Experimental Test Results Research Articles

Development of Deployable Reflector Antenna for the SAR-Satellite, Part 3: Environmental Test of Structural-Thermal Model

The concept of synthetic aperture radar (SAR) has the advantage of being able to obtain high-quality images even when the target area is at night or covered with obstacles such as clouds or fog. These imaging capabilities have led to a rapid increase in demand for space SAR imagery across a variety of sectors, including government, military, and commercial sectors. The SAR-based deployable reflector antenna was developed in this series of paper. The satellite performance is influenced by the aperture size of an antenna. To improve the image acquisition performance, the SAR antenna has the configuration of several foldable CFRP reflectors. In this paper, the experimental investigation of the Structural-thermal model deployable reflector antenna is performed. During the launch condition, the satellite and payload are subjected to the dynamic load. In the STM phase, the acoustic test was conducted to evaluate the structural stability of the deployable reflector antenna within the acoustic environment. The sinusoidal vibration test was implemented to investigate the fundamental frequency for inplane/normal directions and evaluate the structural stability of reflector antenna. By using experimental data obtained from the thermal-balance test, the well-correlated thermal analysis model was established to execute the orbital thermal analysis. The experimental results of the environmental test in STM phase show that the deployable reflector antenna has structural stability for the structural/thermal environments. The configuration of the deployable reflector antenna determined in STM phase can be applied to the qualification model.

Superior energy storage capacity of polymer-based bilayer composites by introducing 2D ferroelectric micro-sheets

Dielectric polymer capacitors suffer from low discharged energy density and efficiency due to their low breakdown strength, small dielectric constant and large electric hysteresis. Herein, a synergistic enhancement strategy is proposed to significantly increase both breakdown strength and dielectric constant while suppressing hysteresis, through introducing 2-dimensional bismuth layer-structured Na0.5Bi4.5Ti4O15 micro-sheets and designing a unique bilayer structure. Excitingly, an ultra-high discharged energy density of 25.0 J cm−3 and a large efficiency of 81.2% are achieved in Na0.5Bi4.5Ti4O15-poly(vinylidene fluoride-co-hexafluoropropylene)/Na0.5Bi4.5Ti4O15-polyetherimide bilayer composites under a dramatically enhanced breakdown strength of 8283 kV cm−1. Finite element simulations along with experimental test results demonstrate that greatly improved breakdown strength is ascribed to uniform and horizontal alignments of Na0.5Bi4.5Ti4O15 sheets (~1–2 μm) in the matrix and interface effect of adjacent layers with large dielectric differences, which effectively inhibit electrical tree evolution and conduction loss. This work provides a strong foundation for developing high-performance polymer-based energy storage devices.

Influence of Resin Grade and Mat on Low-Velocity Impact on Composite Applicable in Shipbuilding

In this study, the composition and mechanical properties of composites designed for shipbuilding are described. Four different composites were designed and fabricated by the research team, using quadriaxial glass fiber fabric (eight layers in all composites), two different resins (the epoxy resin SikaBiresin® CR82 with the hardener CH80-2 or the polyester resin Enydyne H 68372 TA with Metox-50 W as the accelerator), and a middle layer of Coremat Xi 3 (only applied in some composites). The experimental results of low-velocity impact tests are also discussed, including the graphics force (displacement) and absorbed energy (displacement and velocity). The displacement and composite quality were evaluated through several parameters, such as maximum force, absorbed energy, and maximum displacement. Impact tests were carried out using four impact energy values (50–200 J), with an average impact velocity in the range of 4.37 ± 0.05 m/s. Only partial penetrations were obtained for all tested composites. For the low energy tests (50 J), the four composite materials were not well differentiated by graph shapes and parameter values, but for the higher energy tests, the composites containing Coremat Xi 3 displayed better behavior, having Fmax reduced with 10.8% to 29.08%. The higher absorbed energy of these composites can be explained by the plateau generated by the force from a longer impactor displacement in contact with the composite. The results generated in this study confirm the suitability of the designed composites for shipbuilding applications. Still, the composites have light differences in terms of energy absorption in low-velocity impact and a significant reduction in maximum force.

Investigation of 3D steel frames with a reduced beam section and various web-opening shapes under internal column loss

ABSTRACT The sudden loss of columns due to abnormal loads demonstrates a remarkable example of a localized failure that might ultimately result in the progressive collapse of the complete steel-framed structures. In this study, finite element (FE) simulations are implemented by utilizing ABAQUS-Explicit to investigate the progressive collapse of two-storey steel reduced beam section (RBS) frames with web openings. The reliability and accuracy of the FE models are validated by comparing the obtained results with currently available experimental test results. A numerical investigation is conducted on twenty-eight RBS frames, each with a distinct web opening form (i.e. circular, square, and hexagon holes), different sizes of (D = 75, 90, and 105 mm), and varying distances of (25, 50, and 100 mm) from the center of the flange-reduced to the web opening. The failure modes, load-displacement characteristics, and development of catenary action are evaluated. The results showed that the specimens with square holes showed a greater degree of damage and lower load-carrying capacity compared with the specimens that have circle and hexagonal holes. In addition, an increased opening size resulted in a decrease in load-bearing capacity at small distances, thereby resulting in an increased capacity at a large distance.

Turning Agricultural Biomass Ash into a Valuable Resource in the Construction Industry—Exploring the Potential of Industrial Symbiosis

This paper presents a circular business model (CBM) designed to promote the valorization of agricultural biomass ash for producing an alternative binder in construction, aiming to reduce CO₂ emissions and landfill waste. The circular economy framework emphasizes regeneration and restoration to minimize resource and energy use, waste generation, pollution, and other environmental impacts. Aligned with these principles of sustainability, the construction industry, energy sector and food processing industry can establish a shared interest through industrial symbiosis. In the proposed CBM, waste from one industry becomes an input for another. The model leverages industrial symbiosis by using sunflower husk ash (SHA) as an alternative hydroxide activator for alkali-activated materials. A case study of companies in the Republic of Serbia that produce SHA as waste forms the basis for this model, featuring promising results of experimental testing of three alkali-activated mortars produced by activating ground-granulated blast furnace slag (GGBFS) with different SHA contents (15, 25 and 35 wt% GGBFS), instead of commercially available hydroxide activators. The potential of SHA as an alternative activator was assessed by testing flow diameter and compressive strength at 7 and 28 days of curing. The highest 28-day compressive strength was attained for the addition of 25% SHA (28.44 MPa). The promising results provided a valid basis for CBM development. The proposed CBM is stream-based, resulting from merging and upgrading two existing industrial symbioses. This study highlights the benefits of the CBM while addressing the challenges and barriers to its implementation, offering insights into the possible integration of agricultural biomass ash into sustainable construction practices.

Asymmetric hysteresis characteristics of magnetorheological elastomer embedding the tilt chain-like structure on the translational shear test: experiment and modeling

Abstract The Magnetorheological Elastomer (MRE) with tilt chain-like structure can significantly enhance the magnetorheological effect, but its hysteresis nonlinearity in the stress-strain responses is still unclear, especially the effect of the chain-like structure angle, which is essential for effective designs of controllable MRE-based devices. In this study, the hysteresis characteristics of the tilt chain-like structure MRE in the stress-strain curve of the translational shear test are investigated through the experiment and modeling. The experimental results of shear testing indicated that the stress-strain relationships of MRE with the tilt chain-like structure show an asymmetric hysteresis loop together with an obvious offset, which is different from the isotropic MRE and anisotropic MRE with the symmetric chain-like structure. In order to describe the asymmetric hysteresis loop in the translational shear characteristic, a stop operator-based modified Prandtl-Ishlinskii (PI) model is established considering a hyperbolic-tangent envelope function. The comparisons between model-predicted and measured data demonstrate that the established modified PI model can accurately describe the asymmetric hysteresis loops of MRE with different chain-like structure angles for wide ranges of excitation conditions and magnetic fields.

A Constitutive Model for Anisotropic Sand Considering Fabric Evolution Under Proportional and Non‐Proportional Loadings

ABSTRACTA critical state plasticity model is proposed to describe the anisotropic sand behaviour under both proportional and non‐proportional loading conditions. An evolving fabric tensor is introduced into the model to reflect the influence of fabric anisotropy on the stress‐strain relation of sand. By employing a fabric‐dependent plastic flow direction, the non‐coaxial response can be simulated in a simple way. A non‐proportional loading mechanism is incorporated to consider the plastic deformation induced by the stress increment tangential to the yield surface. The influence of accumulative plastic strain on the dilatancy function and plastic modulus is properly considered, enabling the model to reasonably capture the evolutions of volumetric and deviatoric strains under both drained and undrained principal stress axes rotation. The model was validated based on the simulations of experimental results for monotonic loading and pure principal stress axes rotation tests covering a wide range of conditions.

Durable, Transparent, and Superhydrophobic Film Design for Flexible Substrate

Transparent superhydrophobic films/coatings have recently gained significant attention in the solar energy field due to their ease of preparation, low cost, self‐cleaning process, and high effectiveness in reducing dust adhesion to the surface. Compared to the rigid glass cover, the organic one has an advantage of flexibility and light weight, but the dust deposition impact is more serious. The aim of the present study is to design a transparent and superhydrophobic film with good durability on the organic glass surface, to recover the module efficiency reduction caused by dust deposition. Based on a soft photolithography and hot‐pressing process, periodic microcavities are prepared on the organic glass surface as an armor structure, and hydrophobic SiO2 nanoparticles are sprayed into the microcavities to achieve anti‐reflection and superhydrophobicity. The experimental test results show that the designed film possesses a large contact angle around 160°, a sliding angle of 3°, and a high visible transmittance over 90%. The unique armor structure design greatly improves the wear resistance of the film, and after encountering harsh conditions such as sandpaper friction, water flow impact, acid immersion, UV exposure, and repeatable bending, it still maintains excellent superhydrophobicity.

Vibration prediction model and vibration characteristics of mining riser used in deep-sea gas hydrate extraction based on deep-learning

During the deep-sea gas hydrate mining riser operation, the vibration prediction is obtained using a simplified theoretical model, and its accuracy cannot be effectively guaranteed. Deep learning methods can effectively solve this problem. Therefore, a three-dimensional vibration prediction model for the deep-sea gas hydrate mining riser is established using a long short-term memory network based on deep-learning, which can be trained with the help of the vibration data of the mining riser obtained in the field, and realize the advance prediction of the vibration response of the mining riser in the later period. In order to effectively verify the correctness of the model, a similar principle is used to develop an experimental rig for simulating the vibration of the mining riser under the excitation of internal and external flows. The experimental test results are compared with the model prediction results, and the decision coefficient (R2) reaches 99%, which verifies the correctness of the prediction model. Moreover, to further verify that the model can achieve vibration prediction of the deep-see mining riser, the energy method and Hamilton's principle are used to establish a theoretical model of gas–liquid–solid three-phase flow-induced vibration of the deep-sea hydrate mining riser. The results of the predictions in the later period are compared with the results of the theoretical model calculations. It is found that the coefficient of determination (R2) reaches 94.59%, which further verifies the effectiveness of the deep-learning prediction model. On this basis, the vibration responses of the mining riser are predicted under different shear flows, heave motion parameters of platform, lifting flow rate, hydrate abundance, and hydrate particle size. The influences of operational and structural parameters on the vibration response of the mining riser are investigated, and the vibration characteristics of the mining riser are revealed. The study results provide a theoretical foundation and a predictive modeling tool for the safety of hydrate mining risers.

Digital-image Correlation and Cohesive Fracture Analysis of Fibre-reinforced Concrete Experiments: The Sergipe Test

Fibres are added to the concrete mix to improve its tensile strength and fracture properties, and they are used in several engineering applications. Therefore, fracture energy is a well-known quantity worth measuring. Some experiments in the technical literature are designed to quantify fracture energy. This paper proposes a new experiment to analyze the mechanical properties of fibre-reinforced concrete, named the Sergipe test. Such experiment consists of a square hollowed specimen submitted to a flexural test, where tensile cracks appear in different locations. Digital image correlation was used to analyze the cracking behaviour and crack opening displacement (COD). Regarding the experimental results of the Sergipe test, both specimens reached similar force-displacement and force-COD results despite different cracking locations at the specimens’ bottom. Such characteristics might indicate the suitability of the proposed experiment for fracture energy measurement. Regardless, the proposed experiment may be a benchmark for future non-linear models. To analyze such conditions, the well-established cohesive fracture model implemented in ABAQUS® is used to reproduce the experimental observations numerically, achieving good accuracy. Keywords: Cohesive fracture, Digital image correlation, Fracture energy, Fibre-reinforced concrete, Sergipe test.

Study on the influence of TiO2 nanoparticles on the breakdown voltage of transformer oil under severe cold conditions.

The modified nanoparticles can significantly improve the insulation characteristics of transformer oil. Currently, there is a lack of research on the actual motion state of particles in nanofluid to further understand the micro-mechanism of nanoparticles improving the insulation characteristics of transformer oil. In this study, the nanofluid containing 0.01g/L of TiO2 with a particle size of 20nm is prepared using the thermal oscillation method. Breakdown voltage tests are carried out. The experimental test results show that adding nanoparticles can significantly reduce the breakdown probability of transformer oil. The more the water content, the less the enhancement effect of the nanofluid on breakdown voltage. The higher the temperature, the stronger the enhancement effect of the nanofluid on breakdown voltage. Finally, the polarization process of nanoparticles and the trajectory of charged particles in the transformer oil under different electric fields are simulated using COMSOL to further analyze the influence mechanism of nanoparticles on the insulation characteristics of transformer oil. The simulation results show that under the action of the electric field, nanoparticles polarize and generate charge shallow traps to adsorb electrons, reducing the high-speed free charges in the oil, and indirectly increasing the breakdown voltage.

EXAMPLE OF EQUIPMENT DESIGN BY ASSESSING THE TECHNICAL CONDITION OF SEALING ELEMENTS OF ANTI-BLOWOUT MECHANISM

The materials of the article consider examples of calculations and selection of technical solutions for modernization of the design: the spot preventer was improved by establishing an indicator by which the position of the preventer piston can be observed; the reliability of the anti-blowout equipment used in well drilling was assessed. When introducing the modernized design of the universal preventer, the reliability of operation, the service life between overhauls, durability and maintainability of the preventer are increased. The reliability of the obtained results is evidenced by their mutual consistency, correspondence to the literature data, correlation of theoretical calculations with the results of experimental studies and positive results of industrial tests. The obtained results correlate with previously known ones, which confirms the validity of the scientific provisions, conclusions and recommendations formulated in the work.

Fatigue Behaviour of PA66 GF30 at Different Temperatures.

A comprehensive experimental investigation to understand the mechanical properties and fatigue behaviour of glass-reinforced polyamide (PA66 GF30) at different temperatures is presented in this paper. The specimens for quasi-static and fatigue testing were machined from previously extruded plates, where two orientations were considered: (i) the extrusion direction (ED) and (ii) the direction perpendicular to extrusion (PED). Both the quasi-static and fatigue tests were performed under different temperatures (22 °C and 100 °C). The fatigue tests were performed in a load control regime under pulsating loading (R = 0.1) to create S-N curves for all the temperatures and loading directions. The experimental results of the quasi-static tests showed that the test specimens manufactured in the extrusion direction have better mechanical properties when compared to those of the specimens manufactured perpendicular to the extrusion direction. Furthermore, the analysis of the quasi-static tensile test results showed that tensile strength, yield strength, and the modulus of elasticity are significantly dependent on the temperature and deteriorate when the temperature is increased from 22 °C to 100 °C. The results of the fatigue tests showed that at both the temperatures (22 °C and 100 °C), the samples produced in the direction of extrusion exhibited higher fatigue strength than those produced perpendicular to the direction of extrusion. For all the sample orientations, the fatigue strength decreased significantly with increasing temperature. The obtained experimental results could be very useful when designing and dimensioning different dynamically loaded engineering components made of PA66 GF30 subjected to high temperatures.

Experimental Determination of the Equivalent Moment of Inertia and Stresses of Aluminium Profiles with Thermal Breaks

This paper presents the results of experimental tests and computer simulations on the stiffness of composite aluminium mullions used in unitised façades. The elements analysed were subjected to bending in order to simulate the actual operating conditions of aluminium façades subjected to significant wind pressure or suction loads. The basic mechanical and physical properties of the materials from which the analysed type of aluminium façade is made (Aluminium EN AW-6060 in the T66 temper and polyamide PA66 25GF), the test method, and the results obtained are described. As a result of the tests, equivalent moments of inertia of the composite profile (aluminium profile with the thermal break) were determined, which are strongly dependent on the strength of the connection between the individual elements, the asymmetry of the cross-section, and the properties of the thermal break. Strain measurements carried out using FBG (Fiber Bragg Grating) strain sensors installed in the profiles under tests allowed for determining the actual stress values of the aluminium profiles under consideration. The results obtained were compared to theoretical (numerical) values, indicating discrepancies at higher load values. The methodology presented in this article is to be used to monitor the deformation of the aluminium façade mullions of HRB (High-Rise Buildings).

Simulation of Load–Sinkage Relationship and Parameter Inversion of Snow Based on Coupled Eulerian–Lagrangian Method

The accurate calibration of snow parameters is necessary to establish an accurate simulation model of snow, which is generally used to study tire–snow interaction. In this paper, an innovative parameter inversion method based on in situ test results is proposed to calibrate the snow parameters, which avoids the damage to the mechanical properties of snow when making test samples using traditional test methods. A coupled Eulerian–Lagrangian (CEL) model of plate loading in snow was established; the sensitivity of snow parameters to the macroscopic load–sinkage relationship was studied; a plate-loading experiment was carried out; and the parameters of snow at the experimental site were inverted. The parameter inversion results from the snow model were verified by the experimental test results of different snow depths and different plate sizes. The results show the following: (1) The material cohesive, angle of friction, and hardening law of snow have great influence on the load–sinkage relationship of snow, the elastic modulus has a great influence on the unloading/reloading stiffness of snow, and the influence of density and Poisson’s ratio on the load–sinkage relationship can be ignored. (2) The correlation coefficient between the inversion result and the matching test data is 0.979, which is 0.304 higher than that of the initial inversion curve. (3) The load–sinkage relationship of snow with different snow depths and plate diameters was simulated by using the model parameter of inversion, and the results were compared with the experimental results. The minimum correlation coefficient was 0.87, indicating that the snow parameter inversion method in this paper can calibrate the snow parameters of the test site accurately.

Comparative Study of Granite and Expanded Clay Aggregate as Backfill Materials for Masonry Vaults.

The paper presents the results of experimental and numerical tests on barrel vaults with backfill material. The thickness, internal span, and rise of the vaults were 125 mm, 2000 mm, and 730 mm, respectively. In experimental studies, vaults with backfill of expanded clay aggregate or granite aggregate were tested. Moreover, three types of extrados finishing were considered in the experiments: masonry with flush joints, PVC film, and steel angles attached to the bricks. The numerical simulations increased the number of cases analyzed by conducting a parametric analysis for four additional backfill materials with varying bulk density or internal friction angle, as well as modifying the friction coefficient at the backfill-vault interface for each of the analyzed materials. The main goal of the analyses was to investigate the impact of the bulk density, the internal friction angle of the backfill material, and the friction coefficient between the backfill and the vault on the load-bearing capacity of the buried vault. Both the laboratory tests and numerical simulations indicate a significant impact of the internal friction angle, bulk density of the backfill materials, and the finishing method of the extrados of the vault on the load-bearing capacity of buried vaults.

Compressive Load Capacity of Concrete Structures Made of Hollow Blocks with Voids Filled with Concrete of Various Features.

A masonry made of hollow concrete blocks in modern constructions differs from the traditional one in that the empty space (up to 70%) makes it possible to create complex high-strength load-bearing structures by filling the voids with monolithic or reinforced concrete. The aim of this study was to examine specimens of concrete structures made of hollow blocks with voids filled with concretes with various features. The research methodology is based on the results of numerical and experimental tests. Laboratory studies were conducted to determine the influence of the concrete filling on strength, deformability and the nature of destruction of the experimental specimens. The numerical analysis was performed on the basis of FEM with the use of the ANSYS 2021 R1 software. The method for determining the load capacity of multi-component structures using strain diagrams of constituent materials has been improved. There is strong agreement between the numerical and experimental results for all masonry prisms. Additionally, a good correlation was observed between the experimental results and the analytical calculations performed using the proposed methodology.

A study on the effect of crack orientations, crack types and SHPB characteristics on the failure behaviour of pre-cracked sandstone rock specimens

The present study aims to understand the experimental and numerical behavior of intact and pre-cracked fine-grained sandstone specimens under indirect dynamic tensile loading conditions. The dynamic experimental analyses are carried out using the split Hopkinson pressure bar (SHPB) device to determine the tensile strength of sandstone rock. In addition to the dynamic tests, the physical, petrological, and mechanical tests under static loading of the sandstone rock are also studied. Thereafter, a three-dimensional (3D) finite element (FE) numerical model is developed, and a strain rate-dependent modified Drucker Prager constitutive model is used to validate the numerical model with the indirect dynamic tensile experimental test results. The validated parameters are then used to determine the behavior of pre-cracked sandstone specimens through numerical simulations. Two sets of numerical models with diametral cracks and cross-sectional cracks are introduced into the intact rock specimens. The orientation of the crack is changed from 0° to 90° and the numerical analyses are performed for 0°, 30°, 45°, 60°, 75° and 90° crack orientations with respect to the loading axis of the bars in the SHPB setup. Along with crack orientations, the loading rate is changed with varying gas gun pressures for the two sets of numerical models. The stress-strain responses are retrieved from the center and tip of the pre-crack introduced in the sandstone specimen. A comparative analysis is conducted for the responses obtained at the center and tip of the diametral and cross-sectional cracks and the results are stated herein.

Improved Method for the Calculation of the Air Film Thickness of an Air Cushion Belt Conveyor.

The air film thickness is an important parameter of an air cushion belt conveyor, which directly affects the compressed air supply power and operating resistance of the system. Therefore, it is important to calculate the bottom thickness of the gas film accurately in the design stage. A calculation method for the thickness of a conveyor air cushion was derived based on the mathematical model of the air cushion flow field for a multi row uniformly distributed air cushion structure. Meanwhile, the algorithm was validated based on a Fluent 3D flow field numerical simulation and experiments. Through verification, it was found that due to the algorithm's assumption that the increase in the gas flow rate only existed at the axis of the gas hole, there was a sudden change in the calculation results of the gas flow rate at the axis of the gas hole. The sudden change in the gas flow rate had caused the calculation results of the air cushion thickness to experience abrupt and discontinuous changes. Furthermore, the calculation method for air cushion thickness was revised based on the verification results. Compared with the experimental test results, the average error of the calculation results of the algorithm proposed in this paper was 14.27%.

Evaluation of biomass‐based cook stoves in Ethiopia: A transition strategy from conventional to modern cook stoves

AbstractPerformance improvement of cookstoves has a vital role in reducing indoor air pollution and deforestation. In this study, biomass‐based cook stoves onsite data survey and experimental approaches were carried out to evaluate the performance of different cook stoves. Based on this feasibility research, it was shown that firewood accounted for 75% of the fuel type usage. The results of several studies and experimental performance testing indicated that the efficiency of cook stoves for 3‐stone, lakech, mirt, gonze, tikikil, and pyrolysis stoves was 10%, 25%, 48%, 50%, and 76%, respectively. Merely 87 out of the total 1986 families with kebeles had improved cookstoves; the remaining households used 3‐stone stove types. According to the study, the pyrolysis stove had the lowest fuel consumption rate and cooking time, while the 3‐stone stove had the greatest fuel consumption rate and cooking time. The improvement stove reduced emissions, and the highest emission reduction stove was the gasifier stove, with a magnitude of 1.229 tons CO2/HH/Year. Among cooking stoves, gasifier stoves have a great advantage in producing energy and biochar.