Table of Content

25 January 2011, Volume 22 Issue 2

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A Molecular Dynamics Study of Chip Formation on Nano-grinding Processes

ZHANG Wei-Wen, GUO Gang, HUANG Yun, HUANG Zhi

2011, 22(2):  127-132. 

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A study of chip formation of nano-grinding process using molecular dynamics method was presented. Based on the MD simulation results, the nano-grinding processes were analysed using the equivalent stress distribution, temperature field and neighboring changing ratio distribution.Then a chip formation model of nano-grinding was presented, and the chip formation mechanism of nano grinding was proposed.

Moreover,it is found that {111} slip deformation occurres under the work piece subsurface while large pressure is applied on the grit.

Design of Raceway Groove Structure for Megawatt Wind Power Generator Yaw Bearings and Life Studies

LI Yan, SHU Liang, XIAO Ji-Meng, LI Chu-Juan

2011, 22(2):  132-137,143. 

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According to the actual withstanding wind loads of wind power generator yaw bearings, using theoretical design and calculation methods,it was designed for megawatt yaw bearing on the raceway groove structure, and checked the static load bearing capacity and dynamic life. Afterwards, a three-dimensional model was established for yaw bearings using the finite element analysis method, the fatiguing life analysis of bearing model was specifically conducted based on united loads, overturning moment and boundary conditions. Then, the fatiguing life numerical simulation including contact stress, strain, and fatigue life was acquired for wind power generator yaw bearings in the loading process. Eventually, theoretical design calculations and the finite element simulation results were verified the proposed design meets the application requirements and can guarantee the calculation precision.

Neural Network Control Based on Hybrid Trajectory of Space Flexible Manipulators

HONG Zhao-Bin, CHEN Li

2011, 22(2):  138-143. 

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A sliding mode-neural network scheme based on hybrid trajectory was proposed to track the hybrid trajectory of a space flexible manipulator, meanwhile, the flexible vibration can be suppressed. In order to actively suppress the flexible vibration, the hybrid trajectory for sliding mode-neural network controller was generated by using the virtual control force concept, which reflected the flexible variables as well as the rigid desired trajectories. Based on the hybrid trajectory, the new sliding mode-neural network control can be designed. Simulations results confirm that the proposed control scheme can dominates the trajectory tracking the coordinated motion and actively suppress the vibrations in the presence of parameter uncertainty.

Analysis and Modeling of Dynamic Error Compensation of CMM

LIU Yi, QU Ying, LUO Zai, KONG Meng

2011, 22(2):  144-148. 

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In order to resolve the problem of reducing the dynamic errors for CMM,the dynamic error sources were firstly analyzed. A model of CMM’s dynamic errors was built up with BP neural network, which broke through the limit which was modeling only for each component of the system. Also the derivation of complicated mathematical relationships can be avoided. As the BP network has the problem of

local minimum value and its approximation rate is slow,the particle swarm optimizer algorithm for BP network was introduced. Initial weight of BP neural network model for CMM was optimized by PSO, and it can improve the ability of global optimization for BP network and processing speed. In order to get training data a standard ball was measured on CMM of type Global Class 9158, and error compensation model was established.Experiments were made to verify the model. Results show that the mean error of CMM can be reduced 2.3μm by using the model.

Effect of Time-varying Friction Coefficient on Dynamics of Spiral Bevel Gears

WANG Shi-Long, FENG Chi-Heng, LEI Song, XIAO Gong

2011, 22(2):  148-152. 

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A generalized 3-dimensional multi-DOF dynamics model for spiral bevel gears was proposed and the influence of time-varying friction coefficient on the gear dynamic responses was analyzed. Mixed EHL model was also proposed to predict the instantaneous friction coefficient at each contact grid cell along the contact zone.

The comparison results to published empirical friction coefficient formulae show that mixed EHL model can predict friction coefficient more accurately.Lastly,comparing to time-varying friction coefficient, constant friction coefficient and without friction case,

 the simulation results of dynamic meshing forces and dynamic transmission errors are demonstrated that sliding friction and time-varying friction coefficient have greater effects on dynamics of spiral bevel gears.

Kinematics Characteristics Research of Spherical 4R Mechanism and Its Application Explore

ZHOU Xiang-Qin

2011, 22(2):  153-158. 

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In order to apply spherical 4R mechanism to meet various reciprocating movements,based on spherical 4R weft insertion mechanism of GTM rapier loom, an output kinematics function of mechanism was established. Some important properties of kinematics function were proved with mathematic method, and the mapping between structure parameters and appearance of kinematics function curve was built. After creative design some structural parameters, some different appearances of kinematics function curve were obtained and the mechanism was changed. This changed mechanism can be used in designing weft mechanism and shed mechanism.The results indicate that many kind of applications can be obtained by reasonably combining two structure parameters in spherical 4R mechanism.

Optimization of Grinding Conditions and Prediction and Control of Surface Roughness

CHE Long-Zhu

2011, 22(2):  158-161. 

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Based on S/N-ratio experimental design and quadratic regression design technique, the effects of spindle speed, workpiece speed, depth of cut and grain size of wheel on the surface roughness of workpiece during plane grinding were investigated.It is found that the successive impact factors for the surface roughness are grain size, depth of cut, spindle speed and workpiece speed, respectively.An unary

linear regression model about the surface roughness was established and tested by F method. The test results show the significance level of the unary linear regression model is 0.01, which means a good regression effect.

Fatigue Life Prediction of Aeronautic Rescue Mechanism under Random Vibration Based on Sample Approach

GAO Qing-Zhen, WANG Yao-Hua, ZHANG Xiao-Na

2011, 22(2):  162-165. 

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The vibration fatigue life prediction process of an aeronautic rescue mechanism was discussed based on the analysis of sample approach. Consequently, the calculational steps were displayed detailedly to obtain the rescue mechanism fatigue life that was contrasted with test results. It indicates:the predicted results show a good agreement with the experimental data and the error between them is as 7.02%, which validates the fatigue life estimation result and demonstrates the suitability of sample approach. 

Research on Mechanisms of Locust’s Jumping Legs

CHEN Dong-Liang, TUN Lei, WANG Kang, FANG Kun, ZUO Yong-Qing

2011, 22(2):  166-169. 

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Based on the research of hopping mechanisms and hopping leg’s muscle structure of a locust, a kind of 3D model of hopping leg’s mechanisms was built, and the trajectory of the locust’s leg jumping was described by a kind of bionic four-bar linkage. The mechanisms and mechanics of this four-bar linkage were analyzed, and the curve of mechanical advantage and forces on foot cusp were worked out. Furthermore, a bionic prototype, based on the four-bar linkage, was manufactured.The results indicate the prototype has high bionic characteristics and good jumping ability.

Innovative Design and Analysis of Membrane Coupling with Compensatory Membrane

WANG Liang-Shen, ZHENG Lei, ZHENG Gong-Xia, HOU Jie

2011, 22(2):  170-173. 

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In order to solve the problem of frequent failure for traditional membrane coupling,a new membrane coupling with compensatory membrane was designed based on the contradiction matrix of TRIZ theory. In addition,fatigue stress for traditional coupling and membrane coupling with compensatory membrane

was analyzed by CosmosWorks. As a result:the high-stress zone and lower safety factor zone are located around gemels. So that damage may often be done at the zone; at the same condition, the high-stress zone and lower safety factor zone are reduced and anti-fatigue ability is increased in new coupling construction compared with traditional ones.

Analytical Robust Design of Trunk Type Headstock of Large Internal Gear Milling Machine

WANG Han-Chao, CHEN Yong-Liang, ZHANG Jian, GU Pei-Hua

2011, 22(2):  174-178,226. 

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For the needs of analytical robust design of trunk type headstock of internal gear milling machine, a theoretical model of the headstock was established. The formulas of natural frequency and deformation were derived respectively with Rayleigh method and integral method. The robust analyses of the headstock structure show that the headstock inner and outer wall thickness make a greater impact on the deformation. After optimization, the integrated static stiffness increases by 4.69%,the mass increases by 0.3%, and first-order natural frequency increases by 4.9%.The variances and sensitivity of all functional requirements declines generally, which greatly improves the robustness of the headstock.

Solving for Vibration Problem of Grinding Block Holder of Polishing Machine Grinding Head and Experiments

XU Bin, SHAO Dun-Feng, LIU Jia

2011, 22(2):  179-184. 

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In order to investigate the influences of vibration frequencies of grinding block holder on tile fragmentation and grinding efficiency,combined with a given example of prevalent applied large size swing-style tile polishing grinding block holder,the holder of polishing grinding block was simplified as a cantilever beam.Natural frequency of transverse vibration of the grinding block holder was obtained, according to the finite difference equations of grinding block holder.K was revised by extrapolation method. By sample analysis, natural frequency of transverse vibration of the grinding block holder is 5.68Hz. It will produce resonance when the spindle frequency and grinding block holder frequency of the step come closer, the resonance is the main reason of tile fragmentation. The results were verified through experiments. The spindle frequency can be controlled within 8.7Hz range. As a result, high grinding efficiency, low tile fragmentation can be achieved.

 

Optimization Construction of Collaborative Manufacturing Chain Based on Distance Model of Manufacturing Task Parameters

CHENG Fang-Qi, XIE Fei-Fan

2011, 22(2):  184-189. 

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To construct an effective collaborative manufacturing alliance of enterprises under network environment, a conception of CMC was presented.Through analyzing the formal description of the manufacturing task parameters and the optimization construction process of CMC,an optimization model based on the distance of the manufacturing task parameters was founded. Based on the adaptive genetic algorithm,

a case calculation was conducted with the manufacturing process of a metal product enterprise. The calculation analysis indicates that it is better than that of the TOPSIS approach in extending the effective search interval. The results show that it is feasible to optimize the CMC from the manufacturing task parameters.

Multi-objective Optimization Scheduling for Job Shop of Batch Production with Multiple

 Process Flows

CENG Jiang, YANG Yo, WANG Yong-Zhi, CHENG Bo

2011, 22(2):  190-196. 

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A multi-objective optimization scheduling method for Job shop of batch production with multiple process flows was proposed. Aiming at the scheduling characteristics of job shop of batch production with multiple process flows, a multi-objective optimization model was established with the objectives to minimize the makespan and the manufacturing cost. An improved multi-objective optimization NSGA-II algorithm for the model was presented and designed. In the algorithm, four new techniques were introduced: object-oriented technique, segmented variable length coding technique,

segmented hybrid crossover and mutation technique and delicacy scheduling technique.The effectiveness of the proposed method was validated by case studies.

Research on Three-ply Reconfigurable CNC System 

WANG Chao, LIU Qing-Jian, WANG Ta-Yong, WANG Li-Wen

2011, 22(2):  197-201. 

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A software-hardware reconfigurable platform of CNC system was proposed.Then the reconfiguration strategy of hardware system was given and a guided software-reconfiguration development platform was designed. Through analyzing the functions of CNC system,the system reconfiguration was divided into kernel-function reconfiguration, task-function reconfiguration and auxiliary-function reconfiguration. On the basis of that, the interaction and co-design of hardware reconfiguration, software reconfiguration and modular reconfiguration was discussed.

Variable-metric Algorithm of Maximum Entropy for Reliability Evaluation Oriented Prior Information

DAI Yi, WANG Zhong-Min, LING Guang

2011, 22(2):  201-203. 

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The problem of how to obtain Bayes prior distribution for NC system oriented reliability evaluation was discussed, and then a nonlinear constrained optimal model of probability density function based on the principle of maximum entropy was established. By using Lagrange multiplier this constrained optimal problem was transformed to a non-constrained optimal one, which was solved rapidly by BFGS variable-metric algorithm. The simulation examples show that this method is simple and effective.

Non-priority Maintenance Activity and Modeling Based on Petri Net

QU Chang-Zheng, XU Yong-Li, DAO Feng-He

2011, 22(2):  204-207. 

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In order to describe the activity relationship of maintenance processes,a concept of non-priority maintenance activity was brought forward, and the similarities and differences comparing with traditional maintenance relations were analyzed.The non-priority disassembly and non-priority maintenance process model were constructed based on Petri net, where operation characteristics were represented by process of Petri net. Applying the model, an equipment maintenance process was analyzed, which validated the effects of non-priority maintenance activity upon maintenance process. 

Mechanism of Magnetic Force and Electromagnetic Torque for Spherical Reluctance Motor with Magnetic Levitation

CENG Li, WANG Jun, ZHANG Dan

2011, 22(2):  208-211. 

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This paper presented a novel multi-degree-of-freedom spherical reluctance motor with magnetic levitation,and analysed mechanism of magnetic force and electromagnetic torque that spherical motor generated.A comprehensive control of the spherical motor was conducted and analysed.The simulation experiments show that the state synchronization suspension control owns high precision and immunity to interference.

Internal Cylindrical ELID Grinding Experiment of Bearing Rings

YANG Li-Jian, LIN Cheng-Jie, JIN Xin-Min

2011, 22(2):  212-214. 

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A novel internal cylindrical ELID grinding method was proposed,which used a conduction work piece as the cathode directly, and cast-iron-bond CBN wheels as the anode. In the grinding process, the work piece electrode dressed the wheel to maintain the grinding process as same as traditional ELID grinding, and the stability of grinding process was ensured.Surface roughness value Ra0.03μm can be obtained by using W10 wheel.

Study on Frequency Response for a 2D Digital Servo Valve

LI Qing, RUAN Jian, MENG Ban

2011, 22(2):  215-219,242. 

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The working principles of a 2D digital servo valve were described firstly, then the mathematical model of electro-mechanical converter was established and simulation analysis was executed. Finally a special controller for 2D digital servo valve was designed and the experimental research of electro-mechanical converter and the prototype of 2D digital servo valve were performed. Both theoretical simulation and experimental study illustrate that the electro-mechanical converter has an excellent dynamic response

whose frequency width is 250Hz at -3dB and -90° approximately, and the frequency width of 2D digital servo valve is about 130 HZ at 25% maximum spool displacement.

Influences of Three-route Gas Flows on Powder Converging Behavior in Coaxial Powder Feeding Nozzles

FU Wei, ZHANG An-Feng, LI Di-Chen, SHU Gang-Xian, LU Qiao-Bo, LU Zhong-Liang

2011, 22(2):  220-226. 

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In the laser direct metal manufacturing process with coaxial powder feeding, when the powder was injected to the molten pool in the substrate,some of the metal powders would rebound. The rebound powders would clog nozzles and the dusts would pollute the laser lens. As a result, a mid-route gas was introduced. When the three-route gas (the mid-route gas, the carrier gas and the outer shielding gas) was simultaneously injected under hindered jet condition, by using the discrete phase model of FLUENT software, the influences of each gas on powder convergence were studied respectively to determine the range of each gas flow rate. Then the optimal mix relationship of the three-route gas was simulated using orthogonal method in order to guide experiments. The influences on powder convergence of three-route gas were verified through indirect methods. The results show that:experimental results are consistent with the simulation ones.

Function Matching and Selection for Product Design Based on Dependency Constraints

LIANG Hua-Dong, GE Feng, YANG Yo, BAO Bei-Fang

2011, 22(2):  227-231. 

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Collaborative efficiency is crucial for the selection of function selection in product design; however, there is no sufficient facility or clear opinions provided by research work to address this now. Function dependency logic was defined by dependency analysis method in CT and digraph definition in graph theory(GT). Then function selection optimization model based on improved genetic algorithm was proposed with the definition of function coordination degree and part-function mapping relationship.Case study

 was demonstrated to illustrate the feasibility and applicability.

Study on Rotation Capability and Fatigue Strength of Elliptical Flexure Spherical Hinge

LI Cheng-Gang, YOU Jing-Jing, TUN Hong-Chao

2011, 22(2):  231-234. 

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Based on the Castigliano’s second theorem, the equations were formulated for the compliance and precision of an elliptical flexure spherical hinge. A new concept of compliance accuracy ratio of flexure spherical hinge was proposed, which was used as the performance index of hinges. Optimization was done, and the results show that materials of hinges should be with high elastic modulus and low shear modulus; all of the wide-angle, the ratio of long half axis to short half axis and the ratio of the minimum thickness to short half axis of ellipse should be as little as possible on the premise of ensuring strength. A view point was proposed,that fatigue strength must also be considered except for improving performance while designing the flexure hinges, and the check formula of fatigue strength was derived. 

Digital Synchronic Control System for Twin-arc Co-pool High Speed Submerged Arc Weld(SAW)

HE Kuan-Fang, HUANG Dan-Sheng, LI Hua-Jun, XIAO Dong-Meng

2011, 22(2):  235-239. 

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A digital synchronic control system for twin-arc high-speed SAM was presented by IPC(industrial personal computer) and PLC.By adopting the way of software programming, the functions of parameters optimization settings, digital control for the timing of twin arc-starting and arc-ending were achieved, which was to achieve precise control of arc energy parameters and to guarantee stability of synchronic control among the arcs. The design of hardware and software of the digital synchronic control system was also discussed. The results of weld experiments demonstrate that the developed digital synchronic control system meets the design requirements. The process of the twin-arc high speed SAW are stable, perfect forming of weld seam, which achieves technology of twin-arc high-speed SAW.

Formability of AZ31 Magnesium Alloy Sheet under Warm and Electromagnetic Forming Condition

MENG Zheng-Hua, HUANG Chang-Yu, HU Jian-Hua, HU Ting-Ting

2011, 22(2):  239-242. 

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EMF and warm forming were combined to improve the formability of Mg alloy sheets herein.The limit strains of AZ31 magnesium sheet using warm and electromagnetic forming (WEMF) at different temperatures (25-230℃) were obtained. The forming limit diagrams (FLD) of AZ31 magnesium sheet under WEMF conditions were established to contrast with FLDs of traditional warm forming. The results show that: the forming limit of AZ31 sheet of WEMF increases with the temperature; in comparison with EMF and warm forming respectively, WEMF improves the formability of Mg alloy sheets. 

Aerodynamic Optimization of Cross Sectional Shape for a Sports Car’s Rear Wing Based on Kriging Surrogate Model

RONG Jiang-Lei, GU Zheng-Qi, YANG Yi, JIANG Chao, YIN Yu-Qi

2011, 22(2):  243-247. 

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A method which combined numerical optimization with CFD optimization was discussed. A sports car’s rear wing was optimized by this way, firstly the cross-section of rear wing was parameterized by NURBS curves, then the method of Latin design of experiments was adopted to generate test sample points, and mathematical model was built based on the Kriging approximation model, at last the global optimization design was preformed.The drag force of the optimized vehicle reduces by 2.35%, while the negative lift force increases by 25.93%, so its aerodynamics is improved greatly. The results show this method can provide certain engineering guidance for the aerodynamic optimization of car accessories.

Steering Ability Analysis of Rhombic Vehicle Based on Flexible Dynamics

CHA Yun-Fei, ZHONG Zhi-Hua, YAN Xiao-Lei

2011, 22(2):  247-251. 

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Since the deformation of vehicle frame will lead to axial steering, a flexible two freedom model of rhombic vehicle was modeled considering the attached angular displacement produced by axial steering.The rhombic vehicle was simplified as the continuous beam supported by three points, the relationship among the attached angular displacements produced by axial steering and the lateral acceleration was analyzed by three moment equations. The comparisons between the flexible two freedom model and the rigid two freedom model of the rhombic vehicle suggest that the deformation of the vehicle frame affects stability of the rhombic vehicle, reduces the flexibility of the rhombic vehicle and reaction capability of the rhombic vehicle to the driver’s operation.