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  • Author: Vasile Năstăsescu x
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Abstract

This paper presents some results of the author’s researching in connection with SPH (smoothed particle hydrodynamics) method and underwater explosion numerical modelling. All about cavitation fundamentals are considered known and about cavitation effects upon the structures. The authors, deeply preoccupied in using of SPH method, as well in modelling of the underwater explosion effects upon structures, had to take into consideration the bulk cavitation. A main issue in this study was the knowing of the bulk cavitation domain and its characteristic parameters. Such researching was possible to be successfully carried out, only by using of the SPH method. Finally, the paper presents the relations and the working way for knowing of the bulk cavitation domain and also a numerical model using SPH method is presented. The numerical example regarding shape and dimensions of the bulk cavitation is presented together putting in evidence of some parameters which can make damages upon a structure that is in the bulk cavitation area.

Abstract

The paper is based on the experience gained in creating eLearning courses to keep the student’s interest high, to encourage them to study additional materials in order to achieve the level of complexity proposed by the discipline objectives. The combination of specific gaming-techniques with simulation elements has been combined into designing the e-learning content. The degree of motivation and the interest in the discipline were appreciated by comparing the results obtained by students attending a blending-learning to those students who did the didactic activities in the traditional way. At present, there is a decrease in students’ interest in technical subjects. On one hand, the complexity of these disciplines is high, and moreover, in order for the students to achieve the didactic objectives of the discipline, they must make a sustained effort and combine the individual study with the explanations in the classroom.

Abstract

In the first part of the paper, using the numerical simulations with FEM and the results of some investigations made with different experimental techniques, a calculation methodology was developed for the study of the stress waves propagation in the short tronconical bars subjected at axial impact. Because a good agreement between data obtained from numerical analysis and experimental investigations was observed, the numerical model of calculus conceived for this study was considered validated. The calculus model established was used to investigate other aspects connected of stress wave propagation in the short tronconical bars. In the second part of the paper, using established calculus model and numerical analysis with Finite Element Method the influence of bar conicity on stress wave propagation and on stress distribution in different cross sections of the bar was analyzed

Abstract

This paper presents some authors’ results regarding numerical modelling of the acoustic wave propagation, using the Ansys program. The acoustic wave propagation is studied under conditions of existence of acoustic absorbing panels. Different materials are taken into account (aluminium, foam, oak, polystyrene) for considered acoustic absorbing panels. Also, different dimensions and different cases for fixing the panels were considered. The acoustic wave propagation was studied in stationary conditions and in dynamic conditions at different values of sound frequencies. A comparative analysis is performed regarding the influence of different conditions upon acoustic wave propagation. Our studies presented in this paper are referring to the acoustic propagation in an open space, like on airports or around the acoustic sources placed in open space. The aim of this paper is to offer our experience in this field for a numerical analysis of the ways for sound level reduction. Also the facilities of the Ansys program for the solving of such problems are presented in a practical manner of use.

Abstract

This paper brings in front of the interested researchers using one of the most known and used meshfree method, Element-Free Galerkin (EFG) method, in modelling of a technological process. It is about the deep drawing process of thin plates made of steel or aluminium. The paper gives information both for EFG method and for deep drawing process. The modelling as well the results are presented in a comparative way towards the using of Finite Element Method (FEM). The numerical analysis is based on the Ansys/Ls-Dyna program, in which EFG method is implemented. This numerical method is less known in our country and much less used, in spite of some advantages comparatively with the FEM. Of course, the EFG method is still under developing, but it can be successfully used in many problems. This paper is a proof in this sense and an urge to use the EFG method.

Abstract

The foam materials, by construction and by characteristic properties (low density, large deformations, great flexibility, Poisson ratio practically zero etc.), are widely used in many and various domains. The numerical simulation of the foam material behavior raises some difficulties, which can be impassable under certain circumstances. This paper presents some of our researching results in numerical modeling of foam materials, which can be very useful for those interested in numerical modeling of the foam materials. Numerical modeling used by the authors is based on the finite element method (FEM) and on the element-free Galerkin (EFG) method. The results are presented in a comparatively way and they also present how some usually running errors can be avoided. The conclusions and the results are considered by the authors very useful in modeling of the foam materials and in choosing of the most fitted method too.

Abstract

Estimating the degree of vulnerability of a region implies both the identification of the dependencies as well as of the interdependencies. The dependencies refer to a set of physical, social, economic, environmental and political-military conditions and processes and the interdependencies have in view physical, cyber, geographical and logical aspects that may indirectly affect the daily rhythm of the population, the economy or even the national security. The present paper aims at estimating the degree of vulnerability by constructing a model that would determine the index of vulnerability associated to a given area, an index that is directly dependent on demographic, economic, governmental factors, on the interdependence with other sectors and also on the history of the events that occurred in the area in the recent years.