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DEGRADATION OF THE SURFACE OF SINTERED SAMPLES BASED ON CORDIERITE AND TALC UNDER THE EFFECT OF CAVITATION
No full textIn the paper, the cavitation resistance of refractory cordierite samples with the addition of 10%, 15% and 20% talc, sintered at 1200⁰ C, was investigated. The quality control method of the obtained sintered samples was investigated using the ultrasonic vibration method with stationary sample according to the ASTM G 32 standard. The formation and development of damage to the surface of the samples was monitored using a scanning electron microscope and the level of damage to the surface of the samples was quantified using image analysis. The change in the mass of the samples as a function of the cavitation time was monitored and the cavitation rate was determined. By measuring the mass loss and morphological analysis of the pits formed on the surface of the sintered samples of the mixture of cordierite and talc, the mechanism of degradation and resistance to the effect of cavitation was monitored. The obtained results were compared with the results of earlier tests of cavitation resistance of sintered cordierite samples. It was shown that the addition of talc in the mixture with cordierite significantly improved the properties of the sintered material compared to sintered pure cordierite. Small mass losses, small surface damage of samples of sintered cordierite with the addition of talc, indicate the possibility of obtaining a refractory materials with imroved properties of resistance to the effect of cavitation. The tests were done primarily to see the potential application of this material in hydrodynamic conditions, and especially because of the strong corrosion resistance of these refractory materials. Tests have shown that the application of the ultrasonic vibration method is suitable for a quick assessment of the quality of sintered samples and a forecast of resistance and stability during exploitation under cavitation conditions
SIMULATION OF MEASUREMENT ON CMM BY IMPLEMENTING A DIGITAL TWIN MODEL
No full textThe purpose of this paper is to improve the quality of measurement inspection process, reduce and complete eliminate collisions, and quantitatively increase productivity by minimizing the time required for measurement. Digital twin models are becoming more significant in industrial environments as they enable monitoring, control, and simulation of measurements, while also offering the possibility of inspecting objects or processes in a digital environment. In this study, a digital twin model for the quality control of a prismatic part was created. To define and
display a realistic simulation in the digital space, the following were modeled: a coordinate measuring machine (Mitutoyo CRYSTA Apex), workpiece, and auxiliary equipment. The workpiece underwent an analysis of metrology for defined form and location tolerance, while for the virtual measuring machine, it was necessary to establish kinematic links between all subsystems of the machine. For the digital twin of the measuring machine to have consistent movement, it was necessary to define the connections between the coordinate systems of the workpiece and
the measuring probe, as well as between the workpiece and the measuring machine. The advantage of this digital twin model is that, in addition to off-line mode, it can be directly integrated (on-line mode) into complex technological systems
Sintering process in dentistry
No full textThe importance of sintering is explained in this abstract, with a focus on how it helps achieve the
precise fit, structural stability, and natural aesthetics that are necessary for dental restorations to
be effective. A crucial method in the creation of dental prostheses, especially dental bridges, is
the sintering process. Through a regulated heating procedure, dental ceramic particles are fused
together to create a final product that is both visually beautiful and extremely durable. The ideal
mechanical qualities, such as strength and biocompatibility, are ensured by the high-temperature
amalgamation of ceramic particles. A dimensional examination of the collected dental samples
can be carried out by the 3D scanning process, and a comparison with the 3D models that served
as their foundation is made. The 3D scanner used in this research is the Atos Core 200, while the
comparison with the 3D model was made in the GOM Inspect program (GOM Metrology GmbH,
Braunschweig, Germany). Based on the measurements obtained by 3D scanning, the average
deviations characteristic of individual technological processing procedures were obtained. This
approach enabled more precise model-making and savings on materials
A comparative analysis of algorithms for the determination of resonant-affected zones for surface mining and bulk material handling machines
No full textUsing two different approaches, identification of the resonant-affected zones
was performed over the domains of two variable parameters of the
superstructure of a stacker machine that was in the design stage – the
inclination angle of the discharge boom and the velocity of the belt conveyor,
which is the key parameter of the variable periodic excitation load caused
by the eccentricity of the discharge pulley of the conveyor. The first method
varies the velocity of the belt over the entire domain in fixed step increments,
whereas the second method searches for the boundaries of the resonantaffected zones around the resonant velocities of the belt by adaptively
varying the step size. In the first approach, the fixed step size was divided by
10 in each subsequent analysis until all zones were fully defined and the
results satisfied the predefined criterion of precision. Quality of the results
obtained by the two methods were compared with regards to precision and
time-to-completion. Although both methods have produced satisfactory
results, the step size needed to obtain the required degree of precision using
the fixed step approach has resulted in excessive computation times, with
debatable feasibility for practical application of such an approach
Theoretical Assessment of Agro-Waste for Biogas Production Based on Novel Methodology Related to Biochemical Potential
No full textAgricultural and waste biomasses present viable solutions for utilization in the energy sector, achieving sustainable and long-term transformation into energy and fuel. However, it is important to carefully evaluate the competing applications for these feedstocks, considering both short- and long-term stability. Biomass for biogas production in agriculture and waste management is used due to its availability and ease of handling. Considering everything mentioned, evaluating the most suitable raw materials for biogas production is crucial for meeting sustainability criteria and promoting biomass as an energy source. In this paper, an examination of different biomass sources as possible feedstock to produce biogas by applying a theoretical approach to the proximate and final analysis results of those materials is presented. Based on data from the raw material analysis, the theoretical biochemical methane potential (TBMP) for the considered samples was calculated. Furthermore, the mass and energy balance for the case study biogas plant was also performed. According to the obtained results, the considered feedstocks show the validity of their use for biogas production considering the fulfillment of the raw material minimum quantity, mandatory residue arrangement, and achieving higher efficiency of the energy conversion process
Analysis of Service Problems of Caustic Tanks Installed in Oil and Gas Plants
No full textThe paper deals with the one of the most general classifications of atmospheric tanks according to their roof type in oil and gas plants. An overview of recommended periods of inspection of storage tanks is given, together with their structural characteristics. Upon irregularities in the process of water purification, the caustic soda tank is prematurely open for inspection. Visual inspection of the major elements, ultrasonic thickness measurements, penetrant tests of welded joints, and checking the functionalities: cathodic protection system, level controller, electric heater, are performed on the tank. On that occasion, it is noticed that the electric heater is found distorted and inoperative. The damaged heater made of Incoloy 800 is carefully removed from its holder and a new heater is welded to the holder by GTAW procedure. The necessary NDE is performed and required electric parameters after repair welding are confirmed
Finite Element Analysis of product tanker deckhouses under severe sea state conditions
No full textRegulatory bodies for ships (i.e., classifications societies) generally require finite element analysis when
existing ship structures are modified or non-conventional structures are added onboard. On each of two sister
ships (product tankers), both classed and with an overall length of 183.2 m, deckhouse structures were
mounted on the decks after years of navigation. These deckhouses, made of standard shipbuilding steel
comprising plates and stiffeners, are intended to store ballast treatment systems due to the lack of internal
storage inside of ships. The deckhouses are subjected to various load combinations that simulate extreme
conditions ships can encounter, including roll, heave, and pitch. The loads considered consist of the weight of
the structure and its internal equipment, as well as dynamic loads such as wind velocity, seawater pressure on
the deckhouses’ walls, and accelerations due to the ship rolling in severe sea and weather conditions.
Therefore, finite element analysis is performed following the procedure outlined in Lloyd’s Register’s Rules and
Regulations for the Classification of Ships, using the Von Mises stress criterion to assess the structural response
of the deckhouses. Moreover, three scantling cases are considered, varying based on the addition of corrosion
allowances to the net thicknesses of elements. Since the requirement was to prevent a significant increase in
the total steel weight of the ship after the installation of the deckhouses, the analysis aimed to determine the
minimum scantlings necessary to withstand the loads.
The results indicated that some cases failed to meet the criteria, primarily due to large spans of stiffeners
lacking transversal support. It was particularly the case with the port side deckhouse (larger structure and
spans) in almost all loading and scantling cases, whilst the starboard deckhouse needed structural
modifications in critical areas to satisfy the requirement
On estimating convergence for Pickard sequences in quasi b-metric and rectangular quasi b-metric spaces
No full textIn this paper, using the same contractive condition as in [ 3], we give an estimate of the d(xn, x∗) for a sequence {xn} in a quasi b-metric space. In addition, we give another proof for the convergence of a sequence {xn}. Examples of estimation for Banach’s, Kannan’s, and Reich’s fixed point theorems are given. Following the same idea, in the second part of talk (paper) we shall introduce notion of the rectangular quasi b-metric spaces and present estimation in this class of spaces. At the end, we give some open problems
where research can be continued
RECENT ADVANCES IN THE FIELD OF BEEHIVE TEMPERATURE MONITORING
No full textThe most significant pollinator insect is the honey bee (Apis mellifera), which also provides honey and other
valuable products. The goal of smart apiculture is to assist beekeepers in remotely monitoring honey bee
colonies and recognising various colony states. Given that swarming can significantly reduce productivity, one
of the monitoring objectives through temperature measurement is the remote identification of this
phenomenon. Experiments show that before swarming, there is a warm-up phase of 1.5–3.4°C, approximately
20 minutes before takeoff, which varies from the usual range of 34–35°C in beehives. The temperature of
beehives was significantly impacted by the presence of bees. Hives missing bees had mean temperatures that
were 5.5°C lower and had wider temperature variations than hives with bees. Regardless of colony strength,
hives without bees attain their highest temperature earlier than hives with bees. Using wireless sensing
technologies, this apiculture method could be applied to monitor various bee colony parameters in real-time.
This would improve the detection of colony collapse disorder (CCD), which is an important issue in managing
the honey bee population. Machine learning algorithms are developed to predict temperature fluctuations in
bee colonies using daily thermal patterns with a root mean square error (RMSE) of less than 0.5%
ADITIVNE TEHNOLOGIJE KAO ALAT ZA UNAPREĐENJE PROCESA INJEKCIONOG PRESOVANJA
No full textU današnjem industrijskom okruženju, zahtevi za poboljšanjem kvaliteta proizvoda, većom efikasnošću procesa i potrebom za malim serijama uz smanje troškova, postavljaju izazove proizvođačima plastičnih proizvoda. Aditivne tehnologije, nude rešenja koja omogućavaju bržu izradu prototipa, prilagođavanje dizajna, a u poslednjih nekoliko godina i direktnu izradu alata. U početku ove tehnologije su bile limitirane samo na mali broj pretežno polimernih materijala pravljenih posebno za svrhu izrade prototpiova, međutim danas je spektar materijala značajno proširen i naročiti akcenat se stavlja na metalne materijale i temperaturno otporne polimere. U ovom radu biće analizirana mogućnost upotrebe aditivnih tehnologija za optimizaciju alata za injekciono presovanje na primerima upotrebe konformnih kanala za hlađenje kod metalnih alata, kao i fabrikaciju polimernih umetaka za izradu malih serija