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Elastic metamaterials with double negativity can manipulate the propagation of elastic waves at sub-wavelength scales by inducing multiple resonances to achieve different negative effective parameters. Numerous efforts have been made to control the dynamic behavior by directly tuning the frequency range of double negativity in elastic metamaterials. This study examines the impact of tensile loads on double negativity in relation to ligament inclination angle. The findings will aid in the direct tunability of double negativity in single-phase chiral metamaterials. The study examines a simple single-phase four-ligament chiral unit with low-order double negativity. The presence of double negativity was verified through band structure analysis and calculation of the four effective dynamic parameters. Additionally, the effects of two geometrical factors on the frequency ranges of negative parameters were investigated through parametric scanning. The results indicate that the frequency range of double negativity reaches its maximum at a ligament inclination angle of around 45° and disappears as the angle approaches 65°. Given that the ligament inclination angle of the unit cells can be easily altered by external tension, this intriguing outcome is leveraged to achieve the emergence and vanishing of double negativity. This characteristic is confirmed through the examination of negative refraction phenomena via simulation examples. [ABSTRACT FROM AUTHOR]

This study presents photothermal imaging results of subsurface material defects within fiber metal laminates utilizing the virtual wave concept. Therefore, we theoretically analyze the propagation of the virtual wave signal in a hybrid composite laminate via the method of images. For provoking local material damage, the hybrid composite sample is subjected to a defined impact loading. The results obtained from photothermal defect imaging, utilizing rectangular laser pulse excitation, are compared with results obtained from 3D x-ray computed tomography. To sum up, we demonstrate a fast, non-invasive, and easily interpretable reconstruction of defects within macroscopic hybrid composite laminates based on the virtual wave concept. [ABSTRACT FROM AUTHOR]

As the main merits, self-stabilization and no magnetic resistance make the high-temperature superconducting (HTS) magnetic levitation technology a crucial area for high-speed magnetic levitation development. To guarantee a stable operation of superconducting magnetic levitation systems, the dynamic characteristics of superconducting bulk materials occupy a significant place. However, in the previous research, there is still a lack of a simulation method that can describe 6 degree of freedom (DOF) motion of the superconductor. In this paper, an electromagnetic–thermal–dynamic coupling calculation model was established first. Then, the damping characteristics of 5-DOF superconducting levitation were experimentally tested, and the response analysis of the superconductor under 1–20 Hz excitation was carried out to explore the coupled motion relationship between the various degrees of freedom of the superconductor. In addition to the above, the operating conditions and primary resonance intervals that should be avoided by the HTS maglev system were identified. Additionally, a numerical simulation was conducted to investigate the dynamic response of the HTS maglev system under impact loads. All in all, this study explored the temperature rise conditions of superconducting bulk materials under excitation force through magnetic-thermal-force multi-physics coupling research. This 6-DOF model can provide a comprehensive simulation method for superconducting maglev systems in superconductor's motion behavior, attitude, and thermal state monitoring. [ABSTRACT FROM AUTHOR]

The behavior of energetic materials is significantly influenced by the spatial distributions of microstructure heterogeneities and voids. We pursue the concept of Functionally Graded Energetic Materials whose microstructure features (e.g., grain size, grain volume fraction, void size, and void volume fraction) change spatially such that they may allow the behavior of the materials to be tailored. We explore using gradients in the density of voids to alter the detonation behavior of a polymer-bonded explosive (PBX) echoing PBX9501 with HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) grains and Estane binder. Five cases, two graded void distributions from 1% to 10% and 10% to 1% by volume along the length of the sample, and three uniform distributions matching the lowest (1%), average (5.5%), and highest (10%) void densities are considered. An Arrhenius reaction burn model is used to account for the chemical kinetics of HMX. Different detonation behaviors are obtained from the same graded sample when impact loading is from 1% void end and from the 10% void end as well as from the uniform cases. The SDT (shock to detonation transition) behaviors are analyzed in terms of the run distance, the time duration and shock velocity changes over the SDT process. The computational results are presented in the context of available experimental data for PBX9501 with which agreement is obtained through a parametric study. Overall, it is shown that gradients in microstructures of PBX can lead to SDT behaviors different or not obtainable from microstructures without gradients, thereby offering a mechanism for designing and tailoring new materials. [ABSTRACT FROM AUTHOR]

A single-layer and double-layer corrugated core sandwich structure consisting of carbon fibre–reinforced polymer (CFRP) panels and aluminium alloy core layers was designed. Numerical simulations were carried out in HyperMesh/LsDyna, and the simulation results of single-layer and double-layer corrugated sandwich structure were compared with the experimental results to verify the reliability of the proposed numerical model. Compared with the results of single-layer and double-layer corrugated sandwich structure, the superiority of a double-layer corrugated sandwich structure in anti-collision performance is verified. Considering the effects of impact energy and impact position on impact force, energy absorption capacity, and failure mode, a series of low-velocity impact finite element simulations was carried out. It was found that the main failure mode of composite laminates included fibre damage, matrix damage and delamination, and core buckling. At the same impact position, the higher the impact energy, the greater the initial slopes of the contact force-time and absorbed energy-time curves, the higher the peak force, and the larger the energy absorption capacity. Under the same impact energy, when the impactor hit the wave crest of the sandwich structure, the damage to the structure was small; however, the maximum impact force on the structure was large (∼8 kN). [ABSTRACT FROM AUTHOR]

In engineering, soft rock is often damaged by dynamic loads such as dynamic compaction, vibrating compaction and blasting, resulting in varying degrees of damage. To understand the compressive response, fracture characteristics and energy dissipation characteristics of red bed soft rock under different dynamics, we carried out a series of dynamic impact tests by the separated Hopkins pressure bar system. The experimental results show that the dynamic peak stress, critical strain and toughness of red bed soft rock increase with the increase in strain rate with the increase in strain rate, which ranges from 37 to 102 s−1. Specifically, the dynamic compressive strength of red bed soft rock at 98 s−1 is 4.63 times that of the quasi-static average. As the strain rate increases, the fracture characteristics: integrity, slightly split and pulverized, and the size of fragments decrease and the number of fragments increases. When the strain rate exceeds the critical value 72 s−1, the fracture characteristics are pulverized. The energy dissipation density increases with the strain rate and increases faster when the strain rate exceeds the critical value. The energy utilization first increases and then decreases, when the strain rate is 88 s−1, the maximum utilization rate is 38%. [ABSTRACT FROM AUTHOR]

This paper investigates the modal parameter identification technique utilizing a drop impact load. A 12-DOF mathematical model of a Railway Vehicle System (RWVS) was constructed, followed by theoretical calculations, simulation analysis, and tests with four different drop impact loads. The responses to these loads were inspected through FFT, and the modal frequencies of the RWVS were determined by the Peak Picking (P-P) method. The simulation demonstrated that four types of drop impact loads can activate the bounce, pitch, and roll modes of the RWVS. The theoretical calculation and simulation analysis revealed that the maximum error of modal frequency identification is no greater than 6.5%. The experimental results verified that the drop impact excitation method can be used to identify the modal parameters of a complex railway vehicle system, which is highly beneficial for the design and verification of the vehicle structure. [ABSTRACT FROM AUTHOR]

Conventional sensors can detect the various physical and chemical changes that occur during deformation and the states of materials with a high accuracy. However, almost all existing sensors are bulky and stiff, making them highly susceptible to failure when used in large deformation-compliant structures. By contrast, despite their relatively-low resolution and accuracy, the demand for flexible and stretchable sensors used in detecting human motion and vital signs has drastically increased. There are several types of stretchable sensors that contain functional materials such as carbon nanotubes (CNTs). These stretchable sensors have different working principles and applications based on the attributes of their core components. Several electrical signals are used in the measurement of the different physical parameters such as the electrical resistance and capacitance. Triboelectric nanogeneration or voltage signals that can be identified under contact or impact loading conditions are employed in some measurement methods. Additionally, an array of microstructures with a special shape that is directly related to movement and deformation detection, as well as conductive nano-particles that are elaborately aligned along a certain direction for specific sensor applications, are used in the other methods. In this study, a review of the recently-developed high-performance stretchable sensors made from functional materials using new sensing mechanisms for wearable robot applications is provided. [ABSTRACT FROM AUTHOR]

Composite overwrapped pressure vessels are designed to contain fluids that operate under high pressures. In addition to internal pressure, the design needs to account for out-of-plane loading in the form of low-velocity impact. In this study, a numerical analysis of four models of composite overwrapped pressure vessels with different stacking sequences is performed. A three-dimensional explicit finite element model using multi-layer stacked shell elements was used in the impact zone region to obtain reasonable computation time. Utilizing the bilinear traction-separation law, cohesive zone elements were used to simulate the delamination failure and as bonding between eight layers of CFRP covering the aluminum liner. The simulation results were then validated using drop-weight impact tests, which revealed that the response of contact force to impact time was comparable for both types of analysis. Prediction of failure was carried out by assessing the quantity of energy absorbed by the CFRP layers and was confirmed by shell element data that failed during simulations. In addition, the Hashin damage model confirmed that the matrix tensile failure mode was the predominant failure mode for all discussed impact scenarios. Model-A with Al + [90]8 stacking sequence was found to have the highest impact resistance based on the prediction of the composite's failure area and the energy absorbed by the CFRP layers. Furthermore, it was found that COPVs with combinations of helical and hoop sequences tend to have larger areas of delamination due to high interlaminar shear stress between the CFRP layers. [ABSTRACT FROM AUTHOR]

In the present research, glass and basalt fiber-reinforced polypropylene composites' behaviour in quasi-static and dynamic conditions is studied. Composites were fabricated by vacuum assisted Compression molding method. Composites failure under quasi-static tension and compressive conditions was studied along with its failure behaviour under low-velocity impact and super-sonic shock loading under dynamic conditions. The study results showed that basalt fiber-reinforced polypropylene (Basalt/PP) composite's tensile and compressive strength is higher than glass fiber-reinforced polypropylene (Glass/PP). The Basalt/PP showed no penetration against low velocity impact (LVI) with negligible deformations till 50 J. However, the Glass/PP perforated at 50 J with various failure patterns occurring at back side. The fiber-matrix interface adhesion plays an important role in super-sonic shock loading by absorbing shock wave energy due to ductile nature of polypropylene and the two composites absorbed energy via matrix and fibers failure, no brittle failure of laminates occurred under shock loading. [ABSTRACT FROM AUTHOR]

Polygonalization is a typical non-uniform wear phenomenon that affects the performance and comfort of the vehicle/track system. Therefore, the vehicle system performance could be strictly troubled by polygonal damage close to the wheel circumference at the wheel/rail contact. A 3D vehicle/track an EMU type train consisting of 8 coupled vehicles model has been established. The coupled model car body and bogie frame are considered rigid and integrated with the flexible wheelset, rail, and slab track to investigate the elastic deformation caused by the impact load induced by the wheel polygonalization. The flexible track can be incorporated into the multi-body vehicle model using the movable reference frame formulation. Uncertainty parameters are presented, such as passenger weight, wind force, coefficient friction, and suspension variation. The proposed research is validated based on the existing research work and shows excellent agreement. The simulation result deliberated the vertical wheel-rail force, wheelset acceleration, rail acceleration, rail displacement, and slab track acceleration. The results of this study show that as the wheel polygonal damage amplitude increase, the value of wheel/rail normal forces and the dynamic vibrational response of the wheelset axle increase. Additionally, polygonal wear-induced impact stresses may cause the wheelset axle to resonate. When wheel polygonal damage amplitude and uncertainty parameters are corporate into the system dynamics, the maximum magnitude of the wheelset, rail, and slab track acceleration increases. Besides, the train failure degree is comparable to the polygonised wheel harmonic order, defect parameters, and amplitude of out-of-roundness. [ABSTRACT FROM AUTHOR]

In sharp contrast to prefabricated cracks, the damage to rock masses resulting from external disturbances such as excavation disturbances and tectonic movement varies substantially as to the incidence, density, and magnitude of defects. The growth ratio of the energy dissipation density proportion D(Rω (α)) of the damaged rock under impact loading is closely related to the static damage factor D(α) and is theoretically explored based on the Weibull distribution in this paper. Sandstones with varied damage levels after distinct static precompression, as described by CT imaging, are used to evaluate the impact load of different driving pressures. In addition, a high-speed camera and geometric fractal are used to exhibit the ejection and fragmentation characteristics of the pulverized sandstones after impact loading. The experimental outcomes confirm the theoretical study where the function of D(Rω (α)) involving D(α) obeys the Weibull distribution, and the D(Rω (α)) slowly rises with the expansion of the damage factor. With the increase of either the damage level or driving pressure of the sandstone, the number of pulverized rocks, the fragmentation degree, and the D(Rω (α)) all increase. These results further advance rock dynamic theory and corroborate the energy evolution, ejection, and fragmentation characteristics of damaged sandstone under impact loading. These results can also serve as references for rock dynamic risk mitigation under dynamic catastrophes.. [ABSTRACT FROM AUTHOR]

Large-scale high-speed granular avalanches can be catastrophic; however, small-scale model tests cannot reproduce the high-speed impact effect, resulting in barrier designs lacking detailed knowledge considering the prototypical dynamic conditions of granular avalanches (e.g., high moving velocities and varied material volumes). In this paper, a well-designed centrifuge model is adopted to reproduce high-speed granular avalanches with variable flow velocities and material volumes, and a calibrated DEM model is also used to offer further insights. The results indicate that under high-speed impact conditions, the effect of granular volume on the pressure distribution pattern dominates, but its influence on the impact loading rate is less obvious. To estimate the high-speed impact force, a constant pressure coefficient of 1 can provide a reasonable estimation for the dynamic component if boulder impacts are excluded, and the static component can be calculated using the weight of the dead zone based on the assumption of a static state of the dead zone. In addition, considering the transition of the impact pressure distribution model caused by different granular volumes and flow velocities, a rectangular pressure profile is suggested for barrier design against high-speed dry granular avalanches when the peak total impact force is adopted as the design load. [ABSTRACT FROM AUTHOR]

This investigation examines the influence of braking on the reliability of bituminous pavements. For this purpose, different loading conditions of a two-axle truck are simulated using vehicle dynamics software. Individual response surface methodology models to predict critical strain values are developed for various thickness and modulus values and loading combinations. Monte Carlo simulations are then used to generate random variabilities of input parameters, and the reliability is estimated accordingly. Three different cases are simulated. In the first case, it is assumed that all the vehicles impact the pavement by braking, and the reduced reliability is found to vary between 99.8% and 1.2% for the different loading and braking conditions. In the second case, the allowable load repetitions for fatigue damage are computed for a given reliability of 90% and are found to vary between 24 and 1 million standard axle (MSA). In the third case, different combinations of braking conditions are investigated, and the reliability is estimated. [ABSTRACT FROM AUTHOR]

In this work, the response of an ammonium perchlorate (AP)‐hydroxyl‐terminated polybutadiene (HTPB) composite material under impact loading is presented, utilizing computational cohesive finite element method (CFEM) simulations that are validated with drop hammer experiments. This study examined the impact behaviour of AP crystal sizes between 200 and 400 μm by varying impact velocities between 3 and 10 m/s. Based on the outcome of CFEM simulations, analysis of variance (ANOVA) tests and a response surface method (RSM) were utilized to construct a mathematical model approximating the relationships between simulation inputs and outcomes. Both computational and experimental results show that the local strain rate has a considerable positive correlation with crystal size, and the rate of temperature change has positive correlations with both crystal size and impact velocity. Further, it was observed that stiffness and compression energy are the primary factors to variances in local strain rate and rate of change of temperature. RSM has been found to be an effective tool for modelling impact responses of materials under varying experimental conditions. [ABSTRACT FROM AUTHOR]

This study investigates the nonlinear dynamic response of an auxetic sandwich structure under impact load. The core is made of a micro-cellular auxetic structure. The main point of interest is studying the micro-cellular core properties' effects on the structure's nonlinear dynamic response. First, the mechanical properties of the micro-cellular auxetic core are introduced based on modified strain gradient theory (MSGT), followed by experimental and numerical validation. Then, Hamilton's principle is applied to derive the sandwich structure's nonlinear governing partial differential equations. Lastly, Galerkin's method paved the way to achieving the final solution. So as to perform frequency-response analysis, the four-dimensional averaged equations are obtained using the perturbation method. In order to carry out experimental validation, a nanosecond laser system is used for micro-cellular auxetic sample fabrication, and the tensile tests are carried out per ISO 6892 standard. The comparison between the experimental and the theoretical results indicates an excellent agreement among the results. It can be concluded that MSGT plays a significant role in the mechanical properties and the nonlinear dynamic response of the micro-cellular auxetic structures. The present study is applicable in the field of protective panels, sensors, and energy harvesters. [ABSTRACT FROM AUTHOR]

Creating lightweight and impact-resistant box structures has been an enduring pursuit among researchers. A new energy-absorbing structure consisting of a bionic gradient lattice-enhanced thin-walled tube is presented in this article. The gradient lattice and thin-walled tube were prepared using selective laser melting (SLM) and wire-cutting techniques, respectively. To analyze the effects of gradient pattern, mass ratio, diameter range and impact speed on structural crashworthiness, low-speed impact at 4 m/s and finite element simulation experiments were conducted. The study demonstrates that the design of inward radial gradient lattice-reinforced thin-walled tubes can effectively enhance structure's energy-absorption efficiency and provide a more stable mode of deformation. It also shows a 17.44% specific energy-absorption advantage over the uniformly lattice-reinforced thin-walled tubes, with no significant overall gain in peak crushing force. A complex scale evaluation method was used to determine the optimum structure and the structure type with the best crashworthiness was found to be a gradient lattice-filled tube with a thickness of 0.9 mm and a slope index of 10. The gradient lattice-reinforced thin-walled tube suggested in this investigation offers guidance for designing a more efficient thin-walled energy-absorption structure. [ABSTRACT FROM AUTHOR]

This paper introduces a unique finite element analysis (FEA) technique designed to predict elastic response in polymer matrix composites (PMCs). Extensive research has been conducted to model the manufacturing process of multiple 'L'-shaped components, fabricated from SPRINTTM materials (GLP 43 and GLP 96) at two thicknesses (15 mm and 25 mm). Three distinct FEA methodologies were utilised to determine the impact of thermal loads and rigid fixtures. An error deviation of 3.23% was recorded when comparing simulation results to experimental data, thereby validating the effectiveness of the FEA methodology. [ABSTRACT FROM AUTHOR]

A novel three-dimensional mechanical metamaterial with low frequency bandgaps and negative Poisson's ratio is designed, consisting of a conventional three-dimensional reentrant structure and periodic resonators, with the aim of achieving vibration isolation and impact mitigation. The bandgap characteristic of the proposed metamaterial is determined computationally, and its dispersion diagram exhibits both partial bandgaps and a complete bandgap within a frequency band of interest. The mechanism for bandgap occurrence is characterised as the local resonance of ligaments and resonators, according to a vibration mode analysis. The wave attenuation capacity of the proposed metamaterial is derived numerically and experimentally from semi-infinite and finite-size metamaterial models, showing a good agreement with the predicted bandgap. Additionally, a thorough study on the design flexibility indicates that the bandgap characteristic can be directly tailored by changing the geometrical parameters of the proposed metamaterial. This allows further optimisation of the metamaterial for potential applications. The dynamic performance of the proposed metamaterial under an impact load is investigated by a finite element model. This demonstrates that the metamaterial reduces the transmitted force by a factor of 1.6 (for peak value) and 2.0 (for root mean square value) under a pulse impact with a duration of 0.88 ms. The impact mitigation result obtained from the impact test confirms that the metamaterial shows a mitigation capacity which is approximately 20% better than that of the conventional reentrant structure. [ABSTRACT FROM AUTHOR]

Steel cord materials were found to have internal porous microstructures and complex fluid flow properties. However, current studies have rarely reported the transport behavior of steel cord materials from a microscopic viewpoint. The computed tomography (CT) scanning technology and lattice Boltzmann method (LBM) were used in this study to reconstruct and compare the real three-dimensional (3D) pore structures and fluid flow in the original and tensile (by loading 800 N force) steel cord samples. The pore-scale LBM results showed that fluid velocities increased as displacement differential pressure increased in both the original and tensile steel cord samples, but with two different critical values of 3.3273 Pa and 2.6122 Pa, respectively. The original steel cord sample had higher maximal and average seepage velocities at the 1/2 sections of 3D construction images than the tensile steel cord sample. These phenomena should be attributed to the fact that when the original steel cord sample was stretched, its porosity decreased, pore radius increased, flow channel connectivity improved, and thus flow velocity increased. Moreover, when the internal porosity of tensile steel cord sample was increased by 1 time, lead the maximum velocity to increase by 1.52 times, and the average velocity was increased by 1.66 times. Furthermore, when the density range was determined to be 0–38, the pore phase showed the best consistency with the segmentation area. Depending on the Zou-He Boundary and Regularized Boundary, the relative error of simulated average velocities was only 0.2602 percent. [ABSTRACT FROM AUTHOR]

Due to the widespread use of carbon nanotube (CNT)‐reinforced polymers in various industries, investigating the dynamic mechanical response of these materials under impact loading is of significant importance. A three‐dimensional viscoelastic (VE)–viscoplastic (VP) constitutive model for CNT/epoxy nanocomposites is developed. A proper rheological model is established using the generalized Maxwell model to represent the VE behavior and propose an exponential function to express the elasto‐VP response. Employing an empirical logarithmic relationship to estimate material properties at different strain rates, the VP behavior is modeled based on the overstress concept. The 3D numerical discretization of the proposed rate‐dependent material model is also carried out to develop a user‐defined material model (UMAT) for the commercial finite element (FE) software of Abaqus. The performed FE simulations based on the proposed rate‐dependent constitutive material can properly capture stress relaxation and hysteresis behaviors of the nanocomposites. Comparing the estimated tensile and shear stress–strain curves through developed material models with experimental measurements, an excellent agreement is observed. Highlights: Tensile/shear properties of CNT/epoxy are measured at three strain rates.An empirical constitutive model is proposed for any arbitrary strain ratesViscoplastic behavior is captured based on over‐stress conceptA 3D incremental form of a viscoelastic–viscoplastic material model is developed. [ABSTRACT FROM AUTHOR]

This article reports a carbon fiber–reinforced plastic Kagome composite honeycomb sandwich structure reinforced with polymethacrylimide (PMI) foam (PKCSS). Low‐velocity impact performances on the node, rib, and two cell centers of the PKCSS were experimentally compared with those on a composite Kagome honeycomb sandwich (CKHS), and the failure mechanism of the PKCSS was investigated. The impact process was analyzed through an explicit numerical analysis using ABAQUS. A three‐dimensional Hashin failure criterion was introduced using the VUMAT subroutine. Results confirmed that the PKCSS exhibits higher impact and specific loads than the CKHS, with the maximum improvements of 69.7% and 39.5%, respectively, under 50‐J impact energy. As an uncrushable material, the PMI foam provides strong impact resistance during its plateau stage. This technology of cell filling can be used to fabricate lightweight all‐composite honeycomb sandwiches for potential use in ultrahigh engineering applications. Highlights: Cell filling is applied in an all‐composite Kagome honeycomb sandwich.The LVI performances of the PKCSS and CKHS are experimentally compared.C‐scanning is used to analyze the failure of the considered structures.The PKCSS's numerical model is established to investigate the impact process.The enhancement mechanism of the PMI foam is analyzed. [ABSTRACT FROM AUTHOR]

This paper aimed to investigate the energy absorption characteristics and damage mechanism of carbon fiber reinforced plastics/aluminum (Al‐CFRP) under radial impact. In this study, the damage mode of the hybrid tube is analyzed by falling hammer impact experiments, and the correctness of the finite element model is verified by comparing the experimental and numerical simulation results. Then, the damage mechanism of the hybrid tube under impact loading and the effects of the increase of the fiber angle, the wall thickness of Aluminum, and the number of outer CFRP layers on the impact resistance were analyzed according to the model. The comprehensive performance model of the hybrid tube was established by using the complex scale comprehensive evaluation method, and the genetic algorithm was used to optimize the hybrid tube and determine its optimal performance under radial impact load. The results show that the Al‐CFRP hybrid tube's overall stiffness and deformation resistance under radial impact is improved with the increase of the fiber angle, the wall thickness of the Al tube, and the number of outer CFRP layers. Combined with the parametric analysis of the numerical simulation results, a comprehensive performance evaluation model based on the complex proportionality assessment method (COPRAS) was developed and a genetic algorithm (GA) under back propagation (BP) neural network prediction was used. The optimal hybrid tube form with the best overall performance under radial impact was obtained using GA with BP neural network prediction. Highlights: The energy absorption characteristics of hybrid tubes under radial impact are investigatedA comprehensive performance evaluation model of hybrid pipe based on the complex proportional assessment method (COPRAS) is developedThe failure process and energy absorption mechanism of the hybrid pipe under radial impact are analyzedA genetic algorithm (GA) with backpropagation (BP) neural network prediction was used to obtain the hybrid pipe form with the best overall performance under radial impact [ABSTRACT FROM AUTHOR]

Impact damage is the most destructive effect on the seeds during harvesting, handling, and storage, both on‐farm and off‐farm. The chickpea seeds' dicotyledonous characteristics and large mass and size make them susceptible to mechanical damage under impact loading. Tests were conducted to determine the extent of damage to chickpea seeds due to the impact caused by free fall. The extent of internal damage to the chickpea seeds was determined, which included the measurement of seed deterioration by the accelerated aging method (percentage loss in germination in the accelerated aging test) and the measurement of electrical conductivity. Three independent variables were used in the test, namely: (a) drop height (3, 6, 9, and 12 m), (b) impact surface (concrete, metal, plywood and seeds on seeds), and (c) seed moisture content (10%, 15%, 20%, and 25% w.b). The results showed that drop height, impact surface, and moisture content had significant effects (p <.01) on the loss in germination percentage and change in electrical conductivity of chickpea seeds. In terms of loss in germination, the highest damage to seeds occurred at the metal impact surface (41.96%) and the least at the seed on the seed (29.71%). The highest amount of electrical conductivity was related to the seeds dropped on the metal (36.09 μS cm−1 g−1) and the lowest was related to seed‐on‐seed contact (21.68 μS cm−1 g−1). By increasing the drop height from 3 to 12 m, the loss in germination and electrical conductivity of seeds increased from 27.74% to 48.08% and from 18.72 to 40.47 μS cm−1 g−1, respectively. Increasing the moisture content of chickpea seeds from 10 to 25% causes a decrease in the amount of damage to the seeds in terms of electrical conductivity (from 38.40 to 21.18 μS cm−1 g−1), but increases the damage in the form of a loss in the percentage germination in the accelerated aging test (from 29.22% to 42.88%). To reduce the impact damage to peas caused by free fall, the height of the fall should be limited to about 6 m, and they should be prevented from hitting hard and rough surfaces. [ABSTRACT FROM AUTHOR]

Investigating the resistance of materials in some applications, such as aerospace, to ballistic shocks is of great importance. This article used molecular dynamics simulation to study the effect of mechanical shock under impact loads. In the ballistic shock simulation of aluminum-graphene nanocomposites, the Mishin, Tersoff, and Lennard–Jones potentials were used for aluminum, carbon in the projectile, and aluminum-carbon nanocomposites. The study results show that the presence of graphene sheets in aluminum increases its mechanical properties, including Young's modulus and yield strength. Adding graphene prevents projectile penetration into the material, so aluminum with a higher percentage of graphene will have maximum absorption in less time. Furthermore, the effect of adding more graphene layers to aluminum was also investigated. Specifically, single to five-layer graphene sheets absorb 11, 28, 53.5, and 90% of the projectile's energy, respectively. Furthermore, some optimal configuration for withstanding along the external projectile was discussed here. [ABSTRACT FROM AUTHOR]

In recent years, legged robots have been more and more widely used on non-structured terrain, and their foot structure has an important impact on the robot's motion performance and stability. The structural characteristics of the yak foot sole with a high outer edge and low middle, which has excellent soil fixation ability and is an excellent bionic prototype, can improve the friction between the foot and the ground. At the same time, the foot hooves can effectively alleviate the larger impact load when contacting with the ground, which is an excellent anti-slip buffer mechanism. The bionic foot end design was carried out based on the morphology of the yak sole; the bionic foot design was carried out based on the biological anatomy observation of yak foot skeletal muscles. The virtual models of the bionic foot end and the bionic foot were established and simulated using Solidworks 2022 and Abaqus 2023, and the anti-slip performance on different ground surfaces and the influence of each parameter of the bionic foot on the cushioning effect were investigated. The results show that (1) the curved shape of the yak sole has a good anti-slip performance on both soil ground and rocky ground, and the anti-slip performance is better on soil ground; (2) the curved shape of the yak sole has a larger maximum static friction than the traditional foot, and the anti-slip performance is stronger under the same pressure conditions; (3) the finger pillow–hoof ball structure of the bionic foot has the greatest influence on the buffering effect, and the buffering effect of the bionic foot is best when the tip of the bionic foot touches the ground first. [ABSTRACT FROM AUTHOR]

Understanding fundamental track behaviors under dynamic load conditions is important to optimize design practices and achieve high-quality track performance. The American Railway Engineering and Maintenance-of-Way Association provides recommended practices to estimate trackbed pressures, which are primarily based on the Talbot equations. The Talbot methodology for computing crosstie-ballast (CT-B) interfacial pressures may "not" be valid for modern railroad design due to several factors, including the sensitivity of pressure measuring equipment, the presence of uneven support conditions, and the implementation of jointed rails in testing different wheel loadings, which contributed to overestimation of pressure readings as a result of impact loading. However, modern railroad infrastructure has been designed with a smooth track layout and well-supported rails as well as incorporating rolling stock equipped with smooth wheels, particularly in high-speed train operations. This study proposes a new approach to estimate the pressures at the CT-B interface, which was developed using measured in-track CT-B interfacial pressures taken from an active mainline. The data from the in-track measurements were filtered by using a signal processing tool and analyzed to develop basic equations to predict interfacial pressures as a function of basic train characteristics, including train speed, wheel loads, and wheel spacing, assuming no impact loading from wheel defects. To validate the efficacy of the square wave theory, the predicted pressures were compared with the data obtained from in-track tests. Further, a method to estimate dynamic pressures of a moving train at the CT-B interface was developed using square wave theory. By representing the vehicles of a train as a periodic square waveform, the dynamic CT-B interfacial pressures can be predicted for an unlimited number of locomotives and cars for smooth track geometry, smooth wheels, limited rail surface roughness, and well-supported track. [ABSTRACT FROM AUTHOR]

Through a series of static mechanical tests and (SHPB) dynamic impact tests, the static and dynamic mechanical parameters of rock as represented by yellow sandstone are determined, and the Holmquist-Johnson-Cook model parameters of the rock are calibrated using the test data and theoretical calculations. The feasibility of a numerical model is verified, and numerical analysis of the SHPB impact process under different radial pressure pre-loading is carried out on the basis of good verification. The results show that with increasing impact load, the degree of rock breakage increases, as does the dynamic tensile strength. With the application of increasing pre-static pressure, the dynamic tensile strength of the rock decreases gradually, and the maximum radial cumulative strain increases continuously under a given impact pressure, indicating that micro-cracks in the rock develop initially and then expand under the influence of pre-static pressure; the rock is more easily broken, and its weakening degree increases. Under coupled dynamic and static loading, the energy utilization rate of rock in the Brazilian splitting process is jointly affected by axial compression ratio and impact load. Too large a pressure ratio will reduce the strain-rate sensitivity of rock, resulting in low energy utilization rate, while too low an axial compression ratio will make the dynamic tensile strength of rock relatively high, which is not conducive to tensile failure. Therefore, on the premise of clear fracture form requirements, a suitable combination of axial compression ratio and impact velocity can improve the rock crushing effect and energy utilization rate. [ABSTRACT FROM AUTHOR]

In order to effectively improve the seismic and impact resistance performance of soft rock tunnels, a composite support method was proposed and validated in the paper. The UDEC (Universal Distinct Element Code) model of soft rock layers was established, and the movement and subsidence characteristics of the roof and floor of the rock layers under impact loads was simulated and calculated. As a result, a composite support scheme with good cushioning performance was proposed. The top and sides of the tunnel were supported by a combination of anchor rods of different lengths and metal mesh, reinforced by steel beams and vibration absorbing filler around. The anchor rod was designed as a segmented loading structure, and can be set to different preloading forces based on the internal deformation of the rock layer. The dynamic response testing scheme was designed, and the results indicate that the segmented loading anchor rod has a significant buffering effect on the response to impact load, and can provide reasonable tension feedback at different stages. Research has found that when the water cement ratio is 0.5-1.5, the curing efficiency and strength are both higher. In order to compare the seismic performance of composite support and traditional constant resistance anchor rod support, local blasting experiments were conducted. Based on a blasting vibration tester, a data detection and transmission system were designed to obtain the vibration speed of the tunnel roof during the vibration process. The research results show that composite support can reduce the maximum vibration by more than 40 %, stabilize the fragmentation coefficient at 1.38, and have a very significant vibration reduction effect. [ABSTRACT FROM AUTHOR]

This study conducted both three-dimensional physical model tests and numerical back-analyses to examine the performance of a single pile subjected to twin tunnelling beneath the pile toe in dry sand. Moreover, numerical parametric analyses were carried out to assess the impact of working load level and tunnel volume loss on pile behaviour. The findings revealed that the first tunnelling induced a 1.9%dp (pile diameter) settlement in the pile when the pile toe was 0.5 D (tunnel diameter) above the twin tunnels, which had a 1.0% volume loss. The settlement was accompanied by an upward load transfer mechanism. The second tunnelling had a reduced impact and induced only 76% of the settlement caused by the first tunnelling. The study also showed that tunnelling-induced shearing behaviours weakened beneath the pile toe with a decrease in working load, resulting in reduced pile head settlement. Moreover, the computed pile settlement increased by 178% when the tunnel volume loss increased from 0.5% to 2%. The findings of this study offer valuable data for the validation and calibration of numerical models. In addition, the outcome from this study provides useful insights into the prediction of the pile-soil-tunnel interaction when subjected to twin tunnelling. [ABSTRACT FROM AUTHOR]

Protecting pipelines from impact load due to rockfall in mountainous regions is a challenging problem. Many researchers have studied rockfall characteristics and impact loading, however, there is still a lack of large-scale studies about the impact of rockfall on steel buried pipes. In this study, three large-scale tests were carried out to investigate the response of steel buried pipe, including rock penetration, impact force during penetration, circumferential strain, and vertical deformation of the pipe under different falling heights of a large spherical mass. In order to establish a well-based connection between prototype and large-scale models, a comprehensive scaling rule was applied in a way that the response of the prototype and large-scale models approached the same values. The results showed that increasing drop height causes an incremental rate of peak deceleration of the falling mass, and therefore larger impact forces were measured on the trench surface. The equivalent stiffness of the soil-buried pipe system during the impact load proved that the response of the system was mostly governed by the soil rather than the pipe. For this study, the through-wall bending stress of the pipe at drop heights of 3.5 and 4.5 m exceeded the recommended permissible range, and so failing to satisfy this design criterion. [ABSTRACT FROM AUTHOR]

To investigate the dynamic response and fire performance of steel beams under high temperature, drop hammer impact tests and numerical simulations were conducted on steel beams subjected to high temperatures. Three finite element (FE) models were established using the element coupling method to predict the impact dynamic behavior of the steel beams under the combined effects of fire and impact loads. The reliability and applicability of the developed FE models in predicting the impact dynamic response of steel beams in fire was examined through comparison of numerical results with experimental results. Based on the experimentally and numerically observed failure modes, a generalized plastic yield criterion for I-shaped steel beams section was proposed, which considers the synergistic effects of axial force, shear force, bending moment, strain rate, and temperature with the plastic deformation of the entire cross section as the criterion. The interaction functions and spatial characteristics between internal forces were presented. A new generalized yield (G-Y) method for evaluating the failure of components due to plastic hinges development without restricting the load type was proposed based on four types of interaction relationships combination, and the sensitivity of the G-Y method to different parameters for assessing the development of plastic hinges was systematically studied. Based on the proposed G-Y method, the mechanical behavior of steel beam subjected to multiple extreme load coupling effects was revealed. [ABSTRACT FROM AUTHOR]

The greatest challenge when performing large deformation simulations using the CFD‐DEM coupling method lies in the dynamical update of the fluid meshes. To address this problem, a novel CFD‐DEM coupling method integrated with the dynamic unstructured grid is proposed in this work. The mesh initialization and reconstruction are performed by the Constrained Delaunay triangulation (CDT) implemented by the tetgen algorithm. Moreover, the equation of state (EOS) is introduced to consider the impact of fluid compressibility. The reliability of this coupling method is preliminarily verified by the particle sedimentation test. Additionally, undrained triaxial shear and one‐dimensional consolidation tests are conducted to examine the applicability of the proposed method in simulating geotechnical cases. From our analysis, it is found that the shear responses in the undrained triaxial shear test obtained from the proposed method with dynamic mesh are in direct accordance with those led by the constant volume (CV) method. However, difficulties arise in accurately describing the moving boundary by the fixed mesh, leading to unreliable results. Moreover, in the one‐dimensional consolidation test, both the dynamic and fixed grids can capture the Mandel—Cryer effect, which is more pronounced under the dynamic grid, mainly due to the dual impact of the loading device and particle skeleton on the fluid. A greater compressibility specified under the dynamic grid led to a weakening of this effect, whereas its duration is increased. Our work provides valuable insights for effectively dealing with dynamic fluid boundaries. [ABSTRACT FROM AUTHOR]

The movement of the Earth's surface mass, including the atmosphere and oceans, as well as hydrology and glacier melting, causes the redistribution of surface loads, deformation of the solid Earth, and fluctuations in the gravity field. Global Navigation Satellite Systems (GNSS) provide useful information about the movement of the Earth's surface mass. The impact of surface loading deformation over 145 GNSS sites in Africa was investigated using vertical height time series analysis. The study investigates and quantifies the impact of surface loading on the GNSS coordinates utilizing GNSS Precise Point Positioning (PPP) approach. The German Research Center for Geosciences (GFZ) EPOS.P8 software was used to process and analyze eleven years of GPS data from all the stations, as well as dedicated hydrological and atmospheric loading correction models given by the Earth System Modeling group at Deutsches GeoForschungsZentrum (ESMGFZ). The results of the hydrological loading corrections arising from the surface-deformation were analysed to determine the extent of station improvements. The results revealed about 40% of the stations showed improvement with an average Root Mean Square Error (RMSE) residual of 7.3 mm before the application of the hydrological loading corrections and 7.1 mm Root Mean Square Error (RMSE) after the application of the hydrological loading corrections. Similarly, the atmospheric loading corrections gave an improvement of about 57%. Furthermore, the amplitude values decreased from 4.1–8.1 mm to 3.5–6.2 mm after atmospheric loading corrections. This finding presupposes that applying loading corrections to the derived time series reduces amplitude in some African regions. [ABSTRACT FROM AUTHOR]

Aluminium foam and Carbon Fiber Reinforced Plastic (CFRP) are widely used composite materials in automobile industries due to the benefits of lightweight and energy absorption capacity. Therefore, in this study, the numerical crashworthiness analysis of 2014 Aluminium-SiCp (2014AA-SiCp) foam filled in CFRP tube has been performed under impact loading. Quasi-static compression tests have been conducted on 2014AA-SiCp foam to extract the mechanical parameters required for numerical simulations. To understand the crushing behavior under the axial impact loading, 2014AA-SiCp foam-filled CFRP tube has been numerically modelled using ABAQUS® software. The parametric study was carried out to explore the effects of filler material, foam densities, and impact velocities on crushing behavior. It was found that load increases with the rise in foam density and impact velocity. Moreover, the deformation increases with the increase in impact velocity. Results showed that the load carrying capacity of foam filled CFRP tubes was significantly improved compared to that of empty CFRP tubes. The foam filled CFRP specimens exhibited peak load of 122 kN and an energy absorption capacity of 3012 J, showcasing an approximate improvement of 43% and 11% respectively, over the values obtained for empty CFRP tubes. [ABSTRACT FROM AUTHOR]

Fillers play a decisive role in the mechanical properties of polymer composites. In this paper, different particle sizes of nitroguanidine were obtained to regulate the internal filler structure of triple‐base propellants (TBP) to improve their mechanical response in different environments. A series of morphological and structural characterizations on nitroguanidine (NQ) particles were conducted using techniques. The results indicated that the obtained NQ particles maintained a high level of crystalline quality while preserving their molecular integrity. The mechanical properties of TBP were systematically evaluated under various loading conditions, including cryogenic tensile, compressive, and impact loads, as well as dynamic thermomechanical effects. Additionally, three‐point bending simulations were employed to elucidate the mechanical responses and damage mechanisms. Under axial tensile and compressive loads, reducing the particle size of NQ significantly enhanced the tensile and compressive strength. The maximum tensile strength and compressive strength can reach 344.62 MPa and 104.79 MPa. Moreover, the compressive failure mode transitioned from cracking to axial shrinkage. Conversely, when subjected to radial bending loads, TBP exhibited contrasting behavior, including a decrease in the glass transition temperature from 84.73°C to 76.93°C and a non‐monotonic trend in impact strength (initially increasing from 4.96 to 8.85 kJ/m2 and then decreasing to 2.27 kJ/m2). This study provides valuable insights into the mechanical performance of TBP, supporting the development of high‐energy, high‐strength TBP formulations. Highlights: SEM analysis confirms the pronounced orientation effect of rod‐like NQ.The orientation and particle size of NQ decide TBP's radial impact resistance.Submicron NQ enhances the compression resistance property of TBP.Submicron NQ brings about a shift in the microscopic damage morphology of TBP. [ABSTRACT FROM AUTHOR]

In this study, the behavior of composite material produced using basalt, a natural fabric, under ballistic and Charpy impact loads was investigated. The damage resistance of target plates under ballistic loads is an important design parameter in the structures that will be exposed to these loads. Cross‐ply fiber‐reinforced composite plates were produced with different numbers of layers. The composite specimens are produced using the vacuum infusion method, cross‐ply laminated with 3, 6, 9, and 12 layers ([0/90]3, [0/90]6, [0/90]9, and [0/90]12). Carbon/Epoxy specimens were also produced in identical sequences to be used as comparison material. The study aimed to understand the absorbed energy under ballistic loads and the required energy level under the Charpy impact loads of Basalt/Epoxy composite specimens with different thicknesses. Ballistic loads are applied to the specimens using a test set‐up including the sample holder mechanism and a firing system. Charpy impact tests were conducted using a standard test machine. According to the results, for 12‐layer specimens, the residual velocity difference between Basalt/Epoxy and Carbon/Epoxy is approximately 1.5 times. For the Basalt/Epoxy plate, increasing number of layers from 3 to 12 increases the amount of energy absorbed approximately 13 times. Although this increase is approximately 19 times for the Carbon/epoxy plate, when Basalt/Epoxy and Carbon/Epoxy plates are compared, Basalt/Epoxy absorbs more energy for all layer numbers. For the Charpy impact cases, it has been observed that Basalt/Epoxy absorbs approximately 34% more energy for flat wise impact and approximately 24% more energy for edgewise impact. Highlights: The behavior of composite material produced using basalt, a natural fabric.Cross‐ply fiber‐reinforced composite plates.Effect of different number of layers considered.The damage resistance of target plates under ballistic loads.Comparison of basalt and carbon‐reinforced composites. [ABSTRACT FROM AUTHOR]

This study investigates the effect of damage interference resulting from impact loads on the mechanical response and impact fatigue life of E‐glass/epoxy composite laminate shells. The analysis involves single impacts at different points to evaluate the impact strength's dependency on boundary conditions. Notably, there is a gradual reduction in both maximum impact force and absorbed energy beyond 10 mm from the centre, towards unconstrained edges, accompanied by an increase in displacement. Specifically, at a distance of 30 mm, the maximum force and absorbed energy register a decrease of 9.4% and 7.9%, respectively, while the displacement rises by 14.5%. The findings reveal that the damage severity decreases as the impact point is closer to the unconstrained edge of the specimen, which can be attributed to a stiffness reduction, which can reach up to 22%. Symmetrically induced pre‐damages exhibit no discernible effect on the subsequent impact response. It is observed that beyond 10 mm from the shell's centre, the number of impacts required to reach puncture increases by 10.5% and 21.1% for distances of 20 and 30 mm, respectively. Furthermore, it is also found that alternating impacts between symmetrical points show no inclination towards a preferential point for puncture. Highlights: The single impact strength's dependents on the boundary conditions.Reduction in both maximum impact force and absorbed energy near the unconstrained edges.Damage severity decreases as the impact point is closer to the unconstrained edges.Symmetrically induced pre‐damages have no discernible effect on the subsequent impact response.Alternating impacts between symmetrical points show no inclination towards a preferential point for puncture. [ABSTRACT FROM AUTHOR]

In this study, the low‐velocity impact behavior of polymer composites produced separately by reinforcing with natural fiber fabrics such as linen, hemp, jute, and bamboo was investigated for three different thicknesses (2.5 ± 0.1, 5 ± 0.1, and 7.5 ± 0.1 mm) by vacuum infusion method. Low‐speed impact tests were performed at three different energy levels of 20, 35, and 50 J by striking the geometric center of the composite samples with a hemispherical impactor. The impact strengths of the composites were evaluated by comparing the contact force‐displacement, contact force‐time graphs, and impacted sample images. The types of damage occurring in each experimental sample were evaluated. Increasing the thickness had a positive effect on the impact strength of the composites. When the thickness of the composite plates increases, the peak contact force increases, the displacement decreases and capacity to carry impact loads increases due to the increased stiffness of the composites. However, except for the damaged 5 ± 0.1 mm thick bamboo and jute samples, the energy absorption ability of the samples generally increases with the increase of impact energy. Bamboo, jute, and hemp reinforced samples with a thickness of 2.5 ± 0.1 mm were completely perforated under 20 J impact energy. Also, it was determined that linen reinforced composites have the best impact resistance among natural fabric reinforced composites. Highlights: Low‐velocity impact behavior of natural fiber fabric reinforced PMCs was studied.The impact strength of PMCs increased as the thickness increased.Linen reinforced composites had the best impact resistance.The main damage modes are matrix cracking and delamination at low‐impact energies.As the impact energy increases, perforation and fiber breakage or separations are observed. [ABSTRACT FROM AUTHOR]

During the coal mining process in soft rock mines with abundant water, the rock mass undergoes cyclic loading and unloading at low frequencies due to factors such as excavation. To investigate the mechanical characteristics and energy evolution laws of different water-containing rock masses under cyclic disturbance loading, a creep dynamic disturbance impact loading system was employed to conduct cyclic disturbance experiments on various water-containing soft rocks (0.00%, 1.74%, 3.48%, 5.21%, 6.95%, and 8.69%). A comparative analysis was conducted on the patterns of input energy density, elastic energy density, dissipated energy density, and damage variables of different water-containing soft rocks during the disturbance process. The results indicate that under the influence of disturbance loading, the peak strength of specimens, except for fully saturated samples, is generally increased to varying degrees. Weakness effects on the elastic modulus were observed in samples with 6.95% water content and saturated samples, while strengthening effects were observed in others. The input energy density of samples is mostly stored in the form of elastic strain energy within the samples, and different water-containing samples adapt to external loads within the first 100 cycles, with almost identical trends in energy indicators. Damage variables during the disturbance process were calculated using the maximum strain method, revealing the evolution of damage in the samples. From an energy evolution perspective, these experimental results elucidate the fatigue damage characteristics of water-containing rock masses under the influence of disturbance loading. [ABSTRACT FROM AUTHOR]

Pupil size is a significant biosignal for human behavior monitoring and can reveal much underlying information. This study explored the effects of task load, task familiarity, and gaze position on pupil response during learning a visual tracking task. We hypothesized that pupil size would increase with task load, up to a certain level before decreasing, decrease with task familiarity, and increase more when focusing on areas preceding the target than other areas. Fifteen participants were recruited for an arrow tracking learning task with incremental task load. Pupil size data were collected using a Tobii Pro Nano eye tracker. A 2 × 3 × 5 three-way factorial repeated measures ANOVA was conducted using R (version 4.2.1) to evaluate the main and interactive effects of key variables on adjusted pupil size. The association between individuals' cognitive load, assessed by NASA-TLX, and pupil size was further analyzed using a linear mixed-effect model. We found that task repetition resulted in a reduction in pupil size; however, this effect was found to diminish as the task load increased. The main effect of task load approached statistical significance, but different trends were observed in trial 1 and trial 2. No significant difference in pupil size was detected among the three gaze positions. The relationship between pupil size and cognitive load overall followed an inverted U curve. Our study showed how pupil size changes as a function of task load, task familiarity, and gaze scanning. This finding provides sensory evidence that could improve educational outcomes. [ABSTRACT FROM AUTHOR]

It is widely accepted that cognitive load plays a crucial role in online learning. However, despite neurodevelopmental conditions being the largest category of qualifying disabilities in education, and the rise of online learning, there is little understanding of the factors impacting cognitive load in online learning for neurodivergent students and how these factors differ from those affecting neurotypical students. This study used qualitative comparison groups with neurotypical and neurodivergent students to examine their experiences of cognitive load in online learning. A sample of 26 university students (14 neurotypical and 12 neurodivergent) participated in focus group discussions. While neurodivergent students reported many similar experiences of cognitive load in online learning compared to their neurotypical peers—such as confusion in navigating the content and technical issues—some difficulties were more present for neurodivergent students—such as transcripts including mistakes and inaccessible content presentation—creating additional barriers in effectively engaging with the educational content. The results suggest that neurotypical and neurodivergent students experience similar challenges, albeit to differing degrees of intensity, and that more research is needed to explore the relationship between neurodiversity and cognitive load in online learning. [ABSTRACT FROM AUTHOR]

In regions heavily affected by recurrent typhoons, the need for more resilient electricity infrastructure is pressing. This emphasizes the importance of integrating resilience assessment, including incorporating resilience metrics, into the planning process of power distribution systems against any disruptive events. Although standardized metrics exist for assessing distribution system reliability, the absence of formalized resilience metrics hampers informed investments in critical infrastructure such as microgrid development. In this work, a set of resilience metrics is proposed by reconceptualizing reliability metrics. The metrics were formulated to account for both the type of extreme event and its specific impact on loads with varying levels of criticality. The effectiveness of the proposed metrics is demonstrated through a Philippine microgrid case study. A Monte Carlo framework incorporating an extreme event model, component fragility model, and system response model was used to quantify the resilience improvement before and after stand-alone microgrid operation of the power distribution system. Results show that the proposed metrics can effectively evaluate resilience enhancement and highlight the value of a holistic approach of considering critical loads and types of extreme events to strengthen societal and community resilience, making a compelling case for strategic investments in infrastructure upgrades such as microgrids. [ABSTRACT FROM AUTHOR]

SHPB simulation of TC4/2024AL/TC4, TC4/TA2/TC4, and TC4/Al3Ti/TC4 laminated composites under different impact velocities of strike bar was carried out by ANSYS/LS-DYNA. Then stress distribution of the laminated composites under impact loading was theoretically analyzed according to the one-dimensional stress wave theory. Influencing factors of stress distribution and energy attenuation were emphatically analyzed, including impact velocities of the strike bar, wave impedance of interlayer, and plastic deformation. The results show that, when the impact velocity is determined, impact resistance is negatively correlated with the impedance of the interlayer. Under certain conditions, impact resistance is negatively correlated with impedance of interlayer, and positively correlated with impact velocity. In addition, the accumulation of plastic deformation could make residual stress distribution along the position coordinate axis shows a trend of gradual increase from both sides to the middle position. [ABSTRACT FROM AUTHOR]

When an impact load is sufficiently small, its influence on the pavement structure is mainly from the surface layer material. To explore the influence depth of an impact load and back‐calculation of the pavement surface modulus, both numerical calculation and experimental testing were conducted, and the results are presented in this paper. The numerical calculation was performed through a DEM‐FDM‐coupled model. After a new modulus back‐calculation algorithm is formed by analyzing the numerical modeling results, experimental tests were also conducted for verification, and the results were analyzed. The max value of the falling weight impact force was closely related to the elastic modulus of the material, and the influence depth was controllable. Finally, it is proved that the method can be used to calculate the surface layer modulus and estimate the surface layer thickness. [ABSTRACT FROM AUTHOR]