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Analysis of Structural Changes Created by the Blast Effect

Abstract

Unfortunately, people can’t live in peace in this century: many wars and terrorist attacks have been witnessed even within the last year. In the case of such attacks, both the people and the civil infrastructure is in danger [1-3]. The modern age (infrastructure) provides electrical networks and communication networks for the citizens. Without electricity and/or communications (e.g. the internet), urban life is paralysed. Explosions create heat and shock waves and their effects can potentially damage the wall and cables of a building as changes in the material structure occur. In this article, the authors introduce a blast load effect testing method in an empirical way. The metal microstructure deformation level is measurable by changes in resistance, because resistance is a physical property which depends on the crystal structure of the metal.

Open access
Applicability Investigation of Joining Technologies for Diamond Core Bits

Abstract

For the joining of two metallic components of different material quality, different methods of welding or soldering techniques are used. In this case, these two material qualities are given by the segments containing diamond particles, and thin-walled steel tube. In our previous paper we analysed welded joints with two different kinds of laser sources. In this paper we extend the previous investigations with the analysis of capacitor discharge welded and flame soldered samples. We examine the microstructure of the joints and record the chemical element maps to determine if alloying was formed. Joints are also subjected to fracture and hardness testing. This investigation shows that the applied joining technology meets the increased technical requirements because the joining zone must bear high mechanical and significant thermal loads during usage.

Open access
The Dynamic Particularities of Contour Ploughing

Abstract

The plough is the basic machine for soil work. It is usually connected to the tractor by means of a suspension system. The suspension system is a bar-shaped arm system fixed to the tractor frame, which fixes and raises the attached machine in three points. Its role is significant. Single-sided ploughing on slopes creates some special situations. This phenomenon was observed during a plowing competition and in this paper we look for solutions related to this topic.

Open access
The Effect of Temperature Gradients on the Exhalation Rate of Radon Generated by Building Materials

Abstract

There is increasing interest in indoor air quality studies. The effect of exhaled radon from soil, walls and ceilings has well-known consequences on human health, so the importance of modelling has been established. The present paper examines radon exhalation, on the one hand, only in the case of diffusion and, on the other hand, diffusion and advection. Comparing the results of the two test types, we can determine how significant the effect of temperature gradients on radon exhalation is. For a broader investigation, we performed the parametric tests on several types of material, wall thickness and radon concentration.

Open access
Modelling and Model-Based Control of an HVAC System

Abstract

An HVAC system contains heating, ventilation and air conditioning equipment used in office or industrial buildings. The goal of this research is to design a controller for the process of cooling an office building that is made up of three rooms. The desired room temperature can be achieved by controlling the fans making up the fan coil units and the cooling medium’s temperature. By these means the building connected to the electrical grid becomes a smart office. The used building model includes several dynamically changing interior and exterior heat sources affecting the inner climate, which introduces a level of uncertain prediction into the system. We have determined the controller’s performance by the rate of deviation from the expected temperature, the consumed electrical energy and the generated noise. The controller was created in Matlab Simulink with the possibility of migration to a Siemens PLC.

Open access
A New Method for the Calculation of Energy and Power Requirements of Bucket Wheel Excavators

Abstract

The bucket wheel excavator (BWE) is a continuous working rock harvesting device which removes the rock by means of buckets armoured with teeth, mounted on the wheel and which transfers rock on a main hauling system (generally a belt conveyor). The wheel rotates in a vertical plane and swings in the horizontal plane and raised / descended in the vertical plane by a boom. In this paper we propose a graphical-numerical method in order to calculate the power and energy requirements of the main harvesting structure (the bucket wheel) of the BWE. This approach - based on virtual models of the main working units of bucket wheel excavators and their working processes - is more convenient than those based on analytical formulas and simplification hypotheses, and leads to improved operation, reduced energy consumption, increased productivity and optimal use of available actuating power.

Open access
Numerical Analysis of Additively Manufactured, Individual Titanium Implants Designed in a Virtual Environment

Abstract

The aim of this study is the design, manufacture, and development of a metallic rehabilitation device (titanium frame structure) that is created with a printing process. Product design is inspired by the Computed Tomography (CT) based reconstruction method, during which a metallic frame structure is designed that perfectly fits the retrieved bone surface. The internal structure of the designed metallic frames is a statically analysed three-dimensional construct which makes it possible to create individual product types. Constructs with different structure are checked by finite element analysis. Our goal is to establish a standardised manufacturing process, in which specific mechanical stressing can be carried out and optimal product type chosen, depending on different cases. At the end of this study, our solution of choice is demonstrated with surgical pictures.

Open access
The Numerical Evaluation Errors of the Geometric Model of the Straight Teethed Shaper Cutter

Abstract

It is well known that straight teethed shaper cutters present a theoretical profile error. The side edges are situated on a common conical rack face with the result that they and their projection in the generating plane can’t be involute curves. The optimization of the cutter requires such a correlation of the edge defining parameters that the potential theoretical profile error is kept to the minimum possible. Thus the relevance of the edge equations is of great importance. This paper deals with the analysis of the edge equations, presenting two different forms of it. The comparison between the two different forms is realized by applying the numerical evaluation, by substitution of the edge point coordinates in the implicit equations of the originating surfaces. The obtained results present a difference of magnitude 10-E3. Finally, it can be concluded that the two forms of the edge equations cannot be used randomly but only in correlation with the goal proposed by the running application.

Open access
The Theory of Optimal Balancing of Mechanisms

Abstract

This paper presents a general theory regarding the balancing of mechanisms. It starts with Stevenson’s theory [1], which proves that any mechanism can be dynamically perfectly balanced if there is a pair of counterweights that are eccentrically positioned in three reciprocating perpendicular axes, passing through the mass center of the body. The system of inertial forces are extended in Fourier series where only the first terms, the basic harmonics, are considered. The proposed goal is to stultify the effect of inertial forces and torques. This paper deals with a situation more appropriate to reality. In common cases there doesn’t exist the possibility of implementing counterweights in three perpendicular axes. In this situation only the minimization of inertial forces and torques remains as a possible solution. The method developed for this case is presented.

Open access
Wind Loading on Solar Panels

Abstract

A fully 3D numerical analysis of turbulent flow over a cluster of solar photovoltaic (PV) panels was performed in order to assess the total drag and lift forces, comparing the results with the values from the guidelines of the national standard. A Reynolds-Averaged Navier–Stokes (RANS) model was used in the numerical simulations, considering two acting directions of the wind along the length of the array (0 degree – front, and 180 degrees – reverse direction).

Open access