Showing papers in "Acta Mechanica Sinica in 1986"
TL;DR: In this article, a simple and efficient triangular finite element is introduced for plate bending application, which is a three-node triangular one with three basic degrees of freedom per node and two internal rotation degrees offreedom, using selective reduced integration.
Abstract: A simple and efficient triangular finite element is introduced for plate bending application. The element is a three-node triangular one with three basic degrees of freedom per node and two internal rotation degrees of freedom, using selective reduced integration. Numerical examples indicate that, despite its simplicity, the element is not only competitively accurate, but also useful as a thick/thin triangular plate bending element. It is also pointed out that this element using selective reduced integration is in fact a mixed element.
32 citations
TL;DR: In this article, the authors review analytical studies of the evolution of thermoplastic shear band, i.e., emergence from uniform deformation, post-instability growth and late stage behaviour.
Abstract: The present paper briefly reviews analytical studies of the evolution of thermoplastic shear band, i.e. emergence from uniform deformation, post-instability growth and late stage behaviour. The case studied is the simple shear of temperature and rate-dependent materials with heat transfer. Uniform mode exists before a critical state, if no heat flows out of testpiece. Upon reaching the critical state, bifurcation appears as a result of disturbances, which leads to instability and the formation of narrow shear band. Initially, the band, due to temperature disturbance, can shrink with increasing temperature and strain rate owing to unsteady flow. Then heat conduction dominates and causes the shear band to expand. The postmortem appearance of thermo-plastic shear band manifests itself as balance of plastic work rate and heat diffusion. Melting may also take place within the band.
24 citations
TL;DR: In this paper, the problem of cracks with an elliptic hole in an infinite plane is investigated, where the fictitious loads on the hole edge and using the Muskhelishvili method are reduced to solving a system of mixed-type integral equations.
Abstract: The problem of cracks with an elliptic hole in an infinite plane is investigated. By introducing the fictitious loads on the hole edge and using the Muskhelishvili method, the problem is reduced to solving a system of mixed-type integral equations in which some are Fredholm equations but others Cauchy-type singular ones. A numerical method is suggested and can be used for the treatment of other similar equations. The numerical results for some typical examples are given, showing that the method is really effective.
21 citations
TL;DR: An extension of the Elastica theory is developed to study the large deflection of an elastic-perfectly plastic horizontal cantilever beam subjected to a vertical concentrated force at its tip as discussed by the authors.
Abstract: An extension of the Elastica theory is developed to study the large deflection of an elastic-perfectly plastic horizontal cantilever beam subjected to a vertical concentrated force at its tip. The entire process is divided into four stages: I.elastic in the whole cantilever; II.loading and developing of the plastic region; III.unloading in the plastic region; and IV.reverse loading. Solutions for stages I and II are presented in a closed form. A combination of closed-form solution and numerical integration is presented for stage III. Finally, stage IV is qualitatively studied. Computed results are given and compared with those from small-deflection theory and from the Elastica theory.
16 citations
TL;DR: In this paper, it was shown that the single-valued demands on the displacements are equivalent to 3m functional constraint equations, wherem is the number of holes, and a numerical method for solving this problem is presented.
Abstract: The theoretical analysis and the numerical computations for the problem of a thin plate with large deflection and some holes become much more difficult due to the multi-valued properties of the stress functionF and the single-valued demands on the displacements. The necessary and sufficient conditions which can assureF to be single-valued are obtained in this paper. At the same time, we prove that the single-valued demands on the displacements are equivalent to 3m functional constraint equationsDC(w,F)=0, wherem is the number of holes. From these conclusions, the single-valued governing-equations of the problem of plates with large deflection and some holes are derived. It is a system of fourth order partial differential equations with 3m unknown constants and constrained equations. A numerical method for solving this problem is presented. The problem of the critical load is considered and an iterative scheme for computing the buckled states is given when a critical load λ is ‘single’.
13 citations
TL;DR: In this paper, the structural reliability analysis taking account of the fuzziness in both earthquake loads and structural resistances is put forward, and the concepts such as fuzzy earthquake intensity, fuzzy response spectrum, fuzzy structural response and satisfaction degree to fuzzy-random constraint are defined.
Abstract: The structural reliability analysis taking account of the fuzziness in both earthquake loads and structural resistances is put forward in this paper. For this purpose, the concepts such as fuzzy earthquake intensity, fuzzy response spectrum, fuzzy structural response and satisfaction degree to fuzzy-random constraint are defined. This procedure may be taken as a basis for establishing a more rational optimum design of structures.
9 citations
TL;DR: In this article, the Lagrange multiplier is used for the correct use of the method of Lagrange multipliers and the fundamentals for the proper use of this method are presented and illustrated by examples.
Abstract: The fundamentals for the correct use of the method of Lagrange multiplier are presented and illustrated by examples. Some misunderstandings of the method are clarified. Equivalent variational principles are defined. It is pointed out that for a given problem of mechanics, there may be many equivalent and unequivalent variational principles. The functional of the so called generalized variational principles of elasticity with more general forms[16] are linear combinations of the well known functionals given by Reissner and Hu-Washizu.
7 citations
TL;DR: In this article, a wedge subjected to tractions in proportion torn (n≥0) is considered and it is shown that the stresses in the solutions of the classical theory of elasticity become infinite when the angle of the wedge is ρ or 2ρ.
Abstract: A wedge subjected to tractions in proportion torn(n≥0), is considered. The stresses in the solutions of the classical theory of elasticity become infinite when the angle of the wedge is ρ or 2ρ. The paradox has been resolved by Dempsey[4] and T.C.T. Ting[5] whenn=0. The purpose of this paper is to resolve the paradox whenn>0.
6 citations
TL;DR: In this paper, the main properties of the two component LDV system developed with the dual-differential frequency shift technique were described, which has the advantages of multiple functions, better SNR and high utilization of information.
Abstract: This paper describes the main properties of the two component LDV system developed with the dual-differential frequency shift technique. It has the advantages of multiple functions, better SNR and high utilization of information. So it offers as a complete technique and method for measuring 2-D complex flows. By applying this system, 2-D turbulent separated flow measurements have been made in a duct with an asymmetrical sudden expansion and in a wind tunnel flow over a 2-D rib. The Reynolds numbers were at 5900 and 4500 respectively.
6 citations
TL;DR: In this article, the parametric minimum complementary energy variational principle is used for nonassociative flow rule in the theory of plasticity, the Drucker postulation can no longer be applied and the classical variational principles fail.
Abstract: The parametric minimum complementary energy variational principle is given in this paper. To the problems of nonassociative flow rule in the theory of plasticity, the Drucker postulation can no longer be applied and the classical variational principles fail, the parametric variation principles can play the role instead. The parametric variational principle can be used for the finite element solution with sequential quadratic programming method to soil mechanics problems.
5 citations
TL;DR: In this article, the stress space and the strain space formulations of the elastoplastic constitutive relations at a singular point on a yield surface were discussed, and the parallelism of the two space formulations was discussed.
Abstract: This paper gives the stress space and the strain space formulations of the elastoplastic constitutive relations at a singular point on a yield surface, discusses the parallelism of the two space formulations and points out that the strain space formulation has a wider range of applicability.
Journal Article•
TL;DR: In this article, the effect of nonparallelism of the boundary layer flow over a flat plate on its stability characteristics has been investigated, and it was claimed that the results of the theoretical calculations are already in good agreement with the experimental observations.
Abstract: The effect of the nonparallelism of the boundary layer flow over a flat plate on its stability characteristics has been investigated by several authors, and it was claimed that the results of the theoretical calculations are already in good agreement with the experimental observations. However, this is not true. In this paper, this problem is reinvestigated, using two different methods. It is found that within the framework of linear theory, the theoretical results are in fact not in good agreement with the experimental observations. To settle this problem, nonlinear effect must be taken into consideration.
TL;DR: Based on the dual theory of nonlinear mathematical programming and the second order Taylor series expansions of functions, an efficient algorithm for structural optimum design has been developed in this paper, where the main advantages are the generality in use, the efficiency in computation and the capability in identifying automatically the set of active constraints.
Abstract: Based on the dual theory of nonlinear mathematical programming and the second order Taylor series expansions of functions, an efficient algorithm for structural optimum design has been developed. The main advantages of this method are the generality in use, the efficiency in computation and the capability in identifying automatically the set of active constraints. On the basis of the virtual work principle, formulas in terms of element stresses for the first and second order derivatives of nodal displacement and stress with respect to design variables are derived. By applying the Saint-Venant's principle, the computational efforts involved in the Hessian matrix associated with the iterative expression can be significantly reduced. This method is especially suitable for optimum design of large scale structures. Several typical examples have been optimized to test its uasefulness.
TL;DR: In this paper, the femur's articular surface of the knee of Pongidae is divided into three types according to the shape of the moire contour fringes of the medial condyle.
Abstract: In this paper, moire contour fringes is applied to study the femur's articular surface of the knee of Pongidae. The preliminary division of the femur's articular surface of knee into three types is proposed. The moire contour fringes ofthe medial condyle is taken as a mark according to the references. Owing to the fact that the moire contour fringes obtained from experiments after the 2nd order of fringe basically follow a certain rule, an investigation is made on the distribution of the angle α which is defined as the angle of the major axis of the 2nd order's near-oval shaped moire contour fringe on the medial condyle with the horizontal axis. Preliminary distribution graphs are given in the paper.
TL;DR: In this paper, the profile and excitation mechanism of vacuum-ultraviolet radiation emitted from a shock tube was investigated in a very thin shock layer in which the mechanism ofX.............. 1∑→b.............. 1 ∑ of N2 is excited with excitation cross sectionQ=2×10−16cm2 and activation energyE.............. *=12.1 ev.
Abstract: The profile and excitation mechanism of vacuum-ultraviolet radiation emitted from shock wave is investigated in a shock tube. For shock wave in argon, the rdiation is due to resonant transition excited by argon-argon collision in the shock front with excitation cross section coefficientS
*=1.0×10−17 cm2·ev−1 and activation energyE
*=11.4 ev. For shock wave in air the radition is emitted from a very thin shock layer in which the mechanism ofX
1∑→b
1∑ of N2 is excited with excitation cross sectionQ=2×10−16cm2 and activation energyE
*=12.1 ev.
TL;DR: In this paper, the results obtained from the microscopic research on the mechanisms of oil displacement by alkaline waterflooding are presented, and the more precise description of the mechanisms and its controlling factors are given.
Abstract: In this paper, the results obtained from the microscopic research on the mechanisms of oil displacement by alkaline waterflooding are presented. Micromodels have been employed to observe directly the process of this displacement. Cinephotomicrographic investigation in the mechanisms of the physical-chemical flow through porous media is made. The types and flow behavior of emulsions formed during the oil displacement by alkaline waterflooding have been systematically studied, including the law of emulsification, flow state and oil bank formation etc. Thus the more precise description of the mechanisms of oil displacement by alkaline waterflooding and its controlling factors are given.
TL;DR: An improved structural dynamic model of an oscillating blade in two degrees of freedom is combined with an unsteady aerodynamic model for the transonic flow about a cascade with separation, which results in a coupled system as mentioned in this paper.
Abstract: An improved structural dynamic model of an oscillating blade in two degrees of freedom is combined with an unsteady aerodynamic model for the transonic flow about a cascade with separation, which results in a coupled system. The system is solved in an iterative way between the two models. As a check on the current energy methods, the stall flutter boundaries for two real rotors are predicted by using the present method and the results are compared with the experiments and those predicted by using an energy method.
TL;DR: In this paper, the exact solutions of the inner-outer-layer-matched simplified Navier-Stokes equations (SNSE) and their exact solutions for the flow near a rotating disk and the flow in the vicinity of a stagnation point for both two-and three-dimensional flows are presented.
Abstract: The Simplified Navier-Stokes equations (SNSE) and their exact solutions for the flow near a rotating disk and the flow in the vicinity of a stagnation point for both two- and three-dimensional flows are presented in this paper The analysis shows that in the aforementioned cases the exact solutions of the inner-outer-layer-matched SNSE[4] are completely consistent with those of the complete Navier-Stokes equations (CNSE) and that the exact velocity solutions of D-SNSE[1,3] agree with those of CNSE, however, the exact pressure solutions of D-SNSE do not agree with those of CNSE The maximum relative pressure errors between the exact solutions of D-SNSE and CNSE can be as high as a hundred per cent
TL;DR: In this paper, an analytic solution for the diffraction of a planar strong detonation wave by a three-dimensional thin body moving in the opposite direction is obtained, where the body can be either supersonic or subsonic relative to the undisturbed stream ahead of the wave or behind the wave.
Abstract: An analytic solution is obtained for the diffraction of a planar strong detonation wave by a three-dimensional thin body moving in the opposite direction. The planform and the thickness distribution of the body can be arbitrary and the speed of the body can be either supersonic or subsonic relative to the undisturbed stream ahead of the wave or to that behind the wave. The solution is a generalization of the previous solution of Ting and Gunzburger for the shock diffraction.
TL;DR: In this article, a new approach which may be called the approximated-asymptotic solution has been developed and it is valid for both small and large values of μ.
Abstract: The series-approach and the asymptotic-approach are usually used to solve the complex variable equation of the toroidal shells under axial symmetric loads. As is known, the convergence of the series-solution is good only for small values of\(\mu = \sqrt {12(1 - v^2 )} a^2 /(r_0 h)\). On the other hand, the convergence of the asymptotic solution is good only for large values of μ. In this paper, based on an earlier work[1], a new approach which may be called the approximated-asymptotic solution has been developed and it is valid for both small and large values of μ. It is shown that the results of the approximated-asymptotic solution for toroidal shell with μ=0.5 coincide very well with those of the series-solution, while the results of the asymptotic solution for this value of μ are not as good, and the results of the approximated-asymptotic solution for μ=15 agree with those of the asymptotic solution.
TL;DR: In this paper, a matrix method for describing fully depolarized light is proposed, and it is proved theoretically that this column matrix (Jones vector) can be used to describe unpolarised light as well.
Abstract: A matrix method for describing fully depolarized light is proposed. According to the properties of fully depolarized light it is proved theoretically that this column matrix (Jones vector) can be used to describe unpolarized light as well. Thus, it enables the problems of holographic photoelasticity, including holographic photoelasticity of unpolarized light, to be simply treated by using a unified matrix calculus (Jones calculus).
TL;DR: In this article, the wake effect on drag factor in the axisymmetric Oseen flow of the finite clusters of equally spaced spheres with same size is studied. And the approximate solution of the O seen flow of finite cluster of spheres and the drag factor for each sphere are presented.
Abstract: In this paper, the wake effect on drag factor in the axisymmetric Oseen flow of the finite clusters of equally spaced spheres with same size is studied. Putting the Oseen lets on the centres of all the spheres, the series solution of the problem is obtained. By truncating the infinite series and applying the collocation method to solve a set of the linear algebraic equations, the approximate solution of the Oseen flow of finite clusters of spheres and the drag factor for each sphere are presented.
TL;DR: In this article, a system of two singular integral equations can be derived by using Fourier integral transformation and boundary conditions of crack problems, and possible crack growth behavior for cracks approaching and going through the interface is discussed.
Abstract: Crack problems for isotropic/orthotropic two-layered strips have been investigated. A system of two singular integral equations can be derived by using Fourier integral transformation and boundary conditions of crack problems. After stress singularities at crack tips or other special points are determined for internal and edge cracks, and for cracks terminating at and going through the interface, the system of singular integral equations is solved numerically by Gauss-Jacobi or Gauss-Chebyshev integration formulas for stress intensity factors at the tips and other singular points of cracks. Finally, possible crack growth behavior for cracks approaching and going through the interface is discussed.
TL;DR: In this article, the fundamental equations for two-phase flows are deduced from the Boltzmann's equation and the collision terms are treated with a method similar to what is used in the classical kinetic theory for handling the transport properties of dense gases.
Abstract: The fundamental equations for two-phase flows are deduced from the Boltzmann's equation. The collision terms are treated with a method similar to what is used in the classical kinetic theory for handling the transport properties of dense gases. It is shown that collision pressure and collision thermal flux exist in gas-particle flows in addition to the general partial pressure and partial thermal flux. Their physical natures are quite different from those of the general partial pressure and partial thermal flux. The applicability of the binary collision assumption and the molecular chaos assumption to gas-particle flows is also discussed. Finally, the equations for two-phase flows obtained by the method of the kinetic theory are compared with those obtained by average continuum models and by the model of particle clouds. The results from the kinetic theory show clearly the physical significance of various parameters and clarify some confusing concepts.
TL;DR: In this paper, the relation between subharmonic bifurcations and horseshoe has been investigated, and it is shown that for centrally symmetric systems, under small disturbance, if it has two independent sequences of sub-harmonic partitions, the system passes to chaos (horeseshoe).
Abstract: In this paper, finite subharmonic bifurcations have been discussed by means of some examples. It is found that for centrally symmetric system, under small disturbance, if it has two independant sequences of subharmonic bifurcations, the system passes to chaos (horeseshoe) through finite subharmonic bifurcations, and that for noncentrally symmetric system, the relation between subharmonic bifurcations and horseshoe is complicated.
TL;DR: In this article, the authors examined the effects of variation in viscosity and normal stress differences on the total resistance and total normal force of a slider bearing and found that under certain conditions the normal stress difference may be neglected compared with the variation of visco-composition.
Abstract: By considering the now in a slider bearing to be a nearly viscometric flow we have examined the effects of variation in viscosity, and normal stress differences on the total resistance and total normal force. We have found that under certain conditions the normal stress differences may be neglected compared with the variation in viscosity. We have found that the effects of variation in viscosity are to reduce the total resistance, and to increase or decrease the total normal force depending on the ratio of the thickness of the liquid at the entry and exit.
TL;DR: In this paper, a new scheme for solving the compressible Navier-Stokes equations is developed, which has second order accuracy in time and in space and is used to solve two-dimensional problem.
Abstract: A new scheme for solving the compressible Navier-Stokes equations is developed. For the inviscid portion of the equations the single step scheme used by the authors is factored according to the sign of the eigenvalues of Jacobian matrix. For the viscous portion of the equations a scheme corrected with operator addition is factored too. The scheme obtained has second order accuracy in time and in space and is used to solve two-dimensional problem. The numerical results of 2-D shock wave-boundary layer interaction are compared with experimental data.
Journal Article•
TL;DR: The obtained result proved the Bossert and Schwartz's conjecture about the water reabsorption in DLH and gave nonisotonic re absorption of water, steady state distribution of sodium ion and area in the DLH.
Abstract: Assuming that the wall of the renal descending limb of Henle(DLH) is made up of semi-permeable membrane, according to the physiological character we propose a quasi-enesolute mathematical model and give nonisotonic reabsorption of water, steady state distribution of sodium ion and area in the DLH.The obtained result proved the Bossert and Schwartz's conjecture about the water reabsorption in DLH. It mainly fits in with the experimental results.
TL;DR: In this article, the influence of temperature on velocity signal in hot-wire measurement of turbulence is analyzed and the method to correct the temperature influence on measuring ρ θu and the procedure to decide experimentally temperature influence coefficient have been given.
Abstract: In this paper the influence of temperature on velocity signal in hot-wire measurement of turbulence is analysed. It is pointed out that when the temperature influence is small, the temperature influence on measured intensity of velocity fluctuations is second order small and negligible. However, the temperature influence on measuring longitudinal heat flux is of first order quantity, and must be corrected, or large error will occur. The method to correct the temperature influence on measuring ρ θu and the procedure to decide experimentally temperature influence coefficient have been given.