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The present article provides a comprehensive analysis of the aging phenomenon of transformer insulation and the corresponding changes in insulation performance that occur over time. The present manuscript outlines diverse insulating materials that are employed in transformers, the fundamental aging mechanism of the insulation, the function of space charges in the aging of the insulation, and various simulation methodologies utilized for diagnosing the insulation status of the transformer. The primary focus of this paper is to examine the various numerical techniques employed in modeling and analyzing the aging characteristics of transformer insulation. The mechanisms underlying the accumulation of charge and distortion of electric fields in insulation are explained through the utilization of numerical modeling techniques. This paper focuses on understanding the mechanism of insulation aging, thereby facilitating the optimization and maintenance of insulation performance throughout its operational lifespan. [ABSTRACT FROM AUTHOR]

An epiretinal membrane (ERM) is a fibrocellular proliferation on the inner surface of the retina causing blurred and distorted central vision. Surgery is the only effective method for ERM removal. This paper investigated the mechanical properties of ERM peeling using the finite element (FE) method. A FE model of ERM formation on the retina surface was constructed. The failure criterion was applied to the attachment pegs to represent the adhesive force between the ERM and retina. The simulation results were consistent with the experimental data in published research. The maximum peeling force was 4.1 mN at a peeling velocity of 2 mm/s and an angle of 30°. The peeling force was minimum at the peeling angle of 45° and increased with the increase in peeling velocity and Young's modulus of the membrane. The outcome of this paper can improve the safety and efficiency of ERM removal. [ABSTRACT FROM AUTHOR]

A new cable-damper stopper equipped for Coal-Fired Thermal Power Plants (CFTPPs) was proposed in our previous paper, where a series of shaking table tests were carried out to investigate its seismic performance, so this paper aims to reveal the working mechanism of the stopper from the theoretical and numerical simulation aspects. The stopper is composed of three main components, i.e. a steel cable, a steel block and a viscous damper. First, the nonlinear restraint stiffness of the steel cable to the boiler was derived; second, the critical damping of the stopper, which makes the vibration of the boiler decay exponentially with no oscillation, was derived; third, an iterative method was proposed to globally tune the CFTPP structure, which makes it possible to obtain the optimal parameters of the cable-damper stopper, including the diameter of the steel cable and damping coefficient of the damper. Finally, finite element models were built and time history analyses were conducted to verify the proposed optimization approach. Firstly, the finite element models were proved valid through the comparison between the results of the simulations and the experiments. Then, based on the results of the simulations, the theoretical procedure was validated. The results revealed that the proposed cable-damper stopper reduced the seismic responses of displacements of the top floor and the boiler significantly, about 30.18% and 60.01% respectively compared with their counterparts of CFTPPs without stoppers. [ABSTRACT FROM AUTHOR]

With the increasing of tunnel mileage, one of the most vital problems of broad-scale structures is the intelligent identification and location of structural defects, which require massive data storage capacity and high data processing efficiency. The full-field point cloud data collected by terrestrial laser scanning (TLS) can be extracted to construct three-dimensional measured models more accurately, therefore, the fusion of TLS and the finite element method (FEM) is particularly beneficial to the deformation analysis of tunnel structures. This paper combines numerical simulation and full-field measurement to interactively verify the reliability of deformation analysis based on FEM simulation and point cloud processing. The innovation of this paper is that a three-dimensional FEM is validated through the measured point cloud data of the tunnel structure. The result of this study indicated that FEM simulation and the structural health monitoring analysis are consistent. [ABSTRACT FROM AUTHOR]

The bone lacunar-canalicular system (LCS) is a unique complex 3D microscopic tubular network structure within the osteon that contains interstitial fluid flow to ensure the efficient transport of signaling molecules, nutrients, and wastes to guarantee the normal physiological activities of bone tissue. The mass transfer laws in the LCS under microgravity and hypergravity are still unclear. In this paper, a multi-scale 3D osteon model was established to mimic the cortical osteon, and a finite element method was used to numerically analyze the mass transfer in the LCS under hypergravity, normal gravity and microgravity and combined with high-intensity exercise conditions. It was shown that hypergravity promoted mass transfer in the LCS to the deep lacunae, and the number of particles in lacunae increased more significantly from normal gravity to hypergravity the further away from the Haversian canal. The microgravity environment inhibited particles transport in the LCS to deep lacunae. Under normal gravity and microgravity, the number of particles in lacunae increased greatly when doing high-intensity exercise compared to stationary standing. This paper presents the first simulation of mass transfer within the LCS with different gravity fields combined with high-intensity exercise using the finite element method. The research suggested that hypergravity can greatly promote mass transfer in the LCS to deep lacunae, and microgravity strongly inhibited this mass transfer; high-intensity exercise increased the mass transfer rate in the LCS. This study provided a new strategy to combat and treat microgravity-induced osteoporosis. [ABSTRACT FROM AUTHOR]

This paper proposes probabilistic demand models to assess fragilities for high-rise buildings with three types of outrigger systems under seismic and wind loads. Parameters of the structural model are determined based on the structural material and geometric conditions. Parameters of the excitation model are determined based on the hazard characterization that varies with the hazard type. This paper involves three types of hazards: high-frequency ground motions, near-fault ground motions, and stochastic wind loads. With the input information from the structural model and the excitation model, 3D finite element models are built and computed using ANSYS to obtain structural responses (output information). Based on a database with the input-output pair obtained, we formulate probabilistic demand models for high-rise buildings with three types of outrigger systems under three types of hazards. These probabilistic models are proposed to estimate three response quantities of interest, the maximum inter-story drift, the maximum top acceleration, and the maximum top displacement. They, therefore, include univariate, bivariate, and tri-variate models. The probabilistic demand models account for both aleatory and epistemic uncertainties and provide unbiased estimates. With a direct and parsimonious formula, they have high accuracy and are extremely convenient to be used in practical engineering. They are finally used to formulate fragility estimates with bounds for an example high-rise building with three types of outrigger systems under three types of hazards. The results indicate that damped outrigger systems can effectively reduce fragilities for high-rise buildings under three types of hazards. [ABSTRACT FROM AUTHOR]

Achieving a correct cooling in glass manufacturing is very important to obtain the desired level of stresses and to avoid breakage. Numerical simulations can be used to optimize the cooling parameters. Such simulations have to be multiphysical coupling thermics and mechanics. Moreover, since glass is a semitransparent material, radiative effects inside the glass have to be taken into account. The present paper is devoted to numerical study of the cooling of a glass square plate on a metallic frame. To this end, the commercial software Abaqus was used to model the thermomechanical behavior of glass using adapted subroutines and was combined with an in-house C++ tool developed to solve the Radiative Transfer Equation. During and at the end of the cooling, weak areas in the glass plate are revealed by the simulation. Depending on the case studied, taking accurately the radiative effects into account leads to difference of residual stresses which can reach 10 MPa in certain cases. [ABSTRACT FROM AUTHOR]

Present study develops the experimental and finite element analysis of an auxetic piezoelectric energy harvester consisting of a cantilever, auxetic substrate, and piezoelectric layer. Firstly, five auxetic models with 1, 4, 9, 16, and 25 honeycomb auxetic cells are presented. Harvested power and stress distribution of the piezoelectric layer for these models are compared with plain piezoelectric energy harvester. All the analysis has been performed using the experimental tests and finite element method. Mesh size sensitivity analysis of the finite element model is presented, and it is verified by previous experimental studies. The model with 25 auxetic cells harvests more power than other models. Furthermore, comparing stress distribution on the piezoelectric layer of these models indicates that increasing the number of auxetic cells leads to increasing the average stress on the piezoelectric layer. The present investigation illustrates that harvested power of an auxetic energy harvester in resonant frequency could improve to twenty times more than a plain harvester. Besides, the new auxetic model with trapezoidal geometry is presented in the present paper. Utilizing this model as the substrate in a piezoelectric energy harvester leads to increasing the efficiency of the energy harvester by 82.5%. The damping ratio of the auxetic energy harvester has been measured by experimental investigation. Also, experimental analysis has been performed to find the optimum energy harvester circuit resistor. The density of the harvested power for the trapezoidal energy harvester with an optimum circuit resistor is 107% more than the rectangular energy harvester. [ABSTRACT FROM AUTHOR]

In this paper, the transverse low-velocity impact behavior of uniaxial and biaxial braided composite tubes is investigated to improve the impact resistance of tubular composite structures and to reveal their energy absorption mechanism. Based on the nonlinear progressive damage model, the finite element method is used for experimental verification and numerical analysis. The composite tubes with different stacking sequences and stacking angles were simulated, and their impact responses were evaluated by the peak load Fmax, the maximum indentation depth αmax and the energy absorption EA. The results show that the numerical simulation results are in good agreement with the experimental data, and can accurately capture the failure behavior in the actual scene. The damage mode of the braided composite circular tube under low-velocity impact load is mainly manifested as matrix cracking and interlayer separation, and the expansion direction of the damaged area is basically consistent with the fiber orientation. The impact resistance depends more on the stacking sequence, while the stacking angle is the main factor affecting the energy absorption. Under reasonable design, the uniaxial/biaxial hybrid braided tube can obtain the best low-velocity impact characteristics. [ABSTRACT FROM AUTHOR]

This paper presents a multibody model of the post-derailment dynamics of a railway vehicle and its impact with a derailment containment wall (DCW) built aside the line and demonstrates the use of the model in the context of the structural sizing of devices intended to mitigate derailment effects. With respect to existing multibody models of railway vehicle dynamics, the innovative features of this model are a new contact model capable to provide a plausible prediction of the derailment process despite a simple and computationally efficient formulation, and the model of the interaction between the derailed vehicle and the impacted derailment containment structure, the latter being described by a Finite Element Model. Results from the model are compared to an established multibody software for a non-derailment case, and then a comparison is performed with a measurement from a derailment experiment published in the scientific literature, finding in both cases satisfactory agreement. The model is then applied to analyse a derailment scenario caused by the sudden failure of an axle for a locomotive vehicle travelling at 300 km/h in a HS curve, deriving the peak values of the impact force and bending moment at the base of the derailment containment wall. [ABSTRACT FROM AUTHOR]

In this paper, the spoke structure of a non-pneumatic tire is optimized. The finite element model of the spoke structure is created and structural dynamic analysis is made using ABAQUS. The optimization goal is to simultaneously reduce three characteristics of the spoke structure, the mass, vertical displacement and acceleration. Simulations are performed according to the center composite design table, and the objective function is estimated using response surface analysis (RSA), random forest regression (RFR), gradient boosting regression (GBR) and artificial neural network (ANN). The genetic algorithm is used for minimization, and the optimization results of each objective function are analyzed through verification simulation. As a result of the optimization, the error between the predicted value and the actual value is 18.6% for RSA 3.1% for RFR, 1.7% for GBR, and 15.0% for the ANN. The ANN proposes the optimum design variables which derive output values smaller than the current minimum value because the ANN properly represents the nonlinear characteristics of the spoke model generated in this study. Highlights Simulation based optimization of the spoke structure of a non-pneumatic tire Various regression models are used and their accuracy is compared A two-step genetic algorithm is used for optimization [ABSTRACT FROM AUTHOR]

This paper presents an analysis of stress developed in flex-gear (FG) cup with conventional strain wave generating (SWG) cam and split-cam SWG in strain wave gear/harmonic drive (HD), using initial load distribution by tooth pairs as a boundary condition in finite element method (FEM). The initial load distribution by tooth pairs is achieved with the assembly of ring gear (RG) and deformed FG before the application of any external load. A closed-form solution to the analytical method describes the exact initial load distribution by tooth pairs in the presence of secondary contacts. However, with spit-cam SWG the phenomenon of secondary contact is completely eradicated. Therefore, the load is distributed by contacting tooth pairs that lie only in the line of action and the tooth pair that lies along the major axis of split-cam SWG experiences maximum load compared to conventional SWG. The strain developed in FG cup based on the load distribution with both SWG cams obtained from FEM is verified with the experiment. The comparison shows a rise of 44 microns in circumferential strain around the major axis of deformed FG, when RG is assembled. This testifies the presence of initial load, which is distributed among all interfering tooth pairs before applying external load. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents the results of numerical predictions for an instrumented piled raft foundation of a tall building in tropical soil. The analysis was performed using 3D finite element analysis and included a comparison of foundation settlements, pile loads, skin friction mobilisation, and raft-soil contact pressure. Initially, the geotechnical model was defined based on field and laboratory test data to conduct a Class A geotechnical prediction. Subsequently, the soil parameters used in the numerical model were re-evaluated to match the measured settlements, aiming for a Class C prediction. The study discusses the main factors that affect the accuracy of the computed settlements, providing valuable insights for foundation designers. Additionally, it highlights the significance of considering the pile-soil-pile and raft-soil-pile interactions in the design of the piles beneath the raft, as these interactions impact the mobilisation of the pile skin friction at different depths. [ABSTRACT FROM AUTHOR]

A new approach based on the limit equilibrium method to calculate the ultimate bearing capacity of a strip shallow foundation is presented in this paper. The bearing capacity estimated with Terzaghi's three-term basic formula using the superposition method has proven to be conservative. A proposed failure mechanism to determine the bearing capacity coefficients of the three parameters, namely, the cohesion (Nc), the surface surcharge (Nq) and the soil weight (Nγ), is developed. The 'individual minimum' of each coefficient is determined using different failure mechanisms; hence, a new analytical approximation is suggested for calculating the 'global minimum' of the bearing capacity with a single failure mechanism without superposition. The rationality of the results of the analytical solutions (bearing capacity and failure mechanism) is verified using finite element analysis with the program PLAXIS 2D and kinematical analysis with the program FIDES-GeoStability. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the use of a graphene oxide (GO)-coated planar inductor as a transducer for gas sensing applications in alternating current (AC) mode. The GO is synthesized using the Hummers method and coated as a functional layer on a square-shaped planar inductor with an area of 16 × 16 mm2 printed on a circuit board (PCB). Preliminary finite element analysis showed that the magnetic field around the inductor was tightened and amplified due to the presence of the GO layer. This result was confirmed by electrical measurements using a vector network analyzer (VNA), revealing that the GO led to an increase in the self-inductance due to its paramagnetic character. In fact, for a frequency of 1 MHz, the series resistance increased significantly by 32% compared to the initial value obtained without GO, while the inductance increased only by 0.18%. After CO2 injection, a frequency screen ranging from 1 MHz to 200 MHz demonstrated that the effect of CO2 is more relevant at low frequencies. Hence, measurements show that for 1 MHz, the series inductance and resistance decrease by about 9.33% and 31%, respectively, from their values measured after GO coating. Accordingly, this work highlights the relevance of the GO-coated inductor as a transducer for CO2 detection working in AC regime. [ABSTRACT FROM AUTHOR]

Previously, we developed an adaptive method in angle that is based on solving in Haar wavelet space with a matrix-free multigrid for Boltzmann transport problems. This method scalably mapped to the underlying P0 space during every matrix-free matrix-vector product; however, the multigrid method itself was not scalable in the streaming limit. To tackle this, we recently built an iterative method based on using an Approximate Ideal Restriction multigrid with GMRES polynomials (AIRG) for Boltzmann transport that showed scalable work with uniform P0 angle in the streaming and scattering limits. This paper details the practical requirements of using this new iterative method with angular adaptivity. Hence, we modify our angular adaptivity to occur directly in P0 space rather than the Haar space. We then develop a modified stabilization term for our Finite Element Method that results in scalable growth in the number of nonzeros in the streaming operator with P0 adaptivity. We can therefore combine the use of this iterative method with P0 angular adaptivity to solve problems in both the scattering and the streaming limits, with close to fixed work and memory use.We also present a coarse-fine splitting for multigrid methods based on element agglomeration combined with angular adaptivity, which can produce a semicoarsening in the streaming limit without access to the matrix entries. The equivalence between our adapted P0 and Haar wavelet spaces also allows us to introduce a robust convergence test for our iterative method when using regular adaptivity. This allows the early termination of the solve in each adapt step, reducing the cost of producing an adapted angular discretization. [ABSTRACT FROM AUTHOR]

This paper presents a finite element analysis (FEA) model of a studded tyre rolling on snow. The model takes into account the mechanical properties of both the tyre and the snow, as well as the interactions between them. The FEA simulations were performed using single set of 99 studs with constant compaction depth, and the results were compared to experimental data. The study found that the studded tyre was able to significantly improve traction on snow-covered roads by a minimum factor of 1.17 at −50% slip and a maximum factor of 1.5 at an interval of 50% to 100% slip, compared to non-studded tyre, and that the FEA model accurately predicted the tyre's behaviour in these conditions. The results of this study can be used to optimise the design of studded tyres and to improve the safety of vehicles in snowy conditions. [ABSTRACT FROM AUTHOR]

Axial forces are generated in the plates of ADAS-yielding dampers when subjected to lateral loading due to their boundary conditions. This on one hand can lead to an increase in strain level of the plates and accelerate the damage process, while on the other hand, the interaction of the bending moment with the tensile axial force leads to increasing strength, which is undesirable in the performance of ductile members. In this paper, a modified ADAS device (MADAS) is introduced to prevent undesirable interaction of axial forces, and its cyclic behavior is evaluated both experimentally and numerically. To this end, in the first step, two test specimens with different number of connection pins were prepared and subjected to cyclic loading in a rigid frame. Experimental and numerical results have shown that due to the removal of the constraint in the vertical direction, the level of forces produced by the damper is almost constant and the X-shaped plates have been able to tolerate significant number of cycles before crack initiation. Afterwards, the cyclic performance of ADAS and MADAS dampers was numerically compared individually and also when placed in the frame. Furthermore, in the frame equipped with ADAS damper, the increase in the level of forces produced by the damper led to the buckling of the braces, while the level of generated forces was totally in the expected range in the frame equipped with MADAS damper. [ABSTRACT FROM AUTHOR]

Earthquake-induced pounding in bridges is a complex contact phenomenon in which the dynamic responses of structures, including collisions between deck and abutments, are strongly related to structural properties and earthquake excitation. The goal of this study is to develop and compare the seismic fragility curves of overall system and individual components of regular and irregular box-girder highway bridges in two cases: with pounding and without pounding. For this purpose, four levels of altitudinal irregularity, ranging from regular to highly irregular, are considered. To extend the results for all bridges in the same class, different sources of uncertainties related to earthquakes, structural geometries, and material properties are taken into account. The analytical fragility curves have been developed based on nonlinear time history analyses in OpenSees finite element software for the cases with and without pounding effects. The process has been repeated for each two-, three-, and four-span classes at four irregularity levels. The fragility function parameters for the two cases with and without pounding have been compared for all classes considered in this study. Using fragility functions, this paper clarifies the interactive roles of irregularity and pounding between deck and abutments for seismic vulnerability of multi-span box-birder highway bridges. The results indicate that collisions often show an adverse effect on all structural components. It has also been observed that the detrimental effect of pounding on seismic fragility is more apparent in irregular bridges when compared with regular ones. In addition, the study introduces a conversion coefficient to clarify the effects of pounding on the fragility of bridge components and the overall system. This coefficient can be applied in both conventional analytical methods like static or simplified analysis and technical earthquake models like HAZUS, adjusting fragility values for pounding and irregularity effects. [ABSTRACT FROM AUTHOR]

This paper aimed to investigate the biomechanical changes during the talus impact with the calcaneus at varying velocities. Various three-dimensional reconstruction software was utilized to construct a finite element model that consisted of the talus, calcaneus, and ligaments. The explicit dynamics method was used to explore the process of the talus impacting on the calcaneus. The velocity of impact was altered from 5 m/s to 10 m/s with a 1 m/s interval. Stress readings were collected from the posterior, intermediate, and anterior subtalar articular (PSA, ISA, ASA), calcaneocubic articular (CA), Gissane Angle (GA), calcaneal base (BC), medial wall (MW), and lateral wall (LW) of the calcaneus. The changes in the amount and distribution of stress in the different regions of the calcaneus that varied with velocity were analysed. The model was validated through comparison with findings from the existing literature. During the process of impact between the talus and calcaneus, the stress in the PSA reached its peak first. Notably, stress was concentrated mainly in the PSA, ASA, MW, and LW of the calcaneus. At varying impact velocities of the talus, the mean maximum stress of the PSA, LW, CA, BA, and MW exhibited statistically significant differences (P values were 0.024, 0.004, <0.001, <0.001, and 0.001, respectively). However, the mean maximum stress of the ISA, ASA, and GA was not statistically significant (P values were 0.289, 0.213, and 0.087, respectively). In comparison with the velocity at 5 m/s, the mean maximum stress increases in each region of the calcaneus at a velocity of 10 m/s were as follows: PSA 73.81%, ISA 7.11%, ASA 63.57%, GA 89.10%, LW 140.16%, CA 140.58%, BC 137.67%, MW 135.99%. The regions of stress concentration were altered, and the magnitude and sequence of peak stress in the calcaneus also varied according to the velocity of the talus during impact. In conclusion, the velocity of the talus during impact had a significant influence on the magnitude and distribution of stress within the calcaneus, which was a crucial factor in the development of calcaneal fractures. It was possible that the magnitude and sequence of stress peaks played a vital role in determining the emergence of fracture patterns. [ABSTRACT FROM AUTHOR]

The paper investigates the stiffness and strength of log walls with standard and dovetail bonded corners under lateral loads. The finite element model is developed and validated with experimental work at small-scale and wall-scale levels. The validated wall-scale model was modified by conducting a detailed investigation on assessing the wall behaviour with varying crucial parameters, including coefficient of friction, vertical load, geometric irregularities, and the wall's aspect ratio. The study suggested various techniques for improving the wall's lateral load resistance capacities and initial stiffness, employing steel and wood pins. [ABSTRACT FROM AUTHOR]

Integral abutment bridges (IAB), especially the short to medium-span IABs, have become more popular throughout the years in Australia as well as globally. IABs have advantages over traditional bridges in terms of their construction and maintenance costs due to the elimination of expansion joints. However, the thermal expansion can develop significantly larger earth pressure behind the abutment, thus leading to excessive forces (i.e. moment and shear force) to the foundation, which are not considered during the design process and can cause cracking and failures, eventually. It is observed from the field monitoring of IABs that the earth pressure model used to estimate the pressure distribution is not adequate to capture possible variations. Further, the performance of IABs highly depends on the complex interaction of abutment-backfill and soil-foundation and the time-dependent and cyclic behaviour of backfill and foundation soils. In this paper, nonlinear finite element model of an IAB considering the time-dependent effects of materials is presented to simulate long-term responses due to thermal loading. The developed IAB model results are validated using field monitoring data and parametric study is performed including the geometry of IAB, thermal loading, and soil properties. The results are used to investigate the functional relationship between input parameters and long-term responses which are further utilised to develop a new earth pressure distribution model for the design and performance assessment of IABs. [ABSTRACT FROM AUTHOR]

In this paper, transmitted surface waves are used to quantitatively detect the length and angle of inclined surface cracks based on laser ultrasonic technique. The interaction between laser-generated surface waves and inclined surface cracks is analysed, and the propagation path and mode conversion process of the transmitted surface waves are considered. Then, the propagation paths of some peaks and troughs of the transmitted surface waves are obtained. Based on the obtained path and modal conversion information, a quantitative detection method for the length and angle of inclined surface cracks is proposed. The finite element method is used to verify the propagation paths and proposed method, and the results show that the arrival time of the theoretical path is consistent with that of the simulation. The relative measurement errors of the surface crack length and angle are less than 15% and 10%, respectively, which verifies the rationality and correctness of the proposed method. [ABSTRACT FROM AUTHOR]

Phase change material (PCM) mixed in soil can effectively adjust the subgrade temperature. In order to analyze the temperature field change of soil containing PCM more accurately from the microscopic point of view, it is a key problem to construct a refined geometric model. This paper scans the fracture plane of soil containing PCM through the stereoscopic microscope and prepares the label image corresponding to the sample image. Then a U-Net semantic segmentation model is established, which can accurately recognize PCM area and soil area. Finally, a geometric model of soil containing PCM that is consistent with reality is established, and its heat transfer characteristics are analyzed by finite element method. The accuracy evaluation of the segmentation model and the visualization of the recognition results show that the evaluation indexes of U-Net are the best. P, R, F1, and MIoU of U-Net are 0.889, 0.918, 0.903, and 0.901, respectively. The refined model established in this paper can not only observe the overall temperature regulation effect of the material but also accurately describe the internal temperature distribution details of soil containing PCM during heat transfer. Through numerical simulation, it is found that the maximum temperature of mixture decreases by 1.6 °C and the minimum temperature of mixture increases by 2.3 °C. [ABSTRACT FROM AUTHOR]

Although Friberg's theoretical analysis is frequently used to analyse the dowel bar-concrete interaction in jointed plain concrete pavement (JPCP) system, the compressive stress concentration at top and bottom of the dowel slot cannot be explained with this theory. In this paper, two modifications including the elastic deformation of concrete support and the stress distribution factor considering the sinusoidal contact stress distribution are proposed to improve the Friberg's theoretical analysis. Modifications are then validated against elastic finite element analysis (FEA) results in terms of the contact stress distribution, the maximum compressive stress as well as the range of compression zone. To further investigate the maximum compressive stress at the joint surface, relevant parameters including the dowel bar diameter, the modulus of elasticity of concrete as well as the joint width are studied through elastic finite element analysis (FEA). Apart from proposing referenced moduli of dowel support, a close relationship between the modified modulus of dowel support and dowel bar diameter is also found and verified. Finally, differences between the Friberg's theoretical analysis and the modified method are summarised in a flow chart at the end of the paper. [ABSTRACT FROM AUTHOR]

Abstract The deterministic methods are efficient for solving the neutron transport equation (NTE), but suffer from discretization errors. The increasingly complex geometric models make spatial discretization errors the primary source of discretization errors. Considering that spatial discretization errors come from inaccurate geometric shape descriptions and low-accuracy numerical schemes, this paper develops a Discontinuous Galerkin Finite Element Method for the NTE on unstructured polygonal meshes to reduce spatial discretization errors. In this method, the physical modal basis is adopted to handle the polygonal mesh and to achieve high-order accuracy in a uniform and efficient way. The numerical results of various fixed-source and k-eigenvalue benchmarks demonstrate that the method developed in this paper can give accurate solutions on polygonal meshes with high convergence rates. [ABSTRACT FROM AUTHOR]

In this paper, a contact slip mechanics model based on pressure distribution is developed, it is formed from multiple contact pairs and can define the contact behavior between contact interfaces. First, we establish the jointed structure's finite element model to calculate the contact interface's nodal pressure. Following this calculation, applying the cubic spline interpolation to the nodal pressure data, we obtain the contact surface pressure. Then using the theory of load equivalence, the contact surface pressure is converted into an equivalent load. The equivalent load is used as the normal pressure of the contact pairs place on the contact surface nodes. Subsequently, to verify the developed modeling approach, we establish a simplified blade model with the tenon–mortise structure for trial calculation. Finally, the nonlinear frictional force is linearized to solve the nonlinear differential equation by the incremental harmonic balance method (IHBM). The results show that the tenon–mortise contact surface exhibits micro-slip characteristics, which means that the pressure distribution characteristics of the contact surface are retained. The contact slip mechanics model developed in this paper is general which can be applied in modeling the contact surfaces of other joints. [ABSTRACT FROM AUTHOR]

The double cantilever beam (DCB) specimen is widely used to characterise the mode I fracture of adhesive joints. This paper analyses some particular characteristics of adhesively bonded composite DCB specimens which could affect test results. Three-dimensional (3D) and two-dimensional (2D) finite element analyses (FEA) were conducted in order to evaluate the effects bondline constraint and adherend through-thickness flexibility on the specimen response. Since beam theory-based data reduction schemes are widespread, beam models were also employed to analyze the effects of adherend through-thickness flexibility and fracture process zone relative size. It is shown that, although composite adherends are usually thinner and have much lower transverse moduli than metal adherends, the level of bondline constraint is similarly high. This may: limit the level of adhesive plastic deformations in the fracture process zone; generate high bondline tractions that increase the likelihood of interface failure and interlaminar damage in the composite adherends. The present analyses also show relevant effects of adherend through-thickness flexibility in the adhesive elastic loading stage. Finally, smaller fracture process zones relative to metal adherend DCB specimens were predicted by a beam cohesive zone model. This may explain lower fracture energy values reported with composite adherends in some studies. [ABSTRACT FROM AUTHOR]

AbstractIn this paper, the Gyroid triply periodic minimal surface is prepared by liquid crystal display photopolymerization technology, and 10 models of the periodic parameter T in [1/5, 2] are designed. Using the method of finite element method and experimental verification, when T = 1/3, there are fewer stress concentration areas on the Gyroid surface, the number of grids is moderate, the compression crush rate is the smallest, and the porosity error is reasonable. Through the microscopic morphology, it is found that the surface, after printing, forms gear shape and resin residue so that the actual volume is larger than the theoretical volume, and the porosity is minor. Keeping periodic parameter T = 1/3 and porosity of 50%, four kinds of Gyroid surface structures were designed by changing the parameter surface offset, wall thickness, offset thickness, and gradient arrangement. The effects of different loading directions on its mechanical properties, deformation behavior, and energy absorption were discussed through compression experiments. The results show that the vertical load is applied to form a fault zone from the upper left angle to the lower right angle of 45°, and the parallel load is applied to create a fault zone from the upper right angle to the lower left grade of 45°. When the load is used in the vertical direction, the energy absorption and energy efficiency of the surface offset Gyroid surface are the largest. When the load is applied in the parallel order, the energy absorption curves of the four structures change similarly, and the deformation amplitude of the wall thickness Gyroid surface during the compression process is relatively stable. The energy efficiency of gradient arrangement Gyroid surface increases fastest in the compaction stage. [ABSTRACT FROM AUTHOR]

A novel high-temperature resistant carbon fiber/bismaleimide resin composite shell is proposed and its bistable characteristics are studied in megathermal environment. Bistable structures are prepared with epoxy resin composites conventionally, which prone to undergone glass transition at high temperature. The study of high-temperature resistant bistable structure become necessary to suit aerospace field. In this work, the effect of elevated temperatures and different ply angles were investigated on curvatures and snap behaviors of carbon fiber/bismaleimide resin composite bistable shells through experiment and finite element analysis. These results provided significant understanding of morphing behaviors for the carbon fiber/bismaleimide bistable structure in megathermal environment. A novel high-temperature resistant carbon fiber/bismaleimide resin composite shell is proposed and its bistable characteristics in megathermal environment are studied in this paper. Bistable structures are prepared with epoxy resin composites conventionally, which prone to undergone glass transition at high temperature. The study of high-temperature resistant composite bistable structure become necessary to suit the actual working conditions. In this work, the anti-symmetric bistable shells with different ply angles (40°, 45°, 50°) are fabricated using T700/QY8911 prepreg. The effect of elevated temperatures and different ply angles were investigated on the principal curvatures and twisting curvatures of carbon fiber/bismaleimide resin composite bistable shells through experiment and finite element analysis. The snap behaviors of the bistable shells with different ply angles at different temperatures were obtained. Furthermore, a novel two-point tensile loading method was applied to the snap-back processes of carbon fiber/bismaleimide resin composite bistable shells with the subtended angles greater than 180°. It is noticed that the bistable shells have better high-temperature stability than carbon fiber/epoxy bistable shells. These results provided significant understanding of morphing behaviors for the carbon fiber/bismaleimide bistable structure in megathermal environment. [ABSTRACT FROM AUTHOR]

This paper presents the demonstration of underwater thermoacoustic (TA) sound generation using three-dimensional graphene (3D-C). 3D-C is able to interface with water as the immediate acoustic medium, resulting in reduced attenuation across solid packaging encapsulation due to favorable acoustic impedance matching. This is shown using array configurations of 2*2 and 4*4 individual 3D-C elements prepared onto printed circuit boards and secured within a watertight cuboid Delrin container with deionized water. Comparisons of underwater acoustic performance between internal medium of water and air shows significant improvement in measured sound pressure level (SPL) with internal water medium, in contrast with internal air medium where SPL were below noise floor. This demonstration opens up new possibilities of 3D-C for underwater acoustic applications. Simulations are conducted using 3D finite element model generated with COMSOL Multiphysics and validated with experimental results. A revised formulation of transmission voltage response (TVR) specific to TA sound generation is proposed due to the difference in power scaling of TA sound generation and subsequently validated using simulation. [ABSTRACT FROM AUTHOR]

An implicit limit state function is predicted with a support vector machine (SVM) for reliability analysis of engineering structures to reduce the number of finite element analyses. The accuracy and predictability of the SVM method are reduced considerably by noise in data. In this paper, density-based spatial clustering of applications with noise (DBSCAN) is applied to reduce the noise in training samples for SVM regression. Then, the SVM model is linked with Monte Carlo simulation (MCS) to find out the reliability of the engineering structures. Four different examples of static and dynamic problems are solved to show acceptability and efficiency of the proposed method. It is observed that the proposed method is suitable for a smaller number of performance function calls. Direct MCS, artificial neural network-based MCS and response surface methods have been used to examine the effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a numerical axisymmetric elastic stress wave propagation analysis of the 2D-FGM hollow thick finite cylinder has been performed. The new accurate material distribution model based on Mori-Tanaka scheme and third-order transition function for 2D-FGMs has been implemented in the graded finite element method with higher-order quadrilateral elements. A non-uniform impulsive pressure has been applied on the one-third of the top inner cylinder wall. Consequently, different wave velocities and reflections from the boundaries have been observed due to the graded distribution of material along with two directions. Moreover, the effects of two-dimensional material property distributions on the stress wave propagations and displacements through the cylindrical wall at different locations have been studied systematically. Normalized effective stresses based on von-Mises criteria has been performed in comparison with the internal impulsive pressure amplitude to provide a measure of the cylinder wall response to the mechanical impact loading, the effective stresses are nearly 2.5 times the internal pressure loading amplitude, closed to the impact location. According to the results, 2D material property gradations has effected the stresses significantly. Alternatively, desired stress values can be achieved through optimal design and appropriate choice of property distribution. [ABSTRACT FROM AUTHOR]

Helical piles have lately emerged as a viable alternative foundation solution in offshore geotechnical applications. The helical piles are typically installed in groups to resist large loads from the structures and may encounter combined loading due to some factor such as the waves from the water surrounding it. Recent research works on group helical piles focused mostly on piles embedded in sand and their response to individual loading regimes. This research has been carried out to examine the behaviour of the helical pile groups embedded in soft clay subjected to combined uplift and lateral loading considering three different configurations (rectangular, triangular, and square) and different spacings between the helical piles (2 to 5 times the helix diameter). A three-dimensional finite element model is developed to predict the load-displacement response of the group and is validated against the 1 g laboratory scale model test results. The findings from the analyses reveal that the influence of combined loading reduces the lateral capacity of the group helical pile. The spacing between the helical piles also has a substantial impact on the response to combined loading. The role of critical spacing ratio for various configurations has also been discussed in this paper. [ABSTRACT FROM AUTHOR]

Remarkable characteristics like simple structure, high starting torque, simple maintenance, good efficiency at all speeds and cost-effectiveness have made switched reluctance machines (SRMs) suitable candidates for electric cars, electric bicycles and variable speed applications (VSAs) such as wind turbines. In this paper, a three-phase Outer-Rotor SRM (ORSRM) with 6 stator poles and 10 rotor poles (6/10) for VSA has been investigated. Unlike conventional SRM structures such as 6/4 and 12/8, an SRM model with higher number of rotor poles can reduce torque ripple much more effective than conventional SRMs. First, the SRM design is done accurately, then, by changing some parameters, the sensitivity analysis is performed on torque ripple and average torque. Finally, the optimisation process on the geometry and structural dimensions of the SRM like rotor pole arc, stator pole arc, rotor yoke thickness, rotor pole height, rotor diameter and the number of turns per phase are executed to minimise the torque ripple and maximise the average torque via genetic algorithm (GA). The initial design, optimisation and performance of the proposed model are validated via a 2-D finite element method (FEM) technique by ANSYS-Maxwell. [ABSTRACT FROM AUTHOR]

A reaction–diffusion problem with discontinuous source term and Dirichlet's boundary conditions on the unit square is considered in this paper. The proposed problem has been discretized using a combination of standard Galerkin finite element method (FEM) and non-symmetric discontinuous Galerkin finite element method with an interior penalty (NIPG) with bilinear elements. Layer adapted mesh of Shishkin type has been utilized to discretize the domain. Standard Galerkin FEM is applied on the layer part of the domain where the domain is dense enough and NIPG is applied to the outside layer part. By means of special choice of discontinuity-penalization parameters, the scheme is proved to be uniformly convergent of order $ \mathcal {O}(\varepsilon ^{1/4}N^{-1} + N^{-1} \ln N) $ O (ε 1 / 4 N − 1 + N − 1 ln ⁡ N). Numerical tests are carried out in support of theoretical findings. [ABSTRACT FROM AUTHOR]

This paper aims to study the effect of stress corrosion on the electrochemical behavior and corrosion mechanism of epoxy zinc-rich coating/steel substrate. The electrochemical impedance spectroscopy (EIS) was applied to characterize the corrosion behavior of the system under different stress conditions (σ1 = 0MPa; σ2 = 120MPa; σ3 = 180MPa and σ4 = 240 MPa), and appropriate equivalent circuits were established. Additionally, the von Mises stress distribution and potential distribution around the pitting pit at the coating-substrate interface were quantified by means of finite element analysis. The approach used different tensile strains and the depths of the pitting pit to relate the corrosion current density and corrosion rate to the corrosion process. The EIS results demonstrate that, given the same time, the failure time of the epoxy zinc-rich coating/steel substrate system with 240 MPa is shortened by 27.8% compared to the system without stress. Meanwhile, the finite element model confirms that the uneven potential distribution around the pitting pit is responsible for coating failure. In-depth profile of the corrosion rate shows an increasing trend over the distance from the opening. Then this local corrosion acceleration will cause further stress concentration, which in turn accelerates the corrosion process of the system. [ABSTRACT FROM AUTHOR]

This paper explores the aero-thermo-elastic properties of variable stiffness composite laminates (VSCLs) with fibers steered along curved trajectories using a refined 1 D model. High-order solutions are generated by the p-version finite element method in conjunction with the Carrera Unified Formulation (CUF), which is applied to structural modeling by employing the improved hierarchical Legendre expansion (IHLE) in particular. The merit of using such a kind of expansion lies in that both the Equivalent Single Layer (ESL) and Layer-Wise (LW) theories can be formulated in a compact and straightforward manner. The linear piston theory is utilized to model the aerodynamic force, whereas the steady-state temperature field is applied during the flutter analysis. The weak-form governing equations are derived by taking a perturbation of the equilibrium configuration, and divergence and flutter instabilities are determined by solving the related eigenvalue problem. The accuracy of the proposed model has been verified through several test cases involving flutter, thermal buckling, and vibration of symmetric and antisymmetric VSCLs. The obtained results were compared to those obtained using the ABAQUS software and the available literature. Finally, the effect of the kinematic order, shear coefficient, and temperature variation on the critical dynamic pressure of VSCLs is thoroughly investigated. [ABSTRACT FROM AUTHOR]

Earthen levees are critical civil infrastructure of coastal regions for flood protection. Earthquakes can cause significant deformation and damage to earthen levees. Seismic performance of such levees under the earthquake hazards is a major concern in their safety evaluation. However, there are significant uncertainties in assessing the seismic behavior of earthen levees and geotechnical uncertainties play a critical role in the probabilistic assessment of earthquake-induced deformation and failures. This paper presents a simplified probabilistic framework for assessing the seismic performance of earthen levees with dynamic analysis and finite element modeling. In this framework, the effects of geotechnical uncertainties are explicitly considered in the uncertainty propagation for probabilistic evaluation of seismic deformations of earthen levees under earthquake hazards. The probability curves are developed to describe the correlations among the probability of exceedance, limiting deformation value, and input peak ground acceleration. The derived probability curves can provide valuable information for risk assessment and risk-informed decision-making of earthen levee infrastructure. The effectiveness of the proposed probabilistic framework is demonstrated through a case study of earthen levee example. [ABSTRACT FROM AUTHOR]

In this paper, a composite excitation method is used to optimize the design of an existing cantilevered cylindrical ultrasonic motor to avoid vibration interference. Modal and transient simulation analysis of the stator structure was carried out by the finite element method. Optimized stator structure is simpler than the original motor. Simulation analysis results show that the circumferential amplitude is increased by more than 35% with 55.7% reduction in ceramic usage. [ABSTRACT FROM AUTHOR]

This paper presents a constitutive model for the behavior of steel fiber reinforced concrete (SFRC) under mixed mode cracking taking into account the fiber orientation effect by using a micromechanical approach. Firstly, the resistant mechanisms of an inclined fiber are modeled by a closed-form analytical function. The bridging force is calculated by integrating on the cracked surface, the product of the fiber extraction force by its orientation probability. A modified model of the aggregate interlock mechanism is combined with the fiber bridging stresses to obtain the cohesive stresses. This mesoscale model is then extended using an elastic damage model and a fixed smeared cracking concept to assess the structural behavior. The model is finally implemented in a Finite Element Analysis (FEA) software, its performance is tested with some experimental results collected in the literature. The model successfully integrates the fiber orientation effect and shows a good prediction of stress transmission. [ABSTRACT FROM AUTHOR]

This paper presents static modelling and simulation of a spherically-shaped hyperelastic balloon actuator subjected to an angular rotation with an internally applied air pressure. These actuators are extensively used in soft robotics because its safe and flexible nature. The balloon actuator is a pneumatic-type actuator made of a polymeric material. A continuum mechanics-based analytical modelling and Finite element method-based simulation are performed to predict the response of the actuator for a given angular rotation with internally applied air pressure. The proposed modelling framework is subsequently utilised to perform the parametric studies for varying pressure, thickness, and rotational speed of the actuator. Various elastic instability curves are also obtained to examine the critical inflation of the rubber balloon actuator. The analytical findings agree well with the FEM simulations. [ABSTRACT FROM AUTHOR]

A new hybrid finite-element model was developed for heat flux and temperature analyses in porous material. The model in this paper was based on an assumed heat flux hybrid finite-element method, which is a twofield functional. An independent heat flux field that meets a priori inner thermal equilibrium was assumed inside the element, and a temperature field was assumed on the cell boundary. Temperature was used as the Lagrange multiplier to introduce the continuous condition of heat flux at the hole edge into the functional, and a modified complementary energy functional was obtained. The element flux field that was built up of polynomial terms and reciprocal terms from the stream function and that can consider the shape of pores in location coordinates was raised for the first time. Several numerical examples are discussed and compared with conventional finite-element methods to validate the accuracy and efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper aims to assess the mechanical characteristics of the orthotropic steel deck (OSD) in heavy-haul railway bridges. Taking the Dongting Lake Bridge as an example, to simulate the transfer effect of the track structure and get mechanical characteristics of the OSD under the service load, the refined segmental finite element model (FEM) of the OSD in a heavy-haul railway bridge was established. Moreover, the Chinese C80 heavy-haul train (the C80) was selected as the applied load to make the analysis results close to the actual situation. And then, the stress influence lines of critical components in OSD were analyzed. Notches at diaphragms of the OSD are more likely to produce stress concentration. Due to the dense distribution and high stiffness of the longitudinal ribs of OSD, the final load influence range of OSD is limited. Since the T-shaped longitudinal ribs (T-Ribs) are located under the position of each rail, and its stiffness is greater than the adjacent U-shaped longitudinal ribs (U-Ribs), so that the T-Ribs are important load-bearing components of the OSD in heavy-haul railway bridges. Furthermore, the influences of the stiffness ratio of T-Rib to U-Rib on the mechanical characteristics of the OSD were analyzed. [ABSTRACT FROM AUTHOR]

Stiffness properties of structural members, such as beam, plate and shell, can change drastically in the presence of axial forces due to geometric effects of the nonlinear strain components. In this paper, the stability behaviour of beam-column is investigated using the governing differential equation and compared with the geometrically nonlinear finite element analysis. The lateral deflection obtained from the theoretical model matches quite accurately with the numerical values for wide range of axial to critical load ratio P/Pcr. It is shown that bending stiffness decreases linearly with the axial load. By extending the theory, an expression for the membrane stiffness of the beam-column is presented in this paper. The geometrically nonlinear finite element analysis can capture exactly the parabolic variation of the membrane stiffness as per the derived expression. It increases initially up to P/Pcr = 0.35 and decreases rapidly to negligible value near the critical load indicating buckling instability. [ABSTRACT FROM AUTHOR]

Overhead conductor rail (OCR) is an important power supply device in tunnel railway lines. The penalty method is widely adopted to model the dynamic interaction behaviour of the pantograph-OCR system (POCRs), while it is difficult to determine a proper contact stiffness value. This paper proposes a three-dimensional contact formulation for the POCRs based on the Lagrange multiplier method. Accurate contact forces can be obtained easily by this contact formulation without the trouble of determining the contact stiffness. Contact force is defined in the global coordinate system as a three-dimensional vector. Coulomb law of friction is adopted in this paper to describe the tangential contact force, and the train speed is included in the contact formulation. The central finite difference approximation method is utilised, and an iteration procedure is elaborated to calculate the accurate contact force vector. The proposed contact formulation is verified by comparing simulation results with in-line measured data. The maximum statistical relative error of the contact force is only 2.63%. The advantages of the proposed contact formulation are also demonstrated by comparing it with the penalty method. [ABSTRACT FROM AUTHOR]

This paper is Part II of the two-paper series 'HALO3D: An All-Mach Approach to Hypersonic Flows Simulation' presenting advances in a monolithic flow simulation software for the design of high-speed aircraft. Part II highlights the methodology behind the continuum regime finite-rate surface chemistry, weak-ionisation, and rarefied regime Direct Simulation Monte Carlo modules. Validation and benchmark simulations of flows over a 2D cylinder, the 3D RAM-C II geometry, and the 3D Lockheed Martin X-33 geometry are provided. Within HALO3D, a Hessian-based multiphysics automatic mesh adaptation methodology yields optimal solutions that ought to provide valuable benchmarks for verifying other hypersonic flow simulation tools. Such mesh optimisation automatically generates a common truly mesh-independent solution across the continuum and rarefied regimes, taking into account various thermo-chemical models. These developments establish HALO3D as a mature, readily extendible software package for hypersonic aircraft analysis. [ABSTRACT FROM AUTHOR]

The identification of the flow pattern within the bearing chamber's oil and gas two-phase flow is crucial for its lubrication design. Aiming at the lack of accuracy and universality of the current bearing chamber oil and gas two-phase flow pattern recognition, this paper introduces a new method for recognising oil and gas two-phase flow patterns based on the Kriging model. In this paper, the oil-gas two-phase flow field in the bearing chamber is modelled in Comsol simulation software using the level set-k- $ \varepsilon $ ε model. Subsequently, the finite element analysis results were used as samples to fit the Kriging model, and the effects of different variables on the flow pattern were analysed and compared with the actual results. The results demonstrate that the flow pattern discrimination results fitted by the Kriging model exhibit higher accuracy and greater generalisability. This holds significant implications for future lubrication and structural design of bearing chambers. [ABSTRACT FROM AUTHOR]

The paper presents a mathematical formulation of the problem of natural and forced harmonic vibrations of electro-elastic thin-walled structures interacting with a flowing fluid. The numerical algorithm based on the finite element method is used to choose optimal parameters of a shunt electric circuit for problems of passive vibration damping. The key idea behind the proposed approach is a solution of eigenvalue problem. It allows us to obtain higher damping rate of free vibrations compared to those evaluated by the commonly used analytical expressions and leads to the smallest difference in the natural frequencies of the structure and the electric circuit. [ABSTRACT FROM AUTHOR]

The optimal experimental design (OED) provides informative experimental resources and reduces the inherent uncertainty of the experiment. The OED is a framework to maximize performed experiments by controlling design variables. This paper proposes the OED framework combined with deep neural network (DNN) surrogate model to find the optimal design over large and complex design space. The OED has the optimization process to maximize the conditional mutual information (CMI) between hidden properties and composite structural performances. Approximate coordinate exchange (ACE) algorithm was applied to find the optimal design over a high and complicated design space. For fast optimization, surrogate DNN model was used instead of finite element analysis. Two examples were executed for the demonstration of the OED frameworks. From the results of each demonstration, OED provided the results that are consistent with heuristic knowledge. [ABSTRACT FROM AUTHOR]