Search Results (3,728)

This manuscript proposes a method for analyzing the stability of the behavior of a cyber-physical system (CPS) under conditions of potential destructive impact, considering the tasks it performs, which does not require labeled sets of abnormal data. The considered CPS has an autonomous decision-making system. The method was formalized in terms of the Markov decision-making process. Proposed metrics for assessing CPS behavior based on changes in its parameters were defined. They allowed classifying the operating mode into three classes: normal, abnormal, and uncertain. Evaluation results prove the efficiency of the proposed method. Despite the proposed method being tested on an unmanned vehicle (UV), it can also be applied to other CPSs, primarily to autonomous mobile robots (AMRs). Full article

The investigation of wave propagation in the geological environment is warranted, and will ultimately help to provide a better understanding of the response of subsoil to excitation. Frequently utilized physical modeling represents a simplification of the global natural system for the needs of the investigation of static and dynamic phenomena with regard to the time domain. The determination of appropriate model materials is probably the most important task for physical model creation. Considering that subsoil represents a crucial medium for wave propagation, an evaluation of suitable model materials was carried out. A plate load test with a circular plate is a non-destructive method for determining the static bearing capacities of soils and aggregates, which are usually expressed by the deformation modulus E_def,2 (MPa) and the static modulus of elasticity E (MPa). A lightweight deflectometer test was used to characterize the impact modulus of deformation E_vd (MPa), which is determined based on the pressure under the load plate due to the impact load. A representative propagation of the load–settlement curve for the PLT and the acceleration–time curve for the hammer drop test were investigated. The calculated E values were found to be in the interval between 2.6 and 5.7 kPa, and depending on the load cycle, the values of E ranged from 2.6 to 3.1 kPa. The modulus E from the hammer drop test was significantly larger than the interval between 10.6 and 40.4 kPa. The values of the dynamic multiplier, as a ratio of the hammer drop value to the PLT value, of the modulus E ranged from 4.1 to 13.0. The output of the plate load testing was utilized for the calibration of the finite element method (FEM) numerical model. Both the physical and numerical models showed practically ideal linear behavior of the mass. However, the testing of gelatin-like materials is a complex process because of their viscoelastic nonlinear behavior. Full article

On 6 August 2022, a fire devastated 80% of the Punta del Este Shopping Center in Maldonado, Uruguay. Originating in the kitchen of a supermarket, the fire ravaged the shopping center for 72 h before being brought under control. This article outlines the studies conducted to assess the fire’s impact on the building’s structure, as well as the strategies and rehabilitation project aimed at ensuring its stability and performance. An in-depth analysis of the concrete, reinforcements, and foundations was carried out using destructive and non-destructive testing. In total, over 150 concrete samples were collected for analysis, and the foundations were studied using indirect methods. Based on these analyses, actions were planned for each area, including structural repairs, reinforcements, or demolition. Due to the tight deadline for resuming commercial activity, special innovative structural solutions were designed to rehabilitate large severely damaged areas with the specific feature of avoiding demolition. This involved altering the static scheme of the structure, incorporating reinforcements and using slabs of the damaged structure as formworks. Complete demolition and subsequent reconstruction would have required timelines incompatible with the clients’ expectations, while the adopted solutions enabled the project to meet its objectives. Full article

Wind energy is one of the most rapidly growing sectors in renewable energy generation, with wind turbines being central to this expansion. Regular maintenance, particularly the inspection of wind turbine blades, is critical to ensure operational efficiency and prevent catastrophic failures. Conventional methods of blade inspection, including ground-based visual inspections, rope-access inspections, and cranes, are time-consuming, expensive, and often hazardous. In recent years, drone-based technologies have emerged as a promising alternative for wind turbine blade inspection. This paper provides a comprehensive review of current drone-based technologies for wind turbine blade inspection, highlighting their advantages, challenges, and future prospects. Full article

In this study, the mechanical performance and failure modes of cold-potted inserts within sandwich structures were examined, focusing on the influence of the potting radius, while maintaining constant insert radius and specimen characteristics. In this research, destructive testing was used to evaluate the pull out, load-carrying capacity, and failure mechanisms of the inserts. The methods of stiffness degradation and acoustic emissions (AE) were employed for structural health monitoring to capture real-time data on failure progression, including core buckling, core rupture, and skin delamination. The results indicated that increasing the potting radius significantly altered the failure modes and critical failure load of the insert system. A critical potting radius was identified where maximum stiffness was achieved. Beyond this point, insert fracture became the dominant failure mode, with minimal damage to the surrounding core and CFRP skins. Larger potting radii also led to reduced displacement at failure, increased ultimate loads, and elevated stiffness, which were maintained until sudden structural failure. Through detailed isolation and observation of each failure event and with the use of AE data, precise identification of system damage in real time was allowed, offering insights into the progression and causes of failure. Full article

This review examines the essential application of non-destructive testing (NDT) techniques in assessing the integrity and damage of composite materials used in aerospace engineering, focusing on polymer matrix composites (PMCs), metal matrix composites (MMCs), and ceramic matrix composites (CMCs). As these materials increasingly replace traditional metallic and alloy components due to their advantageous properties, such as light weight, high strength, and corrosion resistance, ensuring their structural integrity becomes paramount. Here, various NDT techniques were described in detail, including ultrasonic, radiographic, and acoustic emission, among others, highlighting their significance in identifying and evaluating damages that are often invisible, yet critical, to parts safety. It stresses the need for innovation in NDT technologies to keep pace with the evolving complexity of composite materials and their applications. The review underscores the ongoing challenges and developments in NDT, advocating for enhanced techniques that provide accurate, reliable, and timely assessments to ensure the safety and durability of aerospace components. This comprehensive analysis not only illustrates current capabilities but also directs future research pathways for improving NDT methodologies in aerospace material engineering. Full article

We propose herein a metamaterial (MM) dual-band THz sensor for various biomedical sensing applications. An MM is a material engineered to have a particular property that is rarely observed in naturally occurring materials with an aperiodic subwavelength arrangement. MM properties across a wide range of frequencies, like high sensitivity and quality factors, remain challenging to obtain. MM-based sensors are useful for the in vitro, non-destructive testing (NDT) of samples. The challenge lies in designing a narrow band resonator such that higher sensitivities can be achieved, which in turn allow for the sensing of ultra-low quantities. We propose a compact structure, consisting of a basic single-square split ring resonator (SRR) with an integrated inverted Z-shaped unit cell. The projected structure provides dual-band frequencies resonating at 0.75 THz and 1.01 THz with unity absorption at resonant peaks. The proposed structure exhibits a narrow bandwidth of 0.022 THz and 0.036 THz at resonances. The resonant frequency exhibits a shift in response to variations in the refractive index of the surrounding medium. This enables the detection of various biomolecules, including cancer cells, glucose, HIV-1, and M13 viruses. The refractive index varies between 1.35 and 1.40. Furthermore, the sensor is characterized by its performance, with an average sensitivity of 2.075 THz and a quality factor of 24.35, making it suitable for various biomedical sensing applications. Full article

Aircraft fatigue test is a critical step for new aircraft models to obtain certification. The primary task of fatigue test is to detect damage promptly and gather damage data. Therefore, to ensure the timeliness and effectiveness of non-destructive testing (NDT) data, it is essential to control and manage the quality of the NDT process in aircraft fatigue test. This paper, based on the characteristics and work features of NDT in aircraft fatigue test, aims to achieve the goal of timely damage detection by focusing on the five key aspects of NDT quality control, namely: personnel, equipment, materials, methods, and environment. It elaborates on the quality control process, identifies key aspects of quality management, and enhances the quality of NDT in aircraft fatigue test. Full article

This study focuses on selecting a suitable 3D printer and defining experimental methods to gather the necessary data for determining the optimal filament material for printing components of the VEX GO and VEX IQ robotic kits. The aim is to obtain the required data to identify an appropriate filament material and set 3D printing parameters to achieve the desired mechanical properties of the parts while maintaining cost-effectiveness. Another key objective is achieving optimal operational functionality, ensuring the required part performance with minimal printing costs. It is desirable for the modeled and printed parts to exhibit the required mechanical properties while maintaining economic efficiency. Another crucial aspect is achieving optimal functionality of the produced parts with minimal printing costs. This will be assessed by analyzing the impact of key 3D printing technology parameters, focusing in this research phase on material selection. The criteria for selecting filament materials include ease of printability under the conditions of primary and secondary schools, simplicity of printing, minimal need for post-processing, and adequate mechanical properties verified through experimental measurements and destructive tests on original parts from VEX GO and VEX IQ kits. The study analyzed various filaments regarding their mechanical properties, printability, and cost-effectiveness. The most significant practical contribution of this study is selecting a suitable filament material tested through a set of destructive tests, emphasizing maintaining the mechanical properties required for the real-life application of the parts. This includes repetitive assembly and disassembly of various robotic model constructions and their activation for demonstration purposes and applications of STEM/STEAM/STREAM methods in the educational process to achieve the properties of original components. Additionally, the study aims to set up 3D printing such that even a beginner-level operator, such as a primary or secondary school student under the supervision of their teacher or a teacher with minimal knowledge and experience in 3D printing, can successfully execute it. Further ongoing research focuses on evaluating the effects of characteristic 3D printing parameters, such as infill and perimeter, on the properties of 3D-printed parts through additional measurements and analyses. Full article

The calibration of a universal testing machine (UTM) verifies the accuracy of the system instruments responsible for obtaining force and displacement measurements. This process involves comparing the instrument to equipment that has already been calibrated to a known traceable standard. The limit of accuracy is then certified and the traceability of the measurements is determined. There are several internationally recognized standards that are used to calibrate the cross-head speed and displacement (ASTM E2658 and E2309, respectively), strain and load rate (ASTM E2309), measurement of tension, compression (ASTM E4) and dynamic force (ASTM E467). The current study aims to monitor the calibration status of UTMs through the implementation of acoustic methods. A methodology is developed whereby a reference sample is initially identified with suitable material properties, enabling it to be used continuously. The sample is used simultaneously with acoustic instruments to check its natural frequencies, which enables the monitoring of the UTM calibration status. An algorithm is developed that enables the user to interact with the system, thus forming an interface and helping the user to check the calibration status of the equipment. The entire system is validated to check if the equipment and the inbuilt algorithm can predict the calibration status of the machine. It was found that the geometric constraints imposed on the sample influence the output from the algorithm, and hence correct values should be fed to the system. Our sample never lost its elastic characteristics through continuous use, demonstrating that it can be used to continuously monitor the machine’s status. Full article

The increasing challenges related to the reliability and durability of steel pipeline infrastructure necessitate a detailed understanding of degradation and failure mechanisms. This study focuses on selective corrosion and erosion as critical factors, analyzing their impact on pipeline integrity using advanced methods, including macroscopic analysis, corrosion testing, microscopic examination, tensile strength testing, and finite element method (FEM) modeling. Selective corrosion in the heat-affected zones (HAZs) of longitudinal welds was identified as the dominant degradation mechanism, with pit depths reaching up to 6 mm, leading to tensile strength reductions of 30%. FEM analysis showed that material loss exceeding 8 mm in weld areas under standard operating pressure (16 bar) induces critical stress levels, risking pipeline failure. Erosion was found to exacerbate selective corrosion, accelerating degradation in high-stress zones. Practical recommendations include the use of corrosion-resistant materials, such as duplex steels, and implementing integrated monitoring strategies combining non-destructive testing with FEM-based predictive modeling. These insights contribute to developing robust preventive measures to ensure the safety and longevity of pipeline infrastructure. Full article

The interaction between moisture content and soil suction is commonly represented by a soil–water characteristic curve (SWCC). The direct measurement of water content can be easily achieved, but it usually requires a destructive method where the soil sample needs to be oven-dried. Hence, indirect measurement is commonly employed for monitoring purposes. The limitation of this approach is the variability in water content at the wilting point, particularly for plants in different types of soil. While the moisture content at the wilting point varies greatly, suction at the wilting point is typically around 1500 kPa despite varying slightly depending on the type of plant. However, suction measurement using a normal tensiometer is limited to 100 kPa due to cavitation. Hence, it is not sufficient to cover up to the wilting point. The focus of this paper is the establishment of a polymer-based tensiometer utilizing a 15 bar ceramic disc for the measurement of high suction. The suitability of the polymer-based tensiometer in measuring the soil suction of vegetative soil is conducted by performing a soil–water characteristic curve test on vegetative soil. The SWCC produced from the polymer-based tensiometer is verified using SWCC produced from a centrifuge test. The results show that the SWCCs from both polymer-based tensiometer and centrifuge tests are comparable. Hence, suction measurement using a polymer-based tensiometer is deemed reliable. This advancement in suction measurement technology is crucial for improving irrigation practices, optimizing water use, and enhancing agricultural productivity, which in turn contributes to environmental sustainability by minimizing water waste and ensuring efficient soil management. Full article

Ground-Penetrating Radar (GPR) has demonstrated significant advantages in the non-destructive detection of road structural defects due to its speed, safety, and efficiency. This paper proposes a three-dimensional (3D) reconstruction method for GPR images, integrating the back-projection (BP) imaging algorithm to accurately determine the size, location, and other parameters of road structural defects. Initially, GPR detection images were preprocessed, including direct wave removal and wavelet denoising, followed by the application of the BP algorithm to effectively restore the defect’s location and size. Subsequently, a 3D data set was constructed through interpolation, and the effective reflection data were extracted by using a clustering algorithm. This algorithm distinguished the effective reflection data from the background data by determining the distance threshold between the data points. The 3D imaging of the defect was then performed in MATLAB. The proposed method was validated using both gprMax simulations and laboratory test models. The experimental results indicate that the correlation between the reconstructed and actual defects was approximately 0.67, demonstrating the method’s efficacy in accurately achieving the 3D reconstruction of road structural defects. Full article

The aim of this study was to compare the mechanical properties of carbon-fiber-reinforced polymer (CFRP) composites produced using three popular technologies. The tests were performed on composites produced from prepregs in an autoclave, the next variant is composites produced using the infusion method, and the third variant concerns composites produced using the vacuum-assisted hand lay-up method. For each variant, flat plates with dimensions of 1000 mm × 1000 mm were produced while maintaining similar material properties and fabric arrangement configuration. Samples for testing were cut using a plotter in the 0° and 45° directions. Non-destructive tests (NDTs) were carried out using the active thermography method, demonstrating the correctness of the composites, i.e., the absence of structural defects for all variants. Static peel strength tests were carried out for samples with different directional orientations. The tests were carried out at temperatures of +25 °C and +80 °C. At room temperature, similar strengths were demonstrated, which for the 0° orientation were 619 MPa, 599 MPa and 536 MPa for the autoclave, vacuum and infusion variants, respectively. However, at a temperature of +80 °C, only the composite produced in the autoclave maintained the stability of its properties, showing a strength of 668 MPa. Meanwhile, in the case of the composite produced by the infusion method, a decrease in strength at an elevated temperature of 46.5% was demonstrated, while for the composite produced by the hand lay-up method, there was a decrease of 46.2%. For the last two variants, differential scanning calorimetry (DSC) analysis of epoxy resins constituting the composite matrices was carried out, showing a glass transition temperature value of 49.91 °C for the infusion variant and 56.07 °C for the vacuum variant. In the three-point static bending test, the highest strength was also demonstrated for the 0ᵒ orientation, and the bending strength was 1088 MPa for the autoclave variant, 634 MPa for the infusion variant and 547 MPa for the vacuum variant. The fatigue strength tests in tension at 80% of the static strength for the infusion variant showed an average fatigue life of 678.788 × 10³ cycles for the autoclave variant, 176.620 × 10³ cycles for the vacuum variant and 159.539 × 10³ cycles for the infusion variant. Full article

Sclerotinia sclerotiorum is a destructive pathogen responsible for sunflower sclerotinia rot, resulting in substantial yield and economic losses worldwide. Trichoderma species have demonstrated the capacity to inhibit plant pathogen growth through the production of secondary metabolites. However, there are fewer recent studies focusing on the application of Trichoderma metabolites in inhibiting S. sclerotiorum growth and development and controlling sunflower sclerotinia rot disease. Our results showed that five Trichoderma strains (SC5, T6, TN, P6, and TS3) exhibited mycelial growth inhibition higher than 60% in dual culture assays out of the 11 tested strains. The Trichoderma SC5 fermentation filtrate exhibited superior efficacy compared to other strains, achieving a 94.65% inhibition rate of mycelial growth on S. sclerotiorum, 96% inhibition of myceliogenic germination of sclerotia, and 81.05% reduction in the oxalic acid content of S. sclerotiorum, while significantly increasing the cell membrane permeability. In addition, the Trichoderma SC5 fermentation filtrate significantly decreased the activities of polygalacturonase and pectin methyl-galacturonic enzymes and even caused S. sclerotiorum hyphae to swell, branch, twist, lyse, and inhibited the production and development of sclerotia. Moreover, the Trichoderma SC5 fermentation filtrate downregulated genes expression that associated with the growth and infection of S. sclerotiorum. The control efficacies of the protective and curative activities of the Trichoderma SC5 fermentation filtrate were 95.45% and 75.36%, respectively, on detached sunflower leaves at a concentration of 8 mg/mL. Finally, the Trichoderma SC5 was identified as Trichoderma longibrachiatum through morphological and phylogenetic analysis. Our research indicates that the T. longibrachiatum SC5 can be considered a promising biological control candidate against S. sclerotiorum and controlling the sunflower sclerotinia rot disease, both in vitro and in vivo. Full article