CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
Not a member yet
4735 research outputs found
Sort by
ANALYSIS OF CONTACT FRICTION BEHAVIOR IN THE BENDING PROCESS OF SEMI-PARALLEL STEEL WIRE CABLE
Get PDFIn the bending process of semi-parallel steel wire cable, with the increase of the lateral displacement of the bending, the interaction between the steel wires in the cable is remarkable and the mechanical behavior is complicated. In order to study the mechanical behavior of the contact friction between the inner steel wires in the process of cable bending, this paper uses the 37-φ7 semi-parallel steel wire as the research object, and uses the ANSYS to set up the finite element model of the cable bending, and verifies the correctness of the refined finite element model by bending test data. Based on the refined finite element model of the test data verification, the variation rule of the contact friction between the inner steel wires in the semi-parallel steel wire of different boundary conditions in the bending process is studied, and the axial sliding behavior of the steel wires in the cable bending process is analyzed. The results show that the bending and mechanical properties of the semi-parallel steel wire cable can be calculated more accurately by considering the refined finite element model of the contact friction, and the amount of deformation between the steel wires during the bending process of the semi-parallel steel wire cable can be calculated. The contact pressure and the contact friction stress are non-linear with the increase of the lateral displacement of the bending, and there is a maximum value for the contact friction stress for the pre-tension semi-parallel wire cable, and the maximum position of the axial accumulated slip amount between the steel wires is located at the bending cable section of the calculated span of 1/4 or 3/4 times
Brain data and driver\u27s attention during simulated drive
Get PDFThe attention of drivers is a serious issue and one of the critical factors of road safety. The question is whether the electrical activity of the human brain can be correctly measured/collected and utilized to monitor and interpret the driver\u27s attention during simulated driving. This article summarizes four experiments that have been designed, performed, and evaluated in the neuroinformatics laboratory at the University of West Bohemia. Simulated driving under various conditions in a car simulator was organized, and electrophysiology, mainly electroencephalography, data were collected from participants/drivers. The results include experience with the design of such experiments and the suitability of methods based on the collection and interpretation of electroencephalography data for driver attention detection
Theoretical analysis of the influence of the chevron inclination angle on the thermal performance of a gasket plate heat exchanger
Get PDFDifferent models are applied for an experimental and theoretical determination of the thermal and hydraulic performance of gasket plate heat exchanger. One of the relevant aspects of recent works is the influence of the chevron inclination angle between the heat exchanger plates. This work aims to analyse the impact of the chevron inclination angle by applying an effective concept in a sunflower vegetable oil cooler. Comparisons are made with theoretical and experimental results from the literature for works that consider angles of inclination equal to 30◦, 45◦, and 60◦. An analysis model that does not consider the inclination angle as an explicit parameter is included for comparison purposes. In addition to the angle of inclination, two other parameters, the mass flow rate of the cold fluid (water) and the number of plates, are considered crucial for determining and analysing the results. Nusselt number, global heat transfer coefficient, effectiveness, heat transfer rate, and outlet temperatures for hot and cold fluids are presented in a graphical format. The results point to the need to improve models applied to gasket plate heat exchangers concerning the influence of the inclination angle since there are significant differences between those obtained and analysed in this work
Design and simulation of a bearing housing aerospace component from titanium alloy (Ti6Al4V) for additive manufacturing
Get PDFIn evaluating emerging technology, such as additive manufacturing, it is important to analyse the impact of the manufacturing process on efficiency in an objective and quantifiable manner. This study deals with the design and simulation of a bearing housing made from titanium alloy (Ti6Al4V) using the selective laser melting (SLM) technique. The Finite Element Analysis (FEA) method was used for assessing the suitability of Ti6Al4V for aerospace application. The choice of Ti6Al4V is due to the comparative advantage of its strength-to-weight ratio. The implicit and explicit modules of the Abaqus software were employed for the non-linear and linear analyses of the component part. The results obtained revealed that the titanium alloy (Ti6Al4V) sufficiently meets the design, functional and service requirements of the bearing housing component produced for aerospace application. The designed bearing is suitable for a high speed and temperature application beyond 1900 K, while the maximum stress induced in the component during loading was 521 kPa. It is evident that the developed stresses do not result in a distortion or deformation of the material with yield strength in the region of 820 MPa. This work provides design data for the development of a bearing housing for AM under the technique of SLM using Ti6Al4V by reflecting the knowledge of the material behaviour under the operating conditions
Application of strut-and-tie models for assessing RC half-joints not complying with current code specifications
Get PDFThe work described is concerned with an investigation of the effectiveness of the use of strut-and-tie models for the structural assessment of half joints. Such elements form a part of many existing bridges which, although not complying with current code specifications, have not as yet displayed any significant signs of distress in spite of the increase in traffic volume and loads over the years. The work is based on a comparative study of the predicted and experimentally established values of load-carrying capacity and location and causes of failure of half-jointed beams with reinforcement layouts that replicate those found in structures designed in accordance with previous code specifications. The results obtained show significant shortcomings of the assessment method as this is found not only to underestimate load-carrying capacity by a margin ranging between 40 % and 65 %, but also to often fail to identify the location and causes of failure. Therefore, there is a need for an alternative assessment method that will be based on concepts capable of both providing a realistic description of structural-concrete behaviour and identifying the causes of failure leading to the loss of load-carrying capacity
Stone Topography – Useful Tool in Monuments Restoration Process
Get PDFThe surface of building stone on historic buildings often bears the original traces of craftsmanship processing. These are an integral part of the visual appearance of the monument and thus its value, which needs to be protected. For studying and identifying traces and subsequent reconstruction of stonemason\u27s tools, we use the methods of traceology and mechanoscopy. Using modern imaging techniques, we can identify the stonemason\u27s tool used, reconstruct the shape of its blade, and determine how it was used. The obtained results can be used in the process of monument care, especially in the process of preparation and implementation of restoration interventions on the objects, but they are also useful for completing the historical context of the monument. Our research is focused on the systematic study of the surface topography of the stone monuments in Prague. The obtained results were systematically divided according to individual historical period. As a model example of the use of the above-mentioned methods and approaches, we present the topography of stone elements and the development of stonemason\u27s craft in Gothic Prague. The development of the stonemason\u27s craft within one city in a given period can be documented on selected examples arranged chronologically in succession
Applying life cycle assessment with minimal information to support early-stage material selection
Get PDFTraditional life cycle assessment (LCA) is too data intensive and time consuming to be used during typical building design processes. Conducting an LCA during the building design process therefore requires simplifications and assumptions. Such “screening LCAs” are quicker and can be used with less data but introduce greater uncertainty. Unfortunately, uncertainty is not reflected in standard deterministic LCA calculations, which produce single-point values in LCA results. Thus, in this study, data quality scoring has been incorporated into a screening LCA to produce probabilistic predictions of environmental performance based on limited data. The approach has been applied during the design process of a bio-based wall panel designed for a circular economy. A combination of ecoinvent and material data sheets were used to analyse a wide range of novel bio-based insulation materials. The screening LCA analysed global warming potential and identified a short-list of promising materials that were then subjected to a detailed LCA for further consideration in the design. The method uses publicly available information and can be applied at material or building-element level. The method thus helps designers estimate environmental impacts without hindering the design process
Lifelong learning of property managers in enabling sustainable and energy efficient residential buildings: experiences of care project in Tampere region
Get PDFThe existing building stock causes 40% of the total energy consumption in the European Union. The high energy consumption together with ageing buildings put strong pressure on renovation of buildings and lowering of CO2 emissions. The Directives on Energy Performance of Buildings (EPBD) and Energy Efficiency (EED) were established to urge and steer the activities in the EU member countries.There are about 90,000 housing companies in Finland. They consist of 1,7 million apartments and 2,7 million residents, which makes housing companies a significant energy consumer. Around 50 % of the building stock in Finland was built between 1960s and 1980s. The average level of technical building systems is decent. Measures are still needed to tackle the increasing maintenance backlog and energy consumptionobjectives.Management of housing companies consists of the general meeting of apartment owners and a board elected by the general meeting. In addition, a vast majority of housing companies have a professional property manager whose role corresponds to CEO. The property manager’s expertise plays an essential role in planning and execution of maintenance and energy efficiency.The role of the property manager calls for multidisciplinary competencies and continuous learning. The CARE - Resource efficient caretaking of residential buildings project implemented flexible courses and training for property managers to enhance their technical understanding of energy efficient renovations and retrofit of new energy solutions
Calibration of a summer building simulation model based on monitoring of user behaviour
Get PDFOccupant behaviour is a field, that has always been of great interest to researchers. It could significantly modify the operation of the building and the user’s energy needs, and it is also difficult to model it according to reality. Evaluation of measurements is a crucial step to calibrate dynamic simulations. Our goal was to analyse the indoor comfort conditions according to measurements, particularly in summertime, and find what solution closes the performance gap between the measured and simulated results. In this research, we investigated an apartment building that underwent an energy efficiency renovation. We have installed a weather station and monitoring sensors in selected apartments, with which we monitored the temperature, relative humidity, and CO2 values of certain rooms, the presence of the inhabitants and the window opening and the operation of shading. In this paper, we focus on the monitoring and simulation results of the topmost apartment. The results can help us better understand how buildings work and how to implement user behaviour in dynamic simulations, how to calibrate the model according to measurements and make suggestions to increase the comfort of the residents
Towards an automatized and objective assessment of data from visual inspections of building envelopes
Get PDFThe renovation planning process is filled with uncertainties and subjective decisions. These make the decisions upon what and when to renovate a complex and ambiguous problem. Selection of renovation measures related to building envelope are often far from optimal as decisions are usually made based on visual inspections. These are manned and thus prone to subjective assessment and the knowhow of individual inspectors. Furthermore, objective criteria which could indicate non-structural failures are often missing. The objective based planning process allowing the estimation of the current damage status of the building envelope by only using non-destructive measurements is still in its infancy. The first step requires establishing reliable and objective based data collection. These could be efficiently collected by Unmanned Aerial Vehicles (UAV) with subsequent image recognition algorithms allowing the identification of imperfections and store the position and extent of such deviations into the building’s digital assessment database. Such tools do not exist. The aim of this study is to investigate the current objectivization possibilities in the domain of building inspections. The first part provides a literature review describing how an autonomous UAV survey of a building envelope may be planned and what computer vision techniques may be used for automatic damage recognition and classification. Subsequently, an objective detection model based on the YOLO-tiny (You Only Look Once) computer vision framework is employed in a case study investigating a building envelope of historical Tjolöholm castle in Sweden. This study contributes to developing a methodology for an objective based visual inspection process.