Hypersonic liquid film cooling technology is to press out the cooling medium through a series of slits or holes, creat a low-temperature cooling film in the boundary layer of the surface of the aircraft to prevent the aerodynamic heating of the aircraft by hypersonic airflow. As an active cooling method, it has great application potential in surface thermal protection of hypersonic vehicle. In this paper, numerical methods and VOF model are used to study the spreading of liquid film at 25 km flight altitude and Ma=5 airflow. The evolution process and cooling mechanism of liquid film on a flat plate are discussed through the incident velocity, Angle, surface tension and viscosity coefficient of different cooling medium. The results show that under the action of air flow, the liquid film develops downstream to the wall surface, the existence of the liquid film leads to the boundary layer separation, and the continuous liquid film will be broken into liquid blocks at a certain position, and then further broken into droplets. The change of incident conditions and liquid properties will affect the development of the liquid film along the flow direction, which is manifested in the position of the fracture point and the thickness of the continuous liquid film. Within the computational domain set in this paper, the wall heat flow is reduced by 80% ~ 95%, and the cooling efficiency of the liquid film on the wall varies with the the change of the liquid film morphology.
2023, 55(5): 1039-1052.
doi: 10.6052/0459-1879-22-512
In the hydrodynamic and processing research of meandering river, it is implicitly assumed that the relationship between secondary flow and secondary turbulence is the same as that between mean flow and turbulence in open channel flows. However, there is no relevant turbulence research to support this implicit assumption, due to the limitation of DNS model and PIV measurement at high Reynolds number. The differences and similarities research of turbulent structures development between meandering channel and straight channel flow are benefit to the secondary turbulent flow in meandering rivers. A planar two-dimensional NS equation in orthogonal coordinate system and the two-parameter perturbation method were established to solve the weak nonlinear laminar flow and flow instability problem in the meandering channel. And a governing equation, named with extended Orr-Sommerfeld (EOS) equation was derived to solve the eigenvalue problem of planer flow with meandering boundary. The weak nonlinear laminar flow is combination of a series of meandering harmonic components, in which the linear component causes the velocity difference between the two walls, and the nonlinear component increases exponentially with the increase of Reynolds number. The first modal of the disturbance growth rate spectrum is similar to that of the straight channel flow, which is composed of three type curves and divided four disturbance wave bands. However, the disturbance flow field at the longwave band and the shortwave band is different from that of the straight flow. Specially, the velocity disturbance at shortwave band is similar to that of the Kelvin-Helmholtz vortex, may due to the velocity difference caused by linear component of laminar. The two meandering parameters have a certain selectivity to the internal disturbance in channel. The larger the angular amplitude is, the faster the disturbance grows. With the increase of the meandering wavenumber, the disturbance growth rate increases at first and then decreases. The disturbed flow field is formed by superposition of a typical TS wave and a pair of wave packets. The wave packet pair has only longitudinal velocity components, with two envelopes controlled by the boundary wavenumber and interior TS wave with the same parameters as TS wave in the wave packet.
2023, 55(5): 1075-1086.
doi: 10.6052/0459-1879-22-570
Study on drag reduction of turbulent channel flow has its significance in both scientific researches and industry applications. The passive drag reduction technique that has been reported to be effective is to add dispersed materials into the single-phase turbulence. On the other hand, the active drag reduction technique, i.e., spanwise wall oscillation, which can be controlled in advance, has attracted wide attention in recent years. Drag reduction induced by spanwise wall oscillation has been successfully applied to single-phase turbulence, however, there is few attentions is paid to the drag reduction of particle-laden channel flow by the aforementioned active technique. Therefore, the drag reduction of particle-laden channel flow by spanwise wall oscillation is studied in this paper by direct numerical simulations. The major concern is two-folded: the first is the turbulent modulation and mechanism of particle-laden channel flow induced by spanwise wall oscillation, and the second is the coupling effect of laden particles and wall oscillation on drag reduction. Comparing with non-oscillation particle-laden channel flow, the wall drag of particle-laden channel flow is reduced by spanwise wall oscillation. The optimal oscillation period is found to achieve the maximum drag reduction rate, which is similar with the trend of single-phase channel flow. With the same volume fraction, channel flow with small size particle exhibits large drag reduction. Comparing with non-oscillation single-phase turbulence, for small oscillation period scenario the coupling contribution of laden particles and wall oscillation has weak and even negative effect on drag reduction, as the oscillation period increases the coupling contribution becomes significant and the maximum magnitude is around 10% of the overall drag reduction.
2023, 55(5): 1087-1098.
doi: 10.6052/0459-1879-22-590
Non-isothermal viscoelastic fluid flow phenomena widely exist in nature and industrial productions, such as oil reservoir engineering, injection molding, etc. These flows generally exhibit a non-isothermal state. Accurate prediction of non-isothermal flow mechanism and complex rheological properties of viscoelastic fluid has important engineering application value. In this paper, an improved smoothed particle hydrodynamics (SPH) method is proposed for the numerical simulation of non-isothermal viscoelastic complex flow, in which the viscoelastic properties of the fluid are characterized by the eXtended Pom-Pom constitutive model. To improve the accuracy of simulation results, a kernel function gradient correction algorithm is adopted. To enforce the boundary conditions flexibly, a boundary treatment method combining boundary particles and virtual particles is developed. To eliminate the tensile instability in the flow process, the particle migration technology is applied. The improved SPH method is used to numerically simulate the impact of a droplet on the solid wall and injection molding of an F-shaped cavity. The effectiveness of the improved SPH method in solving the non-isothermal viscoelastic fluid is verified by comparing the SPH results with those obtained by the Basilisk software. Good agreement between these two numerical solutions is achieved. The numerical convergence of the improved SPH method is evaluated by using several different initial particle spacings. The different flow characteristics of non-isothermal flow compared with isothermal flow are investigated. It is found that the introduction of temperature leads to stronger contraction behavior of droplet. The influences of some different thermal rheological parameters such as the Péclet number, the Reyonlds number, the Weissenberg number, the solvent viscosity ratio, the anisotropy parameter, the relaxation time ratio and the molecular chain arm number on the flow process are deeply analyzed. The numerical results show that the improved SPH method proposed in this paper can accurately and stably describe the heat transfer mechanism, complex rheological properties, and free surface variation characteristics of non-isothermal viscoelastic fluid.
2023, 55(5): 1099-1112.
doi: 10.6052/0459-1879-22-602
EXPERIMENTAL STUDY ON THE CHARACTERIZATION OF TRANSVERSE JET INTERACTION IN HYPERSONIC RAREFIED FLOW
Jet interaction is an effective approach for hypersonic flight controls with higher agility and improved maneuverability. Previous researches are mainly focused on the mechanisms of jet interaction effects in continuous region, classical flowfield structures of jet interaction based on different models have been proposed theoretically, on the other hand, scarce experimental data on characterizations of jet interaction in rarefied region exist. Therefore, the objective of this work aims to experimentally investigate the effects of jet pressure and hypersonic rarefied flow condition on the characterizations of transverse jet interaction based on a flat plate model, whereas hypersonic rarefied flows are generated in a JFX detonation shock tunnel. Evolution and typical structure of transverse jet interaction in hypersonic rarefied flow are recorded using high-speed schlieren imaging approach, and variations of spatial positions of different shock waves are analyzed using imaging process technique. Compared to the flowfield without the presence of jet flow, the interaction between jet flow and hypersonic rarefied flow makes the flowfield much more complex. Oblique shock could instantaneously penetrate through the flowfield of jet interaction due to the pressure fluctuation of jet flow caused by the incoming flow. With increasing the jet pressure, the affecting region of the barrel shock gradually becomes broader. The spatial position of the oblique shock wave in the upstream of the triple point barely changes with an increase in the jet pressure, while in the downstream of the triple point, the bow shock moves upstream with increasing pressure. The spatial position of the barrel shock would not overlap with the other two when the jet pressure is low. The pressure reduction of the incoming hypersonic rarefied flow can broaden the affecting region of the barrel shock and thus move the bow shock upstream as well, but it has little influence on the spatial position of the oblique shock wave.
2023, 55(5): 1053-1062.
doi: 10.6052/0459-1879-22-599
The interaction between pulsed laser plasma and supersonic flow field has important application value on aircraft drag reduction and heat insulation, ignition and combustion assistance. In order to quantitatively study the velocity field and vortex structure, particle image velocimetry (PIV) experiments were carried out on laser plasma and its interaction with normal shock wave. The nanosecond pulse laser energy deposition system and PIV measurement system were established on the shock tube experimental platform. By quantitatively measuring, the flow characteristics of laser air bubbles and hot core induced by laser plasma are explored. The flow characteristics and evolution of laser plasma under the impact of normal shock waves are revealed, and the influence of laser energy magnitude and deposition position on the interaction process is given. The results show that the velocity distribution in the laser air bubble is not symmetrical about the breakdown point in the laser incidence direction, but the flow velocity near the laser incidence direction is slightly larger than that far from the laser incidence direction. The baroclinic pressure leads to the generation of vortex rings in the early stage of hot core evolution, and the later stage is dominated by shearing force. When the normal shock interacts with the laser air bubble interface and the hot core interface, the baroclinic vorticity is generated. When the laser energy is 87.8 mJ and the normal shock Mach number is 1.41, the vorticity generated at the hot core interface is one order of magnitude larger than that in the static air. The key process of the interaction between the laser and the normal shock wave is that the hot core evolves into a vortex ring under the impact of the normal shock wave. The deposition of laser energy in front of the shock wave can obtain a more significant vortex ring.
2023, 55(5): 1063-1074.
doi: 10.6052/0459-1879-22-580
The dynamic stability of subgrade in transition zones has become a key problem restricting the design of high-speed railway subgrade with a speed of 400 km/h and above. It urgent to explore the amplification mechanism of system dynamic response caused by non-uniform foundation from the perspective of wave and energy. In this paper, the foundation under track is reduced to a elastic layer which has a free surface and rigid bottom. The problem of vehicle induced elastic wave propagation in the transition zones in high-speed railway is refined into the problem of wave scattering in the inhomogeneous elastic layer with rigid base. A plane-strain model of two medium coupling elastic layers with rigid base is established. Facing with the dispersion equation of elastic layer with rigid base, the paper optimizes the method of finding roots in complex plane. Then, the dispersion analyses of the elastic layers that are assigned with geotechnical medium are carried out, and the corresponding multi-mode guided wave characteristics and the distribution of scattered energy are clarified. Furthermore, in terms of the thickness of elastic layer, stiffness ratio of two elastic layers and so on, comparative analyses are carried out at last. The results indicate that all of the guided wave modes in the elastic layer with rigid base have cut-off frequencies. When the thickness of the elastic layer decreases or the Young's modulus of the medium increases, the cut-off frequency of each order guided wave mode becomes higher. In scattering, the fundamental mode of the transmitted field can occupy the main energy. And as modes are excited one by one, the proportion of energy of higher modes of the reflected field and the transmitted field shows a “trade-off” state in the full frequency range. The energy distribution law will not be significantly changed when the elastic layer materials on both sides are exchanged, or the elastic layers thickness and the stiffness ratio is changed. On the whole, the energy is more easily concentrated in the softer elastic layer, and guided wave mode is more active in the initial frequency band after excitation and distributes more energy.
2023, 55(5): 1124-1137.
doi: 10.6052/0459-1879-22-573
The motion with variable acceleration is common in daily life and engineering problems. Variable acceleration dynamics, also known as Newtonian jerky dynamics, has gained wide attention due to its application in chaos theory and nonlinear dynamics. Gauss principle is a differential variational principle with extreme value characteristics. Therefore, it is of great significance to study the generalized Gauss principle of dynamical systems with variable acceleration in both theory and application. In this paper, the generalized Gauss principle for dynamical systems with variable accelerated motion is presented and studied. Firstly, we introduce the concept of the generalized Gaussian variation in the jerky space. We take the derivative of d’Alembert principle of a particle with respect to time, and then calculate its dot product with the generalized Gaussian variation. By using the condition of ideal constraints in the sense of Gauss, we establish the generalized Gauss principle for dynamical systems with variable acceleration. On this basis, the generalized Gauss principle of least compulsion is established and proved by constructing the generalized compulsion function. The Appell form, Lagrange form and Nielsen form of the principle are given. Secondly, the extension of the principle to variable mass mechanics is explored. Starting from Meshchersky equation and taking its derivative with respect to time, and then calculating its dot product with the generalized Gaussian variation, we establish the generalized Gauss principle for variable-mass variable-acceleration dynamical systems with ideal constraints. The generalized compulsion function in the case of variable mass is constructed and the generalized Gauss principle of least compulsion for variable-mass variable-acceleration mechanical systems is established and proved. We take the Kepler-Newton problem as an example, and use the approach of the generalized Gauss least compulsion principle we presented to calculate, and verify the effectiveness of the method.
2023, 55(5): 1174-1180.
doi: 10.6052/0459-1879-23-030
EXPERIMENTAL STUDY ON PERMEABILITY ANISOTROPY OF DEEP RESERVOIR SANDSTONE UNDER TRUE TRIAXIAL STRESS
Permeability anisotropy is a very typical phenomenon in sedimentary bedding structure. On the one hand, it is determined by the primary sedimentary structure (i.e. primary anisotropy) and on the other hand, it is affected by stress and pore pressure (i.e. induced anisotropy). In order to study the primary and induced anisotropy of reservoir sandstone permeability under true triaxial stress, the reservoir sandstone of S6 gas storage in northeast China was taken as the research object. The true triaxial stress-seepage coupling device of hard rock independently developed by Northeastern University was adopted to carry out seepage experiment on reservoir sandstone, and the permeability test of the same sandstone in three mutually vertical directions was completed by steady-state method. The test results show that: in the range of applied stress and pore pressure, permeability of sandstone in parallel bedding direction${k_x}$ is 100.94 mD ~ 113.98 mD, ${k_y}$ is 98.34 mD ~ 111.41 mD, and permeability in vertical bedding direction ${k_z}$ is 54.98 mD ~ 63.29 mD. The permeability of sandstone in three orthogonal directions decreases with the increase of principal stress and increases with the load of pore pressure. The effect of stress perpendicular to the gas seepage direction on permeability is greater than that of stress parallel to the gas seepage direction. When the direction of external stress is perpendicular to the direction of gas flow, the effect of stress perpendicular to bedding on permeability is greater than that of stress parallel to bedding. The linear elastic response of pore pressure to reservoir sandstone permeability is not isotropic. The linear permeability increment generated by pore pressure to horizontal bedding direction is higher than that in vertical bedding direction. The research results provide a reference basis for accurate prediction of sandstone permeability of underground gas storage and a new petrophysical property data for operation and management of underground gas storage.
2023, 55(7): 1-12.
doi: 10.6052/0459-1879-23-051
Interphase energy transfer in turbulence laden with particles is one of the focuses of scholars, and the effect of electrostatic force is an important factor affecting the particles propensity distribution and the efficiency of energy exchange between particles and turbulence in the turbulent channel flow laden with particles. In this paper, the spatial distribution of charged particles in vertical turbulent channel flow with radiation heating and the effect of spatial distribution on the energy transport between particles and turbulent flow were investigated. Direct numerical simulation was used for fluid, and Lagrange-point tracking model was used for particles. The momentum exchange and the heat exchange between particles and turbulent flow were considered. Based on the analysis of particle local aggregation characteristics, velocity correlation between particles and turbulent flow and interphase energy transport, the effect of electrostatic force on particle spatial distribution, kinetic energy exchange and heat exchange between particles and fluid were investigated. The results show that the electrostatic force of the same positive charged particles leads to the weak aggregation of particles in the low speed band area near the two wall, and the spatial distribution of particles is more uniform, which is positively correlated with the amount of charge carried by particles. At the same time, it is found that the electrostatic force attenuates the followability of particles to the fluid in the near wall region, and the electrostatic force is superior to the Stokes drag. Meanwhile, the uniform distribution of particles in the vertical channel improves the mean temperature of fluid and the mean streamwise velocity of the fluid. And it strengthens the kinetic energy exchange and the heat exchange between particles and fluid in the middle area of the vertical channel while weakens the kinetic energy exchange and the heat exchange between particles and turbulent flow near the wall.
2023, 55(6): 1-11.
doi: 10.6052/0459-1879-23-163
The flow-focusing droplet microfluidics achieves continuous generation of monodisperse microdroplets by means of flow-focusing effects and interfacial destabilization phenomenon of discrete-phase liquid filament. The multiphase interfacial flow in this technique exhibits dependence on configuration parameters and shows rich microfluidic device developed in our previous study, numerical simulations are used to investigate the influences of key configuration parameters on droplet generation modes and droplet dimensions. After reasonable simplifications, the study establishes an axisymmetric model of the actual device and combines the adaptive mesh refinement technique to improve the efficiency of the numerical simulation. The accuracy of the numerical simulation is verified through the comparison of several experimental operating conditions. It is found that within the selected fluid combination, geometry, and flow parameters, the droplet generation process exists in four modes: dripping, streaming, jetting, and unstable. Under the fixed discrete phase and continuous phase flow rate combinations, the variation of the distance between the upstream and downstream capillary ends changes the droplet length in the dripping and streaming modes, while it has little effect on the droplet size in the jetting mode. Under the fixed geometry parameters, when the flow rates vary, the change of droplet length is nearly continuous at the transition between dripping and streaming modes, but produces a sudden drop at the onset of the jetting mode. The internal diameter of the downstream capillary has a significant effect on the phase diagram, the dripping mode dominates for the large diameter internal diameter and the jet length changes more significantly in the jetting mode, while the jetting mode dominates for the small internal diameter and unstable modes are found at large continuous phase flows. The results of this paper show that the key configuration parameters have important effects on the flow-focusing microfluidic droplet generation, and the applicable alteration of these parameters can control the droplet size and improve the droplet monodispersity, which provides a basis for the design and optimization of flow-focusing microdroplet generation devices.
2023, 55(7): 1-10.
doi: 10.6052/0459-1879-23-094
In order to solve the complex geometric characteristics description and dynamic connectivity identification problems of reservoir at different scales, a new method of reservoir numerical simulation, connection element method (CEM), based on non-European physical connectivity network with meshless characteristics has been developed in recent years. In this paper, CEM is extended to fractured reservoirs. From the perspective of fluid flow, the reservoir is discretized into physical connected network by the connection element. The generalized difference approximation of the pressure diffusion term is given according to the physical parameters of the node, the radius of the influence domain and the weighted least square method. Meanwhile, the control volume of nodes, the transmissibility between matrix nodes, the transmissibility between fracture nodes, and the transmissibility between matrix nodes and fracture nodes were calculated based on the material conservation equation. Thus, a fully implicit discrete scheme of seepage control equations is constructed to solve dynamic production parameters such as pressure, saturation and water cut. Based on the pressure gradient between nodes solved by each time step, the allocation factors of injection wells at each time step were calculated by the depth-first search algorithm of graph theory to quantitatively characterize the flow relationship and connectivity between well nodes. The algorithm validation shows that the method can freely and flexibly portray complex reservoir geometry including distribution of complex fractures networks and irregular reservoir boundaries. Compared with the traditional grid-based method, this method can retain more abundant flow topologies under the condition of coarser model, so as to achieve a better balance between computational accuracy and computational efficiency. As a result, CEM can better meet the demand of production dynamic simulation and prediction of actual large-scale fractured reservoirs, and provides a new idea for numerical simulation of fractured reservoirs with multi-scale geometric characteristics and complex boundary reservoirs.
2023, 55(7): 1-12.
doi: 10.6052/0459-1879-23-069
In electromagnetic metallurgy, argon is usually used as a power and carrier to blow desulfurizer and deoxidizer into liquid metal, so there is a problem of free movement of bubbles in liquid metal under a magnetic field environment. Flow past a fixed bubble as a special form of free movement, is the first step to study the problem of free movement. In this paper, the global linear stability analysis of the flow past a spherical bubble under the effect of a streamwise magnetic field is simulated by the finite element method. The response of the steady axisymmetric basic flow to the small perturbation of the independent time-azimuthal mode in the range of $\mathit{Re}\leqslant 1000,N\leqslant 60$ is discussed. Eight unstable stationary modes are found, and their neutral curves in the $ \mathit{Re}-N $ parameter plane or $ \mathit{Re}-Ha $ parameter plane are displayed. The results show that the stationary mode with azimuthal wave number m = 1 leads to the first regular bifurcation, this mode has been widely confirmed as the most unstable mode in the flow past axisymmetric objects, which transforms the axisymmetric wake into a plane symmetric wake composed of a pair of opposite vortices. In addition, the results of the neutral curve show the effect of the magnetic field on the instability of the flow past the spherical bubble. The subsequent bifurcations are successively caused by the unstable modes of m = 2, 3,..., 8, these bifurcations provide an important reference value for understanding the wake structure of the flow past a bubble in the magnetic field environment.
2023, 55(7): 1-10.
doi: 10.6052/0459-1879-23-101
Most fish in nature achieve propulsion through undulatory movements, which are the result of the interaction between the deforming fish body and the surrounding fluid. To study the response of the fluid can enhance our understanding of undulatory propulsion and flow control. A two-dimensional deforming airfoil is used to model the carangiform fish. The flow field generated by fish body and the fluid forces acting on the fish body were obtained by using computational fluid dynamics. Using the principle of virtual power, the thrust on the fish body was decomposed into four parts, which are the instantaneous contribution of the boundary acceleration, the contribution of the relative magnitude of fluid rotation and strain rate in the flow field, the wall friction-like component and the wall friction component. The results show that the instantaneous contribution of the boundary acceleration is the main source of positive thrust. The rear 80% of the thrust contribution of this term comes from the instantaneous boundary acceleration movement of the rear 20% of the fish body. The fluid rotation and strain rate in the boundary layer on both sides of the fish tail and the friction contribute to resistance. For low Reynolds number, the negative contribution of the relative magnitude of fluid rotation and strain rate is lower than that of wall friction, while for high Reynolds number, the negative contribution of the relative magnitude of fluid rotation and strain rate is stronger than that of wall friction. However, the wall friction-like component is always smaller compared to the other three terms. In the analysis of the scaling law of undulatory propulsion, it was found that there is a component independent of the Reynolds number which is provided by the first two parts, while the component that is dependent on the Reynolds number is provided by the last three parts. Furthermore, the frictional force and the friction-like force provide constant resistance.
2023, 55(7): 1-12.
doi: 10.6052/0459-1879-23-076
In this paper, we proposed a novel numerical method, Zonal Free Element Method (ZFLM), and used the proposed method to compute thermal stress in composite structures. ZFLM is a strong-form numerical method which solves the governing equations in differential form. For each node, we use two (two-dimension problems) or three (three-dimensions problems) lines to form a cross-line system. Then, we use Lagrange interpolating method to interpolate nodal coordinates and approximate the variables on each line. The gradients in the curvature direction are computed by the gradients of interpolating functions along the line. By a recursive procedure, the second or higher order of derivatives can be obtained by the expressions of the first order derivatives. Substituting the expressions of derivatives into the governing partial difference equations, we obtain the discretized linear system of equations. To solve the problem involving multiple kinds of composite structures efficiently, we use a zonal method. In the zonal method, we divide the computational domain into several regular zones by material types and geometric characteristics. We insert nodes in each zone by interpolating functions and use the finite line method to assemble the discretized governing equations at these nodes. For the nodes at the interfaces which are shared by two or more zones, the traction-equilibrium equations and the compatibility conditions of variables are used to construct the linear algebraic equations. For the irregular geometries and the nodes where the loads jump, we add up the traction-equilibrium equations of each neighbor faces in different directions to improve the robustness of the proposed method. We use the proposed method to solve several thermal stress problems in two- and three-dimension. The results of test cases indicate that the proposed method has good accuracy and a significant priority in problems involving stress concentration. Because the collocation method is used, the stress on the boundary is more accurate.
2023, 55(7): 1-13.
doi: 10.6052/0459-1879-23-003
The development of modern industry inspires higher requirements for material properties and structural dimensions. The design of electromechanical devices is increasingly biased towards miniaturization, high frequency and intelligence. The most recent studies demonstrate that composite materials with magnetoelectric coupling can not only achieve mutual conversion of magnetic, mechanical, and electrical energy with high magnetoelectric conversion efficiencies, but can also avoid direct contact between the structure and the mechanical driving source to achieve non-contact control, which is crucial for the creation of multifunctional micro and nanoscale devices. Based on the multi-physics structural analysis framework developed by Mindlin, this paper studies the dynamic electromechanical coupling response of a sandwich plate composed of a flexoelectric dielectric layer and two symmetric piezomagnetic layers induced by external transverse magnetic fields. The macroscopic piezomagnetic and curvature-induced flexoelectric theories are employed and the classical electromechanical coupling theory is extended to centrosymmetric materials. The dynamic numerical examples of the sandwich plate driven by a sinusoidal global magnetic field and a uniformly distributed local magnetic field show that the magnitudes of displacement and potential are frequency dependent. When the excitation frequency reaches the natural frequency, the amplitude reaches the maximum. In addition, the distribution of symmetrical piezomagnetic layer tends to improve the electromechanical coupling performance of multilayer composite plates. Both the theoretical model and numerical results provide new ideas for the optimization design of magnetic-controlled electromechanical devices.
2023, 55(7): 1-9.
doi: 10.6052/0459-1879-23-103
Dust storms of varying degrees frequently transpire within the Martian atmosphere, and the dust particles present in the atmosphere will cause erosion on the surface of high-speed entering Mars vehicles, leading to increased wall heat flux. Consequently, the design of the vehicle's thermal protection system is confronted with a formidable challenge. In this paper, focusing on the two-phase flow problem in the hypersonic Mars entry environment, a non-equilibrium flow field and particle one-way coupling calculation method based on the Euler-Lagrange framework are established. Moreover, a Mars atmospheric particle distribution model with a modal radius of 0.35 μm is adopted to investigate the motion trajectories of particles with different sizes in the flow field. The effects of the high temperature phase change model on the particle motion and the impact energy distribution of particles with different particle sizes were obtained. The numerical simulation results show that particles are prone to melt or even vaporize during their moving in high-temperature flow fields, and it was confirmed that the high-temperature phase change model engenders a more pronounced effect on the trajectory of smaller particles due to their diminished dimensions. Conversely, particles with diameter above 3 μm exhibited a larger Stokes number, and their motion trajectory remained relatively unaffected by the surrounding flow field, and the radii of these particles remained relatively constant during motion. Particles with a diameter larger than 3 μm account for more than 95% of the impact fraction on the wall, which is the main source of wall impact. The results of the impact energy fraction indicate that particles with diameters between 3 and 10 μm are the main source of impact energy, accounting for approximately 80% of the total impact energy.
, Available online ,
doi: 10.6052/0459-1879-23-192
Robotic assembly in orbit is one of the most promising ways to build large spacecraft, but there are serious dynamical coupling effects between the two when robots work on the surface of space structures, which brings new challenges to space structure construction. A robot-structure coupled dynamics modeling and gait optimization method is proposed for a coupled dynamics problem formed by a three-branch robot walking on a spatially flexible structure. First, a coupled dynamics model was established based on the Lagrangian equation and the Euler-Bernoulli beam model, which can be used to predict the coupled dynamics response of the robot when walking on the surface of the structure. Then, the relationship between robot motion and structural vibration is derived based on the coupled dynamics equation, and the effects of different walking modes of the robot on the dynamic response of the spatial structure are studied; and the optimization study of robot walking gait is carried out. Finally, the numerical simulation of the dynamic response of the space structure under the creeping gait motion of the robot is given with a three-branch robot walking on a cantilevered space structure as an example. The results show that the dynamic response of the space structure is closely related to the robot motion gait, and the faster the step frequency, the longer the step length and the higher the lifting height, the more significant the structural vibration will be. By optimizing the robot gait, the structural vibration can be effectively suppressed.
, Available online
The surface friction between any object can be regarded as the friction between rough surfaces, and most rough surfaces have fractal characteristics. In order to study the friction behavior of fractal rough surface, the molecular dynamics-Green’s function method (GFMD) is used to establish the microscopic fractal rough surface. The contact and friction processes of fractal rough surface are controlled by displacement loading, and the contact cluster distribution is identified by breadth-first search algorithm. Then, the maximum friction coefficient and friction force at atomic scale, contact cluster scale and interface scale are calculated respectively. The influence matrix method is used to study the interaction between contact clusters in the friction process, and the influence of the distance between contact clusters and the area of contact clusters on the interaction is analyzed. The results show that the friction coefficient decreases from small scale to large scale during the friction process. The friction force fluctuates periodically with the displacement. Contact clusters don’t reach the maximum friction force at the same time, but local slip occurs. The friction force obtained by the global slip model is the upper limit of the molecular simulation results. The influence matrix method can simulate the interaction of contact clusters well. The friction force calculated by using the influence matrix is basically consistent with the result of GFMD model, while the friction force calculated by ignoring the influence of local slip is 20% larger than the result of GFMD model. The interaction between contact clusters is inversely proportional to the distance and proportional to the area. The results can provide theoretical basis for interface analysis and optimization of rough surface.
, Available online
The integrated thermal protection structure is usually in a severe unstable thermal environment, and the time effect of thermal load, namely transient thermal effect, is obvious. In order to avoid huge calculation consumption of transient thermal analysis, previous optimization design studies of integrated thermal protection structures usually equivalent transient heat transfer to steady-state heat transfer under the same thermal boundary conditions, and take the temperature field of steady-state heat transfer analysis as the design thermal load. However, previous studies have shown that the steady-state heat transfer cannot accurately equivalent the effect of transient heat transfer, and the transient thermal effect has an important influence on the structural design results. In this paper, the optimization design problem of integrated thermal protection structure considering transient thermal effect is studied, and a topology optimization method of integrated thermal protection structure considering transient temperature and stress constraints is established. Based on the Solid Isotropic Material with Penalization (SIMP) method, two kinds of topology optimization models for integrated thermal protection structures are constructed: 1. The stiffness design model taking minimizing the structural strain energy as objective function, considering material volume fraction, maximum stress and maximum bottom-face temperature constraints. 2. The strength design model taking minimizing material volume fraction as objective function, considering maximum stress and maximum bottom-face temperature constraints. By solving the transient thermodynamic coupling equation, the thermodynamic coupling static analysis results of the structure are obtained. The maximum value of structural response in time domain is represented by the condensed integral function in space and time domains, which was taken as constraint and objective functions. The sensitivity expressions of objective function and constraint functions are derived by adjoint method. The effectiveness of the proposed method is verified by three numerical results. Numerical examples showed that the proposed method could accurately reflect the influence of transient thermal effects on the design results of integrated thermal protection structures under the condition of transient heat transfer. Compared with the design results based on steady-state thermal analysis, the design results considering transient thermal effects were significantly improved.
, Available online ,
doi: 10.6052/0459-1879-22-598
2017, 49(1): 3-21.
doi: 10.6052/0459-1879-16-348
摘要：
作为隧道及地下工程学科的3个基本问题，隧道围岩稳定性、支护——围岩相互作用和结构体系的动力响应一直都是本学科研究的核心问题，本文围绕上述问题重点分析了隧道围岩力学特性及其载荷效应，建立了深浅层围岩结构力学模型，并通过分析深层围岩中结构层稳定性得到了围岩特性曲线的解析公式，提出了围岩结构性特点及载荷效应的计算方法；通过对隧道支护与围岩作用关系的分析，将支护与围岩的动态作用分为4个阶段：即自由变形、超前支护、初期支护和二次衬砌阶段.由此提出了动态作用全过程的描述方法；基于广义与狭义载荷的理念，提出隧道支护具有调动和协助围岩承载基本功能的观点，明确了两种功能的实现方式，即通过围岩加固、超前加固及锚杆支护实现调动围岩承载，通过支护结构协助围岩承载；针对复杂的隧道支护结构体系，提出了多目标、分阶段协同作用动态优化概念，可使各种支护结构的施作实现时间和空间上的协调，提高可靠性；针对极不稳定的复杂隧道围岩的安全性特点，建立了3种模式的安全事故机理模型，基于工程响应特点提出了安全性分级的新理念，并形成了分级指标体系和分级方法；针对水下隧道及富水围岩条件，建立了3种模式的隧道突涌水机理模型，提出了基于围岩变形控制的安全性控制理论和方法.最后，对本学科发展的热点和核心问题进行了分析和展望.
作为隧道及地下工程学科的3个基本问题，隧道围岩稳定性、支护——围岩相互作用和结构体系的动力响应一直都是本学科研究的核心问题，本文围绕上述问题重点分析了隧道围岩力学特性及其载荷效应，建立了深浅层围岩结构力学模型，并通过分析深层围岩中结构层稳定性得到了围岩特性曲线的解析公式，提出了围岩结构性特点及载荷效应的计算方法；通过对隧道支护与围岩作用关系的分析，将支护与围岩的动态作用分为4个阶段：即自由变形、超前支护、初期支护和二次衬砌阶段.由此提出了动态作用全过程的描述方法；基于广义与狭义载荷的理念，提出隧道支护具有调动和协助围岩承载基本功能的观点，明确了两种功能的实现方式，即通过围岩加固、超前加固及锚杆支护实现调动围岩承载，通过支护结构协助围岩承载；针对复杂的隧道支护结构体系，提出了多目标、分阶段协同作用动态优化概念，可使各种支护结构的施作实现时间和空间上的协调，提高可靠性；针对极不稳定的复杂隧道围岩的安全性特点，建立了3种模式的安全事故机理模型，基于工程响应特点提出了安全性分级的新理念，并形成了分级指标体系和分级方法；针对水下隧道及富水围岩条件，建立了3种模式的隧道突涌水机理模型，提出了基于围岩变形控制的安全性控制理论和方法.最后，对本学科发展的热点和核心问题进行了分析和展望.
2016, 48(4): 756-766.
doi: 10.6052/0459-1879-16-159
摘要：
软体机器人是一类新型机器人，具有结构柔软度高，环境适应性好，亲和性强，功能多样等特点，有着十分广阔的研究和应用前景. 智能材料在软体机器人结构设计及实际应用中扮演了重要的角色，其特殊的驱动机制极大拓展了软体机器人的功能. 介绍了软体机器人的发展和研究现状，按其应用场合及功能总结了几种典型的软体机器人. 从仿生机理的角度，介绍了蠕虫、弯曲爬行虫、鱼类游动等几类仿生运动机理以及其相应的软体机器人. 还按不同驱动类型将软体机器人归纳为气动、形状记忆合金、离子交换聚合物金属复合材料、介电高弹体、响应水凝胶、化学燃烧驱动等类型. 介绍了软体机器人的制作方法与工艺，分析了目前软体机器人研究的主要挑战，提出对未来研究的展望.
软体机器人是一类新型机器人，具有结构柔软度高，环境适应性好，亲和性强，功能多样等特点，有着十分广阔的研究和应用前景. 智能材料在软体机器人结构设计及实际应用中扮演了重要的角色，其特殊的驱动机制极大拓展了软体机器人的功能. 介绍了软体机器人的发展和研究现状，按其应用场合及功能总结了几种典型的软体机器人. 从仿生机理的角度，介绍了蠕虫、弯曲爬行虫、鱼类游动等几类仿生运动机理以及其相应的软体机器人. 还按不同驱动类型将软体机器人归纳为气动、形状记忆合金、离子交换聚合物金属复合材料、介电高弹体、响应水凝胶、化学燃烧驱动等类型. 介绍了软体机器人的制作方法与工艺，分析了目前软体机器人研究的主要挑战，提出对未来研究的展望.
2017, 49(1): 22-30.
doi: 10.6052/0459-1879-16-345
摘要：
岩溶隧道突水灾害具有“强突发、高水压、大流量、多类型”等显著特点，其灾变演化过程复杂、动力失稳规律尚不清楚.本文系统提出了不同类型突水灾害的发生条件、判据及安全厚度分析方法，剖析了近期研究进展及发展趋势.首先，给出了隧道突水灾害的概念、类型及构成三要素，从系统论角度分析了隧道突水的灾变过程；其次，总结了隧道突水灾害致灾机理、力学模型、失稳判据和最小安全厚度等方面的近期研究成果；最后，从构成三要素角度分析了隧道突水致灾机理方面的现状与问题，并提出了今后的发展趋势与方向，主要有：（1）灾害源固液气三相置换机制与释能模式，（2）突水通道多相物质迁移与流态演化规律，（3）隔水阻泥结构动力灾变演化机理，（4）突水通道破裂形成过程的模拟分析方法等.
岩溶隧道突水灾害具有“强突发、高水压、大流量、多类型”等显著特点，其灾变演化过程复杂、动力失稳规律尚不清楚.本文系统提出了不同类型突水灾害的发生条件、判据及安全厚度分析方法，剖析了近期研究进展及发展趋势.首先，给出了隧道突水灾害的概念、类型及构成三要素，从系统论角度分析了隧道突水的灾变过程；其次，总结了隧道突水灾害致灾机理、力学模型、失稳判据和最小安全厚度等方面的近期研究成果；最后，从构成三要素角度分析了隧道突水致灾机理方面的现状与问题，并提出了今后的发展趋势与方向，主要有：（1）灾害源固液气三相置换机制与释能模式，（2）突水通道多相物质迁移与流态演化规律，（3）隔水阻泥结构动力灾变演化机理，（4）突水通道破裂形成过程的模拟分析方法等.
2019, 51(3): 656-689.
doi: 10.6052/0459-1879-18-381
摘要：
负泊松比材料和结构具有特殊的力学性能,在单轴压力(拉力)作用下发生横向收缩(膨胀).其在抗剪承载力、抗断裂性、能量吸收和压陷阻力等方面比传统材料更有优势,因而负泊松比材料在医疗设备、传感器、防护设备、航空航海及国防工程等领域有广泛的应用前景,但目前负泊松比材料的应用与普及仍面临一些挑战.本文广泛讨论了国内外关于负泊松比材料的研究成果并介绍了负泊松比材料的最新进展,将负泊松比材料大体概括为以下4类：天然负泊松比材料、胞状负泊松比材料、金属负泊松比材料、多重和复合负泊松比材料.主要介绍了各种负泊松比材料的内部结构、负泊松比机理、力学性能以及在各行各业的新发明、新应用.针对目前负泊松比材料研究理论和实验成果多,而实际应用仍然较少的情况,指出了负泊松比材料的缺点及其推广所面临的挑战.目前负泊松比材料面临的主要问题是制造成本高、孔隙率大而承载力不足以及仅适用于小应变情况等.本文针对此情况详细介绍了金属负泊松比材料及其设计和制作的方法,改善负泊松比材料的不足并推广其应用.
负泊松比材料和结构具有特殊的力学性能,在单轴压力(拉力)作用下发生横向收缩(膨胀).其在抗剪承载力、抗断裂性、能量吸收和压陷阻力等方面比传统材料更有优势,因而负泊松比材料在医疗设备、传感器、防护设备、航空航海及国防工程等领域有广泛的应用前景,但目前负泊松比材料的应用与普及仍面临一些挑战.本文广泛讨论了国内外关于负泊松比材料的研究成果并介绍了负泊松比材料的最新进展,将负泊松比材料大体概括为以下4类：天然负泊松比材料、胞状负泊松比材料、金属负泊松比材料、多重和复合负泊松比材料.主要介绍了各种负泊松比材料的内部结构、负泊松比机理、力学性能以及在各行各业的新发明、新应用.针对目前负泊松比材料研究理论和实验成果多,而实际应用仍然较少的情况,指出了负泊松比材料的缺点及其推广所面临的挑战.目前负泊松比材料面临的主要问题是制造成本高、孔隙率大而承载力不足以及仅适用于小应变情况等.本文针对此情况详细介绍了金属负泊松比材料及其设计和制作的方法,改善负泊松比材料的不足并推广其应用.
2016, 48(4): 767-783.
doi: 10.6052/0459-1879-16-161
摘要：
视觉伺服控制是机器人系统重要的控制手段. 相比传统的在标定条件下使用的视觉伺服系统，无标定视觉伺服系统具有更高的灵活性与适应性，是机器人伺服控制系统未来重要的发展方向和研究热点. 本文从目标函数选择、控制器设计、运动轨迹规划三方面综述了无标定视觉伺服控制系统近年来的主要研究进展. 首先根据目标函数的形式，分析了基于位置的视觉伺服、基于图像的视觉伺服以及混合视觉伺服各自的特点与应用；在控制器设计方面，根据是否在设计过程中考虑机器人的非线性动力学特性，分别介绍了考虑机器人运动学与考虑机器人动力学的无标定视觉伺服控制器的设计，重点突出了雅克比矩阵的构造与估计方法；针对无标定视觉伺服系统运动轨迹可能存在的问题，从空间轨迹优化与障碍规避的角度，阐述了已有的可行解决方案. 最后，基于当前的研究进展展望了无标定视觉伺服的未来研究方向.
视觉伺服控制是机器人系统重要的控制手段. 相比传统的在标定条件下使用的视觉伺服系统，无标定视觉伺服系统具有更高的灵活性与适应性，是机器人伺服控制系统未来重要的发展方向和研究热点. 本文从目标函数选择、控制器设计、运动轨迹规划三方面综述了无标定视觉伺服控制系统近年来的主要研究进展. 首先根据目标函数的形式，分析了基于位置的视觉伺服、基于图像的视觉伺服以及混合视觉伺服各自的特点与应用；在控制器设计方面，根据是否在设计过程中考虑机器人的非线性动力学特性，分别介绍了考虑机器人运动学与考虑机器人动力学的无标定视觉伺服控制器的设计，重点突出了雅克比矩阵的构造与估计方法；针对无标定视觉伺服系统运动轨迹可能存在的问题，从空间轨迹优化与障碍规避的角度，阐述了已有的可行解决方案. 最后，基于当前的研究进展展望了无标定视觉伺服的未来研究方向.
2017, 49(3): 550-564.
doi: 10.6052/0459-1879-17-064
摘要：
工程中航空航天、船舶与海洋结构物及其上装备和精密仪器易受极端环境干扰和破坏，使得非线性隔振理论在近十年来迅猛发展；针对日益严峻的隔振和抗冲击等要求，工程师和科学家们已发展出各种不同的非线性隔振系统，包括主动、半主动、被动和复合隔振。利用非线性改善的被动隔振兼具传统被动隔振的鲁棒性和主动隔振的高效性成为振动控制领域的先进技术。本文主要综述了非线性隔振理论和应用的近十年进展，包括非线性隔振设计、建模、分析、仿真和实验。在隔振系统的构建中，既考虑了刚度非线性又考虑了阻尼非线性；动力学响应的研究中，既有确定性分析又有随机分析。首先提出了适用于非线性隔振系统改进的评价方式；其次综述了高静态低动态刚度隔振及其加强形式非线性阻尼加强和双层非线性隔振，混沌反控制技术、内共振影响、非线性能量阱应用等振动机制利用型隔振和非线性隔振功能材料。最后，对非线性隔振研究发展的热点和关键性问题进行了分析和展望。
工程中航空航天、船舶与海洋结构物及其上装备和精密仪器易受极端环境干扰和破坏，使得非线性隔振理论在近十年来迅猛发展；针对日益严峻的隔振和抗冲击等要求，工程师和科学家们已发展出各种不同的非线性隔振系统，包括主动、半主动、被动和复合隔振。利用非线性改善的被动隔振兼具传统被动隔振的鲁棒性和主动隔振的高效性成为振动控制领域的先进技术。本文主要综述了非线性隔振理论和应用的近十年进展，包括非线性隔振设计、建模、分析、仿真和实验。在隔振系统的构建中，既考虑了刚度非线性又考虑了阻尼非线性；动力学响应的研究中，既有确定性分析又有随机分析。首先提出了适用于非线性隔振系统改进的评价方式；其次综述了高静态低动态刚度隔振及其加强形式非线性阻尼加强和双层非线性隔振，混沌反控制技术、内共振影响、非线性能量阱应用等振动机制利用型隔振和非线性隔振功能材料。最后，对非线性隔振研究发展的热点和关键性问题进行了分析和展望。
2019, 51(1): 1-13.
doi: 10.6052/0459-1879-18-054
摘要：
随着航天重大工程的逐步实施,航天器正朝着超高速、超大尺度、多功能的方向发展,其面临的发射和运行环境也更加恶劣.航天器发射过程中的振动及其主/被动控制、在轨运行中大型柔性航天器动力学建模与动态响应分析、结构振动与飞行器姿态的混合控制等问题越来越复杂且难于处理;航天器结构的大型化和柔性化(如大阵面天线和太阳翼等)也对其地面试验和半实物仿真提出了挑战.本文着重介绍大型柔性航天器涉及到的动力学与振动控制问题,包括航天器发射过程中的整星隔振,大型柔性结构动力学建模与振动响应分析,大型柔性航天器的结构振动与姿轨控耦合动力学及其混合控制等.提炼出航天动力学与控制领域中亟待解决的若干基础科学问题,包括：多刚柔体系统动力学建模与模型降阶(涉及大变形柔性体动力学建模、多求解器合作仿真、模型降阶、组合结构动力学建模的解析方法等);复杂结构状态空间模型构建方法与能控性(涉及状态空间模型构建的理论与实验方法、复杂结构振动控制系统的能观性与能控性等);航天器姿态运动与大型柔性结构振动的混合控制律设计(涉及姿态机动与结构振动的鲁棒混合控制、执行机构与压电控制器的协同控制等).
随着航天重大工程的逐步实施,航天器正朝着超高速、超大尺度、多功能的方向发展,其面临的发射和运行环境也更加恶劣.航天器发射过程中的振动及其主/被动控制、在轨运行中大型柔性航天器动力学建模与动态响应分析、结构振动与飞行器姿态的混合控制等问题越来越复杂且难于处理;航天器结构的大型化和柔性化(如大阵面天线和太阳翼等)也对其地面试验和半实物仿真提出了挑战.本文着重介绍大型柔性航天器涉及到的动力学与振动控制问题,包括航天器发射过程中的整星隔振,大型柔性结构动力学建模与振动响应分析,大型柔性航天器的结构振动与姿轨控耦合动力学及其混合控制等.提炼出航天动力学与控制领域中亟待解决的若干基础科学问题,包括：多刚柔体系统动力学建模与模型降阶(涉及大变形柔性体动力学建模、多求解器合作仿真、模型降阶、组合结构动力学建模的解析方法等);复杂结构状态空间模型构建方法与能控性(涉及状态空间模型构建的理论与实验方法、复杂结构振动控制系统的能观性与能控性等);航天器姿态运动与大型柔性结构振动的混合控制律设计(涉及姿态机动与结构振动的鲁棒混合控制、执行机构与压电控制器的协同控制等).
2017, 49(2): 239-256.
doi: 10.6052/0459-1879-16-255
摘要：
1978年，Barton提出的节理粗糙度系数（joint roughness coefficient，JRC）被国际岩石力学学会作为评估节理粗糙度的标准方法.然而该方法存在人为估值的主观性缺陷.就此，国内外学者围绕岩体结构面粗糙度定量化表征开展了大量的研究工作.首先，从二维节理轮廓线到三维岩体结构面，系统地阐述了其粗糙度定量化表征方法研究进展，并总结了各方法参数与JRC的关系；评价了各表征参数的本质特性及其适用性；指出了各方法参数获取过程中存在的问题，主要有：采样间隔的影响，三角形单元划分的影响，如何确定综合参数法中各参数的权重；针对这些问题，给出了笔者的一些想法、建议.与此同时，对结构面粗糙度表征的两个热点问题，即各向异性和尺寸效应的研究也进行了详细总结分析.最后，笔者认为：（1）分形维数因是描述自然界复杂几何体的一种简洁有力的工具，其仍是结构面粗糙度定量描述的有效方法；（2）3D打印技术的应用，有望在开展结构面各向异性、尺寸效应研究方面取得突破性进展.
1978年，Barton提出的节理粗糙度系数（joint roughness coefficient，JRC）被国际岩石力学学会作为评估节理粗糙度的标准方法.然而该方法存在人为估值的主观性缺陷.就此，国内外学者围绕岩体结构面粗糙度定量化表征开展了大量的研究工作.首先，从二维节理轮廓线到三维岩体结构面，系统地阐述了其粗糙度定量化表征方法研究进展，并总结了各方法参数与JRC的关系；评价了各表征参数的本质特性及其适用性；指出了各方法参数获取过程中存在的问题，主要有：采样间隔的影响，三角形单元划分的影响，如何确定综合参数法中各参数的权重；针对这些问题，给出了笔者的一些想法、建议.与此同时，对结构面粗糙度表征的两个热点问题，即各向异性和尺寸效应的研究也进行了详细总结分析.最后，笔者认为：（1）分形维数因是描述自然界复杂几何体的一种简洁有力的工具，其仍是结构面粗糙度定量描述的有效方法；（2）3D打印技术的应用，有望在开展结构面各向异性、尺寸效应研究方面取得突破性进展.
2016, 48(4): 741-753.
doi: 10.6052/0459-1879-16-069
摘要：
从Inglis 和Griffith 的著名论文到Irwin 和Rice 等的奠基性贡献，对断裂力学中的线弹性断裂力学的K判据，界面断裂力学的G判据，和弹塑性断裂力学的J 判据作了扼要的综述. 介绍了在界面断裂力学G判据的基础上提出的界面断裂力学的K判据，以说明断裂力学的判据存在改进的可能性. 在综述中归纳出断裂力学判据中目前还没有较好解决的几个问题. 在总结以往断裂力学研究经验的基础上，指出裂纹端应力奇异性的源是对断裂力学判据存在的问题作进一步研究的切入点. 探讨了裂纹端应变间断的奇点是裂纹端应力奇异性的源的问题，从而对裂纹端应力强度因子的物理意义进行了讨论. 最后，阐述了进行可靠的裂纹端应力场的弹塑性分析是改进弹塑性断裂力学判据的关键，而进行可靠的裂纹端应力场的弹塑性分析的前提是要通过裂纹端应力奇异性的源的研究来获得作用在裂纹端的造成裂纹端应变间断的有限值应力.
从Inglis 和Griffith 的著名论文到Irwin 和Rice 等的奠基性贡献，对断裂力学中的线弹性断裂力学的K判据，界面断裂力学的G判据，和弹塑性断裂力学的J 判据作了扼要的综述. 介绍了在界面断裂力学G判据的基础上提出的界面断裂力学的K判据，以说明断裂力学的判据存在改进的可能性. 在综述中归纳出断裂力学判据中目前还没有较好解决的几个问题. 在总结以往断裂力学研究经验的基础上，指出裂纹端应力奇异性的源是对断裂力学判据存在的问题作进一步研究的切入点. 探讨了裂纹端应变间断的奇点是裂纹端应力奇异性的源的问题，从而对裂纹端应力强度因子的物理意义进行了讨论. 最后，阐述了进行可靠的裂纹端应力场的弹塑性分析是改进弹塑性断裂力学判据的关键，而进行可靠的裂纹端应力场的弹塑性分析的前提是要通过裂纹端应力奇异性的源的研究来获得作用在裂纹端的造成裂纹端应变间断的有限值应力.
2016, 48(3): 519-535.
doi: 10.6052/0459-1879-15-436
摘要：
斜拉桥的非线性动力学问题一直都是力学、结构和桥梁领域的研究热点.随着新材料(如碳纤维增强聚合物索)和新施工工艺的发展,斜拉桥的跨越能力不断得到提高,从而在桥梁建设中更具有竞争力.然而,斜拉桥跨度的增大和新材料的应用使结构变得更轻和更柔,使结构的非线性振动问题比以往更为突出,可能危及桥梁安全.基于课题组近年来对斜拉桥非线性动力学的研究,围绕大跨度斜拉桥的非线性建模理论及动力学问题,较为详细地评述近十年来国内外的研究进展情况.主要从斜拉索非线性动力学模型、梁的非线性动力学模型、索-梁组合结构的非线性动力学模型、斜拉桥整体非线性动力学模型与理论、以及斜拉桥的非线性振动实验等几个方面对斜拉桥非线性建模方法、力学模型、数学模型、求解方法及相应研究成果进行评述和讨论.研究结果表明,斜拉桥由于多柔性索和大跨度梁的耦合问题,以及环境载荷的复杂性,导致其具有丰富的非线性动力学行为.同时由于高维非线性系统求解方法的欠缺,整体斜拉桥非线性动力学行为又相当复杂,深入研究面临很大困难.最后,基于未来斜拉桥的发展趋势和可能面临的突出问题,对斜拉桥非线性振动问题今后的发展方向进行了探讨和展望.
斜拉桥的非线性动力学问题一直都是力学、结构和桥梁领域的研究热点.随着新材料(如碳纤维增强聚合物索)和新施工工艺的发展,斜拉桥的跨越能力不断得到提高,从而在桥梁建设中更具有竞争力.然而,斜拉桥跨度的增大和新材料的应用使结构变得更轻和更柔,使结构的非线性振动问题比以往更为突出,可能危及桥梁安全.基于课题组近年来对斜拉桥非线性动力学的研究,围绕大跨度斜拉桥的非线性建模理论及动力学问题,较为详细地评述近十年来国内外的研究进展情况.主要从斜拉索非线性动力学模型、梁的非线性动力学模型、索-梁组合结构的非线性动力学模型、斜拉桥整体非线性动力学模型与理论、以及斜拉桥的非线性振动实验等几个方面对斜拉桥非线性建模方法、力学模型、数学模型、求解方法及相应研究成果进行评述和讨论.研究结果表明,斜拉桥由于多柔性索和大跨度梁的耦合问题,以及环境载荷的复杂性,导致其具有丰富的非线性动力学行为.同时由于高维非线性系统求解方法的欠缺,整体斜拉桥非线性动力学行为又相当复杂,深入研究面临很大困难.最后,基于未来斜拉桥的发展趋势和可能面临的突出问题,对斜拉桥非线性振动问题今后的发展方向进行了探讨和展望.
2012, 44(2): 269-277.
doi: 10.6052/0459-1879-2012-2-20120210
Abstract:
2012, 44(2): 252-258.
doi: 10.6052/0459-1879-2012-2-20120208
Abstract:
