GENERAL SITUATION OF THE PARTICIPATION OF EDITORIAL BOARD MEMBERS OF APPLIED MATHEMATICS AND MECHANICS IN THE 16th.INTERNATIONAL CONGRESS OF THEORETICAL AND APPLIED MECHANICS

The 16th.International Congress of Theoretical and Applied Mechanics(ICTAM),which isheld every four years under the auspices of International Union of Theoretical and AppliedMechanics(IUTAM),was held on Aug.19,1984 Aug.25,1984 in Lyngby Industrial University.Copenhagen.Denmark.35 representatives of the People’s Republic of China participated in this     

THE PROBLEM OF INEQUALITY IN SOLID MECHANICS

In this paper the of inequality in solid mechanics,the contents of which consistof some main concepts,methods and results of the stationary and evolutionary aswell as determinate and random problems in variational principle and variational ine-quality studied in detail.     

THE EQUATIONS OF MOTION OF A SYSTEM UNDER THE ACTION OF THE IMPULSIVE CONSTRAINTS

In order to solve the problem of motion for the system withn degrees offreedom under the action of p impulsive constraints, we must solve the simultaneous equations consisting of n+p equations. In this paper, it has been shown that the undetermined multipliers in the equations of impact can be cancelled for the cases of both the generalized coordinates and the quasi-coordinates. Thus there are only n-p equations of impact. Combining these equations with p impulsive constraint equations, we have simultaneous equations consisting of n equations. Therefore, only n equations are necessary to solve the problem of impact for the system subjected to impulsive constraints. The method proposed in this paper is simpler than ordinary methods.     

THE THEOREM OF THE STABILITY OF LINEAR NONAUTONOMOUS SYSTEMS UNDER THE FREQUENTLY-ACTING PERTURBATION

In the paper a theorem on the stability of linear nonautonomous system under thefrequently-acting perturbation has been given and proved on the basis of Malkin＇sTheorem.     

THE CORRECTION OF "ON THE MOTTON OF FLYING PLATE UNDER EXPLOSIVE ATTACK

Chu Chao-hsiang and Jiang Da-he,On the Motion of Flying Plate under Ex-plosive Attack,Applied Mathematics and Mechanics,Vol.1,No.3 (1980).PP.293-304.1.Eq.(2.2)should be as follows:     

THE EQUATIONS OF MOTION FOR A NONHOLONOMIC SYSTEM UNDER THE ACTION OF IMPULSIVE FORCES

The equations of impact for a nonholonomic system described with generalizedcoordinated have been discussed in detail in the general references of classical dynamics.But these equations contain undetermined multipliers which made the problem complicatedThrough the appropiate treatment of mathematics,using the δ-function andexpression of matrix in this paper,the author derived equations of impact for anonholonomic system without undetermined multipliers.Therefore.the problem can besolved more simply.     

ON THE REPRESENTATION OF FINITE ROTATION IN NONLINEAR FIELD THEORY OF CONTINUUM MECHANICS

One of the important basic theoretical problems in the development of continuummechanics is the separation of finite strain and finite rotation at a point in the displacementfield.Now it is certain that S-R decomposition theorem provides a rational theoreticalsolution for this problem.The purpose of this paper is to clarify some misleading basicconcepts of finite rotation of deformed body in current literature,and to promote furtherprogress.     

APPLICABILITY OF THE CRACK FACE ELECTRICAL BOUNDARY CONDITIONS IN PIEZOELECTRIC MECHANICS

The electrical boundary conditions on the crack faces and their applicability in piezoelectric materials are discussed. A slit crack and a notch of ?nite thickness in piezoelectric materials subjected to combined mechanical and electrical loads is consi…     

THE THEOREM OF THE STABILITY OF NONLINEAR NONAUTONOMOUS SYSTEMS UNDER THE FREQUENTLY-ACTING PERTURBATION—LIAPUNOV’S INDIRECT METHOD

In this paper the stability of nonlinear nonautonomous systems under the frequently-acting perturbation is studied.This study is a forward development of the study of thestability in the Liapunov sense;furthermore,it is of significance in practice sinceperturbations are often not single in the time domain.Malk in proved a general theoremabout thesubject.To apply the theorem,however,the user has to construct a Liapunovfunction which satisfies specified conditions and it is difficult to find such a function fornonlinear nonautonomous systems.In the light of the principle of Liapunov’s indirectmethod,which is an effective method to decide the stability of nonlinear systems in theLiapunov sense,the authors have achieved several important conclusions expressed in theform of theorems to determine the stability of nonlinear nonautonomous systems under thefrequently-acting perturbation.     

THE THEOREM OF THE STABILITY OF NONLINEAR NONAUTONOMOUS SYSTEMS UNDER THE FREQUENTLY-ACTING PERTURBATION—LIAPUNOV’S INDIRECT METHOD

In this paper the stability of nonlinear nonautonomous systems under the frequently-acting perturbation is studied. This study is a forward development of the study of the stability in the Liapunov sense; furthermore, it is of significance in practice since perturbations are often not single in the time domain. Malkin proved a general theorem about thesubject. To apply the theorem, however, the user has to construct a Liapunov function which satisfies specified conditions and it is difficult to find such a function for nonlinear nonautonomous systems. In the light of the principle of Liapunov’s indirect method, which is an effective method to decide the stability of nonlinear systems in the Liapunov sense, the authors have achieved several important conclusions expressed in the form of theorems to determine the stability of nonlinear nonautonomous systems under the frequently-acting perturbation.     

THE DYNAMIC COMPUTATION OF CLOSED CYLINDRICAL SHELL UNDER IMPACT LOAD

This article discusses the dynamic computation of the closed cylindrical shell underimpact load.In the text we analyse the changes of the momenta and the energy on eachstage in the impact process,take into account the effect of the mass of impact object and thesystem of the closed cylindrical shell by impact,and transform the distributed mass of thewhole cylindrical shell into an only concentrated“equivalent mass”by the method ofreduced mass.Consequently we derive the dynamic factor of the closed cylindrical shell dueto impact load.The method proposed in this paper is of practical worth and is more convenient incalculations.     

A PERTURBATION-VARIATIONAL SOLUTION OF THE LARGE DEFLECTION OF RECTANGULAR PLATES UNDER UNIFORM LOAD

In this paper,von Kármàn’s set of nonlinear equation for large deflection ofrectangular plates is at first converted into several sets of linear equations by taking centraldimensionless deflection as perturbation parameter,and then,the sets of linear equationsfor plates with various ratios of length to width are solved with application of variationalmethod.The analytical expressions for displacements and stresses as well as formulas fornumerical calculation are worked out.The figures of maximum deflection-load andmaximum stress with ratio λ of length to width as a parameter are given in this paper.Through comparison,it is found that the results of this paper are quite in accord withexperiments.     

THE SYMMETRICAL DEFORMATION OF CIRCULAR MEMBRANE UNDER THE ACTION OF UNIFORMLY DISTRIBUTED LOADS IN ITS CENTRAL PORTION

This paper presents the solution of symmetricaldeformation of circular membrane under the action ofuniformly distributed loads in its central portion.Its limiting case is the solution of circular mem-brane under concentrated load at the center.Thissolution is the third solution of the circular mem-brane problems after the well-known Hencky’s solution     

FURTHER RESEARCH ON THE BENDING OF THE CANTILEVER RECTANGULAR PLATES UNDER A CONCENTRATED LOAD

In this paper we apply the reciprocal theorem to further research on the bendingproblem of the cantilever rectangular plate under a concentrated load acting atany of its points.This method is even simpler and more general.     

TEACHING SYSTEM AND TEXTBOOKS OF ELEMENTARY MECHANICS (III)——FOREIGN TEACHING RESOURSES OF MECHANICS OF MATERIALS AND THE TEACHING SYSTEM ANALYSIS 1)

本文对力学基础教材,着重对《理论力学》与《材料力学》教材与教学体系等方面进行了分析研究。从国内力学课程与教材建设历史概况,国内力学课程教材建设的成绩与问题,国内力学教材使用情况,引进的国外基础力学原版教材情况,国外理论力学教材体系分析,国外材料力学教材体系分析,国外力学相关课程网络资源调研与分析,及教学技术应用与质量评价等多方面进行了阐述。最后,通过对国外教材的研究,因其所具有的综多特点与特色,为国内力学基础课程教材和课程改革提供了思路和方向。 本文为之三,主要阐述国外材料力学教材及其教学体系的比较分析及结尾。     

THE INITIAL POSTBUCKLING BEHAVIOR OF RING STIFFENED SHELLS UNDER HYDROSTATIC PRESSURE

In this article the initial postbuckling behavior of ring stiffened cylindrical shells under hydrostatic pressure is analyzed by Koiter's theory. The nonlinear bending e(?)ations consistent with boundary conditions have been used in prebuckling state. The eigemvalue problem is solved by Galerkin's method. The obtained buckling loads are compared with the results which are based on classical stability theory. As calculating examples, three typ(?)al outside-stiffened cylinders with different ring stiffener parameters are chosen. The results show that the strength of stiffener not only ilfluences buckling load obviously, but also chattges the bnperfection-sensilivity of cylindrical shells.     

ANALYSIS OF THE LOCALIZATION OF DAMAGE AND THE COMPLETE STRESS-STRAIN RELATION FOR MESOSCOPIC HETEROGENEOUS ROCK UNDER UNIAXIAL TENSILE LOADING

The mechanical behavior of rock under uniaxial tensile loading is different from that of rock under compressive loads. A micromechanics-based model was proposed for mesoscopic heterogeneous brittle rock undergoing irreversible changes of their microscopic structures due to microcrack growth. The complete stress-strain relation including linear elasticity, nonlinear hardening, rapid stress drop and strain softening was obtained. The influence of all microcracks with different sizes and orientations were introduced into the constitutive relation by using the probability density function describing the distribution of orientations and the probability density function describing the distribution of sizes. The influence of Weibull distribution describing the distribution of orientations and Rayleigh function describing the distribution of sizes on the constitutive relation were researched. Theoretical predictions have shown to be consistent with the experimental results.     

EFFECT OF TEMPERATURE ON THE FRACTURE MODES OF BHW-35 STEEL UNDER MODE-Ⅱ LOADING

Finite element method(FEM)has been used to analyze the stress and strain fields andthe stress tri-axial levels around the tip of the crack under mode-Ⅱ loading.The results show that:under mode-Ⅱ loading,the direction of the maximum tensile stress and that of the maximum tri-axiallevels(R_ )exist at an angle of-75.3°from the original crack plane:the maximum shear stress andR_ =0 exist along the original crack plane.Mode-Ⅱ loading experiment using BHW-35 steel at different temperatures show that there aretwo kinds of fracture mode.opening mode(or tensile mode)and sliding mode(or shear mode).A de-crease in temperature causes the fracture mode to change from shear mode to tensile mode.For BHW-35 steel,this critical temperature is about-90C.Actually.under any kind of loading mode(modeⅠ,mode Ⅱ,mode Ⅲ or mixed mode),there always exist several kinds of potenital fracture modes(for example,opening mode.sliding mode.tearing mode or mixed mode).The effect of temperatureunder mode-Ⅱ loading is actually related to the change of the elastic-plastic properties of the material.     

LARGE DEFLECTION PROBLEM OF CIRCULAR PLATES WITH VARIABLE THICKNESS UNDER THE ACTION OF COMBINED LOADS

By using the modified iteration method of large deflection theory of plates withvariable thickness,we solve the problem of circular plates with variable thicknesssubjected to combined loads under the boundary conditions of the clamped edges and getcomparatively more accurate second-order approximate analytical solution.If the resultsof this paper are degraded into the special cases,the results coinciding with those of papers[1,2]can be obtained.In this paper,the characteristic curves are plotted and somecomparisons are made.The results of this paper are satisfactory.