力学学报

NONLINEAR STABILITY OF STRUCTURES UNDER MULTIPLE LOADING SYSTEMS

1991, 23(2) doi: 10.6052/0459-1879-1991-2-1995-828

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NUMERICAL SIMULATION OF FLOW SEPARATION AROUND SPHERE-CONE AT ANGLE OF ATTACK

The numerical algorithm developed by authors for solving the Navier-Stokes equations is used to solve viscous hypersonic flow around sphere-cone at angle of attack. For solving the difference equations approximate factorization with special Jacobian matrix splitting is used. Analysis of stability for difference schemes shows that unconditionally stable schemes after approximate factorization may become conditionally stable or even unstable, but with proper coefficient splitting the scheme obtained after app...

1991, 23(2): 129-138. doi: 10.6052/0459-1879-1991-2-1995-819

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STUDY ON THE SHEAR STRESS AND NORMAL STRESS DIFFERENCE OF FOAMS

A theoretical stress tensor model that includes surface tension forces and viscous forces is developed by considering the three-dimensional spatially periodic cells of dodecahedron. Meanwhile, the shear stress and normal stress difference under various shear rates are calculated by computer.The rheological properties of foam have been measured by RMS-605 Rheameter, Rotary Viscositymeter-2 (Rv-2) and Capillary Rheometer. The theoretical results are close to the experimental data when the effect of slip at vi...

1991, 23(2): 139-148. doi: 10.6052/0459-1879-1991-2-1995-820

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NUMERICAL SIMULATION OF MARANGONI CONVECTION IN THE FLOATING ZONE UNDER MICROGRAVITY BY FEM

, Jiachun Li

The convection of melt in a floating zone driven by surface tension due to temperature gradient is studied in this paper. Axisymmetric steady momentum and energy equations along with kinetic and dynamic boundary conditions are numerically solved by FEM. The effects of free surface of the liquid bridge have been firstly taken into account. We finally yield the solutions for the configuration, flow field, temperature distribution and pressure on the interface. It is shown that the dynamic crescent-shaped liqu...

1991, 23(2): 149-156. doi: 10.6052/0459-1879-1991-2-1995-821

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MATHEMATICAL MODELLING OF 3-DIMENSIONAL TURBULENT FLOW BY VORTICITY-VECTOR POTENTIAL METHOD

The vorticity-vector potential method and k-ε two-equation turbulence model are applied for numerical simulation of the 3-dimensional isothermal flowfield in a flat jet combustor. A new equation to calculate the values of vorticity components on solid surfaces is introduced. Conditions which should be satisfied in order to define boundary conditions of vector potential are discussed. The computed results agree with the experimental measurements on the whole. It is shown that the vorticity-vector potential m...

1991, 23(2): 157-164. doi: 10.6052/0459-1879-1991-2-1995-822

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GALIN'S THEOREM HOLDS FOR MOVING PUNCH

This paper presents a formulation for solving three-dimensional moving punch problem. It proves that Galin's theorem holds for the punch. As an example, the study offers some results (including numerical data) of dynamic displacement over an ellipse contact region.

1991, 23(2): 165-171. doi: 10.6052/0459-1879-1991-2-1995-823

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AN ANALYSIS OF ELASTIC CONTACT PROBLEMS FOR SYMMECTRICAL BEAMS SUBJECTED TO BENDING AND TORSION

In this paper an analysis of contact problems about two overlapping symmetrical elastic beams which are subjected to bending and torsion by the action of arbitrary loads is presented. The two beams have different cross sections, stiffnesses, lengths and supported conditions. The laws of the pressure distribution on one-sided and two-sided line contact are developed and the theorems of point contact are proved. An example of statically indeterminate beams is given. The numerical calculation shows that the on...

1991, 23(2): 172-180. doi: 10.6052/0459-1879-1991-2-1995-824

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THE VOIDING DAMAGE INDUCED IN MATERIAL EMBEDDING FLAWS

Study is emphasized on the evolution of microstructural damage induced in material, which initially embeds flaws. Tiny voids surrounding the flaws can be generated and grow large as the external stressing increases. Under certain circumstances, the internal damage caused by such mechanism has drastic difference from that accumulated by pure voiding of large and small sizes. Results indicate that it is not appropriate to use crack length for characterizing the damaging effect of short flaws in microstructura...

1991, 23(2): 181-189. doi: 10.6052/0459-1879-1991-2-1995-825

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VARIATIONAL PRINCIPLES OF PERFORATED THIN PLATES AND THE FINITE ELEMENT METHOD FOR BUCKLING AND POST-BUCKLING ANALYSIS

On the basis of the general theory of perforated thin plates with large deflections, the variational principles in terms of deflection w and stress function F are established. And from these principles the finite element method analysing the buckling and post-buckling of perforated thin plates is established. It can be seen that the porperty of element is more complex due to the multiple connectedness of the region.

1991, 23(2): 190-200. doi: 10.6052/0459-1879-1991-2-1995-826

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一种描述形状记忆合金拟弹性变形行为的本构关系

A constitutive relation to describe the pseudo-elastic deformation in shape memory alloys is presented in this paper. It is able to describe the deformation of polycry-stalline materials under triaxial stress state as well as of monocrystalline materials under one-dimensional condition. The total strain rate is supposed to be composed of elastic strain rate and transformation strain rate. The deformation behaviour of Cu-Zn-Sn alloy and Ti-Ni alloy is simulated by use of the proposed constitutive relation. T...

1991, 23(2): 201-210. doi: 10.6052/0459-1879-1991-2-1995-827

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THE SIMPLIFIED DYNAMIC SYSTEM ANALYSIS OF THE PENDULUM IMPACT TENSILE TEST APPARATUS OF BLOCK-BAR

The pendulum impact tensile test apparatus of blockbar was studied as a dynamic system. A simplified mechanical model of the dynamic system consisting of the pendulum, the block, the specimen and the output bar was proposed. Using the finite-difference method and characteristic method, the numerical computation results were derived, and were compared with test results. The numerical and test results show the dynamic system analysis and computation program are valid and reliable, and the test apparatus is co...

1991, 23(2): 217-224. doi: 10.6052/0459-1879-1991-2-1995-829

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MEASUREMENTS OF TURBULENT ORIFICE FLOW USING AN ON-AXIS 2-D LDV SYSTEM

An on-axis 2-D LDV system for measuring two velocity components in the plane formed by three incident beams was presented. The measuring errors in on-axis direction were discussed and a method for correcting the angular deviation was suggested. Detailed measurements were made in a pipe flow for single and double orifice cases by using: this system. Mean velocity, turbulent intensity and Reynolds shear stress distributions in axial and radial directions were measured at the Reynolds number of 1.4×105.Compari...

1991, 23(2): 225-231. doi: 10.6052/0459-1879-1991-2-1995-830

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SUMMARY OF RESULTS ON THEORY OF CREEP AND CREEP RUPTURE OF METALS

The authors developed a systematic experimental and theoretical study on the behaviour of creep and creep rupture of metals under uniaxial and complex stress state, as well as on durability of constructional elements during creep.In experimental studies the authors considered the behaviour of various metals under constant and variable stresses, stress concentration, influence of way of loading on creep rupture; the authors also suggested new measuring methods of structure damage of material.

1991, 23(2): 232-235. doi: 10.6052/0459-1879-1991-2-1995-831

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REGION-WISE VARIATIONAL PRINCIPLES AND GENERALIZED VARIATIONAL PRINCIPLES ON COUPLED THERMAL-ELASTICITY

Based on previous work [1] and [2] , region-wise variational principles and generalized variational principles on coupled thermal-elasticity have been established and proved in this paper.

1991, 23(2): 236-243. doi: 10.6052/0459-1879-1991-2-1995-832

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ON THE NECESSITY OF THE CONSTITUTIVE EQUATIONS FOR THE PLASTIC SPIN

In the theory of finite elasto-plasticity, the constitutive relation is usually in the form of rate type. Hence the decomposition of strain rate based on the concept of intermediate configuration has become very popular, and among others, works developed by E. H. Lee et al. and Y. F. Dafalias et al. may be considered to be the most influential. Nevertheless, it is shown in this paper that, at least for some special cases, certain relation that the substruc-tural spin should satisfy can be derived. Thus, it ...

1991, 23(2): 244-247. doi: 10.6052/0459-1879-1991-2-1995-833

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ON HYPERELASTIC CONDITION OF RATE-FORM ELASTICPLASTIC CONSTITUTIVE LAW AT FINITE DEFORMATION

It is proved that if the objective stress rate is taken as the Oldroyd rate of the Kirchhoff stress tensor, the integrability condition of the rate-form elastic constitutive law is λ=0, provided that the Lame parameters λ and μ are. constants. This fact renders the rate-form elastic-plastic constitutive law incompatible with the hyperelastic framework in the regime of finite deformation. Several particular situations in which the rate-form elastic con-stitutive laws can be approximately applied to the case ...

1991, 23(2): 248-251. doi: 10.6052/0459-1879-1991-2-1995-834

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BASIC METHODS OF SOLUTION FOR INVERSE PROBLEM OF NONHOLONOMIC DYNAMICS

This paper presents two basic Propositions and methods of solution for inverse problem of nonholonomic dynamics-constitution of equations of motion and repair of equations of motion.

1991, 23(2): 252-256. doi: 10.6052/0459-1879-1991-2-1995-835

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1991 Vol. 23, No. 2

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