Showing papers by "Dalian University of Technology published in 1992"
TL;DR: In this paper, the relation between topology optimization and size optimization of truss structures is studied and the feasibility of adding a new bar to the truss or deleting an existing one is better understood.
Abstract: The paper studies the relation between topology optimization and size optimization of truss structures. The goal of the optimization is to minimize the structural weight under stress constraints and side constraints on member cross sectional areas. The limiting stress concept is defined and the computational formula of limiting stress for truss structures calculated by a finite element method is given. Based on the limiting stress concept the continuity of the stress function at zero cross sectional area is carefully examined which enables us to understand the dilemma of defining the stress function in the closed interval up to zero cross sectional area. By considering the relation between the limiting stress and allowable stress the feasibility of stress constraints is discussed and the difficulty of adding a new bar to the truss or deleting an existing one is better understood. We have also shown that for topology optimization of truss structures the feasible design domain in the design space i...
249 citations
TL;DR: In this paper, a CQC algorithm with high efficiency and simple procedure was proposed to produce a power spectral density matrix of structural responses under the action of stationary random ground motion.
117 citations
TL;DR: A very efficient method is presented, referred to as the aggregate method, for solving nonlinear minimax optimization problems, which converts a minimax problem to an unconstrained minimization on a differentiable aggregate function by means of Lagrangean duality and the Jaynes' maximum entropy principle.
Abstract: This paper presents a very efficient method, referred to as the aggregate method, for solving nonlinear minimax optimization problems, which converts a minimax problem to an unconstrained minimization on a differentiable aggregate function. We derive this function by means of Lagrangean duality and the Jaynes' maximum entropy principle. It can be shown that as a parameter in the function tends to infinity, it approaches the maximum function that denotes a uniform approximation to the problem functions and is non-differentiable. Main features of the present method consist of its algorithmic simplicity and computational high efficiency.
97 citations
TL;DR: In this article, a two-dimensional decagonal quasicrystal (DQC) has been found in binary Al-Co alloys in the composition range Al11Co4 to Al10Co4 after slow solidification from the melt.
Abstract: A two-dimensional decagonal quasicrystal (DQC) has been found in binary Al-Co alloys in the composition range Al11Co4 to Al10Co4 after slow solidification from the melt. The crystalline phase found most frequently coexisting with this DQC is two new structure variants, oneC-centered and the other primitive, of the monoclinic layer compound Al13Co4. Theira andc parameters are roughly τ2 times (τ = (1 + √5)/2 = 1.6180…) larger than the corresponding ones in Al13Co4. Moreover, a new orthorhombic phase Al3Co or Al11Co4 (Pnmn, a = 1.25 nm,b = 0.81 nm, andc = 1.46 nm) has also been found. As shown by the characteristic electron diffraction patterns (EDPs), these crystalline phases can be considered as approximate structures of the DQC. The lattice relationship between these phases has been discussed.
80 citations
TL;DR: In this article, a numerical model to simulate the behavior of porous media interacting with the flow of multiphase immiscible porous fluids is presented, and the governing equations are derived in the light of the generalized Biot theory and a general formulation for effective stress is established.
79 citations
01 Jan 1992
TL;DR: In this article, the authors presented an algorithm which combines the linear prograining with the dynamic programing to solve the problem of fleet planning, which has not only the merits that the linear model for fleet planning has, but also the merit of saving computing time.
Abstract: By analyzing the merits and shortcomings of the linear model for fleet planning, the paper presents an algorithm which combines the linear prograining with the dynamic programing to solve the problem of fleet planning. This approach has not only the merits that the linear model for fleet planning has, but also the merit of saving computing time. And the number of any kind of ships newly added into the fleet in every year are always integers in the last optimal results. This feature of the results directly meets the demand of practical application.The mathematic model of the dynamic fleet planning and its algorithm are both put forward in the paper. A calculating example is also given in the paper.
63 citations
TL;DR: In this article, three mutually related structural variants of Al4Cr, in ad-dition to the well-known monoclinic Ф-Al45Cr7, were found.
Abstract: In a transmission electron microscopic study of rapidly as well as slowly solidified alloys in the composition range Al7Cr-Al4Cr, three mutually related structural variants of Al4Cr, in ad- dition to the well-known monoclinic Ф-Al45Cr7, were found The hexagonal μ-Al4Cr is iso- structural with μ-Al4Mn (P63/mmc), with aμ = 200 nm and cμ = 247 nm The two orthorhombic e- and e′-Al4Cr phases, one being B-centered and the other primitive, havea ≈ √3aμ = 346 nm,b ≈ aμ = 200 nm, andc ≈ cμ/2 = 124 nm These three Al4Cr phases are not only themselves structurally connected, but are also closely related both to the Al-Cr icosahedral quasicrystal found earlier and to the Al-Cr decagonal quasicrystal found for the first time in the present investigation in rapidly solidified Al-Cr alloys with 18 to 22 at pct Cr
58 citations
TL;DR: In this article, a mixed quadrilateral plane element with drilling degrees of freedom using Allman's interpolation scheme is developed and the assumed stress space includes three constant stress modes and four quasi-linear stress modes which are equilibrating for regular element geometry.
52 citations
TL;DR: A new hybrid variational principle with independent variables of strain, stress and displacement and with a weaker constraint condition of interelement continuity is proposed, which is a rational approach for deriving high-performance three-dimensional hybrid isoparametric elements even up to the higher-order 20-node element.
Abstract: In this paper a new hybrid variational principle with independent variables of strain, stress and displacement and with a weaker constraint condition of interelement continuity is proposed. Based on this functional, a general formulation of a refined hybrid isoparametric element method has been established by the orthogonal approach.
The present formulation is a rational approach to be adopted for deriving high-performance three-dimensional hybrid isoparametric elements even up to the higher-order 20-node element.
Several numerical examples are presented to show that the present elements RGH8(8-node) and RGH20(20-node) have high accuracy, excellent computational efficiency and less sensitivity to mesh distortion.
50 citations
TL;DR: In this article, the problem of finding the set of Re-positive definite matrices A such that AX = B was studied. But the complexity of the matrix inverse problem was not considered.
47 citations
TL;DR: Based on the analogy between structural mechanics and optimal control theory, the eigensolutions of a symplectic matrix, the adjoint symplectic ortho-normalization relation and the eigenvector expansion method are introduced into the wave propagation theory for sub-structural chain-type structures, such as space structures, composite material and turbine blades.
Abstract: Based on the analogy between structural mechanics and optimal control theory, the eigensolutions of a symplectic matrix, the adjoint symplectic ortho-normalization relation and the eigenvector expansion method are introduced into the wave propagation theory for sub-structural chain-type structures, such as space structures, composite material and turbine blades. The positive and reverse algebraic Riccati equations are derived, for which the solution matrices are closely related to the power flow along the sub-structural chain. The power flow orthogonality relation for various eigenvectors is proved, and the energy conservation result is also proved for wave scattering problems.
TL;DR: In this article, the assumed spaces of all primary variables are invariant to orthogonal transformations, and any derived models would automatically be invariant, and it is shown that it is not necessary to employ either complete or balanced polynomial expansions of natural co-ordinates in order to preserve the element invariance.
Abstract: In this paper the issue of invariance for various hybrid/mixed models with and without incompatible displacement modes is addressed. Special emphasis is directed to assumed spaces of the primary variables which are based on the natural co-ordinates. It is found that if the assumed spaces of all primary variables are invariant to orthogonal transformations, any derived models would automatically be invariant. In contrast to the traditional concept of choosing the starting stress/strain interpolants based on either global or local co-ordinate systems, it is shown that it is not necessary to employ either complete or balanced polynomial expansions of natural co-ordinates in order to preserve the element invariance. Based on one of the newly proposed classes of stress/strain interpolants, 8–node invariant-assumed stress brick elements are proposed which are close to Loikkanen and Irons' assumed stress counterpart of Wilson's Q6 brick element.
TL;DR: In this paper, a refined hybrid method based on a new variational formulation and orthogonal approach is developed for plane isoparametric elements, which is more rational than generalized hybrid methods and hybrid stress method for improving the computational efficiency.
TL;DR: In this article, a generalized variational principle with two kinds of variables is derived from the minimum potential energy variational principles of the substructural chain, and the canonical transformation matrices for the eigenproblems of the sub-structural chain and LQ control are constructed respectively.
Abstract: The theory of optimal control and the theory of a substructural chain in static structural analysis are mutually simulated issues. From the minimum potential energy variational principle of the substructural chain, the generalized variational principle with two kinds of variables is derived first. By comparing that generalized variational principle with the variational principle in LQ control theory, the simulation relation is established. Based on that relation, the potential energy and mixed energy formulation of the algebraic Riccati equations are derived, then iterative algorithms are proposed which give the upper and lower bounds to the solution matrix. By using the solutions of the positive and negative co-ordinate algebraic Riccati equations, the canonical transformation matrices for the eigenproblems of the substructural chain and LQ control are constructed respectively, which reduce the eigenproblem to half-size. The properties of the solutions are analysed, which establishes the basis for expansion solutions.
TL;DR: In this article, it has been shown by electronic spectra that hydrazone-azo anion equilibria of arylazopyridones exist in various solvents.
TL;DR: In this paper, a microwave irradiation was used to accelerate the rate of the synthesis of p-nitrochlorobenzene, and the enhancement of reaction rate was 144-240fold.
TL;DR: In this paper, a general model for the optimal planning of a cable-stretching process has been formulated and used to obtain solutions for the optimality of the cable stretching process associated with various design and construction considerations.
Abstract: A general model for the optimal planning of a cable-stretching process has been formulated and used to obtain solutions for the optimal planning of the cable-stretching process associated with various design and construction considerations. A structural analysis approach considering the variation of the structural system during cable-stretching has been presented by using the concept of an influence pattern. In the case of segmental cantilever construction, calculation of the initial stress and displacement prior to stretching the stay cables has been investigated. Computational efficiency in solving the optimal planning problem has also been studied.
TL;DR: In this article, a simple and accurate non-layered plastic element which is capable of capturing the development of plastic curvatures across the thickness of the plates is presented and the influence of transverse shear forces on the plastic behaviour of plates is also investigated.
Abstract: A simple and accurate non-layered plastic element which is capable of capturing the development of plastic curvatures across the thickness of the plates is presented in this paper. The influence of transverse shear forces on the plastic behaviour of plates is also investigated here. This non-layered plastic element is based on: (i) the four-node quadrilateral strain element for shear flexible elastic plates given by the authors; (ii) the plastic hinge formulation outlined by Shi and Atluri; and (iii) the modified Ilyushin's yield function which can account for both the development of plastic deformations across the thickness of plates and the effect of transverse shear forces. The numerical examples given here demonstrate that the present non-layered plastic element can achieve the results obtained by the layered element model and the transverse shear forces considerably affect the plastic behaviour of plates under certain load conditions.
TL;DR: In this paper, the behavior of a nonlinear flexible connection is modeled by the Ramberg-Osgood function, and a simple computational model is presented to simulate the sliding at a structural joint.
Abstract: The slipping at a structural joint is represented by the modified Coulomb joint model. The behavior of a nonlinear flexible connection is modeled by the Ramberg-Osgood function. A simple computational model is presented
TL;DR: In this paper, the microhardness and the scratch critical load (Lc) of zirconium nitride coatings with different nitrogen partial pressures have been studied by means of the scratch test, and the adhesion and toughness of the coatings as well as the scratch failure have also been studied.
TL;DR: In this paper, an effective mathematical method to deal with the viscoplastic lubrication model is presented by applying the parametric variational principle (Zhong, 1985), where the plastic slippage of lubricant would occur at the lubricated surfaces under isothermal lubrication.
Abstract: An effective mathematical method to deal with the viscoplastic lubrication model is presented here by applying the parametric variational principle (Zhong, 1985). The plastic slippage of lubricant would occur at the lubricated surfaces under isothermal lubrication. The boundary tangential velocity, therefore, can be taken as the parametric vector (or the control vector) in variational process. The mathematical model of the original problem is finally reduced to a complementarity problem. The algorithm presented in this paper is simple and reliable and shows promise in engineering application.
TL;DR: In this article, the main operations of the algorithm are performed within elements, without assembling and solving the global system equations, which has advantages such as simple formulation, easy programming, small storage space and calculation.
Abstract: A parallel method for structural optimization is described. The main operations of the algorithm are performed within elements, without assembling and solving the global system equations. The method has advantages such as simple formulation, easy programming, small storage space and calculation. Numerical results are presented to demonstrate the accuracy and effectiveness of this method.
TL;DR: In this article, three types of boron-containing ZSM-5 catalysts were prepared, and the pethyltoluene content in the product over the WBZ catalyst was 93%, while the conversion rate was about 18%.
TL;DR: In this paper, a mixed finite element method (MFEM) aiming at solving the problem of three-dimensional analysis of multi-layer composite laminates with a high accuracy is presented.
TL;DR: In this article, the simulation of discrete-time linear quadratic (LQ) control with the substructural chain problem in static structural analysis is given, and the generalized variational principle with two kinds of variables and the dual equations are derived.
Abstract: The theory of optimal control and the semianalytical method of elliptic partial differential equation (PDE) in a prismatic domain are mutually simulated issues. The simulation of discrete-time linear quadratic (LQ) control with the substructural chain problem in static structural analysis is given first. From the minimum potential energy variational principle of substructural chain, the generalized variational principle with two kinds of variables and the dual equations are derived. The simulation relation is then recognized by comparing the variational principle and dual equations of the LQ control theory. The simulation between elliptic PDE in the prismatic domain and continuous-time LQ control is established in the same way, and the interval energy is naturally introduced, as in the case of substructural chain. The assembling and condensation equations can help one to derive the differential equations of the submatrices of potential energy and mixed energy. The well known Riccati equation is one of them. The interval assembling and condensation algorithm can be used to solve the Riccati equation. Some numerical examples are given to illustrate the method.
TL;DR: The phenomenon of separating eutectic silicon in Al-Si alloy unidirectionally solidified with electromagnetic stirring was investigated in this paper, where it was found that the eutectoric silicon could be swept away from the solid/liquid interface by the flow, and transferred by the secondary flow to the wall of the crucible, forming a silicon-rich layer on the periphery of the ingot.
Abstract: The phenomenon of a “separated eutectic” in Al-Si eutectic alloy unidirectionally solidified with electromagnetic stirring was investigated. It was found that the eutectic silicon could be swept away from the solid/liquid (s/l) interface by the flow, and transferred by the secondary flow to the wall of the crucible, forming a silicon-rich layer on the periphery of the ingot.
TL;DR: In this paper, the electrochemical reduction of four azo dyes in acid media was studied by differential-pulse polarography, cyclic voltammetry and constant-potential coulometric methods.
TL;DR: Based on the Hu-Washizu variational principle and the concept of degenerated solid shell elements, a quasi-conforming or hybrid/mixed nine-node degenerated shell finite element csh9 has been developed as mentioned in this paper.