# Ghiţă BÂRSAN

## 32-54 METODĂ HIBRIDĂ DE STUDIU PENTRU ORICE TIP DE SECȚIUNE SUPUSĂ LA TORSIUNE

A HYBRID MeTHOD OF STUDY FOR ANY SECTION

TYPE UNDER TORSIONAL LOADING

This paper presents a methodology regarding the numerical analysis of any section type under torsion loading. This methodology is named a hybrid one, because it practically consist in using of the membrane analogy – an experimental method –  but the solving and result analysis are made by Finite Element Method (FEM). In the modelling of a structure, of a beam, applying of the torsion moment involves some difficulties especially regarding of the local stress concentration. By the methodology presented in this paper, the analysis of the shear stress field can be made with a great accuracy using FEM, without any experimental means. This methodology takes into account all the physical significations of the membrane analogy and all these are evaluated by FEM. That require of the pressure-effort ratio to be -2 is made by a thermal loading, cooling the membrane. By post-processing, the numerical result analysis can be quickly and easily made. The modelling presented in this paper can be used for any section type: whatever the shape, no matter if the section has one or more holes etc. By this methodology, the membrane analogy becomes more efficient, more versatile and more accessible for any section type.

Keywords: torsion, membrane analogy, finite elements

Cuvinte cheie: torsiune, analogia cu membrana, elemente finite

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## 29-70 METODA SPH ÎN PROBLEME HIDROTEHNICE

SPH METHOD IN HYDRAULIC PROBLEMS
Smoothed Particle Hydrodynamics (SPH) method is a meshless
numerical method, which has many advantages comparatively with Finite
Element Method (FEM), regarding those problems where large displacement,
strong nonlinearities or deformations with high strain rates occur (high velocity
impact problems, air or underwater explosion calculus etc.). As fluid mechanics
is concerned, this method is practically completely validated. Some very difficult
problems, like fluid-structure interaction (FSI), free surface evolution of a fluid
and others, can be easier solved by SPH method. In our country this numerical
method is practically unused and even unknown. This paper comes firstly with
theoretical fundamentals of the SPH method, after that an hypothetical
hydraulic problem is solved. It is about the numerical modeling of a gate which
controls the fluid level between two enclosed spaces. In addition to urging the
use of SPH method, this paper presents an available numerical model, based
on this method, for many others similar problems and useful conclusions.
Keywords: free particles, SPH, Navier -Stokes, flowing, fluid
Cuvinte cheie: particule libere, SPH, ecuaţiile Navier-Stokes, curgere,
fluid

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