力学学报

FRACTIONAL DERIVATIVE MODELING OF FREQUENCY-DEPENDENT DISSIPATIVE MECHANISM FORWAVE PROPAGATION IN COMPLEX MEDIA

Cai Wei, Chen Wen

The existing experimental data indicate that the attenuations of acoustic waves propagating in complex media always exhibit a non-integer power-law dependence on frequency. Such phenomenon is di cult to be characterized by traditional damping wave equation or approximate thermo-viscous wave equation, which can only describe the frequency independent or frequency-squared dependent attenuation, respectively. With the dynamic development and wide applications of fractional calculus, wave equations with fractional derivative terms have been successfully applied to depicting the frequency dependent attenuation. Based on the research achievements of our group, this paper aims at presenting a review of the various fractional derivative wave equations, discussing the corresponding mechanical constitutive relationships and statistical interpretation, and laying the foundation for the in-depth study in the future. The time-and space-fractional derivative wave equations for soft matters are introduced, which can be classified into two groups:the constitutive models and the phenomenological models. The connections and di erences between such models are also discussed. Then, the successful applications of fractional derivative in modeling wave propagation in porous media are also summarized. The statistical interpretation for the power-law dependent exponent covering[0, 2] is presented via linking the space-fractional diffusion equation with Lévy stable distribution. Finally, the key problems in such area for future explorations are highlighted.

2016, 48(6): 1265-1280. doi: 10.6052/0459-1879-16-186

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NUMERICAL STUDY OF THE EFFECT OF FORCED PITCHING OSCILLATION ON ROLLING CHARACTERISTICS OF VEHICLE

Chen Qi, Chen Jianqiang, Yuan Xianxu, Xie Yufei

The vehicle may be induced uncommanded oscillation by the disturbance of the gust, this phenomenon would increase the risk of the flight. To study the influence of forced pitching oscillation on rolling characteristics of a square cross section vehicle, the loose couple technique of rigid body dynamic equations and Navier-Stockes equations were developed, and then the steady rolling aerodynamic characteristics, free rolling characteristics and the effect of pitching oscillation at different frequencies on rolling characteristics of the aircraft were studied. The steady results showed that there was a critical attack angle about 13° existing in the free rolling motion, when the attack angle was lower than the critical attack angle, the vehicle was in rapid rolling motion, and when the attack angle was greater than the critical attack angle, the rolling motion was convergent. The results also showed that, the forced pitching oscillation would decrease the level of rolling static instability (stability) as the vehicle was static instable (stable), and increase the level of rolling dynamic stability no matter the vehicle was stable or instable. In the influence of high frequency pitching oscillation, the rolling motion can be convergent even if the vehicle was static instable.

2016, 48(6): 1281-1289. doi: 10.6052/0459-1879-16-132

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LARGE-EDDY SIMULATION OF A BLUFF-BODY FLAME AND THE FORCED IGNITION PROCESS

Yang Tao, Zhang Jian, Lü Jinming, Jin Guodong

Bluff-body burners are widely used in combustion chambers of industrial equipment such as jet engines, gas-turbines and boilers. Safe operation and low pollutant emission in these equipment directly demands understanding and controlling of ignition process in bluff-body burners. In this paper, a large-eddy simulation based on steady flamelet/progress variable approach was applied in a turbulent non-premixed bluff-body flame and its ignition process. Simulating two cases including non-reacting bluff-body flow (NRBB) and Sydney methane/hydrogen flame (HM1E), we comprehensively compared statistical results with experimental measures and previous numerical investigation. Then, we presented an instantaneous ignition process and flame development in Sydney bluff-body burner. Finally, the ignition process was analysed and characterized in detail, and a four-step process of flame ignition was proposed:decaying of ignition source, ignition initiation, generating of ignition kernel, and ignition success, which was identified by variation of peak values of temperature, OH and CH₂O mass fraction. In addition, the ignition kernel stayed at the stern of the outer vortex in the recirculation zone of the cold flow of the bluff-body burner.

2016, 48(6): 1290-1300. doi: 10.6052/0459-1879-16-089

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WIND-TUNNEL FREE-FLIGHT TEST OF BOUNDARY LAYER TRANSITION INDUCED BY TRIPPED THREAD FOR SLENDER CONE

Song Wei, Jiang Zenghui, Jia Quyao

This paper stduy the motion and aerodynamic characteristics affected by boundary layer transition for the hypersonic slender cone re-entry vehicle with the wind-tunnel free-flight testing which the motion freedom is not limited by artificially fixing definite number tripped thread that can produce the change of laminar to turbulent on the 10° halfangle cone surface. The experiment Mach number is Ma=5.0 and we achieve the two Reynolds number's simulation by changing the wind tunnel total pressure P₀. The free flow Reynolds number based on the model length L are 0.84×10⁶ and 1.68×10⁶, respectively. The experimental result shows that artificial tripped thread can not induce the boundary layer transition which have a similar motion and aerodynamic characteristics to the slender cone without tripped thread when the Reynolds number is Re=0.84×10⁶. When the Reynolds number Re=1.68×10⁶,artificial tripped thread can induce boundary layer transition which have a different motion and aerodynamic characteristics to the slender cone without tripped thread and the dynamic stability derivative of the slender cone is below zero which the hypersonic slender cone's motion is steady.

2016, 48(6): 1301-1307. doi: 10.6052/0459-1879-16-128

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SPACE-TIME CORRELATIONS OF FLUCTUATING VELOCTUATING IN POROUS WALL-BOUNDED TURBULENT SHEAR FLOWS

Zheng Yijun, Li Qingxiang, Pan Ming, Dong Yuhong

The space-time correlations are fundamental to the turbulence theory and have a broad application. In this paper, the authors perform direct numerical simulations of turbulent channel shear flows through the lattice Boltzmann method, and then study the space-time correlations of the velocity field. What's more, the authors investigate spacetime correlations of fluctuating velocities in porous wall-bounded turbulence, basing on the lattice Boltzmann equation which containing the Darcy-Brinkman-Forhheimer acting force term. On the one hand, the two-time correlations of velocities in porous wall-bounded shear flows are calculated and discussed. On the other hand, the author analyzes the space-time correlations of velocities in different porosity numbers and Darcy numbers in detail to investigate porous wall-bounded turbulent shear flows. It is found that there are elliptic curves on the iso-correlation contours that have a uniform preference direction and share a constant aspect ratio. Also, there are obvious di erences among the space-time correlations of velocities in different normal-wise positions, such as near-wall region, buffer layer, log-law region and outer layer. These findings suggest that the farther it is away from the wall, the more slender elliptic curves are in isocorrelation contours. The computed results suggest that the correlations are enhanced with the Darcy number decreasing and the porosity number increasing.

2016, 48(6): 1308-1318. doi: 10.6052/0459-1879-16-208

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AN IMPROVED METHOD FOR INITIALIZING HOMOGENEOUS ISOTROPIC TURBULENT FLOWS

Qin Zecong, Fang Le

Homogeneous isotropic turbulence (HIT) is one of the simplest ideal turbulence states, and is also one of the most important subjects in basic turbulence theory researches. HIT fields are usually initialized in the spectrum space via the method proposed by Rogallo, and then transformed in physical space. The current paper points out that initial fields thus generated are anisotropic in axis directions of their computational domain, which can be reflected in structure functions and in possibility density distribution of velocity components. Even though such anisotropy will disappear after an average operation of a large number of initial field samples, the anisotropy fluctuation between samples is considerately big, which is not favorable for the establishment of an HIT. Basing on this existing methodology, we then proposed an improved Rogallo method, named the modulus-averaging method, which firstly conducts the Rogallo method in all the 3 axis directions, then carries out a modulus-averaging operation, and finally control the modulus via a given spectrum function. This method can keep the initial filed spectrum and, reduce the anisotropy fluctuation of each single field to generate "more isotropic" initial fields. Statistically, this new method can lower the relative standard deviations of structure functions and velocity possibility density distribution by about 10%.

2016, 48(6): 1319-1325. doi: 10.6052/0459-1879-16-180

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STRENGTH ANALYSIS OF FIBER REINFORCED COMPOSITE LAMINATES WITH BIG CUTOUTS

Chen Jianlin, Li Zheng, Chu Pengcheng

As a heterogeneous anisotropic material, the failure behavior of composite laminate is very complicated. In order to meet manufactural and functional requirements, it is unavoidable to have cutouts on primary composite structures. However, it makes the failure criterions face new challenges due to the more complicated failure processes of composite laminates with big cutouts. In this paper the strength analysis of carbon fiber reinforced composite laminate with big cutout under unidirectional tension is studied by numerical analysis and experimental tests. Firstly, consider the composite laminates with different layups, such as[0]₁₀ unidirectional laminate,[0/90]₅ and[±45]₅ cross-ply laminates, and different circle cutouts, Hashin criterion and stiffness degradation model are applied to analyze the progressive failure process under unidirectional tension by numerical simulation to obtain the ultimate load and failure mode for each laminate. Furthermore, according to the numerical models, experiments are carried out based on 3D digital image correlation (DIC) method. Results show that the failure mode of fiber reinforced composite laminate with big cutout under unidirectional tension is a typical brittle fracture, and the crack onset happens to the high stress concentration area. In addition, the failure mode and crack propagation strongly depend on the ply sequences and the cutout size. Therefore, comparing to others,[±45]₅ cross-ply laminate with big cutout has the lowest ultimate load for its serious delamination failure mode. The bigger of the cutout size, the lower of ultimate load. After comparison of experimental and numerical results, it is concluded that the numerical simulation for strength analysis of composite laminate should be improved by further developed criterions.

2016, 48(6): 1326-1333. doi: 10.6052/0459-1879-16-169

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MICRO-DAMAGE MODEL OF COMPOSITE MATERIALS WITH PARTICLE AND DEFECT INTERACTION

Fu Yunwei, Ni Xinhua, Liu Xiequan, Zhang Long, Wen Bo

Stress concentration is much bigger around the sharp angle of the non-ellipsoidal particle than around the ellipsoidal particle, and the cracks beside the particles caused by the stress are the primary damage of composite ceramics. Particle caused crack usually extends to the composite matrix to form the penny crack when the particle is stiffer than the matrix and the interface is strong. Considering the crack propagation was controlled by the stress around the particle, the meso-damage mechanical model is obtained based on the effective self-consistent theory, to describe the damage evolution of the composite ceramic under simple tension. The influences of particle shape, sizeand stiffness, and the distance between the crack and the particle on the composite damage are analyzed. The result indicated that the nonellipsoidal particle is more easily to cause crack propagating than the similar ellipsoidal particle, and the damage degree is much higher in the composite with non-ellipsoidal particle than with non-ellipsoidal particle under the same loading. Composite strength with non-ellipsoidal particle is smaller than that with ellipsoidal particle. Stable damage process is more obvious in composite with flat particle and the strength is much higher. Increasing the particle stiffness and the particle volume fraction can improve the composite strength. The stable damage is unobvious in composite when the primary defect size is too large or too small.

2016, 48(6): 1334-1342. doi: 10.6052/0459-1879-16-152

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STABILITY OF A PRESSURIZED ELLIPSOIDAL BALLOON

Geng Yanan, Cai Zongxi

A pressurized ellipsoidal balloon may bifurcate into different shapes depending on its precise shape. For a rugby-shaped balloon, there exists a threshold ratio of the axes in the Z- and R- directions, above which the balloon tends to bifurcate into a pear shape. Otherwise, the pear shape is impossible and when the balloon is slender enough, it may bulge out locally in a symmetric manner more like a tube. However, for a pumpkin-shaped balloon, bifurcation into a pear shape is always possible. In this paper, by using an energy criterion, we determine the stability properties of the primary and bifurcated solutions under pressure control and volume control,respectively. The total energy of the equilibrium state and its disturbed state are calculated, and the di erence between these two states is used to evaluate the stability of current state. Our analyses indicate that under pressure control, both primary and bifurcated solutions that exist on the descending branch of the pressure versus volume curve are unstable, but under volume control, the bifurcated solution is always stable whenever it appears while the primary solution is only stable when there does not exist any bifurcated solution. However, the primary solutions that exist on the two ascending branches are always stable.

2016, 48(6): 1343-1352. doi: 10.6052/0459-1879-16-142

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AN EXPERIMENTAL STUDY ON ADIABATIC SHEAR BEHAVIOR OF TA2 TITANIUM ALLOY SUBJECT TO DIFFERENT LOADING CONDITION

Zhou Gangyi, Dong Xinlong, Fu Yingqian, Hu Hongzhi

Adiabatic shear phenomena is generally considered as a material dynamic instability,which comes from the competition among thermal softening and the strain hardening, strain rate hardening. In this paper, the constitutive and dynamic behaviors of TA2 titanium alloy were studied with hat-shaped forced-shear specimens.. The stress states of its shear zone are firstly studied by theoretical analysis and numerical simulation to obtain the pure state of shear stress with the hat-shaped samples. The shear strain in specimen measured directly by the two-dimensional digital image correlation (DIC-2D) method, and the equivalent stress-equivalent strain curves under forced shear loading can be acquired. Furthermore, the dynamic stress-strain behaviors in compression conditions and hat-shaped shear condition are then studied experimentally for TA2 titanium alloy by split Hopkinson pressure bars technique. Its adiabatic shear failure evolution is investigated by microscopic metallurgical observation of ‘freezing’ sample. The dynamic constitutive and failure behavior of TA2 titanium alloy subject to different loading condition are analyzed. The results show that the dynamic constitutive curves obtained by cylindrical compression are in agreement with the curves of shear testing at the initial stage of plastic deformation, but its stress-strain curve appears separation with the plastic damage accumulation and adiabatic shear band (ASB) formation, which suggests that the plastic damage and ASB origination may be with the relevant the state of stress. It is also shown that the softened stress-strain curve gained by shear loading reflected ASBs initiation and evolution in the hat-shaped specimens, by contrast, the apparent equivalent stress-strain curve obtained by compression testing does not appear to be softening characteristic even if the symmetrical bi-conical ASBs and local crack distribution have appeared in the cylindrical specimen.

2016, 48(6): 1353-1361. doi: 10.6052/0459-1879-16-198

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A METHOD FOR THREE-DIMENSIONAL SATUTARTED SOIL-FOUNDATION-STRUCTURE DYNAMIC INTERACTION ANALYSIS

Chen Shaolin, Zhao Yuxin

Analysis of soil-structure dynamic interaction subjected to seismic wave is a key problem in earthquake engineering. In general, the soil stratum consists of two-phase saturated porous zones and single-phase viscoelastic zones due to ground water. In most cases of soil-structure dynamic interaction analysis, the soil has been assumed to be a singlephase viscoelastic medium for simplicity and little attention has been paid to the saturated porous soil case, even less to case of the viscoelastic soil layered on saturated soil. In this study, an effcient method for three-dimensional saturated soil-foundation-structure dynamic interaction analysis is proposed. The unbounded saturated soil is modelled by lumpedmass explicit finite element method and transmitting boundary condition the structure is analysed through implicit finite element method, and response of the rigid foundation is calculated through explicit time integration scheme. The different time steps can be chosen for the explicit and implicit integration scheme, which can greatly improve the effciency. In addition, based on the fact that single-phase soil is a special case of two-phase saturated soil, the dynamic analysis of single-phase soil can be unified into the analysis of saturated soil by setting the bulk modulus of pore fluid and porosity to be zero. Thus, the soil-structure interaction analysis for the viscoelastic soil layered on saturated soil case is realized, which can approximate the ground water table in practice. The effects of ground water on the response of foundation and structure are examined through numerical examples of soil-structure interaction analysis for saturated soil, single-phase viscoelastic soil and the viscoelastic soil layered on saturated soil, and the results show that the ground water influences the structure and foundation responses greatly.

2016, 48(6): 1362-1371. doi: 10.6052/0459-1879-16-188

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STABILITY OF A FORCE CONTROL SYSTEM WITH SAMPLED-DATA FEEDBACK

Wang Zaihua, Hu Haiyan

Sampled-data control, or digital control, is a major control technology in modern engineering. Based on digital computers, it provides actuators with control inputs in terms of discrete signals. A sampled-data control system is a controlled time-continuous system under sampled-data control. The paper investigates the effects of sampled-data controls on the system stability via an SDOF force control system under sampled PD (proportional-derivative) feedbacks, by means of stability analysis for discrete systems. In order to highlight the role of the sampled-data controls, the uncontrolled system is assumed to be fully free. Unlike in the previous studies where the sampled displacement signal and the sampled velocity signal are synchronic, the study focuses on the system stability for the case when the sampled displacement signal and the sampled velocity signal are not synchronic. A key observation is that when the controller uses the sampled velocity signal as well as the sampled displacement signal delayed an additional sampling period, the controlled system admits a largest stable region of the feedback gains and it decays fastest to the unique equilibrium, among the three sampled-data controllers. The paper gives a discussion of this phenomenon from the viewpoint of mechanics.

2016, 48(6): 1372-1381. doi: 10.6052/0459-1879-16-102

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GENERALIZED VARIATIONAL PRINCIPLE OF HERGLOTZ TYPE FOR NONCONSERVATIVE SYSTEM IN PHASE SPACE AND NOETHER'S THEOREM

Zhang Yi

Compared with the classical variational principle, the generalized variational principle of Herglotz based upon the action defined by differential equations gives a variational description of nonconservative dynamical system. The principle can describe all dynamical processes and nonconservative or dissipative systems. In the present study, the principle is extended to phase space, and the generalized variational principle of Herglotz type for non-conservative mechanical system in phase space is given and Noether's theorem and its inverse of the system are studied. Firstly, the generalized variational principle of Herglotz type in phase space is presented, a variational description of non-conservative system in phase space is given, and the corresponding Hamilton canonical equations are deduced. Secondly, based upon the relation between non-isochronal variation and isochronal variation, two basic formulae for the variation of Hamilton-Herglotz action in phase space are obtained. Thirdly, the definition and the criterion of Noether symmetry are given, and Noether's theorem and its inverse of nonconservative system for the variational problem of Herglotz type in phase space are proposed and proved, and the inner relation between the Noether symmetry and the conserved quantity for mechanical systems in phase space is revealed. The generalized variational principle of Herglotz type reduces to the classical variational principle under classical conditions, and Noether's theorem for the variational problem of Herglotz type reduces to the classical Noether's theorem of Hamilton system. In the end of the paper, we take the famous Emden equation and damping oscillator with second power as examples to illustrate the application of the results.

2016, 48(6): 1382-1389. doi: 10.6052/0459-1879-16-086

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THE ATTITUDE OPTIMAL CONTROL WITH A HYBRID OPTIMAL STRATEGY FOR A FREE-FALLING CAT

Yi Zhonggui, Ge Xinsheng

Researching the twist motion of a free fall cat has an important reference value for exploring the motion rules of astronauts under the condition of weightlessness in space. For the attitude optimal control problem of a free-falling cat which limbs is always land on floor firstly, a hybrid optimal strategy is presented, which combines the Gauss pseudospectral method for feasible solutions with the Direct Shooting Method for exact optimal solutions. Firstly, according to the conversation of angular momentum in the process of the cat free falling, the nonholonomic attitude motion equation of the simplified two symmetry rigid bodies can be deduced; then the attitude nonholonomic motion planning problem of non-drift system can be converted to a nonlinear programming problem by using Gauss pseudo-spectral method, and the feasible solutions of control can be solved through SQP algorithm at a lower LG points without considering the actual index function, and more nodes of control can be obtained through cubic spline interpolation; at last, with the theory of Direct Shooting Method, substituting these control values of interpolation into SQP algorithm as initial values to compute the optimal control inputting, then attitude motion of the cat can be obtained by applying the optimal control into motion equation of system. Through numerical simulating, the attitude motion is smooth, and can reach the predetermined target location at a higher accuracy; the optimal control can satisfy the requirements of zero boundaries control and maximum control. The results demonstrate the robustness and effectiveness of the hybrid optimal strategy.

2016, 48(6): 1390-1397. doi: 10.6052/0459-1879-16-189

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A METHOD FOR SIMULATING STACER'S DEPLOYMENT DEFORMATION

Yu Chunyu, Zhang Congfa, Zhang Peng, Wang Shimin

STACER is a kind of widely used deployable mechanism on spacecraft, whose thin-wall steel strip is scrolled and eventually formed a spiral tube. Because the compressed tube can be extended dozens of times of its initial height; large deflection with large strain appears, and the deformation scope of the strip are continuously changed during the deployment, the deployment force is extremely di cult to solve even for numerical simulation. Here, using the variational method and the geometric characteristics of the deformation, a technique is proposed to solve the deployment force:at first the proper and possible shape function is constructed, and then the principal strain and the deformation energy are calculated by means of the shape function,finally the deployment force is carried out through the principle of minimum potential energy. This method makes the numerical procedure simplified and gives approached expression of the strip shape and the deployment force.

2016, 48(6): 1398-1405. doi: 10.6052/0459-1879-16-141

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THE STRAIN COUPLING PROBLEM AND MODEL DECOUPLING OF ANCF CABLE/BEAM ELEMENT

Zhang Yue, Zhao Yang, Tan Chunlin, Liu Yongjian

The cable/beam structure has already been widely applied in civil engineering, aerospace engineering, etc. Among various dynamic modeling methods of cable/beam, the Absolute Nodal Coordinate Formulation (ANCF) is very suitable for the modeling of large deformed cable/beam to describe the large deformation and rotation of flexible bodies. According to the strain analysis of ANCF cable/beam element, the bending deformation will cause uneven distribution of axial strain within the element, which means axial and bending strains are coupled with each other. The strain coupling effect brings unrealistic strain energy to the element, resulting in an increased stiffness and element distortion. It is known from the analysis of strain and strain energy at various bending angles that the larger the bending deformation is, the more serious the distortion is. The axial and bending strains are decoupled by redescribing axial strain based on a new constructed equivalent 1D rod element. Then the generalized elastic force is deduced and the strain-decoupled model of ANCF cable/beam element is obtained. The statics and dynamics simulations of two beam models are conducted and the results indicate that the unrealistic strain is eliminated by the decoupled model, and compared with the original model, the decoupled model shows better convergence and curvature continuity and more accurate under same number of elements. Meanwhile, as the stiffness is reduced by the decoupled model, there is no high frequency vibration in the velocity curve any more by compared with the original model.

2016, 48(6): 1406-1415. doi: 10.6052/0459-1879-16-127

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MECHANICS MODELING AND INVERSE ANALYSES OF PULSEWAVES SYSTEM WITH DISCUSSIONS ON SOME CONCEPTS IN THE TRADITIONAL CHINESE MEDICINE

Wang Lili, Wang Hui

The objectification and quantification of pulse diagnosis is one of the important research subjects of traditional Chinese medicine (TCM) modernization. Following the holism concept of TCM, the pulse wave system is considered as an entire system of life energy propagating within the blood in the form of wave, and a corresponding mechanics model is then established. The method of inverse analysis in the wave propagation theory in mechanics is generalized to deal with the pulse wave signals. Once the form of pulse wave, e.g. the pressure wave, is measured, the constitutive equation of the system as well as other forms of pulse wave such as the particle velocity wave, the specific volume wave and the internal energy wave can be deduced. It is indicated that a pulse phenomenon includes both the blood flow and the energy wave propagating within the blood. The former is a visible mass-flow with lower velocity, while the latter is an invisible energy-flow with much higher velocity, regarded respectively to the "blood" and the "Qi" in TCM. The propagating characters of pulse wave are mainly determined by the constitutive equation of the system which may correspond to the "body constitution" in TCM. Some intrinsic relationships may exist between them, and should be further investigated. Moreover, the effects of the non-linearity and the viscosity of the constitutive equation on the pulse wave characters are preliminarily discussed.

2016, 48(6): 1416-1424. doi: 10.6052/0459-1879-15-322

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COMPARATIVE STUDY ON SURFACE PANEL METHOD FOR THE HYDRODYNAMIC ANALYSIS OF HYBRID CONTRA-ROTATING SHAFT POD PROPULSOR

Wang Rui, Xiong Ying, Wang Zhanzhi

The present numerical study for the performance analysis of HCRSP (hybrid contra-rotating shaft pod) propulsor is based on the viscous flow method due to the structure complexity and the lacking of effectively potential flow method. In order to developing an effcient numerical method for the performance analysis of HCRSP propulsor, the HCRSP propulsor was divided into two parts, a single forward propeller and an aft podded propulsor. Then an iterative surface panel method was presented based on the single propeller surface panel method and podded propulsor integral panel method. The geometry characteristic and panel singularity strength of HCRSP propulsor were then analyzed, and an integral panel method was presented to treat HCRSP propulsor as a unit. The control equations of the integral panel method were derived in detail, and numerical solution program was developed. Based on these studies, the open water performance of an HCRSP propulsor was analyzed by iterative panel method and integral panel method. Numerical results were compared with experimental data and show that the relative result error of the two surface panel method are all within 5%, but the calculation time of integral panel method is about two thirds of that of iterative method. The integral panel method is more suitable in the design of HCRSP propulsor due to its calculation without iterative process. In the last, the error sources of integral panel method were discussed.

2016, 48(6): 1425-1436. doi: 10.6052/0459-1879-16-199

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TOPOLOGY DESCRIPTION FUNCTION APPROACH USING NURBS INTERPOLATION FOR 3D STRUCTURES WITH SELF-WEIGHT LOADS

Wang Xuan, Hu Ping, Zhu Xuefeng, Gai Yundong

The self-weight of the structure is of great importance for large civil engineering structures like dams and bridges, and should be taken into account at the initial design stage. Three main methods to deal with the di culties arisen in optimization problems with self-weight loads are summarized. In this paper, a modified topology description function (TDF) approach using the non-uniform rational B-splines (NURBS) interpolation scheme is introduced for optimal design of 2D/3D continuum structures with design-dependent self-weight loads. In the present approach, the NURBS basis function is applied for the approximation of both the displacement field and the geometry, as well as the interpolation of the design variables. Based on this, the design model and analysis model can be combined closely to realize the computational analysis directly on exact geometry. The model of TDF approach using NURBS interpolation and its sensitivity analysis are detailed. And the method of moving asymptotes (MMA) algorithm is used to solve this optimization problem. Then several numerical examples are performed. It can be seen that the present TDF approach is a robust, fast convergence algorithm, and can effectively overcome the parasitic effect associated with low material density areas, and the nonmonotonous behavior of the compliance that often encountered in topology optimization problems with self-weight loads.

2016, 48(6): 1437-1445. doi: 10.6052/0459-1879-16-145

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SUMMARY OF THE SECOND NATIONAL SYMPOSIUM ON BIOMECHANICS FOR YOUNG SCHOLARS

Li Zhiyong, Qi Yingxin, Wang Jianshan, Zhan Shige

This paper is a brief introduction and review of the Second National Symposium on Biomechanics for Young Scholars.

2016, 48(6): 1446-1451. doi: 10.6052/0459-1879-16-268

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