Contents of Journal of Mechanical Engineering 54, 5-6 (2003) 


 

KOMPIS, V., DEKYS, V.: Analysis of local stress and displacement 
fields in contact of 3D bodies with curved surfaces                       253 

MAUNDER, E. A. W., RAMSAY, A. C. A.: A basis for an axisymmetric 
hybrid-stress element                                                     263 

von ESTORFF, O., HAGEN, CH.: Dynamic response of blocks on 
a half-space including nonlinear effects                                  277 

ALEXANDROV, S.: Solution behaviour and fracture near frictional 
interfaces in metal forming processes                                     293 

MALENOVSKY, E., POCHYLY, F., KLAS, R.: Contribution to 
the theoretical, computational and experimental analysis 
of Taylor vortices in thin fluid film                                     307 

NAKASHIMA, M.: Unconditionally stable explicit difference schemes 
for a two-dimensional parabolic differential equation with variable 
coefficients (V)                                                          327

Abstracts



Analysis of local stress and displacement fields in contact of 3D bodies with curved surfaces

VLADIMIR KOMPIS, VLADIMIR DEKYS

The paper describes a computational model for displacement and stress fields of elastic bodies with spherical surfaces in contact. It is assumed that the bodies are thin walled, so that the contact area is determined by the penetration of the rigid surfaces in accordance to Hertz theory. The displacement and stress fields are described by the gradients of the first and second order of weak singular integrals. All the integration and differentiation are performed numerically with very good accuracy for all the most important points on and near the surface.

A basis for an axisymmetric hybrid-stress element

EDWARD A. W. MAUNDER, ANGUS C. A. RAMSAY

Recent developments of hybrid-stress elements are presented suitable for modelling axisymmetric problems when a strong form of equilibrium is required. Potential instability problems due to spurious kinematic modes are shown to be avoided by appropriate selection of statically admissible stress fields and edge displacements, and by the use of the macro-element concept. This paper is restricted to elements for problems where a hole occurs along the axis of symmetry; simple numerical examples are included to illustrate element characteristics, to verify the associated software, and to compare with conventional conforming displacement models. Suggestions are included for future work to develop axisymmetric hybrid models further.

Dynamic response of blocks on a half-space including nonlinear effects

OTTO VON ESTORFF, CHRISTIAN HAGEN

In the present contribution, a three-dimensional approach for the direct coupling of FEM and BEM in the time domain is outlined, which allows to take into account physical and geometrical non-linearities, unbounded subdomains, as well as incident wave fields. Employing this approach, the dynamic behaviour of building-like structures, namely blocks and walls, resting on half-spaces, is investigated. The response of these systems to impulse loads and to incident waves is studied, and the influence of soil properties like stiffness and yield strength on the overall dynamic behaviour of the soil-structure systems is analysed.

From the numerical examples it becomes obvious that the presented approach works very well. The three-dimensional formulation allows the investigation of rather realistic problems in dynamic soil-structure interaction and earthquake engineering.

Solution behaviour and fracture near frictional interfaces in metal forming processes

SERGEI ALEXANDROV

Assuming a rigid plastic, hardening material model with a damage evolution equation, it is shown that the velocity fields must in general satisfy sticking boundary conditions at maximum friction surfaces. Exceptions to this rule are also derived in terms of a special velocity distribution and friction surface geometry. Applying sticking friction boundary conditions, a closed form solution for a simple problem is obtained. It is shown that no solution may exist if a conventional fracture criterion is applied. To achieve the existence, a new fracture criterion is proposed.

Contribution to the theoretical, computational and experimental analysis of Taylor vortices in thin fluid film

EDUARD MALENOVSKY, FRANTISEK POCHYLY, ROMAN KLAS

This contribution mainly deals with computational modelling of flow with Taylor vortices between two cylinders. The liquid is assumed to be incompressible and the flow laminar. The theoretical analysis is based on the application of Navier-Stokes and continuity equations. Velocities and pressure fields are solved in perpendicular co-ordinates but for the description of geometrical configuration, curvilinear co-ordinates are used. Using special transformation relations, it is possible to separate the liquid and rigid body motions from each other. This new approach allows to analyze liquid motion based on the solution of eigenvalue problem. Though stationary motion is analyzed, the eigenvalue problem is solved for nonstationary motion as a response to Dirac's pulse. The Bezier body is used for describing the liquid volume and also for approximating the solution (velocities and pressures) by numerical analysis, which is a totally new approach. Many different boundary conditions on the plane, which is perpendicular to the axis of rotation, can be used. The dependence of the eigenvalues on angular velocity is presented, length is analyzed on the model sample, and some results were compared with the experiment. Some analyses of the model sample were also made in Computational Fluid Dynamic (CFD) FLUENT. Generally, a totally new approach is presented, which allows a more precise analysis of liquid motion.

Unconditionally stable explicit difference schemes for a two-dimensional parabolic differential equation with variable coefficients (V)

MASAHARU NAKASHIMA

The computational aspects of heat transfer in engineering structures and materials are important since non-uniform heat flows may have a significant effect on the performance character. Its application area is in the development of advanced structural materials, component behavior and structural design. Several different techniques for numerical analysis of heat transient problems exist. Discretizing the space, time integration methods are often used. However, for a system where, e.g. the thermal diffusion is rapid and variable in time, the numerical integration runs in difficulties when choosing the optimum time step. In the past, implicit methods were used to analyze such systems. Unlike the past efforts in this area, the present paper describes an explicit unconditionally stable method, and the optimum time step problems are overcome. A numerical test model is presented to justify our method.