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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]

The evidence of soil nonuniformity has been reported in several site investigation reports and is well-confirmed for any soil in general. However, studies related to the spatial soil variability of offshore ground are somewhat limited, and current design practices for monopile foundations also overlook the uncertainty of the offshore ground. This paper presents the probabilistic evaluation of the serviceability limit state of monopile foundations considering the spatial variability of offshore ground. The nonuniformity of the ground is modeled utilizing the site-specific undrained shear strength (su) as a stochastic variable, using a spatially correlated Gaussian random field. A hardening soil constitutive model is utilized in 3D finite element analysis of offshore ground, with a focus on parameter calibration. The reliability of the serviceability limit state is assessed based on the allowable load on the pile head. The stochastic behavior of the maximum bending moment and maximum shear force along the depth of the monopile is also investigated. Besides, the paper also highlights the importance of incorporating ground nonuniformity during the design process of a monopile foundation. [ABSTRACT FROM AUTHOR]

Wire ropes are widely observed in many industries such as marine engineering and civil engineering, as a type of structure that can bear huge axial force. There are various kinds of wire ropes in practical engineering, corresponding to different usage scenarios. This paper focuses on 6 × 36SW + 1WR with a diameter of 16 mm. The axial mechanical properties of the wire rope are investigated by experimental, theoretical, and numerical methods. The stress–strain curve and ultimate strength of the steel wire rope obtained in the test are compared with the corresponding results from the finite element simulation. The comparison demonstrates the accuracy and reliability of the finite element model. In addition, a series of parametric studies are conducted to investigate the influence of pitch length and friction coefficient, etc. The purpose of this paper is to propose an accurate and efficient finite element model for the mechanical analysis of wire ropes. [ABSTRACT FROM AUTHOR]

Corroded pipelines are often repaired with Carbon Fibre-Reinforced Polymers (CFRPs) because of their low cost, fast and easy process. In this paper, the Finite Element Method (FEM) was used to establish the model of corroded pipelines repaired with CFRP under bending loads. The progressive damage subroutine was used to simulate the damage of CFRP, and the cohesive element was used to simulate the damage to the interface. The failure modes of repaired and unrepaired pipelines were in good agreement with the experimental results. It was found that the failure order of CFRP and adhesive was different when the thickness of the adhesive changed. Failure competition existed between CFRP and adhesive, which led to different ultimate loads of the repaired pipelines. This research reveals that the failure modes and ultimate loads are relevant to the competition mechanism of different materials in composite structures. [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]

When the gas pipeline leaks, it causes huge economic losses. This paper establishes a digital twin model of a pipeline based on the pressure signal generated by a pipeline leak and researches on pipeline leak detection. First, an online updating of the twin model is established to update the data of the physical information space and the parameters of the twin model online. Second, a visual model is established to display the spatial data of physical information of pipelines and output data of the digital twin of pipelines in real-time. If pipeline leakage is identified, an alarm would be triggered and a corresponding emergency rescue plan would be initiated based on the the leakage. Finally, the pipeline leakage identification model can be established by analysing the finite element model of the pipeline, and the sample data were obtained and preprocessed to extract the feature vectors. The training model of the Support vector machine (SVM) was used to classify the working conditions. Theoretical analysis and experimental results show that the method proposed in this paper has high detection accuracy, so it is feasible to judge gas pipeline leakage by using digital twin prediction. [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]

As basic structural components of the ship hull, stiffened plates suffer both thrust and shear loads while ships sail in rough sea environments. In order to guide the scaled model design effectively, the similarity law is investigated in this paper. The parameters that determine the nonlinear behaviour of the stiffened plate under compression and shear loading are defined and the nonlinear similarity method is improved. This method is applied to design a scaled model under combined bending and torsional moment, and the collapse test is conducted to research the collapse characteristics. The collapse behaviour of actual ship structures under combined loads predicted by the model test is compared with that obtained by the nonlinear finite element analysis. The good agreement represents the capability of the newly improved nonlinear similarity law. The present research provides a proper way to investigate the collapse characteristics of actual ship structures through a model test. [ABSTRACT FROM AUTHOR]

This work describes the natural convection and thermodynamic irreversibility of alumina-water nanofluid filled inside a layered cavity. The local thermal non-equilibrium (LTNE) approach is taken into consideration. The cavity bed is considered as a wavy hot plate of a very thin thickness, while its roof is thermally insulated. The heat is dissipated from the cold vertical walls. A porous layer fills the cavity's lower half and is assumed to obey the Darcy-Forchheimer model. The finite-element method is adopted to compile the numerical results. The relevant parameters assessed in this paper are the Darcy number, waviness of the hot bottom wall, porosity, volume fraction of alumina nanoparticles and the modified ratio of thermal conductivity. The obtained numerical results show that the LTNE condition expands as the Darcy number augments, while a quasi-local thermal equilibrium is attained with a higher modified ratio of thermal conductivity. The waviness of the hot wall raises the Nusselt number of both the fluid and the solid phases but produces more entropy. It is quoted that the augmentations in the fluid and solid phases of the Nusselt numbers and the increase in the maximum entropy production are 42.25%, 69% and 55.5%, respectively. [ABSTRACT FROM AUTHOR]

Rubber-like materials such as sealant with recent developments in formulation are widely used in various structural components, especially in aerospace industry with many applications such as the sealing of bolted joints on aircraft. The objective of this paper is to assess the load transfer distribution in bolted-sealed joints through an approach coupling both experimental and numerical tests. Quasi-static and relaxation tests under uniaxial and pure shear loading were carried out to determine the parameters of phenomenological hyperelastic laws and of the generalized Maxwell model for the sealant PR 1782 C2. The fastener is an alloy steel bolt with a protruding head when the substrates are made from aluminum 2024-T3. Experimental and numerical quasi-static tests were then performed on double-lap bonded and bolted-sealed joints under in-plane loading. The numerical tests are done using 2D and 3D Finite Element (FE) models; they involve the visco-hyperelastic behavior previously assessed for the sealant. Accounting for visco-hyperelasticity makes it possible to better estimate the load transfer between bolt and sealant layer. Typically, the bolt load transfer rate is derived from numerical output for different sealant thicknesses. In the considered geometrical joint configuration, the sealant load contribution is between 7% and 13% according to the sealant thickness. Methodology and results provide a solid basis for the fatigue strength prediction of bolted-sealed joints. [ABSTRACT FROM AUTHOR]

To estimate the fatigue life of lightweight automotive structures in compliance with top-down design principles, there is a need for an accurate adhesive joint fatigue life prediction method that is compatible with industrial finite element modeling practices. This paper proposes a method to split the analytical J-integral solution based on the fracture mode of joints. The split mode I and II J-integrals correspond to the opening mode and sliding mode of the bonded joint, respectively. By splitting the J-integral and introducing the concept of the mixed mode ratio, an improved approach for estimating adhesive joint fatigue life is presented, considering the influence of loading modes. The proposed fatigue life prediction method is validated through fatigue tests on a sub-component level bonded structure. The results of the validation demonstrate that the split J-integral analytical solution method, considering the mixed mode ratio, provides better predictions compared to its predecessor approach. [ABSTRACT FROM AUTHOR]

The combination of a rotor and bearings plays a pivotal role in various industrial applications, including gas turbines, compressors, turbochargers, aircraft engines, and wind generators. Ensuring the structural integrity of the rotor-bearing assembly during static and dynamic conditions is most important, as any failure could lead to unpredictable losses. Due to their continuous operation, high-speed rotors are more susceptible to faults such as misalignment, bow, eccentricity, and cracks. Among these faults, cracks are the most predominant fault that affects the system’s reliability. Despite significant advancements in rotor dynamics, cracks still threaten the integrity and performance of the rotor-bearing assembly. This review paper aims to thoroughly review the challenges and issues associated with crack formation in high-speed rotor systems. Various crack detection methods are also explored using vibration signals obtained from the rotor-bearing unit and their associated processing techniques. This study also gives an extensive overview of different crack modelling and analysis techniques. Furthermore, a novel rotor-bearing model is modelled using the finite element method, and the numerical results obtained from this model are validated with the existing literature model. This review paper will serve as a valuable resource for researchers that offers insights into the latest advancements and emphasises the importance of crack detection for ensuring the reliability of high-speed rotor systems. [ABSTRACT FROM AUTHOR]

The influence evaluation of the additive fibre on concrete structures is a concerned problem especially in strengthening and repairing engineering. Current theoretical studies on the damage mechanisms of tunnel lining are generally based on the tensile and compressive characteristics of the ordinary concrete. Little attention is paid to the toughness and damage development of the fibre reinforced concrete, as well as the influences of high-speed train dynamic loading. In this paper, both tensile and compressive experiments of fibre reinforced concrete with different lengths and volume contents are carried out considering three types of the glass, PVA (polyvinyl alcohol) and hybrid fibres. Afterwards, the damage evolution of fibre reinforced concrete is explored by application of the digital image correlation (DIC) technique. The hypothesis of strain equivalence and damage theory of Najar are employed to determine the damage parameters of the fibre reinforced concrete so as to establish three-dimensional finite element model of surrounding rock-tunnel. Finally, the parameters that affect damage development of concrete tunnel lining incorporated fibre under train loading, including the vehicle speed, fibre type, fibre length, and volume content, are performed. The results show that adding fibre into concrete can effectively enhance the damage resistance capacity of concrete and significantly improve the developing trend of multistep damage of ordinary concrete under train excitation loading. Moreover, fibre reinforced concrete can reduce the final damage values of tunnel lining subjected train loading. The paper contributes to the understanding of damage behaviours of fibre reinforced concrete lining for high-speed trains loading as a potential risk in the course of the operation. [ABSTRACT FROM AUTHOR]

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]

This paper develops a structural model updating method in the time-scale domain based on the wavelet transform of the correlation function and seeks its implementation for damage detection of the ship hull. The quasi-exact sensitivity equation based on the wavelet transform coefficients are used to identify the damage as well as to overcome the drawbacks of incomplete data measurement. Different types of mother wavelets have been studied to select the best wavelet to identify structural damages. The abilities of the method is numerically examined through several damage cases. The robustness of the method against mass measurement and modeling errors is evaluated numerically using Monte Carlo analysis and error-contaminated data. This method proves to be strong against both types of errors for detecting of the damage in shell structures. [ABSTRACT FROM AUTHOR]

In this paper, dynamically propagating cracks in anisotropic plates exposed to a generalised thermal shock are investigated. Here, the governing equations are considered according to the Lord-Shulman (LS) model as a fully coupled generalised thermoelasticity theory. The crack is modelled in the context of the eXtended Finite Element Method (XFEM). To evaluate Stress Intensity Factors (SIFs), a technique based on the J integral and crack tip opening and sliding displacements, previously applied for stationary cracks, is developed for a dynamically propagating crack in orthotropic solids. Besides, a variety of functions for enriching the displacement field are derived relying on the behaviour near the tip of a dynamically propagating crack in anisotropic materials. The maximum hoop stress criterion is also modified by using the asymptotic stress field for a dynamically propagating crack. In addition, the effect of the angular variation of fracture toughness in orthotropic materials is accounted in computing the crack propagation speed. In some examples, dynamic crack growth in complex cracked orthotropic structures subjected to LS thermal shock is studied in detail. The impacts of fibre orientations and LS relaxation time are also investigated in these examples. In conclusion, applying non-Fourier thermal shock for modelling dynamically propagating cracks in orthotropic structures is recommended to obtain more realistic results. In addition, by increasing the LS relaxation time, the crack grows less oscillatory and is more aligned along the material fibres. [ABSTRACT FROM AUTHOR]

This paper is focused on a new structural type - sandwich shell, which includes inner and outer shells connected by hoop connectors to achieve composite action; and a functional layer in the middle. Considering that the hoop connectors are not completely rigid, there will be limited slip between the inner and outer shells, which will lead to partial Degree of Composite Action (DCA). Due to the existence of the hoop connectors and shear lag effect, the stress distribution along the width direction of the shell is uneven, which can be described by effective width. Considering all these factors, this paper first develops an analytical model for sandwich shells with different configurations of connectors; and uses finite element analysis results to verify the analytical model. Next, a parametric study is conducted using the analytical model to study the effects of material strength, the ratio of the thickness of the functional layer to the thickness of the single layer shell, and the ratio of the arc length to the width of the sandwich shell on the effective width. It is found that DCA can significantly affect the stress and strain distributions of the sandwich shell. The effective width for 100% DCA can be used as a conservative value to represent those of other DCAs. Finally, a simplified calculation formula, which can be used in practical design, is derived based on the effective width for 100% DCA. [ABSTRACT FROM AUTHOR]

The timber lounge bridge with cantilever beams is a kind of bridge architectural heritage that is different from the simply supported timber beam bridge and timber arch lounge bridge in typology. It has important historical, artistic, and scientific values. For the preventive protection and repair of the timber lounge bridge with cantilever beams, this paper proposes a scientific and reliable quantitative evaluation method for its structural safety status, taking the typical timber lounge bridge with cantilever beams, Yongqing Bridge, as a case study. The evaluation consists of three stages: firstly, analyzing the typology of the timber lounge bridge with cantilever beams and recording the deterioration; secondly, establishing the evaluation system and grading criteria for the timber lounge bridge with cantilever beams; thirdly, using the finite element method to calculate the importance of the components and quantitative evaluating the structural safety status of the timber lounge bridge with cantilever beams by using the improved analytic hierarchical process (IAHP) and making the final decision. The results of this study can provide a scientific basis for quantitative evaluation of the structural safety status, preventive protection, and repair of the timber lounge bridge with cantilever beams. [ABSTRACT FROM AUTHOR]

Numerical models play a primary role in Cultural Heritage preservation. Nevertheless, the design of a realistic model remains challenging due not only to the complex behavior of masonry but also to the asynchronous building phases, the damage induced by natural and anthropic aggression, and the associated repairs. This paper discusses the impact of the information provided by an in-depth analysis of the construction history on the updating process of a Finite Element building model. The case study is the church of Sant'Agata del Mugello (Italy); for this building, a previous historical–archaeological study identified and recorded the asynchronous construction phases, the repair techniques, and the damage induced by three historical earthquakes (1542, 1611, and 1919) – moreover, a dense ambient vibration survey allowed to identify the modal parameters. The information from previous works is summarized in five Finite Element models with increasing complexity. A vibration-based model updating methodology based on a Particle Swarm Algorithm is developed. This work shows that the best minimization of the difference between the numerical and experimental modal parameters is obtained with the numerical model considering the identified construction techniques, repair phases, and connection relations between the bell tower and the nave. [ABSTRACT FROM AUTHOR]

Bonding technology is used as the main connection mode of coated structures of car interior trim, of which the process and structure are being continuously optimized. In this paper, ABAQUS software is applied to establish the finite element model of the bonded structure of the dash panel. Based on the cohesive zone model (CZM) method, the damage and failure process of surface joints under different displacement loading conditions are numerically simulated. The effectiveness of the finite element model based on CZM for the numerical simulation of the damage and failure processes of bonded surface joints is verified from the perspectives of the numerical calculation method, experimental verification, and numerical result analysis. The results show that the finite element model based on CZM theory can effectively simulate and evaluate the damage and failure processes of multiphase polymers or composite surface joints. By obtaining the load‒displacement curves, the stress nephogram and the damage nephogram, the dynamic processes of damage initiation, damage evolution and failure of the surface joint are observed and analysed, and the bonding strength of the interlayer model is also compared and analysed. Compared with the bonding interface between the skin and cloth, the bonding interface between the frame and cloth is less prone to damage. [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]

Core loss estimation in switched reluctance motor is a complex task, due to non-linear phenomena and non-sinusoidal flux density waveforms. Several methods have been developed for estimating it (e.g. empirical, and physical-mathematic models), each one with merits and limitations. This paper proposes a new method for core losses estimation based on Finite Element Method Magnetics software. The main idea is using the machine phase-current harmonics as input for estimating core losses. In addition, a comparative study is carried out, where the proposed approach is faced up to a different one, based on Fourier decomposition of the flux density waveforms in the machine sections. In order to systematically analyze and compare the applied estimation cores loss techniques, a case study of a three-phase 6/4 SRM for different simulation scenarios is introduced. The outcomes of both methods are discussed and compared, where core loss convergence is found for limited speed and load ranges. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical investigation of RCC (Reinforced Concrete) piles with helical grooves under axial and lateral loads in cohesionless soil. A set of experiments is carried out to assess the performance of RCC piles with helical grooves. To replicate the experimental findings, the Finite Element Method (FEM) is employed using Abaqus software. Three-dimensional (3D) models are created to represent both the pile and the soil using Abaqus. The paper compares settlement characteristics and lateral displacement of plain RCC piles and RCC piles with helical grooves. This study also evaluates the impact of varying the pitch of helical grooves on enhancing pile performance. The results indicate that RCC piles with helical grooves outperform plain RCC piles in terms of both axial and lateral load-carrying capacity, inferred from both experimental and analytical techniques. [ABSTRACT FROM AUTHOR]

Parachute design is challenging to achieve innovative progress if the dominant role of testing continues, as it will be an increasingly expensive and time-consuming work. The aim of this study is to establish a reliable and efficient design tool using existing advanced numerical modeling methods. This paper presents a numerical method based on two-way coupled fluid-structure interaction (FSI) strategies for predicting aerodynamic and flight performance for parafoil design optimization. The nonlinear finite element method was used for the canopy fabric model and flow field, and the fluid dynamics were solved by Reynolds-averaged Navier-Stokes with the Spalart-Allmaras turbulence model. The FSI simulations are performed to assess the aerodynamic performance and structural deformations of full-scale parafoil canopies. The equilibrium shape of the parafoil canopy under steady gliding states and the relevant flow field were analyzed to enhance confidence and understanding in the performance prediction of new parachutes. Three-dimensional FSI simulation results of parafoils show that the inflation caused flexible bulges of canopy cells, and the maximum lift coefficient increased more than 16% with a higher stall angle of attack than that of the rigid body model. A parafoil with a smaller leading edge inlet or a scaling down area can improve the aerodynamic performance, mainly manifested in a higher lift-to-drag ratio and better anti-stall performance. Finally, the prediction results of parafoil glide performance were verified by flight test data, and the prediction accuracy of the flexible model is more than 10% higher than that of the rigid model. This work makes the simulation tools a step closer to practical application. [ABSTRACT FROM AUTHOR]

The tilting of the cab seat when the tractor is in deep ploughing operation changes the sitting position of the driver, which may accelerate lumbar spine injury. This paper adopts the musculoskeletal model and the finite element model of the lumbar L4–L5 segment to predict the maximum Von-Mises stress and maximum strain of the driver's lumbar L4–L5 segment intervertebral disc. In this study, we used 3D motion capture to obtain the driver's spine position spatial data when the tractor tilted at different angles. A tractor-driver musculoskeletal model and a finite element model of the lumbar spine L4–L5 segments were created in AnyBody™ and Abaqus, respectively. The tractor-driver musculoskeletal model was used to calculate the load of the driver's lumbar spine L4–L5 segment at different angles of tractor tilt, which was used as the load condition of the finite element model of the lumbar spine L4–L5 segment, and then the influence of tractor tilt angle and vibration on the driver's lumbar spine L4–L5 disc was studied. The results show that the maximum Von-Mises stress and maximum strain of the driver's lumbar L4–L5 intervertebral disc will increase due to the tilt. The maximum Von-Mises stress occurs in the annulus II, and the maximum strain occurs in the upper end plate of the intervertebral disc. With the occurrence of tilt, the position of the maximum Von-Mises stress changes, which can lead to disc injury to the driver, and vibration may exacerbate this injury. [ABSTRACT FROM AUTHOR]

AbstractTo dampen the loading sequences in the constructions, using the shear walls is recommended. Shear walls, which withstand the lateral forces (i.e., parallel to the plane of the wall) of wind and seismic activity, prevent buildings from collapsing while columns and load-bearing walls support the structure’s compression load all the way to the foundation. Besides, some new techniques are innovated for strengthening the structure like outrigger system. The steel shear walls are mostly used in the steel structures due to their high strength, ductility, and low weight. Recently, implementing Corrugated Steel Shear Walls (CSSWs) has gained more attention because they can absorb much amount of energy compared to flat steel shear walls. There are two important parameters in the CSSWs that play crucial roles in controlling their strength; corrugation geometry and orientation. Therefore, the current research paper aims to study numerically the effects of four corrugation geometries (trapezoidal, square, zigzag, and curved) with two orientations on the cyclic behavior of the CSSWs. Finite Element Analysis (FEA) is used to simulate the seismic loading conditions and finally, this procedure is validated through the comparison of the modeled flat shear wall with the experimentally published results. The difference between the peak loads of hysteresis curves obtained numerically and experimentally is about 8.5%. The stated FEA procedure in this paper can be regenerated by other researchers. The results confirmed the applicability of the CSSWs compared to the flat shear walls. Also, the vertical corrugation infill patterns result in higher strength in comparison to the horizontal ones. For instance, in the zigzag and square corrugation shapes, the plastic energy dissipation of the vertically oriented specimens (13.84 and 14.01 KJ, respectively) is higher around 7% and 29%, respectively than the horizontally oriented ones (12.9 and 10.84 KJ, respectively). Besides, the trapezoidal and curved corrugation geometries show the highest cumulated energy and plastic energy dissipation. [ABSTRACT FROM AUTHOR]

In recent years, the high-strength friction-grip bolt (HSFGB) shear connectors in steel-concrete composite beams as deconstructable connectors are of great research interest since they are aligned with sustainable construction. However, the design strength equation for this type of connector has not yet been provided by the design codes such as AISC and Eurocode 4. In this paper, with regard to the reliability aspect, the design strength equation of HSFGB shear connectors is investigated which is projected into a partial safety factor according to Eurocode 4. Accordingly, the three-dimension finite element (FE) push-out model of the composite connection is developed and verified via experimental results to predict the load-slip behavior and failure modes in this type of bolted shear connector. Then One-Factor-at-a-Time (OFAT) method as a sensitivity analysis and Plackett-Burman (PB) design method as a screening analysis are utilized to identify the effective factors of the ultimate strength of HSFGB connectors. Finally, based on a complete database of all existing experimental findings, the results obtained from 55 three-dimension finite element models conducted in this paper, and appropriate statistical analysis, a high-precision equation for predicting ultimate strength is provided. Then the value of the partial safety factor is determined through a reliability study in accordance with EN1990, which provides an acceptable level of safety for the proposed design equation based on Eurocodes. Reliability analysis found that a partial factor of 1.52 was justified for the design strength of HSFGB connectors, which differed from the partial factor of 1.25 stated in the EC for welded stud shear connectors. [ABSTRACT FROM AUTHOR]

Soft hang-off is an emergency operation for drilling risers to survive under harsh environments. Buckling of the suspended riser and overstroke of the tensioner piston rod would probably occur. Conventional analysis methods usually ignored the dynamic interaction of the riser and tension fluctuation. This paper is devoted to developing an improved coupled model for the axial dynamic analysis of the riser under soft hang-off mode. In the developed model, the mathematical model of the tensioner was established considering gas state variations, internal friction and pressure loss, the mechanical model of the riser considering axial hydrodynamic load was developed, and the two models were coupled through the kinematic variables. A case study is carried out to analyse the axial dynamic characteristics of the riser under soft hang-off mode, and the comparison showed that the conventional tensioner models will underestimate the axial dynamic response of the riser in soft hang-off mode. [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]

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]

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]

This paper proposes an efficient geotechnical reliability analysis framework that integrates the advantages of the first-order reliability method (FORM) and the Karhunen-Loève expansion (KL) to evaluate the reliability of spatially variable soil slopes. The improved Hasofer-Lind-Rackwitz-Fiessler (iHLRF) recursive algorithm is adopted to implement the FORM procedure when coupled with finite element codes for slope stability analysis, and the KL is used to reduce the dimension of random variables representing the soil random fields. To enhance the accuracy of the failure probability estimated by KL-iHLRF, the importance sampling (IS) is also conducted in this study, resulting in an innovative slope reliability analysis framework, KL-iHLRF-IS. It is found that although the FORM analysis by itself may not be able to confidently estimate the failure probability of spatially variable soil slopes because of the very high dimension of random variables and the strong nonlinearity of the limit state function, it provides useful information on the design point values for KL-iHLRF-IS to rapidly compute the failure probability. The efficiency of KL-iHLRF-IS for slope reliability analysis is illustrated by three example slope case studies. The proposed framework is particularly useful when fast yet accurate slope reliability analysis using the finite element method is needed. [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 focuses on the composite design with fibres loaded in the longitudinal direction as well as orientated at some certain angles. The study uses Bombyx Mori Moth Silk (BMM Silk) as fibres and vinyl ester as matrix material. The two sorts of composites having cross ply and angle ply laminate were considered for deformation study using the finite element analysis. According to the ASTM D 3039 testing standard, the tensile test was carried out to design and composite study of their occurred deformation. The rule of mixture was employed in order to evaluate the elastic constants of the prepared orthotropic composite laminate along the fibre direction and the evaluation of orthogonal stresses in transverse direction was carried out using the finite element procedure. The maximum orthogonal stress value of cross ply and angle ply was found to be 44.902 and 47.779 MPa, respectively. Also, the deformation occurred for both laminates was found to be of 0.083603 and 0.076428. This concludes that the deformation occurrence is more in case of angle ply and is less in cross ply laminates. [ABSTRACT FROM AUTHOR]

Steel-concrete composite construction picked up its utility because of efficient combination of steel and concrete offering high ductility, strength and stiffness to the structure. Loading action is one of the key parameters to understand the behaviour of a structural element. An attempt has been made in this paper to review the structural performance of steel-concrete composite beams under different loading actions. In addition, the results of nonlinear analysis of steel-concrete composite beams subjected to static loading, using commercial finite element software ANSYS, have been included. Numerical investigations have been performed to understand the behaviour of steel-concrete composite beams under static loading criteria. Numerical models of beams have been created and two-point loading was applied. Load versus mid-span deflection has been plotted. Earlier, validation has been done by comparing the analysis results by authors with the experimental results obtained by previous authors available in literature. The results obtained have shown that dimensions of shear connectors used are having influence on ultimate load capacity of steel-concrete composite beams subjected to static loading. [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]

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]

Because the resonance of the structure is related to the fundamental frequency in most cases, in order to avoid the resonance of the structure, this paper takes the square plate structure as the research object, and uses the variable density method and draft technology to optimize the square plate, so that the optimized stiffened plate has a higher first-order natural frequency. The optimized stiffened plate is compared with the unreinforced plate and the conventional stiffened plate. The results show that under different mass constraints, the four optimized stiffened forms tend to be consistent in the distribution of main materials. Under the working condition of this paper, when the mass of the stiffened plate is 18.737 Kg, the first natural frequency of the optimized stiffened plate can be increased by 107.68%, 21.54% and 10.03% respectively compared with the first natural frequency of the unreinforced plate and the first natural frequencies of two conventional stiffened plates. When the first natural frequency of the stiffened plate is 537.39 Hz, the mass of the optimized stiffened plate can be reduced by 53.95%, 62.70% and 21.44% respectively compared with that of the unstiffened plate and the two conventional stiffened plates. The optimized stiffened plate is redesigned, and it is found that the designed stiffened plate still has advantages over the unstiffened plate and the conventional stiffened plate. This means that this paper provides a reference for the stiffener of square plates with low mass and high natural frequency. [ABSTRACT FROM AUTHOR]

Today digital qualification tools are part of many design processes that make them dependent on long and expensive simulations, leading to limited ability in exploring design alternatives. Conventional surrogate modelling techniques depend on the parametric models and come short in addressing radical design changes. Existing data-driven models lack the ability in dealing with the geometrical complexities. Thus, to address the resulting long development lead time problem in the product development processes and to enable parameter-independent surrogate modelling, this paper proposes a method to use images as input for design evaluation. Using a case study on the curtain airbag design process, a database consisting of 60,000 configurations has been created and labelled using a method based on dynamic relaxation instead of finite element methods. The database is made available online for research benchmark purposes. A convolutional neural network with multiple layers is employed to map the input images to the simulation output. It was concluded that the showcased data-driven method could reduce digital testing and qualification time significantly and contribute to real-time analysis in product development. Designers can utilise images of geometrical information to build real-time prediction models with acceptable accuracy in the early conceptual phases for design space exploration purposes. [ABSTRACT FROM AUTHOR]

In the present paper, the elliptical tube hydroforming samples have been deformed inside an elliptical die cavity with the help of internal pressure of water. Bulging thickness distribution of tube has been studied experimentally and numerically as well. The tube hydroforming process is depending on various hydroforming variables such as internal pressure, friction factor, axial force etc. In this experiment, axial feed is kept under constrained condition and performed under unique friction factor. The main attention of this paper is to measure the thickness at various major and minor axis points on tube sample deformed under different internal pressures. The percentage thinning of different major and minor axis points has been also discussed and plotted against simulated results. Finite element analysis (FEA) was carried out on elliptical samples using Abaqus software. The simulation results showed an agreement with the experimental data with some relative error which has been also plotted. Comparative results of incremental FEA prediction and experimental data have also been plotted with some deviation. [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]

Conventional micromechanical experiments have difficulties in measuring the normal strength of the fiber/matrix interphase. In this paper, molecular dynamics simulations were used to construct the interphase models from molecular scale and investigate the normal and tangential strength of the fiber/matrix interphase. Furthermore, a multiscale framework for composites considering interphase based on molecular dynamics and finite element method was constructed and validated by transverse fiber bundle tensile (TFBT) experiments used to indirectly measure the interfacial normal strength in the literature. The results showed that the interfacial normal and tangential strengths were 100.9 MPa and 51.9 MPa, respectively. The prediction error of the TFBT specimens by the newly constructed multiscale framework was less than 2%, and the failure mode was the same as that observed in the experiments. The good agreement between the experimental and simulation results indicates that the method can provide a way to study the structural analysis of fiber-reinforced composites. [ABSTRACT FROM AUTHOR]

In recent years, reinforced thermoplastic composite pipe (RTP) is widely sought after because of its high strength and corrosion resistance. The development of a connector that is easy to install and highly reliable is essential for the successful application of RTP. In this paper, the mechanical properties of a butt-welding armoured joint between composite pipes were investigated by theoretical calculation method and finite element method. A plane strain model was established to study the mechanical response of the joint under internal pressure. In order to verify the theoretical results, a finite element model was established to analyse the stress distribution of the joint. Moreover, the finite element results are in good agreement with the theoretical results. The research of this paper provides a valuable reference for the engineering application of the joint in the pipeline system. [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]

This paper is focused on the mechanical performance of the Dou-Gong bracket at the corner under vertical load. A full-scaled specimen was tested under the static compressive load. The load-displacement curves, load distribution law and displacement of components were discussed. A finite element model was established and validated with test results. The deformation and stress of the whole Dou-Gong bracket and main components were analyzed, and the influence of the wood properties and friction coefficients was studied. The results show that there are four stages in the load-displacement curve and the plastic stiffness is 76.36% lower than that in the elastic stage. The components in the oblique 45° direction mainly transfer the force, while the load distribution ratios in the width and oblique 45° directions of the lower layer is closer to 1. The displacements of the components in oblique 45° direction in the No. 2 and No. 3 layers are smaller than those of the components in width direction. With the increase of the compressive strength, the elastic moduli in the radial direction and the friction coefficients, the stiffness in the plastic stage increases and the maximum displacement decreases. However, the compressive strength and the elastic moduli in the longitudinal direction have little effect on the load-displacement curves. [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]

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]