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2011 Vol. 43, No. 1

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Nozzle effects on performance of pulse detonation engines
Li Xudong Wang Chun Jiang Zonglin
Thermal efficiency of pulse detonation engines (PDEs) wasformulated with thermodynamic cycle analysis when the exhaust flow is notperfectly expanded, the quantitative relation of PDEs thermal efficiency andnozzle exit pressure ratio was examined under different initial combustortemperature, the closer the exhaust pressure gets to ambient pressure, thehigher efficiency PDE could achieve. Effects of the CD-nozzle and theD-nozzle on PDE performance are investigated by numerical simulations; theobtained thrust and impulse of PDE are compared with each other fordifferent cases, and nozzle effects on each period of the PDE cycle are alsoinvestigated. In addition, the influence of reflected shock waves from theconvergent section of a CD-nozzle is also studied to show that the reflectedshock waves actually affect the thermodynamic cycle efficiency more or less,but when the shock Mach number is less than 1.5, PDE thermal efficiencyreduction is quite slight and the positive effects of nozzle are dominated.
2011, 43(1): 1-10. doi: 10.6052/0459-1879-2011-1-lxxb2009-754
Lattice boltzmann simulation of the flow around a circular cylinder oscillating streamwisely
Gong Shuai Zhaoli Guo
A newly developed lattice Boltzmann method (LBM) is used tosimulate the incompressible flow past an oscillating circular cylinder. Boththe vortex shedding modes and fluid forces are investigated. The simulationsare conducted at a relatively low Reynolds number (Re \le 200). Numericalresults show the existence of symmetric/asymmetric modes of vortex formationwhich are confirmed by previous experiments in the near wake, including themode which is not found by some traditional numerical methods. Therelationship between oscillation amplitude and lock-on range is studied, andthe results show that the lock-on ranges increase with the increasingoscillation amplitude. The relationship between fluid forces (lift and drag)and oscillation frequency /amplitude is also studied quantitatively.
2011, 43(1): 11-17. doi: 10.6052/0459-1879-2011-1-lxxb2009-702
Energy saving mechanism of ``channeling effect'' in fish school swimming
Wu Chuijie
To reveal the energy saving mechanism in fish schoolswimming, numerical simulation of the basic unit of fish school with threefish is presented. An adaptive mesh projection method is used to solve the2D incompressible Navier-Stokes equations, and the moving boundaries handledwith the immersed boundary method. The direction of swimming is controlledby the oscillating of fish head. The results show that three fish are ableto swim with the same speed and different frequencies. When the middle fishfalls behind about 0.4 times of body length, its swimming frequency is only54% of that of the other two fish, to demonstrate that the ``channelingeffect'' is remarkable. Therefore, to save energy, the fish in shoal shouldbe arrayed closely.
2011, 43(1): 18-23. doi: 10.6052/0459-1879-2011-1-lxxb2010-216
Large eddy simulation of spanwise rotating turbulent channel flow
Liu Ning
Large eddy simulation (LES) is used to predict flow filedin fully developed turbulent channel flow rotating along spanwise axis atsix different angular velocities. Statistically-averaged streamwise velocityprofile consists well with available experimental data near the wall. Thephenomena that turbulence and wall friction are enhanced near pressure sideand depressed near suction side are recovered. Explanation for theevolvement of lower order turbulence correlations is consistent with theanalysis of the transport equation for each turbulence stress component. Thebursting and the shape of near wall streak are also affected by rotationalforces, resulting in variation of wall friction velocity. Furthermore,velocity distribution in streamwise cross section indicates that Coriolisforce induces secondary flow normal to the wall. Such secondary flowgenerates counter rotating vortex pairs in streamwise, which shift towardspressure side as the rotating velocity increases. The results with lowcomputational cost agree with available conclusion, implying possibleapplication of LES for engineering usage.
2011, 43(1): 24-31. doi: 10.6052/0459-1879-2011-1-lxxb2009-316
Numerical simulation for a free-burning argon arc with MHD model
Tian Junguo Deng Jing Li Yaojian Xu Yongxiang Sheng Hongzhi
In this work, the Magneto-Hydrodynamic (MHD) model basedon the magnetic vector potential description is used to simulate a DC argonfree-burning plasma arc. The temperature and velocity fields of the arc areobtained by solving the electromagnetic equations and hydrodynamic equationswith the coupled iterative computation. The simulation results that clearlyshow the phenomenon of high temperature cathode jet of plasma-arc arecompared with the other research results. The effect of the cathode sheathto the simulation results is analyzed specially in this paper. For the argonfree-burning arc, the characteristics of plasma arc flow and heat transferunder different arc current conditons have been obtained, which providessome useful knowledge for industrial applications of arc plasma.
2011, 43(1): 32-38. doi: 10.6052/0459-1879-2011-1-lxxb2009-742
The analytical solution of the stagnation point flow of an upper-convected maxwell fluid with slip
Zhu Jing Zheng Liancun Zhang Xinxin
During recent years, with the rapid development ofscience and technology in micro- and nano-measuring technologies, it hasbeen found that there are many significant differences in fluid flow atbetween macro-scale and micro/nano-scale, such as wall-slip phenomenon.Fluids exhibiting slip are important in technological applications.Therefore better understanding of the phenomenon of slip is necessary. Thispaper presents a theoretical analysis for the MHD stagnation-point flows ofan upper-convected Maxwell fluid towards a stretching sheet with slip.Thegoverning system of partial differential equations is first transformed intoa system of dimensionless ordinary differential equations. By using thehomotopy analysis method, a convergent series solution is obtained.Thereliability and efficiency of series solutions are illustrated by goodagreement with numerical results in the literature.Besides, the effects ofthe slip parameter, the magnetic field parameter, velocity ratio parameter,suction/injection velocity parameter and elasticity number on the flow areinvestigated. The flow and shear stress depend heavily on thevelocity slip parameter \gamma. Also, effect of increasing values of\gamma is to decrease the variation of |f''(0)| and the surface shear stress|f''(0)| is close to 0 with \gamma \to \infty. The dimensionless velocity f'(\eta)decreases with an increase in elasticity number \beta and \gammawhen velocity ratio parameter d is large than 1. However, an opposite behavior has been found when d<1.
2011, 43(1): 39-44. doi: 10.6052/0459-1879-2011-1-lxxb2009-667
On the passive laminar flow control technique of swept wing
Li Yueli Li Dong Yang Yong
The key of swept wing passive laminarflow control based on leading-edge roughness elements array technique is thechoice of control wavelength. The author advanced the quickest wave theoryfrom the view of the physical mechanism of control wave and flowinteraction. The author investigated infinite swept wing optimal controlwavelength through solving three-dimension incompressible Orr-Sommerfeldequation by using Mack method. Numerical results validated 8\,mm is thecontrol wavelength under Saric's experimental condition by fixed wavelengthmethod. By using adaptive searching method the optimal control wavelengthsof this model under different conditions. Transition delaying was achievedthrough wind tunnel experiments. This paper also advanced the technique ofroughness elements array appended by silk-screen, and mixed solventsublimation method, which enriched the experimental means.
2011, 43(1): 45-54. doi: 10.6052/0459-1879-2011-1-lxxb2009-766
Numerical perturbation higher-order accurate reconstruction of quick scheme for the convective-diffusion equation
Zhu Ke Li Mingjun
In this paper some higher-order accurate reconstructionschemes for the convective-diffusion discrete equations, in which theviscous and convection terms are discreted respectively as second-ordercenter and QUICK scheme, are developed by using the numerical perturbationalgorithm presented by Professor Gao Zhi. The reconstruction methods includethe global reconstruction using all node-information in a discrete element,up-stream and down- stream reconstruction using upstream and downstreamnode-information, respectively. By using those two reconstructions, twokinds of numerical perturbation higher-order accurate schemes are obtainedand called as Gao's QUICK scheme (G-QUICK scheme). Simplicity of G-QUICKscheme is the same as QUICK scheme.Gao's algorithm was early used to reconstruct three node schemes of theconvective-diffusion equations. The research in this paper shows that, Gao'salgorithm is also effective for reconstruction of multi-node scheme likeQUICK scheme. Compared with QUICK scheme, G-QUICK schemes for globalreconstruction, up-stream and down-stream reconstructions, have the higherorder accurate and wider stable region. For global reconstruction, G-QUICKschemes and QUICK scheme are conditionally stability; however for the up-and down- stream reconstruction, G-QUICK schemes contain some absolutelysteady schemes. Excellent properties of G-QUICK schemes are proved byanalysis and numerical tests. The G-QUICK schemes of up- and down- streamreconstruction provide a new way for QUICK scheme without artificialviscosity. Multi-node high order accuracy upwind and central schemes havebeen widely used in the calculation of turbulent. New schemes developed inthis paper have the same high order accuracy but the less node, and theiradvantages and effectiveness in calculation of turbulent are worthy offurther study.
2011, 43(1): 55-62. doi: 10.6052/0459-1879-2011-1-lxxb2009-759
Theoretical analysis on the interface defeat of a conical-nosed projectile penetration
Li Jicheng Chen Xiaowei
Based on Alekseevski-Tate model, the present paper theoretically analyses the interface defeat of a conical-nosed projectile in its penetration process and the corresponding formulae of velocity decay and mass erosion of projectile are conducted out. The effects of half apex angle on the kinetic energy loss of conical-nosed projectile are discussed, and comparison between the kinetic energy loss of conical-nosed projectile and that of flat-nosed long rod is declared.
2011, 43(1): 63-70. doi: 10.6052/0459-1879-2011-1-lxxb2009-782
Experimental study on bubble pulse features under different circumstances
zhang Aman Wang Shiping Bai Zhaohong Chao HUANG
Underwater explosion bubbles do severe damage to warshipstructures, and the particularity of underwater explosion and the quality ofwater bring great difficulties to get a clear picture. So lots oflaboratories all around the world make use of discharge or laser to generatebubbles to replace real underwater explosion experiments.Based on the designation from Turangan et al and Abdolranman Dadvand, anelectric circuit with a relatively low voltage 200V and three shunt-wound2200\muF capacitances is used to generate bubbles by discharge ina 500mm\times500mm\times500mm water tank to study underwater bubbledynamics. The experiment setup is safe, stable, low in costs and simple tofix. It can generate bubbles with radius up to 12~15mm.A device generating bubble by a relatively low voltage is designed to studybubble dynamics in detail under various boundary conditions in this paper.Main conclusions are obtained below by comparison and analysis:(1) A voltage of 200 V is adopted to generate bubble by discharge in water inthis paper. The voltage is fairly low yet the bubble generated is relativelylarge in size. The pictures shot are pretty clear as well.(2) There are copper wires burning inside the bubble throughout theexpansion process, causing the temperature inside bubble to rise apparentlyhigher and result in the small calculated value of bubble pulsing period. Sop_v within the bubble is actually very large and the calculated p_v ofa single bubble pulsing in free field is 5.8\times 10^4 Pa.(3) Bubble's second pulsing energy is merely 5{\%}\sim 15{\%} of the firstpulsing energy and the pulsing energy after the second pulse can be ignored.(4) \gamma , the dimensionless standoff is defined betweenbubble and boundary. When \gamma \ge 2.8, the influence of the wall tobubble can be neglected. When 1.95 \le \gamma \le 2.8, no jet is formedduring the first cycle of bubble pulse. When \gamma \le 1.53, jet is formedduring the first cycle of bubble pulse, and the smaller \gamma is, thelarger bubble migration distance and the more fiercely the jet would be.(5) The bubble jetting velocity is minimum when the dimensionless standoff\gamma is around 0.8.(6) Bubble will interact strongly with boundaries when it moves near theshipboard and the free surface. It can be seen from the experiments that thebubble may produce jets that are towards two different directions whencollapsing near the free surface and the shipboard, and this will certainlylead to the weakening effect of bubble attack to the shipboard.
2011, 43(1): 71-83. doi: 10.6052/0459-1879-2011-1-lxxb2010-278
Numerical study of rotor tip ejecting
Zhou Junwei Hou Anping Zhou Sheng
The stall margin of compressor can be effectivelyimproved by rotor tip injection, but the available injectors are complex instructure and will increase the engine weight. The purpose of this paper isto explore a new type of injection, which is easy to implement incompressors without increasing the total weight. A casing modification (CM)method was used on the casing near the rotor tip leading edge, so that theaxial velocity near rotor tip leading edge improved, which has a similareffect on the rotor tip injection. The method was numerically tested on therotor 37, and it was concluded that, the CM method could improve the rotorstall margin by 6.7%, and the efficiency and pressure ratio are improvedslightly. Comparison of different schemes of CM method shows that, thelocation of CM influences stall margin most obviously. The analysis of rotortip flow field indicates that, the CM method could increase the rotor tipaxial velocity, push the tip leakage vortex downstream, weaken the blockageat the rotor tip region, and enhance stability of the rotor therefore.
2011, 43(1): 84-89. doi: 10.6052/0459-1879-2011-1-lxxb2009-603
Experimental study on flow characteristics of polymer solutions in microtubes
Yue Xiang'an Wang Fei Tang Ming Zhang Yu Wang Wenliang
The high shear rate flow (1215~23120\,s^{-1})characteristics of the partically hydrolyzed polyacrylamide (HPAM) insilica micro-tubes with diameters in the range of 10.1~325\mumwere investigated experimentally. It is shown that the effect of themicrotule is obvious in microtubes with diameters less than 100\mum.The experimental averagevelocity is higher than expected which is the flow of the same solution ingeneral-sized tubes. In addition, the discrepancy between the experimentaland the expected average velocities is influenced by the diameter andthe shear rate. Under the same shear rate the smaller the diameter ofthe microtube is, the more obvious the discrepancy is. In microtubes thediscrepancy decreases as the shear rate, however, if the diametersbeyond 30.7\mum, the discrepancy hardly varies with the shear rateany more.
2011, 43(1): 90-96. doi: 10.6052/0459-1879-2011-1-lxxb2009-680
An improved geometrically nonlinear algorithm and its application for nonlinear aeroelasticity
Xiao-min An Xu Min
The coupled algorithm between computational fluid dynamics(CFD) and computational structural dynamics (CSD) referring to nonlinearaeroelasticity are studied in time domain. Based on CR (Corotational)theory, the expressions of tangent stiffness equations and internal forcesof 3D shell element under geometric nonlinear structure are derived, thenintroducing a predictor-corrector procedure, a nonlinear dynamic solutionalgorithm is developed based on approximate energy conservation during thedynamic process. Combined with dual-time marching scheme and geometricconservation law, which are included in the solver of Reynolds averagedNavier-Stokes equation, an coupled algorithm is improved for nonlinearaeroelasticity based on the staggered process with mid-steps. The developednonlinear structural solver is performed on static and dynamic analysis andvalidated by the results of experiments and references. With the applicationon nonlinear aeroelastic respones simulation of AGARD 445.6 wing, it showsthat the improved coupled algorithm has a better stability andpracticability for nonlinear analysis.
2011, 43(1): 97-104. doi: 10.6052/0459-1879-2011-1-lxxb2009-704
Backward integration method in data processing of quasi-isentropic compression experiment
Zhang Hongping Sun Chengwei Li Mu Zhao Jianheng
Quasi-isentropic compression can be used to investigatedynamics characteristics of solid material in large pressure range. But, bynow, only velocity histories of sample surfaces with different thickness canbe measured directly. To obtain the inner information of the solid sample,the backward integration method is used. The traditional backwardintegration method is based on non-viscous fluid model, and is not suitablein solids experimental data processing. Several improvements on the backwardintegration method are presented in this paper: deviatonic stress iscalculated using fluid elastic-plastic model; isentrope derived fromH\"{u}goniot line is used for describing thermodynamic response, and thepressure-volume relation is varied by parameters optimizing method. Usingthis improved backward integration method, experimental data of copper andaluminum samples compressed by magnetic drive and laser drive respectivelyare analyzed. The load histories and quasi-isentropic lines agree well withthe data from references.
2011, 43(1): 105-111. doi: 10.6052/0459-1879-2011-1-lxxb2010-053
Analysis of topography measurement error in atomic force microscope (AFM) and its revision method
Xu Jinming Bai Yilong
In measuring topography of sample, the interaction between tip and sample will cause the deformation on the sample surface and the deformations will be different in the regions with different mechanical property. Furthermore, the deformations will cause non-negligible error in topography measurement. Theory analyses are carried out on this measurement error and further numerical research shows that mixed signals with high-frequency components are able to eliminate the measurement error. However, it is difficult to measure high-frequency signal for normal cantilever. In order to gain a proper high-frequency signal, a modified cantilever is introduced. The new designed cantilever can help us to adjust the relative values of eigen-frequencies of a cantilever and then enhance the high-frequency signal.
2011, 43(1): 112-121. doi: 10.6052/0459-1879-2011-1-lxxb2010-300
Low strain rate compressive behavior of high porosity closed-cell aluminum foams
Li Binchao Zhao Guiping Lu Tianjian
Drop hammer experimental measurements are carried out tostudy the compressive behavior and energy absorption characteristics of highporosity closed-cell aluminum foam specimens subjected to low velocityimpact loading. The dynamic deformation behavior of the specimen is observedby high speed camera and the velocity attenuation of the drop hammer isrecorded. The results demonstrate that the aluminum foam has excellentenergy absorption capabilities under low velocity impact loadings, with itsdynamic compression behavior similar to that obtained under quasi-staticloading conditions. Finite element method (FEM) is employed to obtain stressdistributions in the drop hammer and foam specimen, with and without theeffects of friction on contact surface considered. The presence of frictionrestrains the transverse displacement of the contact surface, causing theobserved convex shape of the foam specimen. As the propagating period ofstresses in the specimen is far less than the attenuation duration time, thevariations of the stresses are similar to those under quasi-static loadingconditions and no obvious stress wave effect is observed. With the effectsof the friction on the contact surface accounted for, an analyticalcolliding model of the drop hammer-aluminum foam system is established. Thepredicted velocity attenuation is compared with both the experimentalmeasurements and FEM simulation results, with overall good agreementachieved. The effects of different impact velocities and mechanicalproperties of foam material on the attenuation process are discussed.
2011, 43(1): 122-135. doi: 10.6052/0459-1879-2011-1-lxxb2009-778
Thermal stress analysis of functionally graded material structures using boundary element method
Gao Xiaowei Yang Kai
This paper presents a new integral equation for 2D and 3Dthermal stress analysis of structures consisting of functionally gradedmaterials. Using this equation together with the three-step multi-domain BEMtechnique, thermal stress analysis can be carried out for complicatedstructures comprised of arbitrarily many numbers of media with varyingmaterial properties. The Kelvin fundamental solutions independent of elasticmodulus are used in this paper. As a result, the resulting integralequations include domain integrals due to the non-homogeneity andtemperature variations of the material. All these domain integrals aretransformed into equivalent boundary integrals using the radial integrationmethod (RIM), resulting in a pure boundary element analysis algorithm.Finally, two numerical examples are given on 2D and 3D thermal stressanalysis of two typical thermal protection systems for space shuttles toverify the correctness of the proposed formulation by comparingcomputational results with those obtained by the finite element method.
2011, 43(1): 136-143. doi: 10.6052/0459-1879-2011-1-lxxb2009-585
Numerical predictions of effective shear modulus and size effect for periodic cellular materials
Zhang Weihong Luo Jinwei Dai Gaoming Zhang Jin
Based on the classical cylinder torsion model, a simpleand efficient method is proposed in this paper to predict the effectiveshear modulus and the size effect of periodic cellular materials. Asrepresentative examples, square-hole and circle-hole unit cells are used toclarify the problem and computing. Analytical expressions are established todetermine the geometrical parameters of the cell in terms of the cell sizefactor $n$. Following conclusions can be drawn out from numeral results. Theeffective shear moduli of the two types of unit cells decrease as the scalefactor $n$ increases; when $n \to \infty $, i.e., the size of the unit cell issmall enough with respect to the size of the whole structure, the effectiveshear modulus tends to be a constant value. The increase of the materialvolume fraction of the unit cell will result in an increase of the effectiveshear modulus of the cellular material. Meanwhile, the unit cellsubstructure concept is proposed to predict the effective shear modulus andthe size effect of the periodic cellular material based on itscharacteristic of structural symmetry. This modeling can greatly increasethe computing efficiency.
2011, 43(1): 144-153. doi: 10.6052/0459-1879-2011-1-lxxb2009-694
An explicit method for numerical simulation of wave motion---constructing recursion formula for interface point
Xie Zhinan Liao Zhenpeng
In the paper, the analytical solution for interfacepoints in a short time window is firstly deduced by combination of thefiniteness of wave velocity and solutions of Cauchy problem of waveequation, then a method of constructing a high order explicit recursionformula for interface points is provided for numerical simulation of scalarwave motion in uniformly layered model. To illustrate the main point, anexample of constructing recursion formula for interface points presented ina piecewise elastic bar is included. Second and fourth order recursionformula for interface in time and space are provided and consistent with thecurrent stable explicit formulas for interior points. Like heterogeneousscheme, the scheme presented in this paper has the same advantage of easyprogramming. Finally, the accuracy and stability of the new scheme arevalidated through numerical tests.
2011, 43(1): 154-161. doi: 10.6052/0459-1879-2011-1-lxxb2009-556
The reliability sensitivity analysis based on saddlepoint approximation and its improved method
Song Shufang Lv Zhenzhou
The saddlepoint approximation (SA) can directly estimateprobability distribution of linear performance function in non-normalvariables space and then calculate the failure probability of structure.Based on the property of SA, SA based reliability sensitivity analysismethod is developed. For the nonlinear performance function, SA method needsthe linearization of performance function firstly, but they neglect theinfluence of nonlinearity of performance function on the failureprobability. So the reliability sensitivity analysis method based itsimproved method, named as SA based line sampling (LS), is presented. Thereliability sensitivity can be estimated by the average of these partialderivatives of failure probabilities with respect to the distributionparameter of random variables, and the probabilities and sensitivities ofthe linear performance functions can be estimated by the SA in thenon-normal variables space. By comparing basic concepts, implementations andresults of illustrations, the following conclusions can be drawn, (1) SAbased reliability sensitivity method is only acceptable for the linearperformance function. The error mostly results from the linearization of theperformance functions. (2) The SA based LS method can obtain the estimatorsof failure probability and reliability sensitivity, which converge to theactual value along with the increase of sample size. The SA based LS methodconsiders the influence of nonlinearity of performance function on thefailure probability and reliability sensitivity; therefore it has the wideapplicability.
2011, 43(1): 162-168. doi: 10.6052/0459-1879-2011-1-lxxb2009-540
Study on numerical manifold method with fixed meshes
Su Haidong
The numerical simulations of large deformations of continuums lead to thechoice of an appropriate kinematical description. In classical viewpoints,Lagrangian and Eulerian description approaches are alternatives. Lagrangianapproach tracks material particles, allowing for a clear delineation ofboundaries of material. However, meshes that adhere to material are easy tobe distorted, inducing a poor accuracy or even computation failure. On theother hand, Eulerian approach is very attractive in the point that fixedmeshes will never be distorted, but it suffers from the complexities ofhandling moving boundaries and convective terms of Eulerian governingequations. Thus ALE (Arbitrary Lagrangian-Eulerian) method, which isreported to take advantages of Lagrangian and Eulerian approaches to acertain extent by allowing motions of meshes, is developed in recent years.Nevertheless, how to devise a good mesh motion algorithm is a great burdento the user, and convective terms are still involved.This paper presents a novel method, numerical manifold method (NMM) withfixed mathematical meshes, for short, fixed-mesh NMM, for analyzing puregeometric non-linear problems. Making well use of the fact that mathematicalmeshes are independent of material boundaries in NMM, this method is basedon the Lagrangian description approach, but using fixed meshes. It has thevirtues of both Lagrangian description approach and Eulerian descriptionapproach, avoiding mesh distortion of the former, and complexities ofhandling moving boundaries and convection items of the latter.Following the time steps, equations of NMM for large deformations areadopted in this paper, providing an easy way to implement fixed-mesh NMM.There are only two special factors to consider: after each time step iscompleted, deformed material boundaries are intersected with fixedmathematical meshes to generate new manifold elements; initial stress loadsare handled in a proper way, which is most important to fixed-mesh NMM.Based on fixed rectangular mathematical meshes and one order polynomialcover functions, two methods are presented to compute initial stresses.Given results of large deflection of a cantilever beam show the feasibilityof the fixed-mesh NMM, and indicate that more research should be furtherdone on computational stability due to initial stress loads.
2011, 43(1): 169-178. doi: 10.6052/0459-1879-2011-1-lxxb2010-123
Identification of intraocular lens constitutive parameters using mixed numerical-experimental method
Ma Xiqin Yang Changqi Tang Liang
Owing to its particular structure and preparationtechnique, the mechanical parameters of intraocular lens are hard to obtainby means of standard methods. A mixed numerical-experimental method is usedto identify the parameters in Mooney-Rivlin constitutive model ofintraocular lens. The result shows that perfect identification precision canbe obtained using Mooney-Rivlin model in certain deformation range ofintraocular lens. Moreover, we simulate the implantation process andoperation state of intraocular lens using finite element numericalsimulation. The method solves the problem of acquiring materials parametersto a large extent, meanwhile, and lays a foundation for wide application offinite element numerical simulation technique in the biomedical field.
2011, 43(1): 179-183. doi: 10.6052/0459-1879-2011-1-lxxb2010-028
Semi-spring contact model and its application to failure simulation of slope
Chun Feng Li Shihai Liu Xiaoyu
The main purpose of semi-spring contact model is to judge anddescribe the contact status, and then to calculate the contact force betweenblocks. Contact blocks are divided into mother block and son block.Semi-spring is located in mother block, and formed by indenting the vertexof block to mother face, while target face lies in the son block. Accordingto the geometry relationship between semi-spring and target face, thecontact force could be obtained directly. There is no need to waste a mountof time to judge the contact type and calculate contact area between twoblocks. The model could calculate the progressive failure of geological bodyunder the conditions of quasi-three-dimension, and some numerical casesabout slope failure are shown to proof its accuracy and reliability.
2011, 43(1): 184-192. doi: 10.6052/0459-1879-2011-1-lxxb2010-080
A viscoplastic damage constitutive model for concrete
Li Jie Ren Xiaodan Huang Qiaoping
Based on the static plastic damage framework forcontinuum, the dynamic-viscoplastic damage model for the nonlinear analysisof concrete structures under dynamic loading was developed in the presentpaper considering the rate-sensitivities of plastic strain and damageevolution. The Perzyna type viscoplasticity in the effective stress spacewas derived to account for the rate-sensitivity of the plastic strainevolution. The rate-dependent damage evolution was extended from the staticdamage evolution using the modified Perzyna type formulations. The uniaxialstatic damage evolution function was developed based on the parallel elementmodel. Then the multiaxial static damage evolution was established bysubstituting the energy equivalent strain into the uniaxial static damageevolution function. The stress-strain curves, the dynamic increase factorand the biaxial dynamic envelopes were simulated in the present paper. Theagreement between numerical results and experimental data indicates thevalidity of the proposed model.
2011, 43(1): 193-201. doi: 10.6052/0459-1879-2011-1-lxxb2009-646
Experimental research of inflatable deployment dynamics of folded membrane booms
Wei Jianzheng Tan Huifeng Miao Changqing He Xiaodong
Inflatable membrane boom used to deploy and support spacestructures is a key component for many space inflatable structures. Z-foldedtype is one kind of basic folded membrane booms. In this paper, an inflationdeployment experimental system in equivalent microgravity environment isestablished based on air track which resolves the effect of that gravitycaused friction. Non-contact photoelectricity measurement effectively avoidsthe disturbance of contact sensor to the inflation deployment process. Theeffects of different inflation flows, variant geometry dimensions andloading/unloading on deployable end on dynamic properties are researched.Inflation flow, diameter, and payload mass are chosen as main parameters inthe experiment. Inflation deployment process is analyzed by dimensiontheory, and analysis of experimental error is carried out. The experimentalresults indicate that the maximal deployment velocity of the folded booms isboth direct relation of gas flow and inverse relation of the boom cubicdiameter.
2011, 43(1): 202-207. doi: 10.6052/0459-1879-2011-1-lxxb2009-406
Stability and bifurcation of the rotor-bearing system with double disks supported by cylindrical bearings
Li Zhaofeng Dai Jishuang Wen Bangchun
Continuous model of rotor-bearing system with double diskssupported by cylindrical bearings is analyzed in this paper. Shooting methodis used in the stability analysis of the continuous system. Therotor-bearing system with double disks is analyzed by considering the diskeccentric magnitude, eccentric initial phase, bearing clearance, dynamicviscosity of the oil and bearing aspect ratio. Some useful conclusions arefound: instability is mainly caused by the period-doubling or quasi-periodbifurcation; instability speed can be increased by decreasing the diskeccentric magnitude or increasing the initial eccentric phase difference ofthe disk; increasing bearing aspect ratio and decreasing bearing clearanceproperly can inhibit the instability occurring early; the higher dynamicviscosity of the oil is not the better, otherwise oil with lower dynamicviscosity can increase the instability speed properly. Research method andconclusions in this paper can provide theoretical reference for thestability design and vibration control of the more complex rotor-bearingsystem.
2011, 43(1): 208-216. doi: 10.6052/0459-1879-2011-1-lxxb2009-494
Relaxation modulus of caudal fin studied by fractional zener model
Chen Ming Jia Laibing Yin Xiezhen
Fish fin plays an important role in fish swimming as apropeller and a controller. The mechanical property of fish fin is ofessential importance in exploration the source of high efficiency duringfish swimming. In this paper, a study of stress relaxation in Crucian Carpfin ray was carried out. The relaxation time was 300 senconds and the decayof force indicated that the caudal fin behaves as a viscoelastic material.The fractional Zener model was used to fit the experimental data. Theresults are compared with the 3-parameter and 5-parameter linearmodels, indicating the fraction Zener model gives a better fit than the3-parameter model and fits as well as the 5-parameter model but withless parameters.
2011, 43(1): 217-220. doi: 10.6052/0459-1879-2011-1-lxxb2010-145
Efficient μ method in predicting robust match-point flutter
Kou Wenjun Qiu Zhiping
Based on the previous u-tool in predicting robustmatch-point flutter of the aeroelastic system with parametric uncertainties,this paper proposes a new modelling approach of uncertain polynomials. Theproper linear fractional transformation (LFT) is firstly applied to obtain amore reduced uncertain description. Furthermore, regarding the computationalcomplexity of real μ problem aroused from parametric uncertainties,another technique involving bisection method to predict the robust flutteris presented, which is based on the simple relationship between the flightspeed and stability of aeroelastic system in certain flight range. The μ method based on bisection search is very computational efficient throughnumerical validation and comparison, due to the avoidance of the high-ordervelocity perturbation block in previous robust match-point flutter model.
2011, 43(1): 221-226. doi: 10.6052/0459-1879-2011-1-lxxb2010-273
Robust topology optimization design of structures with multiple load cases
Luo Yangjun Kang Zhan Deng Zichen
In practical engineering, the structural performancealways exhibit some degree of variations due to the fact that the applied loadsfluctuate dramatically throughout its service life-cycle. Thus, the need ishighlighted to account for uncertainties in topology optimization stage ofthe structural design. Conventional deterministic topology optimizationsearches for minimum compliance without considering the uncertainties inoperating processes. Recently, the robust structural design has attractedintensive attentions because it can reduce the variability of structuralperformance. However, existing robust design methods are confined to thesize and shape optimization problems. This paper aims to incorporate therobust design strategy into the continuum topology optimization problemunder multiple uncertain load cases by minimizing variation of the objectiveperformance. Following the SIMP approach, an artificial isotropic materialmodel with penalization for elastic constants is assumed and elementalrelative density variables are used for describing the structural layout.The considered robust topology optimization problem is thus formulated as tofind the optimal structural topology that minimizes the standard deviationof structural total compliance under the constraint on material volume. Toavoid the difficulties associated with directly evaluating the standarddeviation of the structural compliance, a convenient computing formula ofthe objective function is presented based on the stochastic finite elementmethod. In addition, an adjoint variable method is employed for theefficient sensitivity analysis of the objective function. Then, the gradientbased optimization algorithm (Method of Moving Asymptotes, MMA) is used toupdate the design variables in the optimization loop. Finally, threenumerical examples for topology optimization of 2D and 3D structuresillustrate the applicability and the validity of the present model as wellas the proposed numerical techniques. The computational results reveal thatthe robust topology optimization could yield a material layout with lessvariation of structural compliance than the conventional deterministicapproach. The novelty of the proposed robust topology optimization approachlies in that it introduces the conception of robustness into earlier stageof the structural design, which may be considered as especial useful in somecircumstances.
2011, 43(1): 227-234. doi: 10.6052/0459-1879-2011-1-lxxb2010-147
Deformation and fracture of Zr51Ti5Ni10Cu25Al9 bulk metallic glass under rapid heating and pre-load
Luo Binqiang Zhao Jianheng Tan Fuli Mo Jianjun Sun Chengwei
Bulk metallic glasses are regarded as potentialengineering materials because of their unique mechnical and physicalproperties. Mechanical behavior of bulk metallic glass and its compositeover a wide range of strain rates and temperatures attracted manyresearchers' interests. In this paper, a systematic experimental study wereperformed on Gleeble3500 thermal-mechanical testing system to study theeffects of heating rates on mechanical behavior ofZr51Ti5Ni10Cu25Al9 bulk metallic glass underpre-load. The results show that failure models of this material changes fromheating soften to catastrophic rupture with increasing pre-load and heatingrate. Under low pre-load, yield behavior ofZr51Ti5Ni10Cu25Al9 bulk metallic glass iscontrolled by both pre-stress and heating rate; under high pre-load andheating rate the material failures in shear fracture mode and thetemperature of destructive sample is close to or above the glass transitiontemperature when catastrophic rupture occurs, meanwhile the pre-stress ismuch lower than the strength at room temperature and characters of therupture surface are unusual with quasi-static compression experimentalresults. Structure relaxation of amorphous alloy under changing temperatureis discussed and the relations of yield temperature and heating rate as wellas pre-stress are deduced. The reason of catastrophic rupture under thisexperimental condition is also analyzed based on metallographic observationof recovery samples and a critical failure model is also given out.
2011, 43(1): 235-242. doi: 10.6052/0459-1879-2011-1-lxxb2010-357
2011, 43(1): 243-246. doi: 10.6052/0459-1879-2011-1-lxxb2011-023