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Abstract
Corrosion of steel tubes represents a major challenge for various industries, leading to significant economic and environmental impacts, such as material losses, operational interruptions and safety risks. This study focuses on the metallurgical, chemical and mechanical characterization of corroded steel tubes operating in mining installations using metallographic analysis, X-ray diffraction (XRD), SEM-EDS studies, chemical analysis and micro-hardness measurements. The results reveal the existence of a considerable extent of corrosion, of which, the main corrosion products are magnetite – 72% and goethite – 18.1 associated with corrosion. The corroded tubes measured 0.128% carbon, against 0.23% in new tubes, indicating a loss in weight and mechanical strength properties. The observed tensile strength for the new tubes was 481 MPa while the same for the corroded tubes was to a large extent lower. Furthermore, metallographic examination indicates that indeed the structure is ferrite pearlite as to the composition. This study indicates that 304 L or 316 L stainless steels may be utilized which have better corrosion-protecting coatings thus prolonging service life and reducing maintenance activities.
Abstract
This study conducts an in-depth numerical analysis of debonding behavior in composite structures, with a particular focus on the critical role of thermal effects. Utilizing a frictional contact cohesive zone model, the research characterizes the debonding process while sequentially integrating thermal analysis to assess the impact of thermal loading. A thermomechanical coupled model is developed and implemented using the finite element software ABAQUS. The model's accuracy is validated through the Double Cantilever Beam (DCB) test, ensuring reliable results. The methodology involves a detailed finite element analysis, where thermal loads are applied to composite specimens, followed by mechanical loading to simulate debonding. The frictional contact cohesive zone model accurately captures the interface behavior under varying thermal conditions. Quantitative results indicate that thermal loading significantly affects the debonding process, with a noticeable increase in debonding initiation and propagation rates, highlighting the critical influence of thermal effects on structural integrity.
Abstract
Fused filament manufacturing (FFF), also known as 3D printing, is one of the most commonly used additive manufacturing techniques for creating high-quality materials. This process demonstrates the intricacies and challenges involved in choosing appropriate manufacturing parameters to achieve the desired outcomes. Among these critical parameters is the nozzle temperature, which can be adjusted to enhance the mechanical properties of the 3D-printed Polyphenylene Sulfide (PPS) parts. The main objective of this study is to investigate the influence of the printing temperature on the mechanical properties and failure characteristics of 3D printed polyphenylene sulfide (PPS) parts during impact testing. To do this, a series of simple and repeated impact tests were carried out on printed PPS samples in the nozzle temperature range (320–350 °C). CHARPY tests were carried out on the samples manufactured with different sequences for the optimal orientation of the filaments. Furthermore, the impact energy absorption capacity and the induced damage as a function of nozzle temperature were evaluated. CHARPY test results showed that samples with stacking sequence (0/0) had the best impact resistance and specific absorbed energy (SEA). This sequence, printed horizontally, was used to test different print temperatures in single and repeated impact tests. Furthermore, the results indicated that samples printed with a nozzle temperature of 340 °C exhibited higher CHARPY impact resistance and specific absorbed energy (SEA), with a percentage difference of 45.57%, 41.95% and 44.21% compared to samples printed with nozzle temperatures of 320 °C, 330 °C and 350 °C respectively. For repeated impact tests, the results also show that samples printed with a nozzle temperature of 340 °C have a higher initial energy absorption rate and a greater number of impacts before complete failure of the sample. This result proves also that the changing of nozzle temperature does not have a significant effect on the induced damage after CHARPY and repeated impact.
Abstract
The investigation of the effect of petrography and diagenetic features on the geomechanical properties of the sandstone and their relationship to rock failure are of vital importance for different construction projects. The present study involves analyzing multi-vertical lithofacies profiles around the region of Wadi Halfa, North Sudan. The sandstone is dominantly composed of monocrystalline quartz grains (60%) accompanied by some polycrystalline quartz, feldspars, lithic fragments, micas, and heavy minerals. Iron oxides are the main type of cementing materials (14%), with some (2%) of carbonates and clay minerals. The average porosity of all studied samples is 12%. The compressive strength ranges widely, influenced by weathering, grain size, cementing materials, and bedding planes. The uniaxial compressive strength is more influenced by wetting when the load is parallel to bedding planes. Sandstone anisotropy is suggested by a U-shaped curve, with lower values at 45° and higher values at 90° and 0°. The geomechanical behavior of rocks masses in Wadi Halfa was evaluated through a combination of field and laboratory analyses which revealed a variable Rock Mass Rating (RMR) ranging from 58 to 92 and a Geological Strength Index (GSI) ranging from 33 to 61.
Abstract
This research investigates the complex interplay between stress impact, concrete shrinkage, and its implications on crack development. Utilizing theoretical and computational methods, the study analyzes the detrimental effects of structural cracks caused by stress variations. A distinctive behavior of long-term shrinkage concerning stress levels was observed. It was found that, positive stress enhances the mean Young's modulus, while negative stress reduces modulus under negative stress conditions, heightened susceptibility to crack propagation under negative stress and improved resistance under positive stress. Temperature's uniform impact on long-term shrinkage is demonstrated, highlighting differences among various cement classes.
Abstract
To highlight the systemic interdependencies in office building design, this paper dives into the complexities of converting old structures into modern workspaces. The study addresses the challenges of adaptive reuse by concentrating on case studies and design issues and provides insights into how to maintain historical integrity while satisfying the demands of contemporary workplace needs. The research concludes with a real-world example that shows how design concepts derived from the analysis may be successfully used.
Abstract
The paper focuses on describing the developed low-cost mobile mapping system for the purpose of automated mapping using simultaneous localization and mapping techniques. The paper also focuses on testing the light detection and ranging that form that system. The mobile mapping system consists of a combination of multiple sensors, including a trio of 2D and 3D light detection and ranging a stereo camera, an inertial measurement unit, and rotary encoders.
The components make up three subsystems, which are detailed described. A section of the paper is dedicated to the light detection and ranging tests performed in the accuracy of measured distance and measured geometry. In the final section of the paper, planned tests for the remaining components of the mobile mapping system are described.
Abstract
In this paper, a multiphase method based on the Level Set Method is employed to study the sloshing phenomenon of two-layer liquid inside a two-dimensional rectangular container subjected to horizontal excitation. Validation of the multiphase approach is conducted through a comparative analysis with existing studies. Results show a fair agreement between the numerical model and available numerical and experimental data. Initially, a series of simulations were used to compare the sloshing behaviour of a two-layer fluid with that of a single-layer fluid. Even under identical external excitation, layered fluids demonstrate different sloshing patterns compared to single-layer liquids. Furthermore, the influence of the periodic excitation frequency on the sloshing dynamics was examined. Analysis was also conducted to explore the effect of internal baffles on the oscillatory behaviour of layered liquid sloshing. The findings reveal that the baffles significantly mitigate the sloshing of the layered fluid.
Abstract
In recent years, the number of road traffic crashes showed a decreasing trend in Hungary, but this cannot be stated about crashes at road-railway level crossings. The Hungarian Railways has repeatedly called attention to the dangers of rail transport. The main goal of this paper is to develop a new safety inspection method for road-railway level crossings based on the existing road safety inspection method. Based on the experiences of road safety inspections completed at ten locations suggestions were given for the adaptation of the method to railway crossings. The most important findings of the safety inspections are also presented in the paper.
Abstract
Based on air quality index data for the period 2018–2022, Hungary ranks as the 80th most polluted country in the world. Given the air pollution data measured in Hungary and the health impact of air pollution, it is of utmost importance to measure air quality in Hungary focusing on PM10 and PM2.5 pollutants. One possible solution for high-density measurement is to utilize low-cost sensors at the population level. The calibration procedure has to be carried out in a way that does not incur extra costs and maintenance at the physical level. A potential solution is the development of an algorithm to perform the calibration with remote access. This publication presents a fragment of this development, where we attempted to implement the procedure using a neural network and performed a comparative analysis with official data.
