Table of Content

29 February 2016, Volume 50 Issue 02 Previous Issue    Next Issue

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Design and Strength Analysis of Porous Titanium Scaffold WANG Chunxiao,LI Xiang,LUO Yun 2016, 50 (02):  165-168.  Abstract ( 976 )   Save Abstract： Five Ti alloy scaffold models with different pore structures were designed and fabricated using the 3D printing technology. The micro porous feature and strength of the scaffold model were observed and tested. The results indicate that there is a certain error between the microstructure design feature and the fabrication feature, but within a controllable range. Under the condition of near porosity and the same pole sectional size, the threedimensional structure with different unit cells has a great impact on scaffold strength. The Vstructured model scaffold strength is closely related to pole intersection angle and pole length. The result of the theoretical analysis is in accordance with the experimental result. References | Related Articles | Metrics

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Numerical Analysis of Reinforcement Effect of Z-Pins withSpecial-Shaped CrossSection Under Mode I Delamination JIN Zhuyu,ZHANG Xiaojing 2016, 50 (02):  169-175.  Abstract ( 854 )   Save Numerical Analysis of Reinforcement Effect of ZPins with Abstract： A 3D finite element model was proposed to simulate a single Zpin for pullout test and for unpinned/Zpinned double cantilever beam (DCB) test. Static and sliding friction coefficients were used to simulate the debonding and pullout process of the Zpin. Connectors were used in the DCB model to simulate the bridging effect of the Zpins with the bridging curves calculated by the pullout model as input data. The bridging curves of the Z-pin with specialshaped crosssection for the pullout test and the loaddisplacement curves for the DCB test were calculated based on the proposed finite element model. The effect of the cross section perimeter of Zpin on the maximum bridging load was also discussed in detail. The simulation results were in good agreement with the experimental data. References | Related Articles | Metrics

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Theoretical and Experimental Study of Added Mass for Underwater Vehicles ZHOU Yong,CHE Chidong 2016, 50 (02):  176-181.  Abstract ( 1033 )   Save Abstract： The model of an infinite long cylinder submerged in fluid, which vibrates vertically, was investigated in this paper. Based on the analysis of incompressible flow field in limited area, the influence of fluidwidth, fluiddepth and submerge enceratioon added mass was analyzed using numerical computation. Thus, based on Lewis’ method, a fast prediction formula for added mass of underwater vehicle was proposed. The results show that the rigid wall leads to an increase in added mass, but as the distance increases (usually 5 times the crosssectional radius), the effect of the wall can be neglected. However, the free surface may reduce the added mass, and the effect can be ignored when the distance between the cylinder and the free surface is up to 6 times the crosssectional radius. The velocity potential on the free surface can be considered as zero only when the cylinder is vibrating at a high frequency or is far away from the free surface. References | Related Articles | Metrics

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Theory and Design of a GravityDriven Orthotic Device for Sitting Posture ZHOU Junfan,LUO Yun 2016, 50 (02):  182-187.  Abstract ( 790 )   Save Abstract： The working principles and limits of existing orthotic devices for sitting posture were analyzed. A novel way to help users easily maintain healthy sitting posture was proposed. By using fourbar linkage, body weight was transformed into torques to rotate the pelvis. A biomechanical experiment was conducted to acquire the relationships between external torques and rotation angles of the pelvis while sitting. Based on the experimental results, the prototype of the gravitydriven orthotic device was built. Its feasibility was proved by a verification experiment. The results showed that this device could help users easily maintain ideal pelvic incidence while relaxing low back muscles. References | Related Articles | Metrics

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Improved Bearing Resolution Approach for MVDR BeamForming ZHENG Enming1,LI Yuansong2,CHEN Xinhua1,YU Huabing1,SUN Changyu1 2016, 50 (02):  188-193.  Abstract ( 1176 )   Save Abstract： An approach was proposed to improve the minimum variance distortionless response (MVDR) beamforming bearing resolution by designing an enhancement factor in its weight vector which is known to be a principal factor in resolution improvement under a high signaltonoise ratio (SNR) condition. This method can provide improved bearing resolution not at the expense of the signaltonoise plus interference ratio gain. The simulation results show that this method can effectively improve the MVDR beamforming bearing resolution without losing the signaltonoise plus interference ratio gain. References | Related Articles | Metrics

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A Damage Model Considering Shear Nonlinearity for Progressive Failure Analysis of Composite Laminates LIU Weiguang,YU Yin,WANG Hai 2016, 50 (02):  194-199.  Abstract ( 1110 )   Save Abstract： A damage model considering the effect of shear nonlinearity was proposed to predict the ultimate load of laminated composites which exhibited significant shear nonlinearity. Shear nonlinearity constitutive relations for the laminates were defined with the RambergOsgood equation. Based on continuum damage mechanics, a three dimensional FE model for damage analysis of composite materials was established. The onset of the damage of composite laminates was modeled with 3D Hashin’s initiation criterion and Ye criterion. The damage index was applied to analyze the damage extension. The model was implemented with a UMAT subroutine. The convergence was improved by using the viscous regularization method. The model was applied to the progressive failure analysis of notched AS4/PEEK composite laminates. Simulation results agreed well with the experimental date, which indicated that the proposed model had a better accuracy than the model published. References | Related Articles | Metrics

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Vibration Characteristics of Cochlear Basilar Membrane in Guinea Pig TA Na1,XU Lifu1,RAO Zhushi1,HUANG Xinsheng2,ZHOU Lei2 2016, 50 (02):  200-203.  Abstract ( 1118 )   Save Abstract： In order to study the auditory mechanism of the guniea pig cochlea, the stapes footplate (SF) and basilar membrane (BM) velocity responses to pure tone were measured using a laser Doppler velocimetry which was able to measure subnanometer vibration from the middle ear and cochlea of the guinea pig. The BM velocity was measured by a reflective microbeads placed onto the scala tympani surface of the BM. The velocity response of the SF was also tested, allowing the calculation of a BM transfer function. The transfer function shows typical tuning features. For a given BM location, the characteristic frequency (CF) of the BM was about 11 kHz. The results show that frequency selectivity and travelling wave exist in the BM. References | Related Articles | Metrics

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Feature Selection of Emg Signal Based on ReliefF Algorithm and Genetic Algorithm HE Tao,HU Jie,XIA Peng,GU Chaochen 2016, 50 (02):  204-208.  Abstract ( 1005 )   Save Abstract： To address the high dimension of signal characteristics and low operation efficiency of electromyography (EMG), an algorithm for feather selection was proposed based on ReliefF feature evaluation and the genetic algorithm. The characteristics of the signal was analyzed, the features of the EMG signal with wavelet transform were extracted, the weight of each feature was assessed using the ReliefF algorithm, and the feature subset which has a obvious influence upon classification result was selected. Then the best feature subset for the classification results was screened out by using the genetic algorithm. Besides, the operation time and classification results of the ReliefFGAWrapper algorithm were compared with those of the global search. The result shows that the proposed algorithm not only guarantees a good classification result but also improves the operational efficiency. References | Related Articles | Metrics

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Coalescence Process of Droplets on DecimillimeterScaled Grooved Surfaces HU Haibao1,HE Qiang1,HUANG Suhe1,XUE Qunji2,DU Xiangdang1 2016, 50 (02):  209-214.  Abstract ( 902 )   Save Abstract： This paper investigated the coalescence of two droplets on decimillimeterscaled grooved surfaces by using a highspeed camera and compared the coalescence process of isometric/anisometric droplets on parallel/vertical grooved surfaces. During the experiment, a syringe needle was inserted from the bottom of the substrates in order to obtain a horizontal coalescence of a preplaced static droplet and a slowly growing quasistatic droplet. The results show that the whole coalescence process can be divided into the coalesce process and the oscillation process. When the droplets are isometric, on parallel grooved surfaces, due to the guiding effect of grooves, they oscillate sharply by the direction of grooves, accompanied by reciprocating contact line. On vertical grooved surfaces, limited by the energy barrier of vertical grooves, the oscillation of droplet is weaker and the contact line is almost fixed, while the vertical amplitude of oscillation is distinct. Different phenomena are observed when the droplets are anisometric: the smaller droplet is attracted to the other side, resulting in an asymmetrical coalescence process. Besides, the height of liquid bridge, the lasting time of coalescence and the length of contact line increase as the overall volume of the two droplets increases. References | Related Articles | Metrics

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Electrochemical Investigation of Corrosion Behavior of 304 and 316L Stainless Steels in HighTemperature Water DUAN Zhengang1,DU Donghai1,ZHANG Lefu1,MENG Fanjiang2,SHI Xiuqiang2 2016, 50 (02):  215-221.  Abstract ( 1825 )   Save Abstract： The effects of temperature and dissolved oxygen (DO) on electrochemical behaviors and the oxide films formed on type 304 and 316L stainless steels in primary water in simulated pressured water reactor (PWR) were investigated by means of potentiodynamic polarization measurements, scanning electron microscope (SEM) observation and energy dispersive Xray spectrum (EDS). The results revealled that the passivity of the oxide films degraded with increasing solution temperature. The corrosion potential (Ecorr) shifted to positive direction while corrosion current density (Jcorr) decreased significantly with the increase of DO. The oxide films formed on 304 and 316L stainless steels showed a doublelayer characteristic, and the size of oxide particles and the space between oxide particles on outer layer increased with increasing temperature but decreased with increasing DO. The type 316L stainless steels exhibited superior corrosion resistant characteristics than 304 SS in all investigated conditions. References | Related Articles | Metrics

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Tribochemical Polishing of Single Crystal Sapphire Wafer LI Gang,WEN Donghui,WANG Yangyu 2016, 50 (02):  222-227.  Abstract ( 1060 )   Save Abstract： In order to reveal the mechanism of tribochemical polishing process between sapphire wafer and silica colloid particles, contact conditions were discussed by using the tribochemistry theory and nanoindentation method. Stress distribution of sapphire wafer under unload condition was simulated by using the finite element method. When the contact stress along the subsurface of sapphire wafer is about 5 to 15 GPa, the activation energy during tribochemical reaction is approximately 14.46 kJ/mol, and 0.07 to 0.23 μm/min for the reaction rate. When the contact radius between silica colloid and sapphire wafer is around 15 to 21 nm during the tribochemistry reaction process, the deformation value is about 6.88 to 10.22 nm. The experimental results for lowloading nanoindentation and polishing process show that when the contact force is less than 0.7 mN, without considering the hardness and form errors between diamond indent tip and abrasive grit, the polished sapphire wafer can achieve a smooth surface with Rt 38.19 nm and Ra 3.62 nm. References | Related Articles | Metrics

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Synthesis of Sulfosalicylic Acid Doped Polyaniline/MultiWalled Carbon Nanotubes Composite Film Modified Electrode and Its Applications SUN Xiaowen,YANG Peng,ZHANG Wenguang 2016, 50 (02):  228-234.  Abstract ( 872 )   Save Abstract： The sulfosalicylic acid (SSA) doped polyaniline/multiwalled carbon nanotubes (PANI/SSA/MWCNTs) composite film modified electrodes were synthesized by electropolymerization. The modified electrode was characterized utilizing the scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR) and electrochemical techniques. The results showed that the morphology of the PANI/SSA/MWCNTs modified Pt electrode was more uniform and compact compared with the PANI Pt electrode. The conductive properties improved significantly and there was an increment in the current from 145 μA up to 1.61 mA. The charge injection capacity of the electrode increased by about 12.1 fold. The electrodes showed a high electrocatalytic activity and good linear current response of ascorbic acid (AA) with a sensitivity of 9.09 A/(mol·cm2) and a correlation coefficient of 0.996 0. In addition, this electrode could be used for selective determining AA in the presence of oxalic acid with a large peak separation of about 340 mV. References | Related Articles | Metrics

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Effect of Process Parameters on Shrinkage and WarPage of Rapid Heat Cycle Molding Plastic Part WANG Menghan,LI Yanzhao,LIU Xiao,XIA Zhizi,CHEN Mingliang 2016, 50 (02):  235-240.  Abstract ( 869 )   Save Abstract： In order to define the effect of process parameters on shrinkage and warpage of large flat plastic parts by rapid heating cycle molding (RHCM), taking an airconditioning panel plastics as an example, MOLDFLOW was used to establish the finite element model and to conduct simulation and analysis. By using Taguchi methods, the effect of process parameters such as melt temperature, packing pressure, heating time, packing time, cooling time and injectiontime on the comprehensive quality was studied. The single factor experiment method was applied to analyze the effect of mold temperature on shrinkage and warpage. Besides, the influence law of other process parameters on shrinkage and warpage at different mold temperatures was also studied. The results show that volumetric shrinkage and warpage decrease apparently with mold temperature rising to the thermal deformation temperature of the polymer material. The comprehensive quality is the best of all when the heating time is 35 s. At different mold warpage temperatures, volumetric shrinkage and warpage of the product increase quasilinearly with the melt temperature rising, but decrease with the packing pressure increasing. However, they fluctuated within a narrow range with the packing time increasing. References | Related Articles | Metrics

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Loading Measurement Method for Residual Stresses of InjectionMolded Part LIU Hong1,JIANG Lanfang2,CHEN Xianli1 2016, 50 (02):  241-245.  Abstract ( 811 )   Save Abstract： Based on the principle of linear superposition, a nondestructive measurement for residual stresses, i.e. the loading measurement method for residual stresses was proposed. In a certain way, it applies loads on the injectionmolded part, measures the strain on the surface measuring points, and calculates the loading stresses and residual stresses on the measuring points of the injectionmolded part. The results show that the loading measurement method has advantages over the hole drilling method and the layer removal method because it has a comparatively lower measuring cost, and it is precise when the loading state of the measured part is under the elastic range. References | Related Articles | Metrics

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Influencing Factors and Characteristics of Hydrodynamic of Conical Cavitator LI Fuyuan,DANG Jianjun,ZHANG Yuwen 2016, 50 (02):  246-250.  Abstract ( 855 )   Save Abstract： In order to get a full understanding of the conical cavitator, an experiment of certain cavitator was conducted in a water tunnel, and a numerical simulation of conical cavitator with different cone angles was conducted. The results of the experiment and numerical simulation were analyzed, and the characteristics of the drag and lift were obtained. The results show that the cone angle have a great influence on force characteristics of the conical cavitator. The hydrodynamic changes with certain regulation when the cone angle expands. The angle of attack has an impact on the drag and lift of the cavitator. Different cone angles have different influences at the same angle of attack. The research results are meaningful for the practical use of the conical cavitator and control method of supercavitating vehicles with a conical cavitator. References | Related Articles | Metrics

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Analytical Methodology of Predicting Mode Ⅰ Stress Intensity Factor for Cracked Panels with Bonded Stiffener HE Shijiu,ZHANG Xiaojing,WANG Hai 2016, 50 (02):  251-256.  Abstract ( 785 )   Save Abstract： A theoretical model for distribution of bridging traction in bonded stiffeners which functioned as crack retarder was proposed. An analytical methodology of assessment mode Ⅰ stress intensity factor for cracked panels with bonded stiffeners was developed based on superposition principles. The analysis included the stress intensity factor solution for cracked skin due to broken and intact stiffeners by using displacement compatibility approach, and the stress intensity factor solution for cracked panels due to bridging stiffener. The methodology was verified by using the finite element method (FEM) and the experimental data from various literature sources. The results show that the theoretical model is effective in obtaining the bridging stress and mode Ⅰ stress intensity factor for cracked panels with bonded stiffeners. References | Related Articles | Metrics

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Influence of Ocean Environment Parameters on Scholte Wave ZHU Hanhaoa,b,ZHENG Honga,LIN Jianmina,TANG Yunfenga,KONG Lingminga 2016, 50 (02):  257-264.  Abstract ( 1364 )   Save Abstract： Based on the Scholte wave model with halfspace ocean bottom, the bottom model was extended to the horizontalstratified medium. With the wave equation of fluids and elastic solids in cartesian coordinates, the solution to Scholte wave, which was based on layered elastic ocean bottom model, was proposed. The particle orbits and displacement were also discussed using the normal modes theory. The influence of ocean environments (including sound speed profile and ocean bottom parameters) on the propagation of Scholte wave was studied. The simulation results show that the shearwave of elastic bottom has the greatest influence on Scholte wave, and the inflexion of its dispersion curve can be used to estimate the thickness of sediment. References | Related Articles | Metrics

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Green’s Function of Internal Waves in Uniformly Stratified Fluid ZHU Renchuan1,GAO Yang1,MIAO Guoping1,YAO Zhichong2 2016, 50 (02):  265-271.  Abstract ( 918 )   Save Abstract： A mathematical model and analysis methods for the internal waves generated by pulsating point sources were theoretically established. When ω2 References | Related Articles | Metrics

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Analysis of Stresses Near an Elliptical Hole With a Random MicroCrack ZHOU Sheng,LI Zhaoxia 2016, 50 (02):  272-277.  Abstract ( 891 )   Save Abstract： In view of the problem of analysis of stress field near an elliptical hole with a random microcrack, which existed widely in practical projects, a theoretical model was proposed in this paper. According to local conformal properties of microcrack in smallscale, the approximate composite conformal mapping function was established. By splitting the microcrack and macrohole, different scale stress fields were obtained, which extended the application range of the complex function method. The research results show that the stress fields and stress intensity factor (SIF) near the microcrack can be obtained by constructing and scale separating composite conformal mapping function. On the condition that the infinite plane containing an ellipse hole with a random microcrack is under vertical uniform load, the bigger the ratio of long axis and short axis of ellipse hole is, the faster the KI is decreased around the edge of ellipse, and the greater the maximum is. When the ratio is sufficiently small, the microcrack position does not affect stress intensity factor of the microcrack. References | Related Articles | Metrics

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Numerical Simulation Methods of MicroBubbles Drag Reduction and Scale Effect FU Huipinga,b,LI Jieb 2016, 50 (02):  278-282.  Abstract ( 989 )   Save Abstract： Based on the mixture model, Eulertwofluid model and population balance model, bubble drag reduction using gas injection for the flow over a twodimension flat plate was numerically simulated. Effects of bubble size and gas injection rate on bubble drag reduction and the scale effect were analyzed. The results show that the decrease of bubble size can increase drag reduction which increases along with the increase of gas injection rates within a certain range. When the gas injection rate is too low or too high, drag reduction would decrease. The results obtained by using the population balance model are closer to the experimental data than those obtained by using other models. If Reynolds number increases due to the increase of the plate size, the drag reduction level would decrease. References | Related Articles | Metrics

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Influence of Cell Rotation on Its Chemical Microenvironment Inmicrochannels LI Peiye,DU Xiaohui,HU Yandong,ZHAO Shexu 2016, 50 (02):  283-287.  Abstract ( 813 )   Save Abstract： The influence of cell rotation on its chemical microenvironment was investigated by performing systematic numerical simulations. The influences of the line speed, rotational direction and the cell size were investigated. The results show that when a till cell starts rotating, the ambient concentration field and the flow field keep changing until they reach steady states. Different cell rotational directions lead to dramatic changes on the disturbing effect; and the peripheral speed of the cell enhances the stirring effect and hence decreases the apparent chemotactic effect.This paper contributes to the development of chemotactic experimental platform and quantitative measurement methodology. References | Related Articles | Metrics

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Stress Intensity Factor Calculation of Surface Crack at Weld Toe of Ocean Engineering Structures Under Wave Loads YAN Xiaoshun1,2,HUANG Xiaoping1,LIANG Yuanhua3,LI Luodong3 2016, 50 (02):  288-293.  Abstract ( 751 )   Save Abstract： This paper proposed a stress intensity factor calculation method for structures under wave loads. The proposed method was proved correct by comparing it with the empirical formulas. Then, the method was applied to the surface crack at weld toe of a bracket between the column and brace of a semisubmersible platform. The results show that the stress intensity factor ranges calculated by empirical formulas are very different from those of the proposed method. The stress intensity factor ranges for all crack sizes of a structure under wave loads can be derived by a part of results obtained by the proposed method. References | Related Articles | Metrics

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Comparative Study of Kinematics Characteristics of Vortex Rings Generated by Piston and Disc QIN Suyang,XIANG Yang,LIU Hong 2016, 50 (02):  294-299.  Abstract ( 940 )   Save Abstract： Numerical methods were used to simulate the formation of vortex rings while the methods of stream function and Lagrangian coherent structures were applied to analyze the physical characteristics of vortex rings. It is found that the vortex rings generated by two mechanisms belong to thin core vortex. The distribution of vorticity in core is Gauss distribution which has a unified model. Due to the difference between formation environments, there are several differences between kinematics characteristics, mainly in transportation velocity and nondimensional core radius. Thus, the pure vortex rings generated by piston can reveal the mechanism of the flow over a body which is like disc and airfoil. References | Related Articles | Metrics

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Simulation Analysis of VibroAcoustic Characteristics of Traditional Guzheng DENG Xiaowei1，YU Zhengyue1，YAO Weiping1，CHEN Minjie2 2016, 50 (02):  300-305.  Abstract ( 1022 )   Save Abstract： Based on the vibroacoustic principle, the simplified model of traditional Guzheng was proposed. A 3D finite element model (FEM) of the Guzheng structure was established to analyze the vibration frequency response with the force of the strings and bridge acting on the panel as the vibration condition. The acoustic FEM and its analysis were established with vibration frequency response as the acoustic boundary conditions, and the frequency response characteristics of radiated sound pressure were obtained. The results show that the simulation results of Guzheng vibration are consistent with the experiment while the peak frequency of the radiated sound pressure of Guzheng is consistent with the simulation results. The acoustic radiation efficiency between 350 and 550 Hz is higher than that before 350 Hz. The upward acoustic radiation of Guzheng vibration is stronger than the downward one. References | Related Articles | Metrics

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Characteristics of NonSmooth Surface Drag Reduction Influence on Centrifugal Pump Impeller MOU Jiegang1,DAI Dongshun1,GU Yunqing1,LIU Jian1,ZHENG Shuihua1,WANG Evan2 2016, 50 (02):  306-312.  Abstract ( 830 )   Save Abstract： To analyze the influence of nonsmooth surface on the performance of centrifugal pump, a nonsmooth surface centrifugal pump impeller calculation model with flow drag reduction effect was established based on the characteristic of bionic pit surface drag reduction. The internal flow field of it was numerically simulated through RNG kε turbulence model, the flow regularity in nonsmooth unit cell was analyzed, and the near wall influences of nonsmooth unit cell on the velocity distribution, shear stress, internal flow field of the centrifugal pump were studied. The results show that the pit shaped nonsmooth surface can reduce the torque caused by viscous resistance by maximumly 5.8%. The nonsmooth surface well controls the near blade wall boundary layer flow and reduces the wall shear stress of the blade. The pit shaped nonsmooth surface can reduce the fluid turbulent flow in the centrifugal pump impeller, reduce the energy dissipation caused by the turbulent, make the fluid flow more stable in the impeller, and improve the efficiency of the centrifugal pump. References | Related Articles | Metrics

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Financial Prediction System Based on Combinaton of Genetic Algorithm with BP Neural Network SONG Xiaoyong,CHEN Niansheng 2016, 50 (02):  313-316.  Abstract ( 870 )   Save Abstract： Neural network can deal with nonlinear systems effectively and is applied widely on financial early warning and financial forecast. Neural network coupled with genetic algorithms is an intelligent simulaton algorithm in predicting financial parameter system. Genetic algorithm predicts the coefficient of the topology layers in neural network predicting the financial parameter system. This paper predicts business debt ratio. It proves that the combination of genetic algorithm with BP neural network can improve the efficiency and the predicting precision of network system. References | Related Articles | Metrics