In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method (HAM) is employed to obtain the expressions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 208-214, 2011]]>Chaotic vibrations of flexible non-linear Euler-Bernoulli beams subjected to harmonic load and with various boundary conditions (symmetric and non-symmetric) are studied in this work. Reliability of the obtained results is verified by the finite difference method (FDM) and the finite element method (FEM) with the Bubnov-Galerkin approximation for various boundary conditions and various dynamic regimes (regular ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 36-43, 2011]]>The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 152-163, 2011]]>This paper develops a coupled dynamics model for a linear induction motor (LIM) vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 297-307, 2011]]>This article studies on Cauchy’s function f (z) and its integral, $$ (2\pi i)J[f(z)] \equiv \oint_C {f(t)dt/(t - z)} $$ taken along a closed simple contour C, in regard to their comprehensive properties over the entire z = x + iy plane consisted of the simply connected open domain D + bounded by C and the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 135-151, 2011]]>The extended finite element method (X-FEM) is a novel numerical methodology with a great potential for using in multi-scale computation and multi-phase coupling problems. The algorithm is discussed and a program is developed based on X-FEM for simulating mixed-mode crack propagation. The maximum circumferential stress criterion and interaction integral are deduced. Some numerical results are ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 406-415, 2011]]>A new higher-order continuum model is proposed by considering the coupling and lane changing effects of the vehicles on two adjacent lanes. A stability analysis of the proposed model provides the conditions that ensure its linear stability. Issues related to lane changing, shock waves and rarefaction waves, local clustering and phase transition are also investigated with numerical experiments. The ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 228-236, 2011]]>A new video-based measurement is proposed to collect and investigate traffic flow parameters. The output of the measurement is velocity-headway distance data pairs. Because density can be directly acquired by the reciprocal of headway distance, the data pairs have the advantage of better simultaneity than those from common detectors. By now, over 33 000 pairs of data have ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 346-353, 2011]]>The behavior of a precracked bi-material structure interface under given static and dynamic axial loading is an interest object in the present paper. Firstly, it is shown that the shear-lag model is a proper tool to analyze a delamination process in a precracked bi-material structure undergoing static loading. Secondly, the “shear-lag model” is applied to the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 80-89, 2011]]>Discontinuous Galerkin (DG) method is known to have several advantages for flow simulations, in particular, in flexible accuracy management and adaptability to mesh refinement. In the present work, the DG method is developed for numerical simulations of both temporally and spatially developing mixing layers. For the temporally developing mixing layer, both the instantaneous flow field and time evolution of momentum ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 318-329, 2011]]>A considerable number of viruses’ structures have been discovered and more are expected to be identified. Different viruses’ symmetries can be observed at the nanoscale level. The mechanical models of some viruses realised by scientists are described in this paper, none of which has taken into consideration the internal deformation of subsystems. The authors’ models for some viruses’ elements are ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 125-129, 2011]]>A well known chaotic mapping in symbol space is a shift mapping. However, other chaotic mappings in symbol space exist too. The basic change is to consider the process not only at a set of times which are equally spaced, say at unit time apart (a shift mapping), but at a set of times which are not equally spaced, say ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 114-118, 2011]]>This article deals with solutions of transient vibration of a rectangular viscoelastic orthotropic thin 2D plate for particular deformation models according to Flügge and Timoshenko-Mindlin. The linear model, a general standard viscoelastic body, of the rheologic properties of a viscoelastic material was applied. The time and coordinate curves of the basic quantities displacement, rotation, velocity, stress and deformation are ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 98-107, 2011]]>Numerical simulation methods of aerodynamic heating were compared by considering the influence of numerical schemes and turbulence models, and attempting to investigate the applicability of numerical simulation methods on predicting heat flux in engineering applications. For some typical cases provided with detailed experimental data, four spatial schemes and four turbulence models were adopted to calculate surface heat flux. By analyzing ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 339-345, 2011]]>A frequency equation for the vibration of an engine seating and an equation for pressure under the bottom of the engine are obtained. The present approach extends the so called Muravskii model possessing high practical accuracy of the ground modeling with its simultaneous simplicity.

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 68-71, 2011]]>The paradox of destabilization of a conservative or non-conservative system by small dissipation, or Ziegler’s paradox (1952), has stimulated a growing interest in the sensitivity of reversible and Hamiltonian systems with respect to dissipative perturbations. Since the last decade it has been widely accepted that dissipation-induced instabilities are closely related to singularities arising on the stability boundary, associated ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 2-6, 2011]]>Gaseous jets injected into water are typically found in underwater propulsion, and the flow is essentially unsteady and turbulent. Additionally, the high water-to-gas density ratio can result in complicated flow structures; hence measuring the flow structures numerically and experimentally remains a challenge. To investigate the performance of the underwater propulsion, this paper uses detailed Navier-Stokes flow computations ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-12, 2011]]>For fiber reinforced ceramic matrix composites (CMCs), oxidation of the constituents is a very important damage type for high temperature applications. During the oxidizing process, the pyrolytic carbon interphase gradually recesses from the crack site in the axial direction of the fiber into the interior of the material. Carbon fiber usually presents notch-like or local neck-shrink oxidation phenomenon, ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 382-388, 2011]]>This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios, which is defined as the ratio of the layer thickness to the gap width. The flow domain is ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 360-370, 2011]]>This paper presents a new passive-biped model consisting of a simplest walking model beneath an upper body, with no kinematic constraint. The upper body is attached to the legs with a linear torsional spring. The model is a passive dynamic walker, so it walks down a slope without energy input. The governing equations of motion are derived and simulated ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 277-284, 2011]]>This article studies on Cauchy's function f ( z) and its integral, (2pi i)J[f(z)] equiv oint_C {f(t)dt/(t - z)} taken along a closed simple contour C, in regard to their comprehensive properties over the entire z = x + i y plane consisted of the simply connected open domain D + bounded by C and ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 135-151, 2011]]>The paper presents two methods for the formulation of free vibration analysis of collecting electrodes of precipitators. The first, called the hybrid finite element method, combines the finit element method used for calculations of spring deformations with the rigid finite element method used to reflect mass and geometrical features, which is called the hybrid finite element method. As a result, ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 72-79, 2011]]>The Lagrange-I equations and measure differential equations for multibody systems with unilateral and bilateral constraints are constructed. For bilateral constraints, frictional forces and their impulses contain the products of the filled-in relay function induced by Coulomb friction and the absolute values of normal constraint reactions. With the time-stepping impulse-velocity scheme, the measure differential equations are discretized. ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-6, 2011]]>Dynamics of a ball moving in gravitational field and colliding with a moving table is studied in this paper. The motion of the limiter is assumed as periodic with piecewise constant velocity—it is assumed that the table moves up with a constant velocity and then moves down with another constant velocity. The Poincaré map, describing evolution from an impact...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 130-134, 2011]]>The Bauschinger and size effects in the thin-film plasticity theory arising from the defect-energy of geometrically necessary dislocations (GNDs) are analytically investigated in this paper. Firstly, this defect-energy is deduced based on the elastic interactions of coupling dislocations (or pile-ups) moving on the closed neighboring slip plane. This energy is a quadratic function of the GNDs ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 266-276, 2011]]>A discrete model of a rope is developed and used to simulate the plane motion of the rope fixed at one end. Actually, two systems are presented, whose members are rigid but non-ideal joints involve elasticity or dissipation. The dissipation is reflected simply by viscous damping model, whereas the bending stiffness conception is based on the classical curvature-bending ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 108-113, 2011]]>The FCSE controlling equation of pinned thin-walled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory, dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 452-460, 2011]]>Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 285-296, 2011]]>This study explores the fluid mechanics and force generation capabilities of an inverted heaving airfoil placed close to a moving ground using a URANS solver with the Spalart-Allmaras turbulence model. By varying the mean ground clearance and motion frequency of the airfoil, it was possible to construct a frequency-height diagram of the various forces acting on the airfoil. ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 164-178, 2011]]>Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 308-308, 2011]]>

The unsteady motion of an incompressible micropolar fluid filling a half-space bounded by a horizontal infinite plate that started to move suddenly is considered. Laplace transform techniques are used. The solution in the Laplace transform domain is obtained by using a direct approach. The inverse Laplace transforms are obtained in an exact manner using the complex inversion formula of ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 354-359, 2011]]>The unsteady motion of an incompressible micropolar fluid filling a half-space bounded by a horizontal infinite plate that started to move suddenly is considered. Laplace transform techniques are used. The solution in the Laplace transform domain is obtained by using a direct approach. The inverse Laplace transforms are obtained in an exact manner using the complex inversion formula of ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 354-359, 2011]]>Imperfect bonding between the constitutive components can greatly affect the properties of the composite structures. An asymptotic analysis of different types of imperfect interfaces arising in the problem of 2D fibrereinforced composite materials are proposed. The performed study is based on the asymptotic reduction of the governing biharmonic problem into two harmonic problems. All solutions are obtained in a closed ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 90-97, 2011]]>Facing the lateral vibration problem of a machine rotor as a beam on elastic supports in bending, the authors deal with the free vibration of elastically restrained Bernoulli-Euler beams carrying a finite number of concentrated elements along their length. Based on Rayleigh’s quotient, an iterative strategy is developed to find the approximated torsional stiffness coefficients, which allows the reconciliation ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 56-62, 2011]]>Facing the lateral vibration problem of a machine rotor as a beam on elastic supports in bending, the authors deal with the free vibration of elastically restrained Bernoulli-Euler beams carrying a finite number of concentrated elements along their length. Based on Rayleigh's quotient, an iterative strategy is developed to find the approximated torsional stiffness coefficients, which allows the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 56-62, 2011]]>Modified rotor kit Bently Nevada was used for dynamic characteristics measurements of new developed aerostatic bearings. Mathematicalmodel of these bearings is considered as linear. Model was identified with the help of harmonic force excitation independently from the speed of journal rotation. The stiffness and damping matrices were identified for different air inlet pressures. The calculated spectral properties allow to determine ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 63-67, 2011]]>J ep-integral is derived for characterizing the fracture behavior of elastic-plastic materials. The J ep-integral differs from Rice’s J-integral in that the free energy density rather than the stress working density is employed to define energy-momentum tensor. The J ep-integral is proved to be path-dependent regardless of incremental plasticity and deformation plasticity. The ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 251-258, 2011]]>This paper presents an analytical solution for the interaction of electric potentials, electric displacements, elastic deformations, and thermoelasticity, and describes electromagnetoelastic responses and perturbation of the magnetic field vector in hollow structures (cylinder or sphere), subjected to mechanical load and electric potential. The material properties, thermal expansion coefficient and magnetic permeability of the structure are assumed to be graded in ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-11, 2011]]>A time domain model is presented to study the vibrations of long slender cylinders placed in shear flow. Long slender cylinders such as risers and tension legs are widely used in the field of ocean engineering. They are subjected to vortex-induced vibrations (VIV) when placed within a transverse incident flow. A three dimensional model coupled with wake oscillators is ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 330-338, 2011]]>The large eddy simulation (LES) approach implemented in the KIVA-3V code and based on one-equation sub-grid turbulent kinetic energy model are employed for numerical computation of diesel sprays in a constant volume vessel and in a Caterpillar 3400 series diesel engine. Computational results are compared with those obtained by an RANS (RNG k- ε) model as well ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 519-530, 2011]]>Cavitation typically occurs when the fluid pressure is lower than the vapor pressure at a local thermodynamic state, and the flow is frequently unsteady and turbulent. To assess the state-of-the-art of computational capabilities for unsteady cavitating flows, different cavitation and turbulence model combinations are conducted. The selected cavitation models include several widely-used models including one based ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-15, 2011]]>The velocity field and the associated shear stress corresponding to the torsional oscillatory flow of a second grade fluid, between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. At time t = 0, the fluid and both the cylinders are at rest and at t = 0+, cylinders suddenly begin to oscillate around their common ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 222-227, 2011]]>Nonlinear dynamic response of nanomechanical resonator is of very important characteristics in its application. Two categories of the tension-dominant and curvature-dominant nonlinearities are analyzed. The dynamic nonlinearity of four beam structures of nanomechanical resonator is quantitatively studied via a dimensional analysis approach. The dimensional analysis shows that for the nanomechanical resonator of tension-dominant nonlinearity, its dynamic nonlinearity ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, 2011]]>In this paper the effects of hydrophobic wall on skin-friction drag in the channel flow are investigated through large eddy simulation on the basis of weakly-compressible flow equations with the MacCormack’s scheme on collocated mesh in the FVM framework. The slip length model is adopted to describe the behavior of the slip velocities in the streamwise and spanwise ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 200-207, 2011]]>In this paper, a revisiting Hughes’ dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimensional continuous walking facility scattered with a circular obstruction. It is assumed that pedestrians prefer to walk a path with the lowest instantaneous travel cost from origin to ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 215-221, 2011]]>Based on the theory of continuum damage mechanics, a bi-variable damage mechanics model is developed, which, according to thermodynamics, is accessible to derivation of damage driving force, damage evolution equation and damage evolution criteria. Furthermore, damage evolution equations of time rate are established by the generalized Drucker’s postulate. The damage evolution equation of cycle rate is obtained by integrating ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 416-425, 2011]]>The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 189-199, 2011]]>Network simulation method (NSM) is used to solve the laminar heat and mass transfer of an electrically-conducting, heat generating/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations, in a single independent variable, ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 389-398, 2011]]>Network simulation method (NSM) is used to solve the laminar heat and mass transfer of an electrically-conducting, heat generating/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations, in a single independent variable, ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 389-398, 2011]]>Earlier measurements in large synchronous generators indicate the existence of complex whirling motion, and also deviations of shape in both the rotor and the stator. These non-symmetric geometries produce an attraction force between the rotor and the stator, called unbalanced magnetic pull (UMP). The target of this paper is to analyse responses due to certain deviations of shape in ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 18-27, 2011]]>Wrinkling analysis of a rectangular membrane with a single crease under shearing is performed to understand the wrinkle-crease interaction behaviors. The crease is considered by introducing the residual stresses from creasing and the effective modulus into the baseline configuration with assumed circular cross-sectional crease geometry. The wrinkling analysis of the creased membrane is then performed by using the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 550-558, 2011]]>We present a new analytical model for electrostatically actuatedmicrobeams to explore the size effect by using the modified couple stress theory and the minimum total potential energy principle. A material length scale parameter is introduced to represent the size-dependent characteristics of microbeams. This model also accounts for the nonlinearities associated with the mid-plane stretching force and the electrostatical ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 445-451, 2011]]>A two-stage damage detection approach is proposed and experimentally demonstrated on a complicated spatial model structure with a limited number of measurements. In the experiment, five known damage patterns, including 3 brace damage cases and 2 joint damage cases, were simulated by removing braces and weakening beam-column connections in the structure. The limited acceleration response data generated by ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 399-405, 2011]]>An elusive phenomenon is observed in previous investigations on dynamic fracture that the dynamic fracture toughness (DFT) of high strength metals always increases with the loading rate on the order of TPa·m1/2·s−1. For the purpose of verification, variation of DFT with the loading rate for two high strength steels commonly used in the aviation industry, 30CrMnSiA and ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-8, 2011]]>In the present paper we discuss the magnetohydrodynamic (MHD) peristaltic flow of a hyperbolic tangent fluid model in a vertical asymmetric channel under a zero Reynolds number and long wavelength approximation. Exact solution of the temperature equation in the absence of dissipation term has been computed and the analytical expression for stream function and axial pressure gradient are established. The ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 237-250, 2011]]>A system designed for a rigid and flexible pipe laying purposes is presented in the paper. Mathematical and numerical models are developed by using the rigid finite element method (RFEM). The RFEM is an efficient solution in the time domain. Static and dynamic problems related to pipe installation are solved by taking the advantage of simple interpretation and implementation of ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 44-55, 2011]]>In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer (PDPA) and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes (RANS) model and a large-eddy simulation (LES). The results of the measurements yield the axial and radial time-averaged ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-8, 2011]]>When ocean waves propagate over the sea floor, dynamic wave pressures and bottom shear stresses exert on the surface of seabed. The bottom shear stresses provide a horizontal loading in the wave-seabed interaction system, while dynamic wave pressures provide a vertical loading in the system. However, the bottom shear stresses have been ignored in most previous studies in the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, 2011]]>Deforming a cracked magnetoelastic body in a magnetic field induces a perturbed magnetic field around the crack. The quantitative relationship between this perturbed field and the stress around the crack is crucial in developing a new generation of magnetism-based nondestructive testing technologies. In this paper, an analytical expression of the perturbed magnetic field induced by structural deformation of an ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 259-265, 2011]]>A penny-shaped interfacial crack between dissimilar magnetoelectroelastic layers subjected to magnetoelectromechanical loads is investigated, where the magnetoelectrically impermeable crack surface condition is adopted. By using Hankel transform technique, the mixed boundary value problem is firstly reduced to a system of singular integral equations, which are further reduced to a system of algebraic equations. The field intensity factors and energy ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 371-381, 2011]]>Level set methods are widely used for predicting evolutions of complex free surface topologies, such as the crystal and crack growth, bubbles and droplets deformation, spilling and breaking waves, and two-phase flow phenomena. This paper presents a characteristic level set equation which is derived from the two-dimensional level set equation by using the characteristic-based scheme. An explicit ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, 2011]]>Due to uncertain push-pull action across boundaries between different attractive domains by random excitations, attractors of a dynamical system will drift in the phase space, which readily leads to colliding and mixing with each other, so it is very difficult to identify irregular signals evolving from arbitrary initial states. Here, periodic attractors from the simple cell mapping method are ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-9, 2011]]>Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 426-437, 2011]]>The design of mobile robots that can move without wheels or legs is an important engineering and technological problem. Self-propelling mechanisms consisting of a body that has contact with a rough surface and moveable internal masses are considered. Mathematical models of such systems are presented in this paper. First, a model of a vibration driven robot that moves along ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 7-17, 2011]]>The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is extended to flows with shock waves in this paper. Using the newly developed second-order cell-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 2, pp. 179-188, 2011]]>Experimental investigation of hypersonic boundary layer instability on a cone is performed at Mach number 6 in a hypersonic wind tunnel. Time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 28 stations on the cone surface in the streamwise direction to investigate the development of the unstable disturbance. Wavelet ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-6, 2011]]>This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free stream velocity ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 502-509, 2011]]>A boundary layer analysis is presented to investigate numerically the effects of radiation, thermophoresis and the dimensionless heat generation or absorption on hydromagnetic flow with heat and mass transfer over a flat surface in a porous medium. The boundary layer equations are transformed to non-linear ordinary differential equations using scaling group of transformations and they are solved numerically by ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 531-540, 2011]]>A stochastic optimal control strategy for a slightly sagged cable using support motion in the cable axial direction is proposed. The nonlinear equation of cable motion in plane is derived and reduced to the equations for the first two modes of cable vibration by using the Galerkin method. The partially averaged Itô equation for controlled system energy is further derived...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-9, 2011]]>This paper analyses robotic signals in the perspective of fractional dynamics and the pseudo phase plane (PPP). It is shown that the spectra of several experimental signals can be approximated by trend lines whose slope characterizes their fractional behavior. For the PPP reconstruction of each signal, the time lags are calculated through the fractal dimension. Moreover, to obtain a smooth ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 28-35, 2011]]>This is a series of studies on Wu’s conjecture and on its resolution to be presented herein. Both are devoted to expound all the comprehensive properties of Cauchy’s function f(z) (z = x + iy) and its integral taken along the unit circle as contour C, inside which (the open domain D +) f(z) is regular but has singularities ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 309-317, 2011]]>This is a series of studies on Wu's conjecture and on its resolution to be presented herein. Both are devoted to expound all the comprehensive properties of Cauchy's function f( z) ( z = x + i y) and its integral J[ {f( z )} ] equiv ( {2pi i} )^{ - 1} oint_C {f( t )( {t - z} )^{ - 1} dt} taken along the unit ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 309-317, 2011]]>In this paper, we investigate the evolution of spatiotemporal patterns and synchronization transitions in dependence on the information transmission delay and ion channel blocking in scale-free neuronal networks. As the underlying model of neuronal dynamics, we use the Hodgkin-Huxley equations incorporating channel blocking and intrinsic noise. It is shown that delays play a significant yet subtle role in ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, 2011]]>This paper presents a coordinating and stabilizing control law for a group of underwater vehicles with unstable dynamics. The coordinating law is derived from a potential that only depends on the relative configuration of the underwater vehicles. Being coordinated, the group behaves like one mechanical system with symmetry, and we focus on stabilizing a family of coordinated motions, called relative ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 3, pp. 438-444, 2011]]>The Lattice Boltzmann method (LBM) is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself, but ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 510-518, 2011]]>In vitro experiments have shown that subtle fluid flow environment plays a significant role in living biological tissues, while there is no in vivo practical dynamical measurement of the interstitial fluid flow velocity. On the basis of a new finding that capillaries and collagen fibrils in the interosseous membrane form a parallel array, we set up a porous media model ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 1-9, 2011]]>Liesegang patterns of parallel precipitate bands are obtained when solutions containing co-precipitate ions interdiffuse in a 1D gel matrix. The sparingly soluble salt formed, displays a beautiful stratification of discs of precipitate perpendicular to the 1D tube axis. The Liesegang structures are analyzed from the viewpoint of their fractal nature. Geometric Liesegang patterns are constructed in conformity with the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, no. 1, pp. 119-124, 2011]]>Liesegang patterns of parallel precipitate bands are obtained when solutions containing co-precipitate ions interdiffuse in a 1D gel matrix. The sparingly soluble salt formed, displays a beautiful stratification of discs of precipitate perpendicular to the 1D tube axis. The Liesegang structures are analyzed from the viewpoint of their fractal nature. Geometric Liesegang patterns are constructed in conformity with the ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 119-124, 2011]]>The paper is discussing problems connected with embedment of the incubation time criterion for brittle fracture into finite element computational schemes. Incubation time fracture criterion is reviewed; practical questions of its numerical implementation are extensively discussed. Several examples of how the incubation time fracture criterion can be used as fracture condition in finite element computations are given. The examples include ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 27, pp. 541-549, 2011]]>This paper focuses on studying the integration method of a generalized Birkhoffian system. The method of variation on parameters for the dynamical equations of a generalized Birkhoffian system is presented. The procedure for solving the problem can be divided into two steps: the first step, a system of auxiliary equations is constructed and its general solution is given; the second ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, 2011]]>Although the genetic algorithm (GA) for structural optimization is very robust, it is very computationally intensive and hence slower than optimality criteria and mathematical programming methods. To speed up the design process, the authors present an adaptive reanalysis method for GA and its applications in the optimal design of trusses. This reanalysis technique is primarily derived from the Kirsch’s combined ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 2, pp. 225-234, 2010]]>Numerical simulation and control of self-propelled swimming of two- and three-dimensional biomimetic fish school in a viscous flow are investigated. With a parallel computational fluid dynamics package for the two- and three-dimensional moving boundary problem, which combines the adaptive multi-grid finite volume method and the methods of immersed boundary and volume of fluid, it is found ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 1, pp. 45-65, 2010]]>The velocity field and the associated shear stress corresponding to the longitudinal oscillatory flow of a generalized second grade fluid, between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. Initially, the fluid and cylinders are at rest and at t = 0+ both cylinders suddenly begin to oscillate along their common axis with simple ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 4, pp. 541-550, 2010]]>The lateral dynamic flight stability of a hovering model insect (dronefly) was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. The main results are as following. (i) Three natural modes of motion were identified: one unstable slow divergence mode (mode 1), ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 2, pp. 175-190, 2010]]>As a vehicle passing through a track with different weld irregularities, the dynamic performance of track components is investigated in detail by using a coupled vehicle–track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are discretely supported by ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 3, pp. 449-465, 2010]]>Based on the standard spaces of the physical presentation, both the quasi-static mechanical approximation and the quasi-static electromagnetic approximation of piezoelectric solids are studied here. The complete set of uncoupled elastic wave and electromagnetic wave equations are deduced. The results show that the number and propagation speed of elastic waves and electromagnetic waves in anisotropic piezoelectric solids are ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 2, pp. 241-246, 2010]]>The existence and propagation of transverse surface waves in piezoelectric coupled solids is investigated, in which perfect bonding between a metal/dielectric substrate and a piezoelectric layer of finite-thickness is assumed. Dispersion equations relating phase velocity to material constants for the existence of various modes are obtained in a simple mathematical form for a piezoelectric material of class 6 mm. ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 3, pp. 417-423, 2010]]>In this article, transverse free vibrations of axially moving nanobeams subjected to axial tension are studied based on nonlocal stress elasticity theory. A new higher-order differential equation of motion is derived from the variational principle with corresponding higher-order, non-classical boundary conditions. Two supporting conditions are investigated, i.e. simple supports and clamped supports. Effects of nonlocal nanoscale, ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 5, pp. 755-765, 2010]]>Although the analytical solution of the starting flow of Maxwell fluid in a pipe has been derived for a long time, the effect of relaxation time λ on start-up time t s of this flow is still not well understood. Especially, there exist a series of jumps on the t s–λ curve. In this paper we introduce a ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 2, pp. 209-215, 2010]]>Bending analysis of functionally graded plates using the two variable refined plate theory is presented in this paper. The number of unknown functions involved is reduced to merely four, as against five in other shear deformation theories. The variationally consistent theory presented here has, in many respects, strong similarity to the classical plate theory. It does not require shear correction ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 6, pp. 941-949, 2010]]>The paper deals with analytical models of the elastic energy gradient W sq representing an energy barrier. The energy barrier is a surface integral of the elastic energy density w q . The elastic energy density is induced by thermal stresses acting in an isotropic spherical particle (q = p) with the radius R and in a cubic cell of an isotropic ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 1, pp. 101-106, 2010]]>This paper deals with an analytical model of thermal stresses which originate during a cooling process of an anisotropic solid continuum with uniaxial or triaxial anisotropy. The anisotropic solid continuum consists of anisotropic spherical particles periodically distributed in an anisotropic infinite matrix. The particles are or are not embedded in an anisotropic spherical envelope, and the infinite matrix is imaginarily ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 5, pp. 695-709, 2010]]>Large eddy simulation (LES) of low Mach number compressible turbulent channel flow with spanwise wall oscillation (SWO) is carried out. The flow field is analyzed with emphases laid on the heat transport as well as its relation with momentum transport. When turbulent coherent structures are suppressed by SWO, the turbulent transports are significantly changed, however the momentum and heat transports ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 3, pp. 391-399, 2010]]>In a microfluidic system, flow slip velocity on a solid wall can be the same order of magnitude as the average velocity in a microchannel. The flow-electricity interaction in a complex microfluidic system subjected to joint action of wall slip and electro-viscous effect is an important topic. This paper presents an analytic solution of pressure-driven liquid flow ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 1, pp. 73-80, 2010]]>Numerical simulation of nanoparticle nucleation and coagulation in a mixing layer with sulfuric acid vapor binary system is performed using the large eddy simulation and the direct quadrature method of moment. The distributions of number concentration, volume concentration, and average diameter of nanoparticles are obtained. The results show that the coherent structures have an important effect on the distributions of ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 4, pp. 521-529, 2010]]>A new method is developed for stabilizing motion on collinear libration point orbits using the formalism of the circular restricted three body problem. Linearization about the collinear libration point orbits yields an unstable linear parameter-varying system with periodic coefficients. Given the variational equations, an innovative control law based on characteristic exponent assignment is introduced for libration point orbit maintenance. ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 3, pp. 495-500, 2010]]>In general, triangular and quadrilateral elements are commonly applied in two-dimensional finite element methods. If they are used to compute polycrystalline materials, the cost of computation can be quite significant. Polygonal elements can do well in simulation of the materials behavior and provide greater flexibility for the meshing of complex geometries. Hence, the study on the polygonal element is ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 5, pp. 685-693, 2010]]>Breaking down the entire structure of a material implies severing all the bonds between its atoms either by applying work or by heat transfer. Because bond-breaking is indifferent to either means, there is a kind of equivalence between heat energy and strain energy. Based on this equivalence, we assume the existence of a constant maximum storage of energy that ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 2, pp. 235-239, 2010]]>A theoretical study is presented herein on the penetration of a semi-infinite target by a spherical-headed long rod for Y p > S, where Y p is the penetrator strength and S is the static target resistance. For Y p > S, depending upon initial impact velocity, there exist three types of penetration, namely, penetration by a rigid ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 4, pp. 573-583, 2010]]>Of the three mutually coupled fundamental processes (shearing, compressing, and thermal) in a general fluid motion, only the general formulation for the compressing process and a subprocess of it, the subject of aeroacoustics, as well as their physical coupling with shearing and thermal processes, have so far not reached a consensus. This situation has caused difficulties for various in-depth ...

Journal: Acta Mechanica Sinica - ACTA MECH SINICA, vol. 26, no. 3, pp. 355-364, 2010]]>