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MECHANICAL CHARACTERIZATION OF 3D-PRINTED EXPERIMENTAL PRTS USING DIC METHOD
No full textThe main objective of this paper is to investigate the mechanical behaviour of 3D-printed Pipe Ring Specimen (PRTS) made of polymer materials, with a focus on the influence of infill density and specimen geometry on tensile performance. Two types of PRTS specimens were analysed—PRTS-T1 and PRTS-T2—manufactured using Fused Deposition Modelling (FDM) technology, with varying infill levels (60%, 90%, and 100%). An additional aim of the study is to assess the applicability and limitations of the Digital Image Correlation (DIC) method in characterizing surface deformations during tensile testing of non-standard geometries. Based on the observed fracture locations and the quality of strain field data, recommendations are made regarding specimen selection for further research. Another goal is to compare the experimental results of PRTS specimens with data from the literature concerning flat tensile specimens produced with similar 3D printing parameters. The comparative analysis includes tensile strength values, strain distribution, and deformation patterns, taking into account differences in cross-sectional areas and infill structures. The paper also aims to identify the optimal combination of specimen type and infill percentage that ensures valid and reproducible results while minimizing material usage and production time. This research contributes to establishing testing procedures for non-standard specimens in additive manufacturing and provides a foundation for the further development of experimental methodologies in the field of mechanical characterization of 3D-printed polymer components
APPLICATION OF SEM ANALYSIS IN THE EVALUATION OF SURFACE CHARACTERISTICS OF CONTEMPORARY PROSTHETIC MATERIALS AFTER PROFESSIONAL HYGIENE PROCEDURES
No full textScanning electron microscopy (SEM) offers a high-resolution method for detecting microstructural surface changes in dental materials caused by routine professional hygiene procedures. This in vitro study utilized SEM to investigate the effects of ultrasonic scaling and professional brushing on the surface microtopography of zirconia restorations, fabricated by CAD/CAM milling or veneered with ceramic. Specimens (n = 36; 4 × 4 × 2 mm) were obtained from 3Y-TZP-LA zirconia blocks and divided into four groups based on surface finish (polished or glazed) and fabrication method. Each subgroup was subjected to either ultrasonic scaling or brushing with an abrasive polishing paste for 1 minute, repeated in 10 cycles to simulate the effects of five years of clinical maintenance SEM imaging at 150×magnification (Model JSM-6390, JEOL, Japan) was performed before and after treatment to evaluate micromorphological changes. SEM allowed precise identification of surface defects, including microcracks, abrasive wear and glaze degradation. The most significant changes were observed in glazed samples exposed to ultrasonic scaling, with surface alterations measured at 88.31 μm for veneered zirconia and 45.38 μm for CAD/CAM-milled zirconia.The results demonstrate that standard professional hygiene procedures can significantly affect the surface integrity of glazed zirconia restorations. SEM analysis proved to be an essential diagnostic tool for early detection of clinically relevant surface damage, offering insights into material behavior and supporting the development of tailored maintenance protocols
Enhanced wave attenuation through inertial amplification in periodic beam-rigid body structure
No full textWe address the fundamental challenge of achieving low-frequency wave attenuation in periodic structures without increasing system mass -a critical limitation in current design of metastructures. Traditionally, low-frequency attenuation has been achieved through the use of local resonators, which can be tuned to a specific low-frequency range by increasing their mass. To overcome this trade-off, we investigate the influence of two inertial amplifiers with distinct configurations: one with auxiliary masses connected to both beam and main mass and another with auxiliary masses suspended between the main mass and a fixed support. The transfer matrix method, combined with the spectral element method, is employed to analyze how design parameters influence the dispersion properties of each system. Our findings show that purposeful structural design of these inertial amplifiers can lead to as much as 50% broader attenuation bands across both high and low-frequency ranges. We also demonstrate near-coupling phenomena between local resonance and Bragg scattering mechanisms, which result in an ultra-wide low-frequency band gap. This study provides a method for robust wave control in periodic structures made of elastic and rigid segments such as buildings and bridges, particularly for low-frequency, lightweight acoustic and seismic isolatio
Estimation of residual operability and energy efficiency optimization of oil purification column
No full textThis paper examines the process of oil distillation in upstream oil and gas facilities, along with the
main equipment involved. A vertical column, a key component of the stabilization system that has
been in operation for almost 20 years, was tested. The column was temporarily taken out of
service to conduct a detailed, non-destructive inspection. Due to its long-term operation, aging,
and exposure to corrosive environments—especially oil corrosion—it represents high-risk
equipment with potential environmental and financial consequences in the event of failure.
This study aims to determine the optimal operating mode to improve output product quality.
Ultrasonic thickness testing (UTT) was performed, revealing wall thinning in critical areas. The
maximum calculated corrosion rate was 0.0722 mm/year, and the remaining service life was
estimated at 26 years. Based on the risk-based inspection (RBI) analysis, the column falls into the
high-risk category, emphasizing the importance of optimized inspection planning. An RBI analysis
was conducted using API 581 methodology, classifying the column as high-risk equipment with
potential financial consequences exceeding €2.7 million per year. In parallel, four different
operating regimes were tested to optimize energy utilization and product quality. The optimal
regime achieved a heat transfer of 100.07 MW, minimal CO2 and H2O concentrations, and
maximum recovery of C3–C5 hydrocarbons. This paper highlights the importance of condition
monitoring, targeted inspection strategies, and energy optimization in extending equipment life
and reducing operational risks. This approach enhances reliability and cost-effectiveness in oil
and gas facilities while prioritizing environmental protection.451-03-136/2025-03/200105, 451-03-136/2025-03/200051, 451-03-136/2025-03/200066, 451-03-136/2025-03/ 200213, 451-03-137/2025-03/20010
Hybrid GA-ANFIS and PSO-ANFIS techniques for nonlinear DC motor system modeling
No full textThis research focuses on nonlinear modeling techniques for direct current (DC) motor, with permanent magnets in the stator, using optimized adaptive neuro-fuzzy inference systems (ANFIS). The traditional linear model fails to accurately represent the dynamics of a DC motor due to nonlinear friction effects. To address this limitation, a nonlinear model incorporating Tustin’s friction model is proposed and evaluated against experimental data. Despite improvements over the linear model, challenges remain due to the discontinuity introduced by the signum function in friction representation, necessitating smoother approximations like hyperbolic tangent for control applications. The nonlinear modeling approach also does not fully capture the dynamics of the real-world behavior of the object. To achieve a robust and accurate model across all operational conditions without approximations, three ANFIS variants are developed. These models employ diverse approaches to generate fuzzy rules, such as grid partitioning and fuzzy C-Means clustering. The second and third models undergo optimization using two different nature inspired optimization algorithms. Comparative analysis reveals that all ANFIS models yield superior performance, with GA-ANFIS on top, accurately predicting DC motor velocity under varying input conditions such as step, sinusoidal, and chirp signals. Experimental validation demonstrates that the optimized ANFIS model closely tracks the real-world behavior of the DC motor, offering promising prospects in every type of control, especially in direct inverse control in which the
system model is inverted and used as a controller. This approach enables precise control actions based solely on observed system dynamics, avoiding the pitfalls of approximation-based methods
Performance assessment and techno-economic analysis of the thermal plasma gasification of biomass using air and steam as gasification medium
No full textIn this study, a techno-economic analysis of biomass gasification using a thermal plasma with air and steam as gasification media is presented. The analysis includes a parametric evaluation of various operating parameters, including process temperature, equivalence ratio and steam-to-fuel ratio. The aim is to determine the optimum gas composition characterized by a high proportion of combustible components and minimal harmful by-products. The parametric study covered a temperature range of 500–2000 K, equivalence ratios of 0.1–0.7 and steam-fuel ratios of 0.5–2.5. The results show that the optimum process temperature is around 1200 K. Furthermore, the analysis shows that the best energy properties of the producer gas are achieved at the lowest gasification medium-fuel ratios. The energy analysis favors steam plasma gasification over air plasma gasification. When using air, the produced gas has a heating value of 9.42 MJ/Nm3 and an H2/CO ratio of 1.03, whereas when using steam as the gasification medium, the heating value of the gas is higher, amounting to 10.36 MJ/Nm3, and the H2/CO ratio is 1.74. The economic analysis also favors steam gasification and shows significantly lower costs for energy production, estimated at 47.5 €/MWh compared to 74.5 €/MWh for air plasma gasification. The sensitivity analysis also shows that under certain conditions, when biomass is available at minimal or no cost, the cost of producer gas by steam plasma gasification can fall below the market price of natural gas. These results underline the techno-economic advantages of steam plasma gasification in converting biomass into a competitive and sustainable energy source
Structural integrity assessment of oil storage tank: Non-destructive
No full textThis work presents the method for monitoring the integrity of oil methanol tanks located in Serbia and Norway. Considering the importance of safe operation of such equipment, it was necessary to use advanced non-destructive testing inspection for this purpose. The inspection, which involved state-of-the-art ultrasonic testing method, was completed in order to collect data required for evaluation of structural integrity and fitness for continued service of the tanks in question. Inspection and structural integrity analysis will include assessment of the most critical elements of these tanks, including their foundations, shell, roof and floor/bottom of the methanol tanks. This analysis included the calculation of thickness in various parts of the tanks, and it was determined that they were all within the allowed limits, implying that both tanks were safe for continued service
Self-tuning intelligent PID controller for robot manipulators
No full textThis article tackles the problem of tuning model-free intelligent PID controllers for nonlinear systems such as robot manipulators. Based on the ultra-local model formulation, intelligent PD position control parameters are tuned for each discrete time step. The Particle Swarm Optimization (PSO) is used to tune control parameters based on chosen objective function. Finally, the performance of the proposed tuning approach is verified through simulation and comparative analysis.No. 451-03-137/2025-03/200105 from 04.02.202
INFLUENCE OF INFILL DENSITY ON THE TENSILE STRENGTH OF 3D-PRINTED PLA SPECIMENS
No full textAdditive Manufacturing (AM), widely known as 3D printing, has significantly evolved, transitioning from model prototyping to the production of functional components. Fused Deposition Modeling (FDM), one of the most commonly used AM technologies, enables the fabrication of parts with varied m echanical properties depending on printing parameters. This study investigates the influence of infill density on the tensile strength of 3D printed PLA (Polylactic Acid) specimens. A series of specimens were designed in SolidWorks, prepared for printing u sing Wanhao Cura 18.04 software, and fabricated on a WANHAO Duplicator 6 printer. All samples were printed under controlled conditions, maintaining constant parameters such as layer height, shell thickness, and printing speed. The study focused on differen t infill densities (20%, 60%, and 100%). Tensile strength tests were performed following standardized procedures to evaluate the mechanical
properties of the specimens. The results demonstrate a direct correlation between infill density and tensile
strengt h, with higher densities exhibiting superior load carrying capacity. The findings contribute to the
optimization of 3D printing parameters for applications where mechanical performance is critical. Future
research may explore the effects of other factors s uch as build orientation, material, infill patterns, and layer
height to further enhance the mechanical properties of 3D printed components.Grant number 51 03 137/2025 03/ 20010
