271-1277. 
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     Firstly, the present sphericity measurement techniques of micro sphere were divided into contact and non-cantact measurement technology according to their principles, and the latter was mainly based on optical image or laser interferometry. Then, the domestic and foreign research progress of sphericity measurement techniques of micro sphere were reviewed and compared, and the main problems of them needed to be solved were listed. In order to overcome the shortages of these techniques, such as low accuracy, lager object size, limit of object material, et al, new developing sphericity measurement techniques of micro sphere were discussed. Finally, the summary and prospect of sphericity measurement technology of micro sphere were given.