Table of Content

10 October 2013, Volume 24 Issue 19

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Simulation of Temperature Field for Si3N4 Ceramics during Laser Assisted Micro-detonation Machining with Striking Arc

Tian Xinli;Li Fuqiang;Wang Pengxiao;Wang Long;Tang Xiujian

2013, 24(19):  2557-2561. 

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The paper introduced simply the technologies of laser assisted micro-detonation machining with striking arc and established its theoretical model of temperature field. Based on finite element theory, the temperature field of Si3N4 ceramics during laser assisted micro-detonation machining with striking arc was simulated with the aid of finite element analysis software. Furthermore, the influence of process parameters on temperature distribution was studied. The simulation results show the highest temperature is enhanced from 12 600℃ to 14 381℃ only with micro-detonation machining with striking arc. The temperature increases with increment of the laser power and decreases with growth of the size of light spot. With the increase of distance between the laser heating point and processing position, the temperature rises firstly and then drops. The effect of feeding speed on temperature is not so outstanding. The simulation results is reliable and can provide theory evidences for uncovering the machining mechanism of laser assisted micro-detonation machining with striking arc and choosing proper process parameters.

Dynamics Analysis of Lunar Lander and Key Structures in Taking-off Stage

Chen Jinbao1;Nie Hong1;Zhang Zemei2

2013, 24(19):  2562-2566. 

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Lunar lander will be in complex and severe dynamic environment during taking-off stage. The dynamic characteristics of a lunar lander in stowing stage was studied herein. Firstly, the model of lunar lander and rover and solar panels were built. Secondly, the modal analysis of stowing lander was studied based on MSC.Patran/Nastran. The natural frequencies and the vibration modes of the stowing lander were given. Finally, frequency analysis on stowing model of the lunar lander was implemented in the excitation of rocket. The results show that the vibration modes of the lunar lander are mainly bending of landing legs and solar panels, and provide some scientific basis for reducing the structural vibration and improving the reliability of the lunar lander.

Research on Influence Factors of Critical Pretension Force in Pre-stressed Assembled Lower Beam

Guo Baofeng;Yu Linlin;Jin Miao;Dong Xiaochuan

2013, 24(19):  2567-2572. 

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The lower beam of a large forging hydraulic press is usually assembled with a few pieces of beam body using some preload bolts due to the restrictions of the processing, transportations and installation conditions, so how to accurately calculate the pretension force become the crucial problems in strength, stiffness and integration property design of the assembled lower beam. A simplified analysis model of lower beam was assumed herein as a large forging hydraulic press prototype and the influence factors of critical pretension force in center and reaming working condition of the assembled lower beam were systematically studied,so as to find out the critical factors and the influence rules. The results show that the load and ratio of span and height are the critical factors, the beam width and bolt position have less influence on the critical pretension force, and the critical pretension force coefficient increases linearly with the increase of the ratio of span and height. On the other hand, the critical pretension force coefficientis also set when the ratio of span and height is as a fixed value. The experimental model of the assembled lower beam with the ratio 1∶7.2 was designed herein, which verifies the simulation results based on the model and provides a theoretical basis for the determination of the assembled lower beam of the large forging hydraulic press.

Research on Damping Characteristics of Hydraulic Circuit of Load Sensing Outlet Pressure Compensation

Luo Yanlei;Chen Lunjun

2013, 24(19):  2573-2576,2583. 

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Taking load-sensing pressure compensation multi-way valve as an object, the working mechanism of outlet pressure compensation valve and the role of bypass damping orifice were analyzed in depth theoretically. On the basis of that,a mathematical model of the dynamic damping property was established to lay the foundation for the next analysis, the relevant structure parameters that affect the pressure fluctuation were presented, and the damping characteristics were also analyzed. These results can be as a theoretical foundation for design of compensation valve and damping orifice.

A Structural Reliability Sensitivity Analysis Method for Hybrid Uncertain Model with Probability and Non-probabilistic Variables

Jiang Chao1;Li Wenxue1;Wang Bin1;Zhou Guilin2;Liu Yuxiang2

2013, 24(19):  2577-2583. 

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Based on hybrid uncertain model, a new reliability sensitivity analysis technique was developed for uncertain structures. Random distributions were used to deal with the uncertainty, while some key parameters in the distribution functions were given variation intervals instead of precise values. Hybrid reliability model was employed to evaluate the reliability degree of an uncertain structure based on the reliability index approach(RIA). Six sensitivity indices were used for the sensitivity of the average reliability and reliability bounds with respect to the averages and widths of intervals. Equations of these sensitivity indices were derived. Two examples were used to demonstrate the accuracy and effectiveness of the proposed method.

Analysis on Static Characteristics of Rayleigh Step Bearing under Coexistence State of Fluid with Laminar Flow and Turbulence

Wang Yingjia;Dong Qiwu;Guo Hong;Cen Shaoqi

2013, 24(19):  2584-2587,2591. 

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This paper mainly discussed the high-speed step bearing with shallow
and deep cavities on the inner surface of the bearing.With considering the coexistence
state and different hydrostatic pressure between bearing endings,the pressure distribution
was calculated first using the continuity equations and the static characteristics in the
whole flow domain such as pressure distribution,load-carrying capacity,friction force and
friction coefficient were analyzed.It is shown that the optimum bearing parameters are
dependent on the turbulence factor of deep cavity and the variations of the
pressure at the boundaries.Finally,under certain conditions associated conclusions are
drawn by comparison between results under the coexistence state and under the laminar state.

A Backing Pressure Control Method for Electrical Injection Molding Machine Based on Quadratic Curve

Zhou Huicheng;Xu Yingpeng;Wu Jichun;Song Lizhi

2013, 24(19):  2588-2596. 

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A method which was based on quadratic curve to control backing pressure was supplied. It is proved that this method can realize the control requirements in electrical injection molding machine. Experiments completed under the condition of several different setting backing pressures show the effectiveness of the approach. It indicates that the method can satisfy the control requirements of one stage or multistage backing pressure effectively.

Connection Algorithm about Closed Angle Vertical Transition of Tool Path Track without Tool-retraction

Yang Feng1,2;Liao Wenhe1;Dai Ning1;Zhang Changdong1;Guo Baosu1;Sun Yuchun3

2013, 24(19):  2592-2596. 

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How to efficiently link the tool path track to contour-parallel tool path plays an important role in complicated pocket machining. Closed angle vertical transition of tool path track without tool-retraction was presented. Equidistant offset tracks were generated based on sub-regions of vector angular bisector. Then path track array and several singly linked lists were established. A single root tool path loops tree was generated with adding outside offset tracks in sequential order and inside offset tracks in reverse order. A tool path without tool-retraction can be generated by traveling the tree with closed angle vertical transition and the validity of the algorithm was proved by building acceleration and deceleration mathematical model. Several tests show that the method can produce high efficiency,can obtain tool path without tool-retraction and is proved to be useful by the practice.

Image Recognition and Data Analysis of Ray Detection for Titanium Alloy Pipe Fitting Welding Seam

Ji Weixi1;Li Xiaobing1;Jia Jiyong2

2013, 24(19):  2597-2601. 

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According to low efficiency and low accuracy of defect identification by workers in the inspection process of ray detection image for titanium alloy pipe fitting welding seam, the authors come up with a solution to use the computer image recognition technique to form, preprocess, analyze and extract the characteristics of digital image for the location of pipe fitting welding seam defects. Also, in order to automatically recognize the welding seam defects, a software system named ray detection data analysis and quality judgment was researched and developed,and the automatic judgment of the quality of pipe fitting welding seam was realized.

Research on Relationship between Temperature Drift and Thermal Expansion of Sensing Structure in Sandwich Micro-accelerometer

Dai Qiang1，2;Su Wei2;Zhang De2;Peng Bo2;Yang Lin1

2013, 24(19):  2602-2606. 

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To cope with the temperature drift of sandwich capacitive micro-accelerometer, based on mechanics and thermal principle, the geometrical change of sensing structure due to the thermal expansion was analyzed. Then, in light of the geometrical change and accelerometer's closed loop operation mode, the output change was obtained, which implies that the output variation is less than 0.002gn per 10℃.Meanwhile, an experiment was conducted, which indicates that the output change due to the temperature is from 0.1gn to 0.2gn per 10℃. The results illustrate that the geometrical change is not a dominant reason for temperature drift.   

Analysis of Jet Pipe Servo Valve Feedback Spring Components

Zhao Kaiyu;Yuan Zhaohui;Zhang Ying

2013, 24(19):  2606-2610. 

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In order to obtain an optimization design of  jet pipe hydraulic servo valve feedback components.The authors made theoretical derivation about the structure and properties of feedback components on the jet pipe servo valve.In view of the mathematical derivation of the feedback lever stiffness  is not accurate,we focused on the finite element analysis about curvature of the feedback lever.The best bending angle of the feedback leveris was determined as 135° ,the feedback force enhanced by 8.6% relalively to any other angle.This work makes  the design ideas about the feedback components clearly.Then,a finite element analysis model was used to simulate the spool and the jet pipe nozzle displacement when the electromagnetic torque acting on thearmature components. The relationship among torque, spool and the jet pipe nozzle was summed up.

Research on Modeling Method of Language Knowledge of Brand Style on Bayesian Network

2013, 24(19):  2611-2616. 

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In view of the evolution phenomenon and its rule of  brand style,the research of  mapping relation between brand image and form language
was expound profoundly,and the typical form semantic was extracted with the KISS system and the improved design format  analysis methods,a model of form
language was established by the modular thought based on Bayesian network.In the model,firstly the cognition experiments on image cognition were conducted,and the learning and the reasoning of the Bayesian network were advanced through the score functions and search algorithms.Then the form syntax subnetworks U,the imager words subnetworks V and the mapping subnetworks W were divided specifically,the Gestalt organization attributes and the image words structures were interpreted.The tacit knowledge rules were further analysed and discovered according to the relationship among the nodes and the distribution trend of the conditional probability.Finally,a case study was completed to illustrate the validity and the applicability of the modeling method.

System-oriented Tolerance Semantics and Its Mathematical Model for Plane

Huang Qiang1;Zhang Genbao2;Wang Jian3

2013, 24(19):  2617-2622. 

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According to the requirements of digital precision analysis and tolerance design for a machine tool system,taking the plane as an example,
the system-oriented tolerance semantics and its mathematical model were proposed.This tolerance semantics was defined as the 6-DOF output of which the tolerance on a
part surface acted  on its associated part.Conforming to the modeling principle proposed herein,
the mathematical description for tolerance area was based on the feature points of the part's three-dimensional contouring,and was applicable in part lay out and assembly.The six output parameters of plane tolerance were calculated and expressed as a homogenous coordinate conversion matrix,then,it was realized that the mathematical model of tolerance is compatible with the error model of machine tool system.In the end,an application demonstration about tolerance adjustment was provided.

Study on Embedded NC System Based on Heterogeneous Multi-core Processors

Lu Xiaohu1,2;Yu Dong2;Hu Yi2;Lin Liming1,2

2013, 24(19):  2623-2628. 

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Owing to the low scalability and poor performance of traditional embedded CNC, this paper described an embedded numerical control system which took the advantage of heterogeneous multi-core processor technology. The embedded CNC was based on a heterogeneous dual-core processor.
Two different operating systems ware introduced to run on cores of heterogeneous dual-core processor.  With a reasonable task division, the NC system could improve the stability and enhance the real-time ability. A well-designed static task division mechanism prevented the system from a potential memory access conflict caused by different processor cores with different architectures. The realization of the embedded NC system used the field bus technology to realize the control of the motor servo. The experiments show that the proposed embedded numerical control system has high real-time ability and scalability to meet the requirements of high-performance embedded numerical control system. The results prove the rationality of the system design.

Three Dimensional Mapping Work Decomposition Model for Complex Product Development Project

Dai Yulei1,2;Li Nan1;Yang Li3

2013, 24(19):  2629-2634. 

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In view of the complex product development project characteristics,a project work decomposition model was presented herein,
which integrated  PBS,OBS and WBS together.By the definition of PBS model,OBS model and WBS model,the analysis of model mapping and model workflow,establishment of complex product responsibility assignment matrix(PRM) from PBS-OBS model mapping,generation of project work breakdown structure(PWBS) from PRM-WBS model mapping,the project  WBS for complex  product development  were constructed in standardization and formalization.Finally,the application process of the proposed model was illustrated with a case of launch vehicle.This proves the method effectiveness and maneuverability.

Design and Implementation of a Stereo Matching Method in Binocular PMP Vision Measurement

Xiong Wei;Li Wenlong;Yin Zhouping

2013, 24(19):  2635-2640,2646. 

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In order to resolve the mismatching problems caused by the large change in the depth of the objects or the complex surface shape in the field of PMP visual measurement,this paper proposed a stereo matching method based on region segmentation and parallax correction. The basic principle of four-step phase shift method and the multi-frequency heterodyne were investigated, and stereo rectification method in OpenCV software package was used to rectify the raster image. The field of view of the cameras was analyzed according to the characteristics of the PMP vision measurement system. Using the characteristics of the phase information in the field of view and the parallax constraint, the principle and the method of region segmentation were proposed based on the mixed threshold. Furthermore, the valid parallax maps were obtained by parallax solving and parallax correction, and several test experiments were carried out to demonstrate the effectiveness of the proposed stereo matching method in PMP visual measurement system.

Multi-scale Permutation Entropy and Its Applications to Rolling Bearing Fault Diagnosis

Zheng Jinde;Cheng Junsheng;Yang Yu

2013, 24(19):  2641-2646. 

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A definition of MPE was presented to extract the fault characteristics of dynamics changes from bearing vibration signals. And in combination with SVM, a bearing fault diagnosis approach was put forward based on MPE and SVM.Firstly the algorithms of PE and MPE were introduced. Then experimental data were used to demonstrate the validity of the approach. Also for comparision with SVM, the BP neural network was used and the analysis results indicate that the proposed approach can extract the fault feature and identify the fault categories effectively.

Parameter Identification of LuGre Friction Model Based on Interval Analysis

Liu Baixi;Yao Haoxiong;Nie Songhui

2013, 24(19):  2647-2651. 

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An approach, based on bounded-error estimation via interval analysis, was presented to identify dynamic parameters of LuGre friction model herein. The approach assumed the error of measurement output data of dynamic system with LuGre friction force was bounded. Hence, the problem of parameter idelification can be transformed into that of set inversion, which will be effectively solved via interval analysis. The four static parameters of LuGre friction model were estimated using least-square method in sliding regime, which deceased sharply the amounts of parameters identified using interval analysis. In comparison with the traditional estimation methods the main advantages of the proposed method  are that, as it is global, it bypasses the problem of initialization. Moreover, the method avoids amount error due to transformation of measurement output data. An identification example was given to show the correctness and efficiency of the proposed method.

Free Vibration Analysis of Flexible Ring for a New Bar-type Piezoelectric Motor

Li Huaiyong;Xu Lizhong

2013, 24(19):  2651-2656. 

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Free vibration of flexible ring for a new type of bar-type piezoelectric motor was investigated herein. The working principles of the motor were described. The free vibration equation of the flexible ring under the meshing force was given with the Donnell shell theory. The frequency equation and modal function equations of the flexible ring were obtained. The changes of the vibration frequencies and mode shapes along with structural parameters were discussed. The results lay the foundation for performance evaluation and design of this motor.

Nonlinear Sliding Mode Motion Control and Double Elastic Vibration Active Suppression of Free-floating Flexible-joint and Flexible-link Space Robot

Xie Limin1,2;Chen Li1

2013, 24(19):  2657-2663. 

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A dynamics modeling, motion controller design and joint-link double flexible vibration suppression problem of free-floating flexible-link and flexible-joint space robot were discussed. The dynamic equations of the system were established according to system's momentum conservation, angular momentum conservation and Lagrange-assumed mode method. Based on singular perturbation method, the system was decomposed into three mutual independent subsystems: a “rigid-joint and rigid-link” slow subsystem represented the rigid-joint and rigid-link system's rigid motion, a “flexible-joint and rigid-link” fast subsystem represented the system's elastic vibration caused by flexible-joint and a “rigid-joint and flexible-link” fast subsystem represented the system's elastic vibration caused by flexible-link. Then three controllers were designed for the three subsystems respectively. A nonlinear sliding mode controller was designed to realize the asymptotic tracking of the system's motion trajectory. A feedback controller was used to suppress the flexible vibration caused by flexible-joint based on the velocity difference between the link and the motor. A linear quadric regulator was used to suppress the flexible vibration caused by flexible-link. Therefore, the system's total controller was a composite of the three controllers. The simulation proves the proposed compound controller can guarantee the control system's accuracy and suppress the elastic vibration caused by flexible-joint and flexible-link effectively.

Calculation of Tool State and Trajectory Processing Equal Base Circle Bevel Gear Using Disc Cutter

Wang Bin1;Deng Xiaozhong2;Jia Xinjie1;Li Genggeng2

2013, 24(19):  2664-2670. 

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The purpose of this paper was to achieve NC machining the equal base circle bevel gear with a disc cutter. Based on the equal base circle bevel gear theory, through establishing the disc cutter processing coordinate system of a special bevel gear, the main parameters which decided tool's position and posture were solved. By calculating the disc cutter shaft vector and cutter heart coordinates, the calculation results of tool position in the gear blank coordinate system were obtained. Combined with general five axis NC machine tool, the general coordinate expression of NC machining this kind of gear was obtained. Through 3D modeling, the calculation results of tool position and state were verified. Through the simulation of machining, the correctness of the tool trajectory was verified. The results show that the solution of motion trajectory is correct, machining the equal base circle bevel gear with a disc cutter is feasible.

Deformation Analysis of Automobile Housings Pressed and Formed by Pre-formed Tube

Wang Liandong;Yang Dongfeng;Cui Yaping;Chen Guoqiang

2013, 24(19):  2670-2674. 

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A bulging-pressing compound-deforming technology was introduced for some kind of small automobile axle housings. The deformation on the chosen crossing and longitudinal sections was analyzed qualitatively for pressing the pre-formed tube of axisymmetric shape by the die after it was charged with liquid. The deformation pattern and the change of wall thickness was discovered, and the effects of forming property resulted from the size of crossing section in the axle housing cover part were discussed. Through the FEM simulation and test, the forming property of pressing the tube is deeply inspected, and the wall thickness distribution is quantitatively analyzed. It is founded that when the automobile axle housing of special shaped cross-sections is pressed from the pre-formed tube, the trial samples possesses of good formability, better wall thickness distribution, and lower internal pressure.

Numerical Simulation and Verification of Near-net-shaping Inconel625 Powder Disk under Hot Isostatic Pressing

Lu Heng;Wei Qingsong;Xue Pengju;Wang Jiwei;Shi Yusheng

2013, 24(19):  2675-2680,2686. 

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To once-forming Ni-based superalloys turbine disc, a NNS-HIP method was used. A shape follow-up and a longitudinal symmetry mold schemes were designed. A modified Shima's model was used to simulate the NNS-HIP process of inconel625 powder disk, and an optimal scheme was selected for the test. Simulation results show that the thin canning has large deformation and drives powder densification. The internal core has almost no deformation, and controls the complex internal shape of powder disk; The powder expands first and then compacts in a multi-stage mode. Experimental results show that the size simulation error is less than 3.57%, mainly caused by manufacturing and measurement errors. The simulation values in low density areas is smaller than actual values, because the simulation process ignores some microscopic behaviors such as movement and rearrangement of powder particles. The tensile strength of Inconel625 compacts is bigger than ASTM forging standard, and good plasticity can be received after solution treatment. The simulation can guide the mold's structure design of NNS-HIP.

Fuzzy Comprehensive Evaluation and Verification for Handling Stability of Vehicle

Liu Wenting;Zhao Youqun;Ruan Miqing;Wang Wei

2013, 24(19):  2681-2686. 

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A subjective evaluation of a prototype vehicle is still a main evaluation means used in the automotive industry, and the overall performance of the scoring is more difficult. According to the scoring based on individual evaluation of the real vehicle test, a method used in fuzzy comprehensive evaluation of vehicle handling stability was presented. And the approach was applied in evaluating two prototype vehicles. Based on vehicle steering open-loop model with 3 degrees of freedom and vehicle handling inverse dynamics theory, the vehicle handling inverse dynamics model was established and the control stability of two cars were simulated and analyzed. The two results were compared to verify the feasibility of fuzzy comprehensive evaluation method applied to evaluate vehicle handling stability.

Pure Electric Vehicle AMT Comprehensive Shift Strategy Considering Dynamics and Economic Performances

Chen Shujiang;Qin Datong;Hu Minghui;Hu Jianjun

2013, 24(19):  2687-2692. 

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This paper took two-speed automated mechanical transmission(AMT) of a pure electric vehicle as the research object, studied the differences between power and economic shifts.Some conclusions are obtained: 1)the difference of shift schedule is obvious at low load and high load, not obvious at medium load;
2)the difference of ECE energy consumption is obvious at low load, not obvious at high load;
3)the difference of 0~50km/h accelerating ability is obvious, the difference of 50~80km/h accelerating ability is not obvious. On the basisof above, a kind of comprehensive shift strategy was put forward considering dynamics performance and economic performance. Simulation results show that the comprehensive shift schedule has dynamics performance as power shift schedule, and has economic performance as economic shift schedule.

Control Strategy of DCT Shift Based on Engine with Negative Torque

Sun Dongye;Wang Cong

2013, 24(19):  2692-2697. 

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For the particular engine conditions of negative torque when automobiles were in the downhill, or slowing down, or overtaking, etc, this paper established a system dynamics model of the shift process of DCT power drive system with the experimental data of the negative torque condition of engine. According to characteristics of the torque with the rotating speed when the engine provides negative torque, this paper put forward a kind of control strategy of DCT shift. Through the corresponding simulation analysis, results show that the control strategy is feasible.