Application of Digital Image Correlation for Strain Mapping of Structural Elements and Materials.

The strain gauge method and the digital image correlation (DIC) method are commonly employed for measuring strain in tested objects, including material specimens and structural elements. The optical method enables the assessment of 3D strain fields across the entire area of interest, achieved through cameras and advanced software. The study investigates both quasi-static strength tests and more advanced research of structures. It explores full-scale construction testing, featuring highly stressed components of new wagon designs. The paper reviews the benefits and challenges of using the DIC method to measure large-scale elements. Conducting full-scale object testing is characterized by significant complexity, often involving interactions between elements, complex loading conditions, and the influence of friction. Numerous factors affect the measurements. Therefore, to compare both methods, an initially standard shear by tensile test of CFRP composite was analyzed. The analysis of strain maps provides valuable visualization of deformation patterns occurring during construction loading. The strain gauge method was crucial for verifying the quality of the DIC measurements. The results obtained provide a detailed understanding of how the components behave, highlighting the versatility of digital image correlation technology. For strain values of 0.3% and above, a good match was obtained between optical and strain gauge measurements. Below this value, the results have less accuracy. The results obtained provide a detailed understanding of how the components behave, highlighting the versatility of digital image correlation technology. The error comparison and discussion between different measurement scenarios were conducted. The paper presents a developed methodology for measuring strain and displacement state in complex and crucial structural elements. The method can be applied to measurements of heavily loaded components used in the transportation industry; for example, in railways.

An Experimental Investigation of the Effects of Block Proportion on Bimrocks, Considering Different Block-to-Matrix Strength Ratios.

The rock block proportion is one of the most important factors affecting the mechanical properties of bimrocks. Under different block-to-matrix strength ratios, the influence of rock block proportion is different. To explore the influence of rock block proportion on the mechanical properties of specimens under different block-to-matrix strength ratios, a new indoor test method for making bimrocks was proposed. A uniaxial compression test and a direct shear test were carried out on specimens with different rock block proportions. The results show that this method can control the block-to-matrix strength ratio well, and the influence of rock block proportion is obviously different under different block-to-matrix strength ratios. The strong matrix sample will decrease significantly after reaching the peak compressive strength, while the weak matrix will decrease slowly after reaching the peak strength. The rock block proportion is negatively correlated with the uniaxial compressive strength of strong matrix samples (the reduction was 12.53%) and is positively correlated with the uniaxial compressive strength of weak matrix samples as a whole, but it changes when block proportion is more than 50%. With the increase in normal stress and rock block proportion increases from 30% to 60%, the shear failure zone of the weak matrix sample increases, and the cracks are inclined, while the strong matrix sample has more secondary cracks. The results of this study also show that the effect of volumetric block proportion (VBP) on the internal friction angle and cohesion of the sample is less related to the block-to-matrix strength ratio.

Ductility Variation and Improvement of Strain-Hardening Cementitious Composites in Structural Utilization.

Strain-hardening cementitious composite (SHCC) has the obvious advantages of excellent material properties such as its high tensile and compressive strengths, high tensile strain capacity, and excellent durability against multi-cracking performance with very fine crack widths. In particular, the multi-cracking performance of SHCC during structural utilization is obviously reduced compared to that of SHCC in uniaxial tension tests using dumbbell-shaped specimens of small size. The corresponding tensile strain capacity of SHCC during structural utilization is, thus, significantly decreased compared to that of SHCC in uniaxial tension tests. However, the reduction in the ductility of SHCC during structural utilization has not been sufficiently understood, and further study is required. This paper presents an experimental investigation into the ductility variation of flexural-failed and shear-failed SHCC members as well as the ductility improvement of SHCC members with steel reinforcement compared with that of SHCC in uniaxial tension tests using small-sized specimens. This study focuses on not only the decrease in the crack elongation performance of the SHCC material during structural utilization but also the increase in the crack elongation performance of SHCC members with steel reinforcement. The results demonstrate that the crack elongation performance of flexural-failed and shear-failed SHCC members is significantly reduced compared to that of SHCC in the uniaxial tension tests. Moreover, it was confirmed that steel reinforcement can effectively improve the SHCC member, increasing the strain-hardening capacity and multi-cracking performance. The load-carrying capacity of the flexural-failed SHCC member with steel reinforcement seemed to increase linearly with an increase in the reinforcement ratio, accompanied by an increase in the distribution of multiple fine cracks in the flexural-failed SHCC member with steel reinforcement.

Bridging Inferences and Reference Management: Evidence from an Experimental Investigation in Catalan and Russian.

This article focuses on the choice of nominal forms in a language with articles (Catalan) in comparison to a language without articles (Russian). An experimental study (consisting of various naturalness judgment tasks) was run with speakers of these two languages which allowed to show that in bridging contexts native speakers' preferences vary when reference is made to one single individual or to two disjoint referents. In the former case, Catalan speakers chose (in)definite NPs depending on their accessibility to contextual information that guarantees a unique interpretation (or the lack of it) for the entity referred to. Russian speakers chose bare nominals as a default form. When reference is made to two disjoint referents (as encoded by the presence of an additional altre/drugoj "other" NP), speakers prefer an optimal combination of two indefinite NPs (i.e., un NP followed by un altre NP in Catalan; odin "some/a" NP followed by drugoj NP in Russian). This study shows how speakers of the two languages manage to combine grammatical knowledge (related to the meaning of the definite and the indefinite articles and altre in Catalan; and the meaning of bare nominals, odin and drugoj in Russian) with world knowledge activation and accessibility to discourse information.

Dislodgement of Hydrogen Bubbles in Microchannels with Embedded Pillars: An Analytical, Experimental, and Numerical Study.

Microchannels with integrated pillars have enhanced the production capabilities and performance of various applications due to their high surface-to-volume ratio. However, emerging gas bubbles can become trapped, potentially limiting the functionality or efficiency of the device when scaled down to the low-micrometer scale. Understanding the conditions required to dislodge these bubbles is thus critical for optimizing microfluidic devices with complex physical behaviors. Here an analytical model is presented that outlines the dislodgment conditions and driving forces for such gas-liquid flows. These terms are derived from the gas-liquid interface properties, geometry, and processing parameters. As the density of the pillar arrangement is scaled down, the resistance to bubble dislodgment typically increases. Nevertheless, the bubble is compelled to dislodge at lower pressure loads when critical volumes are reached. This newly discovered effect is particularly noticeable in densely packed arrays and can be explained by the interplay of increased surface tension, geometrical restrictions, and volume-preserving forces. The analytical terms and effects are validated through novel experimental and numerical methods tailored for microchannels in the low-micrometer scale, showing strong agreement.

Experimental investigation of a real-time singularity-based fault diagnosis method for five-phase PMSG-based tidal current applications.

This paper presents a novel real-time singularity-based fault diagnosis method for tidal current applications, specifically utilizing a five-phase permanent magnet synchronous generator with trapezoidal back electromotive forces. The proposed method incorporates an innovative orthogonal signal generator through a second-order filter, enabling the extraction of detectable singularity signatures from phase current signals. The principle of the method is elucidated through step-by-step design procedures, outlining the indicator enhancement approach and adaptive thresholds employed for enhanced robustness and adaptability. Fault detection is performed based on the improved fault indicators and an adaptive threshold law, followed by immediate fault localization that is achieved via twice average operations of the phase currents. To demonstrate the effectiveness and efficiency of the proposed method, a comparative study is carried out with a classical mean current vector-based fault diagnosis method. A small-scale experimental platform emulating a tidal current application is established for a comprehensive evaluation of both methods. The experimental results highlight the superior fault diagnosis performance of the proposed method, particularly in detecting single and multiple open circuit faults in phases or switches, while exhibiting enhanced robustness against variations in torque and speed. The simplicity of implementation and rapid detection mechanism are principal merits for the proposed method.

Performance Analysis and Experimental Research of a Dual-Vibrator Traveling Wave Ultrasonic Motor.

In order to facilitate the widespread application of ultrasonic motors, it is essential to conduct a quantitative study aimed at enhancing their performance. The present paper provides a comprehensive theoretical analysis of an ultrasonic motor equipped with dual vibrators, enabling operation in both the single-driven and dual-driven modes, thereby enhancing versatility in terms of performance adjustment. This study provides a detailed examination of the motor's unique performance characteristics and its varying output responses to different driving signals. Experimental investigations are conducted in both the single-driven and dual-driven modes to validate theoretical predictions. The results demonstrate that the motor exhibits a maximum speed, torque, and power that are 1.59, 1.28, and 1.62 times higher than those of the single-driven stator, respectively. A conclusion can be drawn that the motor will attain the desired performance when operated in the appropriate driven mode.

Comparison of Two Generations of Thoracic Aortic Stent Grafts and Their Impact on Aortic Stiffness in an Ex Vivo Porcine Model.

Objective: Little is known about the cardiovascular changes after TEVAR and regarding the impact on aortic stiffness for different stent graft generations specifically, following changes in device design. The present study evaluated the stent graft induced aortic stiffening of two generations of the Valiant thoracic aortic stent graft. Methods: This was an ex vivo porcine investigation using an experimental mock circulatory loop. Thoracic aortas of young healthy pigs were harvested and connected to the mock circulatory loop. At a 60 bpm heart rate and stable mean arterial pressure, baseline aortic characteristics were obtained. Pulse wave velocity (PWV) was calculated before and after stent graft deployment. Paired and independent sample t tests or their non-parametric alternatives were performed to test for differences where appropriate. Results: Twenty porcine thoracic aortas were divided into two equal subgroups, in which a Valiant Captivia or a Valiant Navion stent graft was deployed. Both stent grafts were similar in diameter and length. Baseline aortic characteristics did not differ between the subgroups. Mean arterial pressure values did not change after either stent graft, while pulse pressures increased statistically significantly after Captivia (mean 44 ± 10 mmHg to 51 ± 13 mmHg, p = .002) but not after Navion. Mean baseline PWV increased after both Captivia (4.4 ± 0.6 m/s to 4.8 ± 0.7 m/s, p = .007) and Navion (4.6 ± 0.7 m/s to 4.9 ± 0.7 m/s, p = .002). There was no statistically significant difference in the mean percentage increase in PWV for either subgroup (8 ± 4% vs. 6 ± 4%, p = .25). Conclusion: These experimental findings showed no statistically significant difference in the percentage increase of aortic PWV after either stent graft generation and confirm that TEVAR increases aortic PWV. As a surrogate for aortic stiffness, this calls for further improvements in future thoracic aortic stent graft designs regarding device compliance.

A state-of-the-art review on experimental investigation and finite element analysis on structural behaviour of fibre reinforced polymer reinforced concrete beams.

Fibre reinforced polymer (FRP) composite is a useful material. It has been utilised to enhance the structural behaviour of reinforced concrete beams (RCB). It is also crucial to summarise the impact of FRP on various types of RCB properties. This study summarises the FRP usage's impact on the RCB's structural behaviour based on previous research by reviewing and discussing the experimental study and finite element analysis (FEA) results. Based on previous relevant literature reviews, the experimental investigation and FEA showed significant improvements in flexure, stiffness, young modulus, load-deflection, ultimate load capacity, fracture pattern, and failure mode when FRP was used in RCB production. This FRP composite material can be used as the external reinforcement for RCB due to its high strength capability, force, load, and corrosion resistance with adhesive and anchorage properties. Using FRP in RCB can benefit civil engineering by increasing its structural behaviour and performance, especially in construction industry.

Hydraulic Vehicle Damper Controlled by Piezoelectric Valve.

In this paper, an original construction of a vehicle vibration damper controlled by means of a valve based on piezoelectric actuator is presented and investigated. The presented valve allows us to control dissipation characteristics of the damper faster than in other solutions adjusting the size of the gap through which the oil flows between the chambers of the damper. The article also presents the results of the experimental investigation of the above-mentioned damper showing the possibility of changing the value of the damping force five times in about 10 ms by changing the voltage supplying the piezoelectric actuator. Based on these results, dissipative characteristics were determined which enabled the identification of the parameters of the damper numerical model. The article also presents the results of numerical investigations a vehicle model equipped with the developed dampers. The results showed that the developed damper controlled by the use of the piezoelectric actuator can significantly affect vehicle traffic safety by reducing the variation of vertical forces acting on the wheels. The results obtained are so promising that the authors undertook preparations to conduct road tests of a vehicle equipped with the developed dampers.

Prediction of outlet air characteristics and thermal performance of a symmetrical solar air heater via machine learning to develop a model-based operational control scheme-an experimental study.

This study develops reliable and robust machine learning (ML) models to predict the outlet air temperature and humidity and thermal efficiency of a solar air heater (SAH). Also, the application of predictive models for optimal control of the SAH operation is proposed. For this, the work contains three main parts: (a) a vertically-mounted symmetrical SAH was installed outside of a building room and operated throughout the winter of 2022. (b) By conducting experiments for five air mass flow rates, a large dataset with more than 62,500 sample points was collected. (c) Six input features containing time, environmental-related attributes, and SAH variables were applied to develop several state-of-the-art ML algorithms. To figure out the most accurate models for predicting output variables, the dataset was partitioned into three parts. Also, various modeling performance evaluation criteria were calculated and compared on the validation and test sets. Among these models, the gradient boosting machine algorithm based on LightGBM implementation achieved the best degree of generalization in modeling the target variables. The results demonstrated that the developed models obtained the lowest R-squared and the highest mean absolute percentage error of 0.9827 and 2.95%, respectively, on the test set. Moreover, the offline analysis of SAH operation based on the proposed control scheme demonstrated that 350 kWh of thermal energy can be generated during the application in the one-year winter season, 24% more than SAH operation without a model-based control strategy.

Experimental investigation of thermal efficiency and thermal performance improvement of compound parabolic collector utilizing SiO2/Ethylene glycol-water nanofluid.

A compound parabolic collector has been used in the present study to lower operating costs per unit of heat increase compared to other tracker concentrators. This type of collector has been given more attention in industrial and domestic applications in the temperature range of 60 to 300 °C. Also, to increase the thermal efficiency, nanofluid containing SiO2 nanoparticles in ethylene glycol-water hybrid base fluid (10-90 vol.%) have been used in three different volumetric fractions. The innovation of this present study includes the utilization of mentioned nanofluids for the first time in this collector, which has good stability and is cost-effective compared to other nanoparticles. In addition, the experimental measurement of thermal and hydraulic properties of nanofluids represents new aspects of the present study. The experiments used three volumetric fractions of 0.5%, 1%, and 1.5% under extensive solar radiation. Thermal performance of the collector at four volumetric flow rates of 1, 1.5, 2, and 2.5 Lit/min have been investigated according to ASHRAE standard 93-2010 (RA2014). According to the experimental data, the thermal efficiency of the collector improved by 5% to 11.6% when the nanofluid was applied. The maximum enhancement of the average Nusselt number of the nanofluid versus the base fluid at the volumetric flow rate of 1 Lit/min and the volumetric fraction of 1.5% was equal to 7.3%. Besides, nanofluid increased the pressure drop, and consequently, the pumping power slightly. Finally, considering both the impacts of heat transfer and pressure drop, performance evaluation criteria and overall efficiency for nanofluid have been analyzed. The results represented that in all volumetric fractions, the values of performance evaluation criteria and overall efficiency enhanced compared to the base fluid. This research provides researchers and engineers with important information to better understand the thermal and hydraulic parameters of the parabolic compound concentrator in the presence of nanofluid to improve its thermal performance. The results also highlight the potential of using SiO2 nanoparticles to improve the thermal efficiency of solar collectors despite their low thermal conductivity compared to other conventional nanoparticles.

Numerical Simulation and Experimental Investigation on Two Strengthening Schemes of Cantilever Brackets.

Cantilever brackets have been widely used in buildings to provide support for all kinds of pipes. In order to improve the bearing capacity of cantilever brackets, two types of reinforcement schemes are proposed, one is to sleeve a pipe, and the other is to add a haunch. Their mechanical properties are studied by numerical simulation and experimental investigation. First, the non-linear finite element (FE) simulation analysis was carried out, and the structural bearing capacity, stress distribution, and failure modes were discussed. Then, the full-scale model tests were completed to provide validation of the FE analysis. On this basis, a comparison of the FE results and test results of three kinds of cantilever brackets was discussed in detail. The results show that two reinforcement schemes can enhance the bearing capacity of the cantilever bracket significantly by 38.3% and 25.9%, respectively, and they are applicable for the reinforcement of existing cantilever brackets.

Influence of the Physical State of Microencapsulated PCM on the Pressure Drop of Slurry in a Circular Channel.

Phase Change Material (PCM) is mainly used in thermal energy storage. The addition of small PCM particles to the working fluid circulating in the heat exchange systems allowed to increase the amount of transported energy thanks to the use of latent heat-the heat of phase change. Encapsulating PCM in microcapsules avoids the disadvantages of PCM emulsions and makes the resulting slurry an attractive heat energy carrier. The paper presents the effect of the aggregate state of PCM enclosed in microcapsules on the flow resistance of the slurry through a rectilinear tubular channel. The tests were carried out with the use of a tube with an internal diameter of 4 mm and a measuring section length of 400 mm. A slurry of 21.5 wt.% PCM microcapsules (MPCM) was used as the working fluid in distilled water. A slurry with temperatures of 18.4 °C (PCM encapsulated in a solid state), 26.1 °C (PCM is in a phase change), and 30.5 °C (PCM in a liquid state) flowed through the measuring section. The mass flow rate of the MPCM slurry reached 70 kg/h (Remax = 2150). It was shown that the higher the Re number, the higher the value of the flow resistance, and the more clearly this value depended on the temperature of the slurry. Detailed analyses indicate that the observed changes were not the result of a change in the viscosity of the slurry, but its density depending on the state of the PCM. Significant changes in the density of the slurry in the range of the phase transition temperature are the result of significant changes in the volume of the microcapsule containing the phase change material in different aggregate states.

Analytical Model of the Frictional Heating in a Railway Brake Disc at Single Braking with Experimental Verification.

A one-dimensional thermal problem of friction was formulated, taking into account the contact pressure increase at the beginning of the process. The obtained solution to this problem allows for the quick calculation of the transient temperature distribution in a railway brake disc during single braking application. In order to validate the developed model, the experimental tests were performed for two friction pairs consisting of the cast iron brake disc and pads comprising two composite materials. Theoretical results were compared with the data measured by thermocouples embedded in the brake disc during the full-size dynamometer tests. The maximum temperature values found based on the analytical solution are convergent with the corresponding empirical data. The consistency of the results obtained for two friction couples demonstrates the usefulness of the proposed computational model.

Experimental Investigation and Numerical Simulation of a Self-Wiping Corotating Parallel Octa-Screw Extruder.

An octa-screw extruder (OSE) is equipment for pelletizing, blending, and mixing polymers and composites. In this study, the degree of resin filling, residence time distribution (RTD) of molten resin, and temperature profile in the octa-screw extruder were evaluated both experimentally and numerically. An intermeshing corotating parallel octa-screw kneading extruder was used for the experiments. For the comparison study, the results obtained from this extruder were compared with the twin-screw extruder. High-density polyethylene was selected as the material for extrusion. Meanwhile, a numerical code, based on a 2.5 D finite element method derived from the Hele-Shaw flow model, was developed to simulate the octa-screw extrusion process. The empirical outcomes suggest that octa-screw extrusion exhibited a narrower RTD of the molten resin compared with the twin-screw extrusion, suggesting better extrudate quality. The octa-screw extrusion also showed a lower temperature profile than twin-screw extrusion. The results of the simulation were also found to be in good agreement with experimental measurements. Experimental and numerical investigations of an OSE enable detailed comprehension and visualization of resin distribution in the entire length of the OSE, thus providing advantages in terms of process optimization.

Mode II Behavior of High-Strength Concrete under Monotonic, Cyclic and Fatigue Loading.

An economically efficient yet safe design of concrete structures under high-cycle fatigue loading is a rather complex task. One of the main reasons is the insufficient understanding of the fatigue damage phenomenology of concrete. A promising hypothesis states that the evolution of fatigue damage in concrete at subcritical load levels is governed by a cumulative measure of shear sliding. To evaluate this hypothesis, an experimental program was developed which systematically investigates the fatigue behavior of high-strength concrete under mode II loading using newly adapted punch through shear tests (PTST). This paper presents the results of monotonic, cyclic, and fatigue shear tests and discusses the effect of shear-compression-interaction and load level with regard to displacement and damage evolution, fracture behavior, and fatigue life. Both, monotonic shear strength and fatigue life under mode II loading strongly depend on the concurrent confinement (compressive) stress in the ligament. However, it appears that the fatigue life is more sensitive to a variation of shear stress range than to a variation of compressive stress in the ligament.

Multigene Expression Programming Based Forecasting the Hardened Properties of Sustainable Bagasse Ash Concrete.

The application of multiphysics models and soft computing techniques is gaining enormous attention in the construction sector due to the development of various types of concrete. In this research, an improved form of supervised machine learning, i.e., multigene expression programming (MEP), has been used to propose models for the compressive strength (fc'), splitting tensile strength (fSTS), and flexural strength (fFS) of sustainable bagasse ash concrete (BAC). The training and testing of the proposed models have been accomplished by developing a reliable and comprehensive database from published literature. Concrete specimens with varying proportions of sugarcane bagasse ash (BA), as a partial replacement of cement, were prepared, and the developed models were validated by utilizing the results obtained from the tested BAC. Different statistical tests evaluated the accurateness of the models, and the results were cross-validated employing a k-fold algorithm. The modeling results achieve correlation coefficient (R) and Nash-Sutcliffe efficiency (NSE) above 0.8 each with relative root mean squared error (RRMSE) and objective function (OF) less than 10 and 0.2, respectively. The MEP model leads in providing reliable mathematical expression for the estimation of fc', fSTS and fFS of BA concrete, which can reduce the experimental workload in assessing the strength properties. The study's findings indicated that MEP-based modeling integrated with experimental testing of BA concrete and further cross-validation is effective in predicting the strength parameters of BA concrete.

Experimental Investigation of the Apparent Thermal Conductivity of Microencapsulated Phase-Change-Material Slurry at the Phase-Transition Temperature.

The article presents the results of detailed studies of the thermal conductivity of the water slurry of microencapsulated PCM (mPCM) and slurry based on water-propylene glycol solutions. The starting product, MICRONAL® 5428 X, which contains about 43% microencapsulated paraffin with a transformation temperature of 28 °C, was mixed with the base liquid to obtain slurries with mass fractions of mPCM of 4.3, 8.6, 12.9, 17.2, 21.5, 25.8, 30.1, 34.4, 38.7, and 43.0%. Detailed measurements were carried out in the temperature range of 10-40 °C. It was found that: (a) an increase in the temperature of the slurry caused an increase in its thermal conductivity, both when PCM was in the form of a solid and a liquid; (b) the thermal conductivity of the mPCM slurry when the PCM was in liquid form was greater than the thermal conductivity of the slurry when the PCM was liquid; (c) during the phase transformation, a significant increase in the thermal conductivity of the slurry was observed, and its peak occurred when the temperature of the slurry reached the temperature declared by the manufacturer at which the phase-transition peak occurs.