machinery
Not a member yet
8395 research outputs found
Sort by
Measuring Reliability and Validity of Operator - Mining Machine System’s Characteristics
No full textMining is widely recognized as a high-risk industry with elevated accident rates, yet the ergonomics and safety issues of machinery in open-pit mining operations remain underexplored in previous research. Therefore, this paper aims to examine the reliability and validity of the characteristics of operator-mining machine systems, based on a questionnaire survey conducted among operators in several Serbian open-pit mining companies. Descriptive statistics were first applied to analyse operators’ and machines’ characteristics. Reliability analysis using Cronbach's Alpha identified and eliminated three questions that did not meet acceptable thresholds. Factor analysis was performed to assess construct validity, and after analysis, one questionnaire item has been removed. The final set of questions was grouped into four groups, each containing one or two components, establishing the instrument’s reliability and validity. This research contributes to the understanding of ergonomic characteristics of operator-mining machine systems and shows that factors such as seat adjustability characteristics, armrests adjustability, vibrations in the cabin, and hand- and foot-operated controls are significant in providing a foundation for improving workplace conditions in open-pit mining environments. These results lay the groundwork for future research, such as regression analysis and/or confirmatory factor analysis, or further studies with larger samples
UTICAJ PROMENE PARAMETARA NA MEHANIČKA SVOJSTVA PROIZVODA DOBIJENIH ADITIVNIM TEHNOLOGIJAMA
No full textSa razvojem tehnologije, aditivne metode proizvodnje nalaze sve veću primenu u izradi delova složene geometrije. Izbor materijala mora biti usklađen specifičnoj primeni i potrebnim mehaničkim svojstvima. Ova studija prikazuje rezultate eksperimentalnog testiranja 3D štampanih uzoraka, s ciljem evaluacije mehaničkih svojstava materijala koji imaju najširu primenu u 3D štampanju FDM tehnologijom, fokusirajući se na svojstvo elastičnosti i zateznu čvrstoću. Među materijalima istakao se PLA, demonstrirajući najviše vrednosti elastičnosti i zatezne čvrstoće. Imajući to u vidu, odabran je za dalja istraživanja uticaja temperature mlaznice i broja zidova na njegovo mehaničko ponašanj
A conservative approach to 2SS modeling of KJc size effect in the transition region
No full textEnormous scatter of fracture toughness (KJc) experimental data in the ductile-to-brittle transition (DBT) region requires statistical methods for engineering design when using ferritic steels at sub-zero temperatures. The data-driven 2SS (two-step-scaling) method has been proposed recently to tackle the closely-related scatter and size effects in the DBT region. The present study introduces a further upgrade of the 2SS technique developed to include a predetermined level of conservatism tailored to specific applications. This controlled level of conservatism is incorporated in the 3-parameter Weibull (K0, Kmin, β) 2SS procedure by prescribing a single multiplier χ ≤ 1 as expressed by Eq. (1) and and illustrated in Figure 1. In Eq. (1), B stands for the C(T) specimen thickness (i.e., the length of the crack front), κ and ξ for the scaling exponents, while B0 and K0 refer to the reference specimen. The practical application of this conservative version of 2SS technique is demonstrated using the EURO fracture toughness dataset for 22NiMoCr37 reactor steel. The KJc experimental data shown in Figure 1, which corresponds to temperature of -91 ºC within the core of the DBT region for the specified steel, is utilized to assess the accuracy of predictions of the KJc cumulative distribution function (CDF) achieved through extrapolation for the specified χ values
BIM – Search for Information
No full textThe digitalization in the AECO (Architecture, Engineering, Construction, and Operations) sector is often heralded as a revolution in the way of working. However, it turned out to be a gradual evolution of the process. An industry accustomed to monolithic representations containing all necessary data for a certain project phase has a hard time changing its habits. The first digitalization step was creating those documents using a computer. The second step is BIM technology, which has the ambition to remain the final form of digitalization in the AECO sector.
The IFC scheme, which represents basis of the openBIM concept enabling connection among all BIM applications, also represents one monolithic digital model. Conceived to represent one AECO project, the IFC scheme contains all data about the single project. Additional technologies such as Data Dictionary and Data Templates, which add more data structures to the basic model, have been developed to enrich IFC.
Currently, the focus in the BIM community is on models containing all the necessary data that users require. Different kinds of information requirements define what data should be included in models. Most of the effort is focused on including the data in the model, and little on how the data will be extracted from the model. The fact that well-structured data does not represent the whole information is recognized in the ISO 7817 standard, which states that when creating the Level of information need, attention should be paid to who, when, why and to what extent will use information, although it does not specify how to use these prerequisites to search for information.
The paper analyzes the ways to search BIM data structures from the simplest browsing using the BIM viewer to more complex techniques. Existing proposals are considered, and original ones based on the latest BIM developments are given
Tribological behaviour of hypereutectic Al-Si composites: A multi-response optimisation approach with ANN and Taguchi grey method
No full textAn optimisation model for small datasets was applied to thixocasted/compocasted composites and hybrid composites with hypereutectic Al-18Si base alloys. Composites were produced with the addition of Al2O3 (36 µm/25 nm) or SiC (40 µm) particles. Based on the design of experiment, tribological tests were performed on the tribometer with block-on-disc contact geometry for normal loads of 100 and 200 N, a sliding speed of 0.5 m/s, and a sliding distance of 1000 m. For the prediction of the tribological behaviour of composites, artificial neural networks (ANNs) were used. Three inputs were considered for ANN training: type of reinforcement (base alloy, Al2O3 and SiC), amount of Al2O3 nano-reinforcement (0 and 0.5 wt.%), and load (100 and 200 N). Various ANNs were applied, and the best ANN for wear rate (WR), with an overall regression coefficient of 0.99484, was a network with architecture 3-15-1 and a logsig (logarithmic sigmoid) transfer function. For coefficient of friction (CoF), the best ANN was the one with architecture 3-6-1 and a tansig (hyperbolic tangent sigmoid) transfer function and had an overall regression coefficient of 0.93096. To investigate the potential of ANN for the prediction of two outputs simultaneously, an ANN was trained, and the best results were from network 3-5-2 with a logsig transfer function and overall regression coefficient of 0.99776, but the predicted values for CoF in this case did not show good correlation with experimental results. After the selection of the best ANNs, the Taguchi grey multi-response optimisation of WR and CoF was performed for the same combination of factors as the ANNs. For optimal WR and CoF, the combination of factors was as follows: composite with 3 wt.% Al2O3 micro-reinforcement, 0.5 wt.% Al2O3 nano-reinforcement, and a load of 100 N. The results show that developed ANN, the Taguchi method, and the Taguchi grey method can, with high reliability, be used for the optimisation of wear rate and coefficient of friction of hypereutectic Al-Si composites. Microstructural investigations of worn surfaces were performed, and the wear mechanism for all tested materials was light abrasion and adhesion. The findings from this research can contribute to the future development of hypereutectic Al-Si composites
Continuous drive friction welded Al/Cu joints produced using short welding time, elevated rotational speed, and high welding pressures
No full textThe present study aimed to enhance the efficiency and efficacy of the Al/Cu joint production process implemented by the company VEMID Ltd., Jagodina, Serbia, by attaining sound joints within a very short welding time. For this purpose, the present study aimed at investigating the accuracy and the quality of the continuous drive friction welding (CDFW) process, as well as the optimum combination of CDFW parameters with highest joint efficiency in terms of investigated properties. The accuracy was estimated through an analysis of temperature–time curves recorded during CDFW using an infrared camera. The quality was evaluated through an investigation of the properties of Al/Cu joints produced using different friction (66.7, 88.9, and 133.3 MPa) and forging (88.9, 222.2, and 355.6 MPa) pressures and a constant total welding time (4 s) and rotational speed (2100 rpm). Thermal imaging with an infrared camera demonstrated that the actual total welding time was 15% longer compared to the nominal value. This was attributed to the slow pressure response of the pneumatic brake system. The relative changes in the maximum surface temperature (TMS) during the CDFW process corresponded to changes in welding pressures, indicating the potential of the thermal imaging method for monitoring and assessing this process. A preliminary investigation demonstrated that Al/Cu joints produced using welding pressures less than 88.9 MPa often displayed the presence of non-joined micro-regions at the Al/Cu interface and a significant thickness of interfacial Al2Cu (up to 1 µm). However, when friction pressure was set at 66.7 MPa, an increase in the forging pressure to 222.2 MPa eliminated the presence of non-joined micro-regions and reduced the thickness of Al2Cu to 0.5 µm on the average level. These Al/Cu joints achieved the highest joint efficiencies in terms of strength (100%) and ductility (61%). They exhibited an electrical conductivity higher than 92% of the theoretical value. A further increase in any welding pressure produced similar or deteriorated properties, accompanied by an increase in the consumption of raw materials and energy. Such turn of events was counterproductive to the original goal of increasing the efficiency and efficacy of the CDFW process
OPTICAL METHODS APPLIED FOR TESTING PIPE RING SPECIMENS
No full textThe Optical methods can be highly useful for analysing Pipe Ring Tensile Specimens (PRTS) since they offer an accurate and non-destructive method of evaluation. Optical technologies have several uses, such as Digital Image Correlation method (DIC method), thermal imaging camera, and 3D scanning. The DIC method is used to measure stresses and full-field displacements. DIC analyses a speckle pattern that is applied to the surface of the specimen and can provide detailed information on strain distribution, deformation gradients, and likely failure spots. An infrared thermal imaging camera can be used to detect defects in pipe specimens, such as
fractures or delamination, by tracking the distribution of surface temperatures. Temperature anomalies can indicate areas of intense stress or material degradation. A 3D scanner is a device that uses the shape, size, and texture of physical objects to digitise them into three-dimensional digital representations. The investigation focused on five distinct PLA PRTS. The study describes how to evaluate PLA PRTS using DIC method, thermal imaging camera, and a 3D scanner. The evolution of strain was monitored using the 3D Digital Image Correlation approach. Using a thermal imaging camera, the temperature field change in the PRTS was investigated during the test. In order to verify the cross-sectional shape of the PRTS after a fracture, 3D scanning was performed on each specimen
DIMENSIONAL ACCURACY OF SINTERED DENTAL METALWORK: EVALUATING 3D PRINTING PRECISION FROM INTRAORAL SCANS TO FINAL FIT
No full textThe precision of 3D printing in the fabrication of sintered dental metalwork is critical for successful clinical outcomes. However, during the initial trial of these metal components on the patient, a dimensional discrepancy often manifests itself, indicating a poor fit despite being modeled from precise intraoral scans. This necessitates additional corrections or reprinting, thus extending the duration of treatment, increasing costs, and raising concerns about the reliability of 3D printing and subsequent processing techniques. This study aims to quantitatively analyze the dimensional changes in sintered dental metalwork from the original intraoral scan to the final product and to evaluate whether these changes are influenced by the complexity of the metalwork design. Using a 3D scanner (Atos Core 200, GOM, Germany), the dimensions of the sintered metalwork were compared to the corresponding CAD models. Preliminary results indicate significant dimensional deviations, particularly in more complex designs, underscoring the need for improved accuracy in
the 3D printing process to enhance clinical outcomes and efficiency
Numerical Analysis of Optimal Hybridization in Parallel Hybrid Electric Powertrains for Tracked Vehicles
No full textTracked vehicles are integral for maneuvering diverse terrains, with hybrid propulsion
systems offering potential benefits in terms of fuel efficiency and performance. However, research
in hybrid electric tracked vehicles remains limited, thus necessitating a comprehensive analysis
to maximize their advantages. This study presents a numerical analysis focusing on optimizing
hybridization in speed-coupled parallel hybrid electric powertrains for tracked vehicles. A dynamic
programming algorithm and custom drive cycle are utilized to determine optimal hybridization
factors and assess parameter sensitivities. The study reveals that a hybridization factor of 0.48 is
optimal for speed-coupled parallel configurations. Furthermore, the sensitivity analysis underscores
the substantial impact of factors such as the engine displacement and bore-to-stroke ratio on the
fuel economy, with a 10% change in these parameters potentially influencing the fuel economy by
up to 2%, thus emphasizing the importance of thorough consideration during powertrain sizing.
Parallel hybrid configurations exhibit considerable potential for tracked vehicles, thus highlighting
the viability of choosing them over series configurations
Educational building renovation using green roof towards energy savings and decarbonization of cities
No full textThis paper presents an analysis of the possible application of green roof on an existing educational building with a flat roof, through an analysis of the degree of energy efficiency improvement and CO2 emission reduction. The goal of the paper is to show, through the preparation of the energy efficiency report and Energy passport, the green roof as an exceptional tool for ensuring sustainable development, decarbonization and improving the quality of life of people in urban areas. This is important because urban areas have limited space for green infrastructure and high level of pollution. The research also clearly defines the impact of green roof installations on energy savings with the share for heating of 15% and air quality contributing to the about 6% lower CO2 emission, with attached methodological explanations for their application. Economic analysis and profitability of the proposed project are also provided as an additional indication of the relevance of this type of practice. In the economic analysis, the key indicators of the profitability of the investment are studied, in this investigation, the net present value (NPV) and the payback period (PBP) of the green roof project. PBP of 22 years was obtained, but it should not be considered separately of the other benefits of green roofs, which are not measurable in money, such as lower pollution in cities, habitats for pollinators, additional green areas for people, prevention of floods, etc