Table of Content

25 August 2007, Volume 35 Issue 8

Previous Issue    Next Issue

Mechanical Engineering

Numerical Simulation of Influence of Roller W orking Surface on Spin-Forming of Rectangular Inner Meshing Gear

Xia Qin-xiang Hu Yu Sun Ling-yan Ye Bang-yan

2007, 35(8):  1-6. 

Asbtract ( 307 )   PDF (366KB) ( 558 )  

Related Articles | Metrics

In order to optimize the equipment for spin-forming and to lay a foundation for the selection of roller working surface and forming parameters , the traditional roller working surface of tubular-shaped workpiece and the characteristics of the spin-forming for cup-shaped thin-walled inner gear are analyzed , and a 3D finite element elastoplastic model is established by using the MSC. Marc software. Then , numerical simulations of the gear spin-forming under different working surfaces are carried out. Moreover , the influence of working surface on the formability of inner gear spinning is investigated. The results indicate that , for the step-type roller, large roundness radius and small forming angle contribute to the spinning of inner gear , and that the quality of spun workpiece is at its best when the circular-type roller is used.

Analysis of Molten Pool Image of TIG Welding ßased on Fractal and Mathematical Morphology

Xue Jia-xiang Liu Xiao Zhu Si-jun wang Zhen-min

2007, 35(8):  7-10. 

Asbtract ( 331 )   PDF (259KB) ( 866 )  

Related Articles | Metrics

The processing of welding images is unavoidably accompanied with noises due to the dust , strong arc light and other interference factors in the welding process. As the traditional methods of image processing are sensitive to the noise , it is difficult to accurately.process the image. In order to solve this problem , this paper presents a novel composite image processing method based on the fractal and mathematical morphology theories. In this methpd , first , the gray-scale image of the molten pool is obtained according to the fractal-based discrete Brown random field theory. Next , the connected domain is detected based on the binary morphology theory and is then used to remove the noise and obtain the target image. Moreover , the successive edges of the image are obtained by means of the Open-Close operation on the basis of the mathematical morphology theory. Experimental results show that the proposed method is of high speed and accuracy in the recognition of molten pool information including the edge , the height , the width and the area.

Multi-Teeth Rolling Formation of Corrugated Sheets for Supporting Catalyst

Pan Min-qiang Zeng De-huai Tang Yong Zhang Yi-hong Lu Long-sheng

2007, 35(8):  11-15. 

Asbtract ( 250 )   PDF (389KB) ( 374 )  

Related Articles | Metrics

In order to effectively apply the conventional catalyst-coating methods to microreactors , a new kind of corrugated sheet as catalyst support was proposed. Then , a machining method named multi-teeth rolling formation was developed to realize the rapid and continuous production of the sheet , and the influences of hobbing and pressing force on the sheet formation were finally studied. The results indicate that (1) there is a negative relationship between the teeth space and the pressing force; (2) when the sheet is fabricated by a group of identical rollers ,there forms regular corrugation and pubescence-like rough rolling surface , which facilitates the adhesion of the catalyst on the sheet; and (3) the catalyst can be tightly coated on the sheet surface by means of slurry-coating method.

Manufacturing of Fine-Grained AZ31 Magnesium AlIoy Sheet by Large Strain Hot Rolling

Zhan Mei-yan Li Yuan-yuan Chen Wan-de Chen Wei-ping

2007, 35(8):  16-21,43. 

Asbtract ( 289 )   PDF (639KB) ( 603 )  

Related Articles | Metrics

In the hot rolling of magnesium alloy , the grain refinement may result in the strength and ductility improvement, and the variation of rolling parameters helps to control the microstructure of the alloy. This paper focuses on the effects of the reduction per pass on the microstructure and properties of AZ31 magnesium alloy. The results show that , with the increase of the reduction per pass , the strain rate improves and a dynamic re-CIγstallization occurs , which results in the grain refinement and hardness improvement. However , surface cracks may occur when the reduction per pass increases to a critical value. Moreover , it is found that hot rolling with large strain may decrease the number of rolling passes. Thus , fine-grained AZ31 Mg sheets with a grain size of about 2 to 5μm can be successfully prepared by hot-rolling with large reduction per pass.

Numerical Simulation of TCGMAW Process Based on Body -Fitted Coordinates

Wang Zhen-min Xue Jia -xiang Zhao Peng-cheng Huang Shi-sheng

2007, 35(8):  22-26. 

Asbtract ( 283 )   PDF (303KB) ( 587 )  

Related Articles | Metrics

In order to reveal the mechanism of the twin-wire co-pool gas-shielded metal arc welding (TCGMA W) and to optimize the corresponding welding parameters , the mathematical model describing the fluid flow in the molten pool is investigated. After analyzing the surface deformation of the molten pool , a body-fitted coordinates transform is introduced to change the complex physical boundaries resulting from the surface deformation into the regular ones in non-orthogonal body-fitted coordinates , which makes the coordinates accord well with the calculated region.Then ，a discrete goveming equation in body-fitted coordinates is established and the energy and momentum boundary conditions are thus dispersed. Moreover , a 3D quasi-steady model is proposed to numerically simulate the fluid flow in the molten pool during the TCGMA W process. Finally , the SIMPLEC algorithm is adopted to simulate the welding process. The results indicate that the proposed method effectively solves the coupling problems among the surface deformation , the fluid flow and the heat transfer with good accuracy.

Selection of Key Control Parameters of Mold-Temperature-Control Solidification

You Dong-dong Shao Ming Li Yuαn-yuan Zhou Zhao-yao

2007, 35(8):  27-31. 

Asbtract ( 330 )   PDF (340KB) ( 565 )  

Related Articles | Metrics

A method for selecting the control parameters of the mold-temperature-control solidification (MTCS) is presented based on numerical simulations , and two significant parameters which are easy to control , are adopted to carry out the investigation. Then , a 3D transient heat transfer analysis is performed in various conditions with the mold-preheated temperatures of 743 , 693 and 673 K and the cooling thresholds of 753 , 293 and 673 K, and a deviance between the numerical and experimental data of less than 8% is obtained. The results indicate that (1) a mold-preheated temperature higher than the melting point of the workpiece contributes to the reduction of shrinkage cavities and the improvement offorming quality; (2) the mold-preheated temperature should be determined by considering both the molding efficiency and the process e盯or; and (3) at a cooling threshold of 753 K, all the cooling channels simultaneously open and obvious shrinkage cavities form in the upper center of the workpiece , while at a cooling threshold of 673 K, seven groups of cooling channels open in sequence and excellent forming quality is achieved since the solid-liquid interface maintains a near-planar surface and the solidification velocity remains fast.

Planning of Generating Motion Trajectory in NC Machining of Spiral Bevel Gear

Liu Kai Zhao Dong-biao Huang Pei-jian

2007, 35(8):  32-37. 

Asbtract ( 297 )   PDF (372KB) ( 689 )  

Related Articles | Metrics

On the basis of the principle of NC machining for the spiral bevel gear and according to the generating motion between the generating gear and the work gear , a mathematical model of the generating motion of the spiral bevel gear tooth surface is proposed to determine the parameters of NC machining. The contact conditions of the gear cutting are then discussed , and the trajectory planning method of the spiral bevel gear in NC machining is presented and implemented to control the gear cutting on the self-developed NC milling machine for the spiral bevel gear. Experimental results show that the proposed trajectory planning method is feasible and effective in the control of NC machining for the spiral bevel gear.

Influence of Air-Bearing Surface on Gas Lubrication Performances of Hard Disk Drive

Niu Rong-jun Huang Ping

2007, 35(8):  38-43. 

Asbtract ( 276 )   PDF (381KB) ( 599 )  

Related Articles | Metrics

In order to lay a theoretical foundation for the optimized design of air-bearing surface (ABS) , a numerical algorithm for the nano-sized gas lubrication is programmed to analyze the ABSs of the positive and negative magnetic heads , and the inf1uences of ABS on the performance of magnetic head/ disk system are investigated. The results indicate that , for the positive magnetic head , the loading points of the maximum pressure and the gas load capacity play a significant role in the performance of the system , and the change of the slider configuration may decrease the maximum pressure and the gas load capacity j while for the negative magnetic head , rhe negative pressure region can be increased by altering those structures that exert obvious influence on the negative pressure , thus weakening the effect of the positive pressure. In addition , the gas stiffness cannot be ignored in the design of the hard disk drive system , and high gas stiffness contributes significantly to the stability of the system.

Development of Novel Pulsed Mechanical Continuously-Variable Transmission

Nie Song-hui Liu Hong-zhao Qiu Ai-hong

2007, 35(8):  44-48,54. 

Asbtract ( 273 )   PDF (372KB) ( 564 )  

Related Articles | Metrics

In order to improve the mechanical performance and transmission efficiency of the traditional pulsed mechanical continuously-variable transmission (CVT) , a novel pulsed CVT is proposed according to the linear characteristic of hypocycloid at specific parameters and by combining the planet gear transmission mechanism with the crank slide block mechanism. Then , the structure of the proposed CVT is designed and the corresponding characteristic parameters are investigated. Analytical results show that (1) the proposed pulsed CVT is of slight fluctuation in the output rotational speed when the output rotational speed is high , while it is of strong fluctuation when the speed is low; (2) as compared with the traditional CVT , the proposed CVT is of less transmission mechanisms and simple structure due to the application of the positive and negative work strokes; and (3) with the proposed CVT, a transmission ratio varying from one to infinite can be achieved , and the output shaft may stop revolving without stopping the machine , which means that the proposed CVT can concurrently serve as a clutch.

Unit-Rood Fast Motion Estimation Algorithm Based on Starting-Point Prediction

Lin Zhao-hua Xie Cun-xi Zou Yan-biao

2007, 35(8):  49-54. 

Asbtract ( 281 )   PDF (393KB) ( 686 )  

Related Articles | Metrics

Complex and time-consuming computation in motion estimation poses a great challenge to the implementation of real-time video coding. In order to improve the real-time performance in motion estimation , the distribution characteristics and spatial correlation of the motion vectors are analyzed , and a unit-rood fast motion estimation algorithm
based on the starting-point prediction is proposed. In the proposed algorithm , the early stop criterion is adopted to predict the starting-point of search by comparing the sum of absolute difference values of the candidate points , and a unit-rood pattem is used to perform the search. Experimental results show that the proposed algorithm, which is of a searching speed of 3 - 17 times that of the Three~Step Search algorithm , 2 - 9 times that of the Diamond Search algorithm and 1. 19 - 4. 42 times that of the Adaptive Rood Pattem Search algorithm , maintains the picture quality well. Moreover , as compared with other motion estimation algorithms , the proposed algorithm is easy to implement and is of less computational complexity , better real-time performance , and performs better in terms of small motion video sequence.

Application of B-Spline Binary Wavelet Transform to Profile Image Processing of Gear

Wu Shang-sheng Fang Fe i-cun Duan Fu-hai Gou Guo-hua

2007, 35(8):  55-58. 

Asbtract ( 254 )   PDF (290KB) ( 811 )  

Related Articles | Metrics

In this paper , a spline wavelet is designed by using the cubic B-spline function and is then combined with the A'trous arithmetic of the 2D discrete binary wavelet and its Matlab programming to realize the edge detection of modular maximum. The proposed edge detection method based on the spline wavelet is theoretically and experimentally compared with the traditional Canny operator. It is found that the proposed method is of higher detection efficiency and can successfully solve the problems caused by the traditional edge detection method. An even better and clearer gear profile is obtained at a smoothing scale of j = 3.

QoS Optimization of Manufacturing Network ßased on Genetic Algorithm

Guo Yu-ming Sun Yan-ming Zheng Shi-xiong

2007, 35(8):  59-64. 

Asbtract ( 266 )   PDF (431KB) ( 702 )  

Related Articles | Metrics

The composition of quality of service (QoS) is a challenge to the system with service-oriented architecture (SOA). The classical optimal criteria for the SOA of a manufacturing network (MN) are the time cost of production and the response time of the system. In this paper , a new method is proposed to optimize the QoS of a MN based on the genetic algorithm (GA). In the proposed method , first , the material and information flows in a MN are modeled respectively with the colored Petri net (CPN) and the queuing theory.Then ,the models are scheduled based on the GA , and a nearly optimal solution to the QoS is thus obtained. In the algorithm , each chromosome is made up of two gene-coding sections that respectively correspond to the priority rules and the weight coefficients and denotes the schedule solution to the material and information flows in the MN , and the choice , the crossing and the variation are all involved in the genetic operation. Moreover , the performance index values of eveIγchromosome in each generation are gained by simulation. The QoS fitness of the MN is then computed by means of fuzzy comprehensive evaluation. Simulation results show that the proposed method can effectively optimize the QoS of a manufacturing network

Multi -Maintenance Management System Based on Prevention Maintenance

Wen Xu-hui Yang Li-hong Zeng Yan

2007, 35(8):  65-69. 

Asbtract ( 269 )   PDF (362KB) ( 697 )  

Related Articles | Metrics

In this paper , four models respectively for the controlled route inspection , the fault analysis , the reliahility management and the condition monitoring are analyzed , and an alarm system for equipment fault is established hy taking the route inspection and the fault analysis as the two cores. Then , based on the theories of conditionhased maintenance , prevention maintenance and reliability-centered maintenance , a multi-maintenance management system focusing on the prevention maintenance is designed. According to the application results , it is found that the proposed system is effectively applicable for the design of equipment operation and maintenance modules in the enterprise asset management system.

Materials Science & Technology

Preparation of ATO-Coated Conductive Fiber

Wu lian-qing Yan Dong-liang Wang Yong-qing Lu Zhen-ya

2007, 35(8):  70-74. 

Asbtract ( 235 )   PDF (366KB) ( 969 )  

Related Articles | Metrics

Conductive fiher was prepared hy coating a layer of antimony-doped tin dioxide (ATO) on the surface of mullite fiher via the co-precipitation method. The influence of the preparation process on the electric resistivity and the color of the prepared conductive fiher was then investigated. The results show that (1) after heat treatment at 600 to 1 000 ℃ , the conductive fiher is of a resistivity less than 50Ω·cm , which is almost the same as that of the ATO prepared in the same conditions; (2) when the heating temperature is higher than 1000℃ , the resistivity of the conductive fiher ahruptly decreases due to the compensative effect resulting from the entry of a pa吐of Al³⁺ into the SnO₂ lattice; (3) the lightness L * of the conductive fiher is higher than that of the ATO prepared at the same temperature , with a difference heing more than 10 units; and (4) the chromatic aherration ΔE between the conductive fiher and the standard harium sulfate sample is less than 10 NBS.

Mechanical Property of PP / CaCO₃ Composite in Vibration Force Field

He He-zhi Wang Yuan Yan Wei-bin Qin Xue-kui

2007, 35(8):  75-79. 

Asbtract ( 266 )   PDF (336KB) ( 568 )  

Related Articles | Metrics

In order to investigate the effects of the novel dynamic three-screw extrusion moulding technology on the mechanical properties of the specimen , PP/CaCO₃ composites were selected as the object to reveal the vibration parameters on the mechanical property and the section morphology structure. In the investigation , the vibration force with a frequency varying from 0 to 60 Hz and an amplitude varying from 0 to 250μm was loaded on a three-screw extruder , and the tensile strength and the impact strength of the specimens were tested , followed by a SEM measurement. The results show that there exists an optimum point for the response of mechanical properties to vibration parameters , and that , as compared with the extrusion in the steady state , the composites sho节an increase in impact strength by 2 1. 7 % at a 20 Hz and 225μm vibration , and an increase in tensile strength by 10. 4% at a 20 Hz and 145μm vibration.

Predication of Percolation Threshold of Conductive Polymer Composites

Liang Ji-zhao yang Quan-quan

2007, 35(8):  80-82,88. 

Asbtract ( 284 )   PDF (249KB) ( 956 )  

Related Articles | Metrics

Percolation threshold is one of the important parameters describing the conductive properties of conductive polymer composites. However , the prediction of percolation threshold is indeterminate due to the complicacy of the inf1uence factors. In order to solve this problem , this paper analyzes the percolation behavior and the mechanisni of conductive polymer composites from the view point of microscopic structure , and proposes a new method to predicate the percolation threshold ψ_c based on the Flory gelation theory and the Bueche infinite network model. A comparison of the predicted results with the results in the literature reveals that the proposed method may lead to a predicated percolation threshold which is even closer to the result from the experiment with conductive high-density polyethylenel carbon black composites.

Synthesis of Quaternary Ammonium Cationic Cellulose Ether

Zhao yao-ming Li yan-ming Gao Guang Liu Hai-min

2007, 35(8):  83-88. 

Asbtract ( 339 )   PDF (385KB) ( 543 )  

Related Articles | Metrics

Alkali cotton cellulose and 3-chloro- 2-hydroxypropyltrimethylamplOnium chloride (CHTAC) were respectively used as the material and the etherizing agent to prepare quaternary ammonium cationic cellulose ether ,'and the effects of1he NaOH/CHTAC molar ratio , the etherization temperature and the etherization time on the preparation were analyzed. Then , the structure of the product was identified by means of IR spectrography. The results show that (1) the cotton cellulose treated in 30% sodium hydroxide solution at 25℃ for lh is of high water-reserving value and good reaction activity; (2) in i-propanol medium with a NaOH/CHTAC molar ratio of 1. 2 , cationic cellulose ether with a degree of substitution (DS) of 1. 15 can be obtained at 45℃ after treatment for 3 h; and (3) in the media such as methanol , ethanol , i-propanol and acetone , the performances of the product improve with the decrease of the solubility parameter 8h , namely the amount of hydrogen bonds , especially in acetone which leads to high-performance product with a DS of 1. 19 and a transparency of 98. 1 %. Moreover , the IR spectrography results show that the cationization of cotton cellulose is successfully implemented.

Effect of Heat Treatment on Chemical Composition and Sheet Resistance of BaPbO₃ Thin Films

Lu Yu-dong Wang Xin Zhuang Zhi-qiang Liu Yong

2007, 35(8):  89-92. 

Asbtract ( 314 )   PDF (253KB) ( 267 )  

Related Articles | Metrics

Conductive perovskite-type BaPbÛ3 thin films were deposited onto Al₂O₃ substrates by a modified sol-gel method , using ethylene diamine tetra-acetic acid , citric acid and tartaric acid as the complex chelating agent and with water as the solvent. Then , the effects of heat treatment and temperature on the chemical composition and sheet resistance of the prepared films were investigated by XRD , EDXS and sheet resistance measurements. The results show that , in contrast with the conventional thermal annealing , the rapid thermal annealing technique requires higher annealing temperature to synthesize the BaPbO₃ phase and , at the same time , the molar ratio of Pb to Ba decreases with the increase of annealing temperature , which results in the increase of sheet resistance of BaPb03 thin films. Moreover , by the conventional thermal annealing technique , BaPbO₃ films with a sheet resistance of 32Ω/ 口and a thickness of 2. 5μm can be obtained by means of annealing at 670℃ for 10 min.

Electrochemical Behaviors of PhosphatedlMolybdate Post-Sealed Hot-Dipped Galvanized Steel Sheet

Lin Bi-lan Lu Jin-tang Kong Gang

2007, 35(8):  93-97,108. 

Asbtract ( 287 )   PDF (383KB) ( 837 )  

Related Articles | Metrics

The hot-dipped galvanized (HDG) steel sheet was phosphated and then post-sealed using molybdate solution. Also , the corrosion performances and electrochemical behaviors of the phosphated/molybdate post-sealed HDG steel sheet in 5 % N aCl solution were investigated , using Tafel polarization and electrochemical impedance spectroscopy (EIS) measurements. The results were finally compared with those of the steel sheet only with phosphating process. It is found that , after the post-sealing of the phosphated HDG samples with molybdate solution , the anodic and cathodic processes of the zinc corrosion are conspicuously suppressed , the corrosion protection efficiency markedly increases , and the electrochemical impedance increases by more than one order of magnitude. All this reveals a synergistic effect of the corrosion resistances of the phosphate coatings and the molybdate films. It is alsQ found that the low-frequency diffusion impedance increases with the immersion time at the initial stage of immersion in 5% NaCl solution , which demonstrates clearly the self-repairing capability of the composite coatings.

Fractal Analysis of Rebound Testing Data for Compression Strength of Concrete

HuXiao-fang Hu Da-wei

2007, 35(8):  98-102. 

Asbtract ( 316 )   PDF (308KB) ( 806 )  

Related Articles | Metrics

Fractal theorγis of special merits in processing random and discrete data. When it is adopted to analyze the rebound testing data of random and discrete compression strength of concrete , much more reliable results can be obtained , as compared with the general regression method. In this paper , the Rebound Measuring Point PositionRebound Value curve (RPV curve) on a 2D coordinate plane is established , and the box-dimension calculation inethod is adopted to design a calculation program to obtain the fractal dimension of the RPV curve and to calculate the compression strength of concrete. The results show that there is a linear relationship between the fractal dimension of the RPV curve and the compression strength , and that the proposed method can calculate the compression strength without testing the carbonation depth. Moreover , it suits the compression strength testing of concrete with big volumes and thus offers a new simplified approach to the detection of the compression strength of concrete.

Contrastive Investigation into Activated Effects of Two Alkali-Activators on Geopolymers

Guo Wen-ying Wen Zi-yun Yin Su-hong Wu Guo-lin

2007, 35(8):  103-108. 

Asbtract ( 292 )   PDF (352KB) ( 615 )  

Related Articles | Metrics

The activated effects of two kinds of alkali-activators , namely , sodium hydroxide solution and sodium silicate solution , on metakaolinite were investigated using the large solid-liquid ratio method. In the investigation , the slurry was separated after a period of activation , and the separated solutions and powders were then analyzed , respectively. It is found that (1) in the separated solution after the reaction between sodium silicate solution and metakaolin , the polymerization degree of Si increases with the reaction time , the soluble Al polymerizes with the siliceous ion , and the separated powder contains both the fragment of metakaolinite and the gel of silicate-aluminium;( 2) in the separated solution after the reaction between sodium hydroxide solution and metakaolin , the contents of Si and Al increase with the reaction time , the soluble Al does not polymerize with the siliceous ion , and the separated powder only contains the fragment of metakaolinite; and (3) the siliceous ion in sodium silicate solution plays a significant role in the geopolymeric reaction.

Mathematical Sciences

Bifurcation and Stability of Steady -State Solutions to a Prey -Predator System

Fu Yi-ping Chen Xia

2007, 35(8):  109-113. 

Asbtract ( 240 )   PDF (279KB) ( 628 )  

Related Articles | Metrics

Based on the bifurcation and perturbation theories , the existence and stability of the steady-state solutions to a prey-predator system of three species with cross-diffusion are discussed. Then , by taking the birth rate of the prey , the death rate of the first predator and the death rate of the second predator as the bifurcation parameters in order , the weak semi-trivial solution bifurcated from the trivial one , the strong semi-trivial solution bifurcated from the weak one and the nontrivial solution are all respectively obtained. The stability conditions for all the bifurcated solutions are finally presented in the paper.

Existence of Nontrivial Solution to a Class of Quasi-linear Elliptic Equation

Yao Yang-xin Zhang Rui-min Wang Rong-xin

2007, 35(8):  114-117. 

Asbtract ( 220 )   PDF (179KB) ( 626 )  

Related Articles | Metrics

In this paper , the existence of the nontrivial solution to a class of quasi-linear elliptic problem is investigated based on the Hardy inequality and the Mountain Pass Geometry. As the basic solution to the discussed problem is difficult to obtain , an estimation of the basic solution is carried out and the corresponding (PS) c condition is proved.

Nonexistence of Solitary Peakon Solution to a Generalized Boussinesq Equation

Zhang Ben-gong Liu Zheng-rong

2007, 35(8):  118-122. 

Asbtract ( 298 )   PDF (211KB) ( 625 )  

Related Articles | Metrics

In this paper , the qualitative theory of differential equations and the bifurcation method of dynamical systems are used to investigate the existence of the solitary peakon solution to a generalized Boussinesq equation. In the investigation , the bifurcation phase portraits of the corresponding traveling wave system are given , which are then adopted to prove the nonexistence of the solitary peakon solution to the equation.

Recognition of DNA Sequences ßased on Hidden Markov Models

Luo Ze-ju Li Yan-hui Song Li-hong Zhu Si-ming

2007, 35(8):  123-126. 

Asbtract ( 329 )   PDF (261KB) ( 1047 )  

Related Articles | Metrics

According to the distribution variation of the L value with the DNA sequence structure in the hidden Markov model (HMM) training and by improving the traditional multiclass vote model , a fast training algorithm superior to the traditional one is proposed to recognize the intron and exon of the DNA sequence. The proposed algorithm only need to train one class of parameter of HMM model and the average accuracy rate of it reaches 90. 8%. As compared with the support vector machine , the proposed HMM model is more feasible in the multiclass classification and is of less time cost and higher recognition rate.