Table of Content

25 August 2015, Volume 26 Issue 16

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Dynamics and Fault Analyses of Certain Airplane Nose Landing Gear Emergency Lowering

Yin Yin, Nie Hong, Wei Xiaohui, Zhang Ming, Ni Huajin

2015, 26(16):  2131-2136. 

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 A dynamics model of nose landing gear retracting system was developed to analyze the emergency lowering faults of an airplane. The landing gear loads were analyzed and calculated during emergency lowering under different modes, based on which the reasons the emergency lowering failed were analyzed in detail and two improved methods were discussed. The results show that, at the end of the emergency lowering, the beneficial torque mutation produced by the spring happens after the adverse torque mutation by the front door. Thus, the total torque will appear to be negative for some times, which will cause emergency lowering faults. The increase of the flight speed is harmful to emergency lowering. Based on analysis results, requirements of nose landing gear emergency lowering can be satisfied by changing the way of the front door retraction linkage.

Experimental Study  of  Surface Integrity  for  Hardened Mould Steel ANSI  D2 Using Dry Grinding

Guo Weigang, Zhao Congrong, Wu Xiaosu, Yuan Julong, Deng Qianfa

2015, 26(16):  2137-2142. 

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Dry grinding  was  widely  used in the manufacturing of  mold because of  its advantages including high machining efficiency,low cost and little pollution.As  one of  the last steps in  the manufacturing process,the  ground  surface integrity determined the product  quality and life.Herein  surface integrity of hardened mould steel ANSI D2 under dry grinding  was experimentally studied. the influences of feeding speed and cutting  depth  on surface integrity including the surface structures,micro-hardness, surface roughness and residual stress were studied,which provides guidance for the determination of grinding parameters and the optimization of dry grinding process of hardened mould steel.

Chatter Depression of Boring Rod Based on Friction Energy Dissipation

Yan Junxia, Ou Bingxian,

2015, 26(16):  2143-2148. 

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 Principles of boring rod with friction energy dissipation were discussed, a mechanics model with nonlinear Coulomb dry friction link was established, and taking friction parameters as variables the vibration absorbing performance was studied through numerical analysis. A new type boring rod was developed based on friction damping principles, combining flutter mechanism and cutting stability theory, vibration suppression effects of boring rod were analyzed under different friction conditions. Contrasting the results of cutting experiments with theoretical simulation, it has sliding friction state and adhesive state in established friction damper, and there is a positive pressure that makes energy consumption by sliding friction to reache the maximum but the system is not in the adhesive state, at this time the system achieves the best vibration suppression effect. Cutting experiments show that the boring rod with friction damping has good effect of chatter suppression.

Hysteresis Torsion Characteristic Model of Circumferential Arc Spring Dual Mass Flywheel

Zeng Rong, Zuo Ting, Jiang Zhengfeng, Chen Lei, Hu Wei

2015, 26(16):  2148-2153. 

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Torsion characteristics of DMF-CS were the effects of the torsional stiffness combined with the system damping, which sophisticatedly explained the vibration isolation and damping characteristics of DMF-CS. With the simulation of the torsion characteristics of DMF-CS, the torsional hysteresis curves were plotted under different friction coefficients. The simulation results show that the hysteresis area increases with the friction coefficients, and the hysteresis curves are framed by the curve without friction force. According to the above results, the hysteresis torsion characteristics model of DMF-CS was established. The torsion characteristics experiments of DMF-CS were completed, and using the experimental data, the model parameters were identified. From comparison, the identification model is close to the experimental one, which validates the reliability of the established model.

Study  on Energy Saving Characteristics  of  Valve  and  Pump  Compound Control System  of  Fast  Forging  Hydraulic Press

Zhai Fugang, Li Xuebing, Yao Jing, Zhou Fang, Kong Xiangdong,

2015, 26(16):  2154-2159,2178. 

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Considering the energy source of fast forging hydraulic press,a kind of valve and pump compound control system on fast forging hydraulic press was proposed to reduce  the overflow loss and pressure loss of the system.The energy-saving mechanism of valve and pump compound control system was qualitatively analyzed  theoretically,and the system energy consumption was quantitatively studied by experiments.The experimental results show that energy utilization rate of valve and pump compound control system reaches 31.9%,and improves  nearly 5 times compared with electro-hydraulic proportional  valve control system.At the same time,the input power of valve and pump compound control system is only 18.4%  of  the proportional valve control system.The study results have important significance to improve energy utilization and reduce the energy consumption of the fast forging hydraulic press.

Full Vector LMD Energy Entropy in Gear Fault Feature Extraction

Wang Hongming, Hao Wangshen, Han Jie, Dong Xinmin, Hao Wei, Ouyang Helong

2015, 26(16):  2160-2164. 

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Gear vibration  signals  in the events  of failure were  often  non-stationary,non-linear.Energy  structure  would change in the fault signals,leading to different energy in different  frequency bands.LMD  was used  to  extract energy entropy of the vibration signals,and energy entropy was used as failure evaluation standards  for fault classification.It is easy to be misdiagnosed with the traditional single channel signal diagnostic method.Full vector LMD energy entropy integrated two-channel homologous  informations  of vibration signals, and reduced the misdiagnosis rate.Through  experiments  the gear  normal state,tooth root crack,broken teeth,missing teeth were simulated,and it is proved that with full vector LMD energy entropy as fault feature can achieve good fault classification results.

Study on Two-stage  Throttle  Port  Cavitation  Characterization

Li Sihai, Yuan Shihao

2015, 26(16):  2165-2169,2221. 

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The cavitation characterization of two stage throttle port was studied,and using classical cavitation definition σ,new-form cavitation characterization index  was obtained,which was applicable,to two stage throttle port.In the calculation formulae of new-form  cavitation  characterization index,all design parameters needed by two-stage throttle port  were included.Applying the calculation formule,cavitation characterization curves of  U  and  V  throttle ports were plotted,and it is observed from the plots that whether U or V throttle port, cavitation concentration region is always around section A2,and that the cavitation characterization index of section A2  when liquid flows into section A1  is always larger than that of  A2 when liquid flows out from section A1;the macroscopic phenomena is that flow rates of different flow directions are different, and also flow rate out of section A1  is  larger   than that of  flow rate into section A1.

A Hybrid Multi-objective Grid Genetic Algorithm for Automobile Production Sequencing Problems

Tang Qiuhua, Hu Jin, Zhang Liping, Cao Xiaojun

2015, 26(16):  2170-2178. 

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Three objectives were expected to be achieved simultaneously when sequencing automobiles in process,including equaling the spare parts consumption,minimizing the total  adjustment cost resulting from exchanging automobile models,calibrating the work position for each  automobile on any station.A new hybrid multi-objective grid genetic algorithm(HmoGA) was proposed based on  Pareto stratum. In the algorithm,a new rejection mechanism was first  considered in the sorting process of Pareto stratum,for the purpose of getting the even distribution of the non-dominated solutions.Then an adaptive grid selection scheme was  designed by integrating  Pareto stratum evaluation,crowding  degree  calculation and distance estimation among adjacent individuals.Thus,higher quality population can be generated,better parent chromosomes can be  selected,and the distribution of the Pareto front can be improved constantly. Finally,the 2-opt shift operator was hybridized into the proposed genetic algorithm so as to broaden the search space and escape from local optimum.Three groups of experiments have done and three metrics including  non-dominated ratio,the number of Pareto optimal solutions and the deviation of distances  between neighbors were used as the performance measures.The results reveal that the proposed HmoGA dramatically outperforms NSGA-Ⅱ in terms of convergence and diversification.

Optimization Method Based  on  Fuzzy Clustering and Cooperative Competition Game

Chen Jiaming, Song Xiaowen, Xu Hao

2015, 26(16):  2179-2182. 

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Aiming at the difficulty of transforming multi-objective optimization problem to game problem  which  was about determining the strategy set  for each partition of game players,a  multi-objective optimization method  was  proposed  by using uniform design  experimentation, regression analysis and F test statistic to obtain data bases for fuzzy clustering and combining cooperative competition game.Taking reducer design optimization as an example,performance of the method was analyzed and verified. Compared with the traditional single-objective  optimization  method,the experimental results show  that the  multi-objective method has fast convergence rate and high computational efficiency,and it is  unneccessary  to determine the weight of each target,which has engineering application values.

A  Assembly Process Operation Management Method of Mechanical Products Based on Internet of Manufacturing Things

Liu Mingzhou, Wu Kun, Ma Jing, Wang Qiang, Ling Lin

2015, 26(16):  2183-2190. 

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To solve the traditional mechanical  product assembly  process  problems such as poor information interactivity  and difficulty in assembly real-time  information  monitoring,this paper established the sensible assembly environment based on the IoMT,and proposed the assembly process operation management system structure  to achieve the acquisition,communication and value-added for the assembly process real-time information.Then combining with multi-Agent and KQML technology, an open and extensible operation management system of assembly process was developed, to implement the digitalization, visualization, and integration control on the assembly process.Finally,the proposed system was  applied in a pickup truck's welding workshop to verify the feasibility and effectiveness of the system.

Study on Preparation of Slurry and Properties of Micro Abrasive Slurry Jet

Wang Chengyong, Wang Rongjuan, Yang Peixuan, Wen Wu, Qiu Chunlin

2015, 26(16):  2191-2197. 

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Micro abrasive slurry jet is a new technology developed in the abrasive water jet machining technology. The sedimentation stability of slurry was improved by adding dispersant and suspending agents. For the preparation of a high quality drilling slurry, the influences of abrasive mass concentration, abrasive type, dispersant volume fraction and suspension volume fraction on glass micro-hole drilling were studied,and the influences of dispersant volume fraction and suspension volume fraction on the sedimentation stability of slurry were also investigated. The results indicate that abrasive mass concentration possesses a best value. Dispersant does not necessarily improve the sedimentation stability of the particles, which is related with the type of the abrasive, the abrasive mass concentration and the dispersant volume fraction and so on. Suspending agents can improve suspension of abrasive, its volume fraction affects the sedimentation stability of slurry and glass micro hole drilling.

Research on Limiting Fuzzy and PID Compensation with Threshold Settings Control for Flow of Variable Speed Hydraulic Source

Ma Yu, Gu Lichen

2015, 26(16):  2197-2202. 

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In view of the existing defects in speed control of variable speed pump controlled hydraulic systems，such as slow response, speed fluctuation and low control accuracy, especially in the fast-changing load conditions, due to the strong coupling characteristics of flow and pressure, flow control became uncertain, variable and highly nonlinear, conventional PID control or fuzzy control were difficult to obtain satisfactory control results. A limiting fuzzy and PID compensation with threshold settings control strategy was presented herein. The control system firstly used limiting fuzzy control, which had fast response of open-loop control to approach target flow, then adopted PID compensation with threshold settings control to eliminate the system steady-state errors，and had a fast response, no overshoot, high precision advantages. The simulation and experimental results show: this method can realize the precise control of flow of variable hydraulic power source on typical conditions. Significantly reducing the steady-state errors of slope response, system control performance is much better than that of simple traditional control methods, and is suitable for the on line control of volume speed modulation of variable speed system.

Reliability-based  Topology  Optimization  of  Implicit  Performance  Function  Structure

Wu Jinsong, Zhou Jinyu

2015, 26(16):  2203-2208. 

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Considering  the  impacts  of  uncertain factors such as external loading,material property etc.  on  structural safety in engineering practice,the topology optimization design with the  structural displacement reliability constrain was discussed.A  mathematical of topology optimization was developed,where the minimization of compliance was taken as objective function,the relative densities of elements were taken as design variables,the material volume fraction  and structural displacement reliability were taken as constraints. The response surface  method was implemented to approximately approach its real performance function, for the situation that the structural performance function was implicit by using finite element numerical method.Then,the simple and efficient first order second moment method was used to obtain the structural  displacement reliability.The strategy that inner loop was the deterministic topology optimization and the outer loop was to control the material volume fraction was implemented to carry out the reliability-based  topology optimization of continuum structure.Finally,two numerical examples  were given to be compared with the results of deterministic topology optimization showing that the design method is efficient and feasible.

Micro Multi-objective Genetic Algorithm Based on Grid Domination

Fu Chunming, Jiang Chao, Liu Guiping, Deng Shanliang

2015, 26(16):  2208-2214. 

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A micro multi-objective genetic algorithm was proposed herein based on grid domination to solve multi-objective optimization problems and it had good convergence and high computational efficiency. The method combined with the concept of the grid dominance and micro multi-objective genetic algorithm. In each generation, the grid value, the grid crowding distance and grid coordinate point distance of every individual were calculated, respectively. Then elite individuals were selected to do crossover and mutation operators based on the grid domination sorting and grid selection strategies. The individuals were iterated toward the Pareto front and the Pareto optimal solutions were obtained. Finally, the proposed algorithm was verified effectively through four test functions and two practical engineering problems.

Grid Connected Control in Fixed Displacement  Pump-Parallel Variable  Motor  of  Main Transmission  System  in  Wind  Turbine

Kong Xiangdong, Song Yu, Ai Chao, Wang Jing,

2015, 26(16):  2215-2221. 

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A  grid connected control method was presented herein,which was used in the main transmission system of the fixed displacement pump-double parallel variable motor  in  hydraulic wind turbine,namely when the first variable motor worked  in the state of grid connected,another variable motor didn't lose stability in startup under the constant pressure control method.The  rotate  speed coupling of the double parallel  variable  motor was eliminated with the principle  of structure invariance,therefore,when another  variable motor was post-launch,the grid connected synchronous rotate speed was controlled under the speed control method.Meanwhile,the grid connected control mathematical model was  established,and simulation  was conducted.With  pressure  and  speed control,the fixed  displacement pump rotate speed,the variable motor swashplate angle,the variable motor rotate  speed and the system high pressure response characteristics in the process of grid connected were obtained under the condition of different wind speed (fixed-displacement pump rotate speed).The grid connected control method was verified in the fixed displacement pump-double  parallel variable motor.This reserach lays a theoretical foundation to expand the hydraulic wind turbine in the applications  of large and super large wind turbine.

SVM  Parameter  Optimization  in  Fault  Diagnosis  for  Wind  Power Gear  Box

Zhao Chunhua, Dong Haijiang, Zhong Xianyou

2015, 26(16):  2222-2225. 

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In  a  wind turbine gearbox,gear  teeth  produced  frequently the  problems  such as broken,pitting and wear failure.This paper will extract non-stationary  nonlinear vibration  signals of  wind power gear box and enhance wavelet packet energy entropy with using  SVM to fault diagnosis processing.To  improve the classification  accuracy  of  the  algorithm,genetic algorithms was used to optimize of parameters. Tests show that the best parameters can improve the prediction accuracy of the SVM to test samples.

Impacts  of  Electro-hydraulic Vibration  Applied  in Cold Extrusion of Metal Plastic Forming Process on Metal Flow Lines and Grain Structure

Yang Qinghua, Hong Xiaoxiao, Wang Zhiheng, Bao Guanjun, Hu Xinhua, Xue Junyi

2015, 26(16):  2226-2232. 

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Cold extrusion process had some disadvantages,such as gigantic metal deformation  resistance,mold wear,etc.a new type of cold extrusion process was proposed,where vibration excitation signals were applied in  the cold extrusion process.Using DEFORM-3D finite element analysis software,the system simulation models  were built  and  the  forming process was simulated on  whether the vibration was  applied  to  this process.Simulation results show that the signal can be applied to facilitate the metal flow,and the metal flow rate reaches  62.4mm/s.The degree of deformation of the mesh flow lines is smaller than  that in  the condition of  traditional  squeeze mode. A  kind of electro-hydraulic vibration experimental  platform  and die were designed for  this project.Experiments were completed on the conditions  of whether the vibration was applied to this process.Etching molded parts with 4% Nital,and SEM was used to observe the part  sections.Experimental results show  that after the application of vibration signals in cold extrusion,the grain size reduce from about  3.3~5.0μm to 1.7~3.3μm,grain deformation becomes more uniform,deformation tissue becomes more dense,metallic  fibrous tissue becomes finer and longer.

On  Quantitative Techniques  of  Corrosion  Pits  of  Aerial  Aluminum  Alloys

Hui Li, Yu Xiang, Xu Liang, Zhou Song, Wang Lei

2015, 26(16):  2233-2236,2243. 

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The quantitative techniques of corrosion pits of 2 series pre-corrosive  aerial  aluminum alloys  were investigated.In  the pre-corrosive conditions,it is found that the fatigue crack starts at the bottom of its corrosion pit to result in a radial propagation and a decrease of the crack initiation life.Thus,a  new  quantitative  method  of corrosion  pits  was  pointed  out  by  ignoring the stages  of the crack nucleation.According to the equivalence principles  of the area,the corrosion pit was equivalent to a semi-elliptical surface crack in order  to  directly predict the fatigue life of aluminum alloys.Based on the NASGRO software,the validation of proposed quantitative techniques of corrosion  pits  and fatigue life prediction methods  was  performed and the research results enable the possibility of the fatigue life evaluation of complicated structures.

Lateral Switched LMIs/H∞ Steering Control Strategy of Intelligent Vehicle Based on Path Error Dynamics Model

Wang Xuanyao, Wang Qidong,

2015, 26(16):  2237-2243. 

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Based on the path error dynamics model,a lateral switched steering controller was designed for an uncertain linear model of the vehicle, which included switched PIDey control of the distance from the centerline of the lane to the center of mass of the vehicle, and switched PDeψ control of the direction errors from the lane to the vehicle. Setting the vehicle theoretic yawing angular velocity as the disturbance, the optimal solution of convex optimization problems of linear objective function, and the corresponding minimum disturbance rejection γ were acquired for the control strategy, which the state feedback γ-suboptimum H∞ norm and linear matrix inequalities(LMIs) were used. The road model of Alt3 from FHWA  was acquired from CarSim, and the reference velocity was obtained from the vehicle model D-Class/Sedan. In order to simplify the model, a sub-model with time-varying velocity was selected as the switching signal for the lateral switched steering controller. On the road with low adhesion coefficient, there  were both verified with 10 degrees of freedom vehicle dynamics model, which was  based on the path error dynamics model of the lateral control law  and have higher path tracking accuracy and stability than L2WVM(linear two-wheel vehicle model). With the changed structure parameters of vehicle model, it is verified that the  switched H∞ controller based on the path error dynamics model has better robustness than the L2WVM.

Study  on  Braking  Rate  of  Disc  Brake  Unit   RZS(Continue)

Xia Demao, Xi Ying, Hua Binbin, Zhu Wenxiang

2015, 26(16):  2244-2248. 

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Firstly,according to the working principles of the braking unit RZS,the kinematic diagram was built up.Then,the DOF of RZS with and without the brake disc was analyzed and compared.The braking rate and its change rules were  calculated and analyzed respectively  under two conditions:the pad clearance was equal to the setting value and  another the pad clearance was reset after braking operation. It is found that:the braking rate of RZS meets the design requirements and there is a linear relationship between the increment of the self-adjustment mechanism and the amount of the pad's 　wear.During the entire service life of the pad, the braking rate of RZS barely changes.

Light-Duty 2-Speed Automatic Transmission with Torque Backlash Shift Schedule

Hao Yunzhi, Chen Jian, Xue Rongsheng, Zhou Qian

2015, 26(16):  2249-2253. 

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To improve the level of automation and operation comfort of light-duty agriculture machines, such as micro-cultivator, a novel 2-speed automatic transmission structure was presented,which could shift according to tillage resistance automatically.The gearshift consisted of friction clutch, overrunning clutch,edge cam and springs, without hydraulic and electrical mechanism. Shift schedule was of single parameter backlash schedule of torque. Torque of down shift was adjusted by spring pre-load, and shift backlash was mainly decided by edge cam angle. During shifting process,torque was translated continuously and clutch pressure was constant to provide a steady torque.This characteristic is good for smoothing synchronization and reduces shifting shock. Prototype experiment was carried on,and the auto-shift function and stability was proved.

State-of-the-Art of Electrical Discharge Dressing Technology for Superabrasive Grinding Wheel

Yu Jianwu, He Lihua, Huang Shuai, Shang Zhentao, Wu Yao, Duan Wen

2015, 26(16):  2254-2262. 

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EDD of superabrasive grinding wheel was developing with electrical discharge machining (EDM) technology, changing the traditional wheel dressing methods based on hard contact. In recent years, many researchers were working on EDM dressing methods of superabrasive grinding wheel and achieving a lot of significant results to contribute to the efficiency and precision grinding. Based on numerous literatures, the research fruits on the development of EDD technology within the last thirty years were reviewed. The basic principles of EDM dressing technology of metal-bonded superabrasive grinding wheel were introduced. According to the dressing applications of CBN and diamond grinding wheels, the effects of different electrodes, different dielectrics, different electrical parameters and modeling with modern design theories were presented. The existing problems in the developing EDD technology were analyzed, and the future developing directions were also discussed.

Overview of Aviation Hydraulic Fittings

Ouyang Xiaoping, Fang Xu, Zhu Ying, Wang Kai, Yang Huayong

2015, 26(16):  2262-2271. 

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The  aviation  hydraulic fitting is one of the most important components which directly affects  the safety and reliability of aircrafts.A comprehensive overview was intended to introduce the general features of the aviation hydraulic fittings.The performance of three main types of aviation hydraulic fittings was demonstrated, including permanent fittings,separable fittings and boss fittings.The structure, principles,applications,design standards and suppliers of each type were illustrated.The characteristics of each main type fitting such as pressure resistance,pull-off  strength,weight  and  installation,were  analyzed and compared.The recommended selections of aviation hydraulic fittings for different pressure levels were summarized.Finally,the developing prospect of aviation hydraulic fittings was given, and the large distance in the aviation hydraulic fittings between China and the international advanced level was pointed out.