NUMERICAL SIMULATION OF FLUID-STRUCTURE INTERACTION BETWEEN FISHING WOBBLER AND WATER

This paper deals with modeling, discretization, and numerical analysis of the two-way fluid-structure interaction between a fishing wobbler and a water stream. The structural domain is an assembly of several bodies that have multiple mutual structure-to-structure interactions. These interactions are mostly nonlinear contacts that significantly influence the time step used in simulations. As a result of these nonlinearities, the numerical solving of such a model requires significant computer resources and a long computational time. The paper also presents the creation and numerical simplifications of the model. However, the model remains very realistic. It is concluded that solving the structural domain in a model that retains the interaction between solid bodies is more computationally sensitive and more demanding than solving the fluid domain

Analytical Algorithm Expressions in Simulation of the Temperature Field in Electric Resistance Spot Welding

The paper presents the method of obtaining mathematical equations named "Analytical algorithm expressions" which enable simple creation of computer programs for simulation of the temperature field in the weld zone in electric resistance spot welding. Knowledge of these equations and the manner of their formulation make creation of program packages easier but they do not change anything with respect to the structure and scope of necessary input data which determine concrete initial and boundary conditions. In addition to providing algorithm description of the temperature field, the considered approach is applied for mathematical description of the field of any other physical value relevant for the welding process (specific current, electric potential, density, etc.). In this paper they are realized in temperature fields, as hierarchically superior to the fields of stress and current density, i.e. fields of physical properties of materials of the sheet and the electrode (superiority refers to the algorithm domain). Results of simulation for the non-stationary period of the welding process at two extreme discreet moments are presented at the end

DETERMINATION OF LOAD SPECTRUM OF BUCKET WHEEL EXCAVATOR SRS 1300 IN COAL STRIP MINE DRMNO

Toothed gear power transmissions are complex mechanical systems and their design is a very challenging engineering task that requires the application of common calculation procedures and contemporary designing methods. Operating conditions of the gear power transmission are important for the design process from the aspect of overload prediction and they are defined within the design process by the operating condition factor KA, which has a wide range of values (1 to 2.5), prescribing various operating situations. However, a good design of the toothed gear power transmission can be achieved if operating conditions are simulated and as such implemented in the calculation/design procedure. Such improvement in the design process can be done with the use of defined load spectra that accurately describe realistic operating conditions. The paper presents the results of tensiometric measurements of torque at the output shaft of the working wheel gearbox of the bucket wheel excavator SRs 1300 TAKRAF in the coal strip mine Drmno, and gives a definition of appropriate load spectra based on these tensiometric measurements. The load spectra are defined by applying the full cycle discretization method and as such afterwards used for the calculations/design of the working wheel of the bucket wheel excavator (gears, shafts, shaft keys etc.)

Basic terms in friction stir welding according to AWS D17.3/D17.3M:2010 i ISO 25239-1: 2011

Zavarivanje trenjem sa mešanjem - ZTM (eng. Friction Stir Welding - FSW) je relativno mlad postupak zavarivanja u čvrstom stanju nastao na Institutu za zavarivanje (TWI) u Londonu, krajem 1991. godine. Prva primena ZTM postupka se vezuje za železnicu i zavarivanje aluminijuma i njegovih legura ali se sa vremenom proširio opseg primene tako da se danas ovim postupkom uspešno zavaruje veliki broj čistih metala, legura, ali i nemetala, u svim industrijskim granama (železnica. avioindustrija, automobilska, brodogradnja itd.). Dve decenije po nastajanju, ZTM postupak se ipak, najviše koristi za zavarivanje aluminijuma i njegovih legura, te nije iznenađujuće što su prvi koraci standardizacije ZTM postupka vezani za zavarivanje aluminijuma. Ovim radom se skreće pažnja na osnovne pojmove kod ZTM koji su dati u postojećim standardima i predlažu odgovarajući pojmovi na srpskom jeziku.Friction Stir Welding is relatively young welding process in solid state which is created in The Welding Institute - London, during 1991 year. The first application is connected with railway and aluminum and aluminum alloys welding but later the application range is extended, so today this process successfully welded many pure metals, alloys also, non-metals in all industrial branches (railway, aircraft, automotive, shipyard etc). Two decades after formation, FSW process is the mostly used for aluminum and aluminum alloys welding, so it is not surprise that the first step in FSW standardization is connected to aluminum welding. The aim of this paper is to draw attention to basic terms for FSW which are presented in actual standards and suggested appropriated terms on Serbian language

Experimental studies of parameters affecting the heat generation in friction stir welding process

Heat generation is a complex process of transformation of a specific type of energy into heat. During friction stir welding, one part of mechanical energy delivered to the welding tool is consumed in the welding process, another is used for deformational processes etc., and the rest of the energy is transformed into heat. The analytical procedure for the estimation of heat generated during friction stir welding is very complex because it includes a significant number of variables and parameters, and many of them cannot be fully mathematically explained. Because of that, the analytical model for the estimation of heat generated during friction stir welding defines variables and parameters that dominantly affect heat generation. These parameters are numerous and some of them, e. g. loads, friction coefficient, torque, temperature, are estimated experimentally. Due to the complex geometry of the friction stir welding process and requirements of the measuring equipment, adequate measuring configurations and specific constructional solutions that provide adequate measuring positions are necessary. This paper gives an overview of the process of heat generation during friction stir welding, the most influencing parameters on heat generation, constructional solutions for the measuring equipment needed for these experimental researches and examples of measured values

Thermal stability of film forming amines‐based corrosion inhibitors in high temperature power plant water solutions

Abstract Film forming amines (FFA) are corrosion inhibitors added to power plant water. The major concern associated with their application is the thermal stability in the high temperature power plant water medium, along with the risk of decomposition into low molecular weight organic acids that can cause corrosive damages in the water/steam cycle. However, there is still a lack of sufficient data on the thermal stability of FFA corrosion inhibitors. This paper presents a comprehensive critical review and state‐of‐the‐art assessment of the results obtained from studying the thermolysis of FFA corrosion inhibitors in power plant water/steam cycle conditions, highlighting the relevance for practical application and research needs. Temperature, exposure time, initial concentration, and alkalizing agents were identified as key factors influencing the thermal stability of FFA in high temperature power plant water. Organic acids are found in concentrations harmless to metal tubes. Advanced scientific background information and additional research are required on this topic

Determining the Competitiveness of Spa-Centers in Order to Achieve Sustainability Using a Fuzzy Multi-Criteria Decision-Making Model

Bosnia and Herzegovina (B&H) possess many natural resources that can be exploited for the development of medical tourism. The offer of medical tourism in B&H is focused on spa tourism. B&H has 16 registered spa-centers offering different types of services. This study provides a complete overview of the assessment of the current state of spa-centres using expert decision-making and methods of multi-criteria analysis. An innovative and novel MCDM model based on integration of the FUCOM (full consistency method) and fuzzy MARCOS (Measurement of Alternatives and Ranking according to COmpromise Solution) methods was used. The model consists of 16 alternatives and eight sustainable criteria. The results of this research have shown that the spa-centers of Ilidža near Sarajevo, Fojnica and Vrućica have the best assessments of the current situation and prerequisites for sustainable business. These spa-centers should be a benchmark to other spas providing direction on how to improve their business to be more sustainable and competitive in the market. These results were confirmed by a sensitivity analysis with two approaches used. The first approach was to compare the results obtained by the fuzzy MARCOS method with other fuzzy methods, and the second approach was to examine the influence of the application of different weights on the final ranking of the spa. The results of this study can serve spa-canter managers to understand the position of their spa-centers in order to exploit advantages they have and eliminate the shortcomings to improve their business

Matlab toolbox for analysis of 3D images

AB Here we describe a MATLAB toolbox for analysis of 3D images obtained using a 3D scanner. Toolbox consists of two main parts: various filters for improving the image quality and a module for surface reconstruction from an unorganized set of points

Analytical Methods for Determination of Film Forming Amine Concentration in Water Solutions

This work presents analytical methods for measuring the concentration of film forming amines. Their advantages and disadvantages are discussed. Special attention is paid to the applicability of each method in power industry