Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Environmental and Social Assessment of SHPP Tearce Bistrica 1 – Expertise
No full textM103 - The expertise is done for Deloitte Consulting co. The investor was EIB (European Investment Bank)
The Relative Values of a Moisture Percentage in Building Envelopes: Moisture’s Spots with a Moisture Meter
No full textThere is a substantial lack of data relating to the hygrothermal traits of existing buildings and building materials. Moisture analysis in building envelopes is 1D (one-dimensional), 2D and 3D effects and feedback can be neglected. Many European standards treat a moisture percentage in building envelopes as surface and interstitial moisture condensation, such as BS EN ISO 10211, BS EN ISO 13788, BS EN ISO 15148, and BS EN 15026. In this manuscript, there was a tendency to capture a relative quantity of superficial moisture, by metering spots on the inner and outer surface of wall lining systems with a moisture meter. The metering specimens were the buildings with different envelopes: a wooden hut-house, a masonry building and a building partially sheeted in stone. The referent heights on wall linings, for taking the moisture data were specified as 50 cm for a wooden and masonry building and 80 cm for a stone-sheeted building, from the ground. The several conclusions were brought. The buidling’s envelope is much influenced by the weather. The outer material surface in a shadow can possess a slight moisture quantity. One of the recommendable issues, originating from this manuscript is to abolish or reduce the buildings’ vulnerability to climate fluctuations immediately at the beginning of construction
Influence of Thickness Ratio on the Aerodynamic Characteristics of a Family of Hybrid Semielliptical Dolphin Airfoils
No full textLongtime evolution and stationary response of a stochastic tumor-immune system with resting T cells
Get PDFIn this paper, we take the resting T cells into account and interpret the progression and
regression of tumors by a predator-prey like tumor-immune system. First, we construct an appropriate
Lyapunov function to prove the existence and uniqueness of the global positive solution to the system.
Then, by utilizing the stochastic comparison theorem, we prove the moment boundedness of tumor
cells and two types of T cells. Furthermore, we analyze the impact of stochastic perturbations on the
extinction and persistence of tumor cells and obtain the stationary probability density of the tumor cells
in the persistent state. The results indicate that when the noise intensity of tumor perturbation is low,
tumor cells remain in a persistent state. As this intensity gradually increases, the population of tumors
moves towards a lower level, and the stochastic bifurcation phenomena occurs. When it reaches a
certain threshold, instead the number of tumor cells eventually enter into an extinct state, and further
increasing of the noise intensity will accelerate this process
Residual life assessment of the historical road riveted bridges
No full textNumerous roads and railways network steel bridges exist with more than 100 years in service, often of great historical value. The in-service safety assessment of these structures is a complex problem which requires interdisciplinary approaches – from civil engineering application of Eurocodes or European recommendation for fatigue life estimation, up to an in-depth assessment by means of fracture mechanics. This article emphasizes the importance of rehabilitating the structure of existing steel bridges, considering the historical monument character of these structures, as well as the reuse of existing structures. Toward this aim, the study case for a historical riveted steel bridge build in the beginning of the twentieth century is presented, with an assessment method considering the structural integrity by means of fracture mechanics. Based on this case study, the paper is proposing an algorithm to assess historical steel bridges. The results of in-depth XFEM analysis with different crack size in the area of a riveted joint are also presented, in order to validate the algorithm
Structural integrity analysis of the pre-stressed concrete dome of the Belgrade fair hall 1
Get PDFBelgrade fair hall 1 is well known for its dome, which is still the world largest self-supported construction made of pre-stressed concrete, with its diameter of 106 m. In this paper the Finite Element Method (FEM) was performed to analyze different loading and supporting conditions. At the same time, crack growth in a support column was simulated by the extended FEM (XFEM). Results of numerical calculations indicate ingenious design of such a complex structure which was based on “hand” calculation decades ago, without computers. In addition to classical engineering and more advanced numerical calculations, risk based analysis was performed taking into account artificially introduced crack and Failure Analysis Diagram, obtained using stress intensity factor and net stress, as well as fracture toughness and critical stress. This analysis, made for the first time for Belgrade fair hall 1, proved that its structural integrity is jeopardized only when a crack reaches half the thickness of a steel bar
Erosion wear of HCCI alloys
Get PDFFailures in industrial plants, which operate under extreme conditions, could occur after a short time of exploitation. Erosion wear of materials is caused by the relative movement of solid particles and the surfaces of components. Such erosive wear can lead to the failure of industrial components in a very short time and/or a sharp decline in the structural integrity of industrial equipment. For example, the wear of the ash disposal system in a coal-burning thermal power plant, due to impact of ash particles with a high content of mineral residues, is a very common case of failure and outages in the operation of such industrial systems.
Two high chromium cast irons (HCCI) were tested to determine the erosion wear. These alloys contain 15% Cr and 25% Cr, and it was tested in as-cast and after heat treatment (annealing). A specially designed installation was used for the gas blast sand erosion test. Type of erodent was foundry quartz sand. Erosion tests were done with high erodent particle velocity (90 m/s) and high erodent feed rate (3000 g/min). This conditions represents those similar to extreme wear conditions of some components of thermal power plants using pulverized high mineral content coals.
Microstructural characterization was done at samples before and after erosion tests, Fig. 1. The main results indicate that matrix plastic deformation and distribution of carbide phase have a significant contribution to erosion resistance of HCCI alloys in such conditions
A Step Towards Smart, Ergonomic and Sustainable Mining Machinery Workplaces
No full textAlthough the mining industry is the oldest one, it is still a major source of pollution with more people hurt or injured than in any other industry, while social conflicts around it are worldwide spread. Namely, mining projects still have direct and indirect environmental impacts and seriously affect land, water, air, biota, and people, while mining equipment focused in this paper has the highest footprint. The reason for the lack of progress in mining industry is the most likely the fact that in current research streams technology-centered design dominates. Our novel Smart Miner concept aims to create a step toward smart, ergonomic and sustainable mining machinery workplaces. It proposes a paradigm shift from pure technology to a Human and Data-Centric Engineering, which could be easily transferred to other industries, and develops solutions for raising the level of environmental quality in complex interactions between phys- ical, behavioral and organizational processes field, by matching advanced operator I4.0&5.0 and society S5.0 standards.
An original idea approval route starts with mining machinery operator wellbeing in its microenvironment and its cyclical alignment with stakeholders in the value chain. After development of smart, ergonomic, non-invasive and reliable operator aid systems for regulation of physical environment job stressors - noise, human vibration, lighting, temperature, air quality, workplace layout issues etc., which solve environmental and human health issues and influence overall performance, research passes to operator macroenvironment determined by organizational contextual factors, which also impair sustainable development results. Micro and macro levels are planned to be connected and balanced by real time analytics to fit high sustainability performance indicators in novel, flexible and scalable system, aimed to increasing productivity and production together with reducing emissions and decrease of accidents rate
An overview of XR technologies usage for industrial robot programming
Get PDFIndustrial robot programming can be a challenging
task, especially in today's age, where robots are more widespread
outside the large manufacturing companies, but rather in small
and medium enterprises where users are not necessarily fully
qualified individuals. The Extended Reality technologies may be
the ongoing answer to improved robot programming experience.
Current solutions for robot programming using Extended Reality
technologies are explored in this overview. In this paper, a
summarized description of certain solutions is given, focusing on
how are the XR technologies utilized in developing the robot
programming systems. Categorization by devices and motion
planners used is also given
RELIABILITY-BASED RISK ASSESSMENT OF AUXILIARY MACHINERY IN OPEN-PIT MINES: A BACKHOE LOADER CASE STUDY
No full textNumerous authors have demonstrated the effectiveness of the risk-based approach in the mining sector. However, the majority of earlier research has ignored the role that auxiliary machines, in total risk management play in favor of heavy machinery. This study aims to analyze backhoe loader maintenance data in order to offer a risk assessment approach for auxiliary machinery in open-pit mines. The severity, occurrence, and detection of failures were the three component indicators that together determined the overall risk, as per the FMEA method. The purpose of the Pareto chart was to grade the detection indicator by illustrating the failure type distribution and distinction. The downtime data statistical testing results enabled analytical calculation of the system's reliability and mean downtime, which in turn allowed for the evaluation of the frequency and severity of failures. As a result, a framework for evaluation was put out, supported by data that was gathered, and included a three-dimensional risk assessment matrix. The focus of further research efforts should be on expanding the present sample data in sense of quantity and also to analysis of other machines in the whole mining system