Search

The mechanical behavior of two packaging paper materials subjected to tensile loading up to complete breakage has been investigated. A model for isotropic strain hardening elastic anisotropic plasticity, coupled to anisotropic damage, is discussed. The constitutive relations, including a gradient enhanced damage model, are developed within a thermodynamical framework. The Helmholtz free energy in the continuum is assumed to depend not only on the strain and stress components but also on the damage in the material.The model has been analyzed in a non-linear finite element procedure. The capability of the model to properly capture and simulate the failure of a paper material subjected to tensile loading is demonstrated by means of several numerical examples that are compared to, and verified with, experiments on packaging paper specimens of varying geometry. [Copyright &y& Elsevier]

Folding of coated paper is examined numerically using the finite element method. Particular emphasis is put on the behaviour of field variables relevant for cracking of the coating layers. In the numerical analysis, the basepaper is modelled as an anisotropic elastic–plastic material (both elastic and plastic anisotropy is accounted for) while the constitutive behaviour of the coating layers are approximated by classical (Mises) elastoplasticity. The numerical results suggest, among other things, that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. It is also shown that delamination buckling, in the present circumstances, will have a very small influence on the strain levels in the coating layer subjected to high tensile loading. [Copyright &y& Elsevier]

This paper presents a new approximate solution to study the settlement of rigid footings resting on a soft soil improved with groups of encased stone columns. The solution development is fully analytical, but finite element analyses are used to verify the validity of some assumptions, such as a simplified geometric model, load distribution with depth and boundary conditions. Groups of encased stone columns are converted to equivalent single encased columns with the same cross-sectional area and the same ratio of encasement stiffness to column diameter. In this way, the problem becomes axially symmetric. Soft soil is assumed as linear elastic but plastic strains are considered in the column using the Mohr-Coulomb yield criterion and a non-associated flow rule with a constant dilatancy angle. Soil profile is divided into independent horizontal slices and equilibrium of stresses and compatibility of deformations are imposed in the vertical and horizontal directions. The solution is presented in a closed form and may be easily implemented in a spreadsheet. Comparisons of the proposed solution with numerical analyses show a good agreement for the whole range of common values, which confirms the validity of the solution and its hypotheses. • A new analytical solution to study the settlement of rigid footings on a soft soil improved with encased stone columns. • A simplified model of a single column with the same area and the same ratio of encasement stiffness to column diameter. • The approximate analytical solution may be easily implemented in a spreadsheet. • A simplified calculation example and the corresponding calculation code are presented. • Comparisons with numerical analyses show a good agreement. [ABSTRACT FROM AUTHOR]

Abstract: Out-of-plane deformations of paper, such as fluting, significantly deteriorate the quality of a printed product. There are several explanations of fluting presented in the literature but there is no unanimously accepted theory regarding fluting formation and retention which is consistent with all field observations. This paper first reviews the existing theories and proposes a mechanism that might give an answer to most of the questions regarding fluting. The fluting formation has been considered as a post-buckling phenomenon which has been analysed with the help of the finite element method. Fluting retention has been modelled by introducing an ink layer over the paper surface with the ink stiffness estimated from experimental results. The impact of fast drying on fluting has been assessed numerically and experimentally. The result of the study suggests that fluting occurs due to small-scale hygro-strain variations, which in turn are caused by the moisture variations created during fast convection (through-air) drying. The result also showed that ink stiffening alone cannot explain the fluting amplitudes observed in practice, but that high drying temperatures promote inelastic (irreversible) deformations in paper and this may itself preserve fluting. [Copyright &y& Elsevier]

Abstract: The creep of paper is accelerated by moisture cycling. This effect is known as mechano-sorptive creep. It is assumed that this is an effect of transient stresses produced during moisture content changes in combination with non-linear creep behaviour of the fibres. The stresses produced by the moisture content changes are often much larger than the applied mechanical loads. If this is the case, the mechanical loads are only a perturbation to the internal stress state, and it will appear as if the mechano-sorptive creep is linear in stress. It is possible to take advantage of this feature. In the present report the pure moisture problem is first solved. The mechanical load is then treated as a perturbation of the solution to the moisture problem. Using this strategy, it is possible to linearize a non-linear network model for mechano-sorptive creep and to formulate a continuum model. As a result, the number of variables in the model is reduced. This is a significant improvement as it will be possible to use the linearized model to describe the material in a finite element program and solve problems with complicated geometries. [Copyright &y& Elsevier]

Finite element analysis of the hip implant is conducted in this paper for representative femoral cross-section geometries and development of stress in the presence of bone cement is elucidated. Differences in cement stresses generated by varying implant cross-sections were compared with conventional features derived from representative implants. The analysis was performed under idealized implant assemblies by constraining the implant movement in the assembly. The cross-sections and implant geometries used are generic and intended to be representative of available geometries. This paper is a part of student research projects, prepared from a series of activities in biomedical implant research currently underway at Ohio Northern and Arkansas Tech Universities. [Copyright &y& Elsevier]

The effect of geometric parameters has been studied in this paper on the development of stress in hip implants. The parameters include: head diameter, neck diameter, and neck angle. Two three-dimensional models were drawn, one modular and one integrated implant. These models were then altered geometrically one variable at a time, and finite element analysis (FEA) was performed on the models. In total, twenty assemblies of implant/bone cement/bone were tested. Stress spectrum was drawn for each case under a combination of hip dimensions. It is shown that as the head diameter increases, the stress at a given location reduces, however, as the surface area from increased head diameter increases, the wear rate increases. Neck angle has been found to concentrate stresses in the select regions of the hip implant. In that an angle of 40° showed low stress combinations. Therefore, a particular combination offering the best performance has not been identified and constitutes a part of an on going research activity in Mechanical Engineering Department at Ohio Northern University. [Copyright &y& Elsevier]

• A complex variable EFG method for hyperelastic large deformation under non-conservative loads was proposed. • Deformation and stress of hyperelastic materials under non-conservative loads were analysed. • The approximation function of the displacement field was established by the complex variable moving least-squares method. • The complex variable EFG method has a great advantage in efficiency and accuracy than other methods. The finite element method is extremely popular in almost all fields of engineering and scientific research due to its powerful and accessible industrial software for computational modelling. However, alternatives including the meshless methods, have received increasing attention on the large deformation problems of hyperelastic materials that need to avoid mesh distortion. In this paper, based on the complex variable moving least-squares approximation, the complex variable element-free Galerkin (CVEFG) method for the large deformation problem of hyperelastic materials under non-conservative loads is established. In the present method, the Newton-Raphson method is used for solving the nonlinear equations. The algorithm for hyperelastic large deformation problems under non-conservative loads are established. Three numerical examples are used to verify the effectiveness of the CVEFG method in this paper. Numerical results show that the solution obtained using the CVEFG method is closer to that obtained by ABAQUS and is more efficient than the element-free Galerkin method. [ABSTRACT FROM AUTHOR]

Abstract: Objective: This brief review essay was triggered by the discovery of two errors that have been perpetuated in the dental literature for the last quarter century and is intended to alert the research community. Methods: An extensive search of the published literature, using PubMed and Web of Science search engines, electronic journal resources, and several trips to the library for manual retrievals of articles were used to retrieve hundreds of articles reporting on finite element modeling – finite element analysis (FEM/FEA) involving periodontal ligament (PDL) and gutta percha (GP). Results: The literature search revealed that erroneous values for the modulus of elasticity of PDL and GP were introduced in 1980 and in 1983, respectively. The identified errors range between two to three orders of magnitude and have been used in hundreds of FEM/FEA papers. Significance: The finding casts serious doubts regarding the validity of the results published in hundreds of papers and highlights the importance of checking the references cited and citing, or at least confirming, primary sources rather than citing citations. [Copyright &y& Elsevier]

In this paper we introduce and analyze a Banach spaces-based approach yielding a fully-mixed finite element method for numerically solving the stationary chemotaxis-Navier-Stokes problem. This is a nonlinear coupled model representing the biological process given by the cell movement, driven by either an internal or an external chemical signal, within an incompressible fluid. In addition to the velocity and pressure of the fluid, the velocity gradient and the Bernouilli-type stress tensor are introduced as further unknowns, which allows to eliminate the pressure from the equations and compute it afterwards via a postprocessing formula. In turn, besides the cell density and the chemical signal concentration, the pseudostress associated with the former and the gradient of the latter are introduced as auxiliary unknowns as well. The resulting continuous formulation, posed in suitable Banach spaces, consists of a coupled system of three saddle point-type problems, each one of them perturbed with trilinear forms that depend on data and the unknowns of the other two. The well-posedness of it is analyzed by means of a fixed-point strategy, so that the classical Banach theorem, along with the Babuška-Brezzi theory in Banach spaces, allow to conclude, under a smallness assumption on the data, the existence of a unique solution. Adopting an analogue approach for the associated Galerkin scheme, and under suitable hypotheses on arbitrary finite element subspaces employed, we apply the Brouwer and Banach theorems to show existence and then uniqueness of the discrete solution. General a priori error estimates, including those for the postprocessed pressure, are also derived. Next, a specific set of finite element subspaces satisfying the required stability conditions, and yielding approximate local conservation of momentum, is introduced, which, given an integer k ≥ 0 , is defined in terms of Raviart-Thomas spaces of order k and piecewise polynomials of degree ≤ k only. The respective rates of convergence of the resulting Galerkin method are then provided. Finally, several numerical experiments confirming the latter and illustrating the good performance of the method, are reported. [ABSTRACT FROM AUTHOR]

Large waves used to cause a lot of ship collapse accidents, resulting in the loss of many lives and property. The response of ships to collapse, including plasticity and buckling, has aroused focused concern among researchers. This paper carries out a hydroelasto-plastic experiment and numerical investigation of a three-cabin ship model to study its structural collapsed response. Firstly, a hydroelasto-plastic model experiment is conducted in a wave tank. A three-cabin experimental model which is made of stiffened plate, has been designed and manufactured. Then the model is forced to collapse in tank waves with measuring wave elevation, wave pressures, structural stress and rotational deformation of model. Secondly, a hydroelasto-plastic numerical approach coupling of CFD (Computational Fluid Dynamics) and nonlinear FEM (Finite Element Method) is used to co-calculate the wave loads and structural collapsed response of a ship model. A hydrodynamic model is constructed and utilized to solve wave loads in the CFD platform, while a nonlinear FEM model of the three-cabin structure is also constructed and solved using a nonlinear FEM solver to obtain the structural collapse response. Finally, hydroelasto-plastic experimental results and numerical results are compared and analysed, the structural collapsed characteristics of the three-cabin structure, which is very similar to a ship structure, are analysed. The numerical approach of two-way coupling of CFD and nonlinear FEM is verified for the hydroelasto-plastic problem. In this paper, the water elastic-plastic test of stiffened cabin structure under wave action is carried out, which provides a new perspective for ship structural design. [ABSTRACT FROM AUTHOR]

A tidal turbine can benefit from exquisitely designed morphing blades with a flexible trailing edge by mitigating up to 90% of the load fluctuation in harsh ocean environments, which reduces the overall cost of tidal energy. However, existing fluid–structure interaction (FSI) methods of resolving flow-induced deformation of the blades is computationally expensive, which poses an important challenge to effective morphing blade design. This paper presents a novel static FSI tool based on deep learning to cost-efficiently analyze the fluid–structure coupling of a hydrofoil. Specifically, adopting a convolutional neural network (CNN) to predict the fluid force and finite element method (FEM) to solve the solid structure response, a new CNN-FEM framework with an iterative scheme for solving the FSI problem is developed to achieve equilibrium between the fluid and structural forces. The new framework is used to predict the elastic deformation of the flexible blade section of the hydrofoil to demonstrate its effectiveness in the FSI evaluation. Comparison of the results to those produced by commercially developed software (i.e., Ansys Workbench) shows that this method yields extremely close prediction results of average equivalent stress and an accuracy of more than 92%. Moreover, it is 100 times more computationally efficient than the commercial Ansys Workbench software, requiring less than 3s for one-way FSI calculation. Taking advantage of this cost-effectiveness, the CNN-FEM can be used to achieve the accurate prediction of the deformation characteristics of the flexible hydrofoil under various flow scenarios that lay a foundation for advanced morphing blade design in the future. [ABSTRACT FROM AUTHOR]

The present paper introduces a global/local approach for the analysis of three-dimensional (3D) stress states of composite laminated structures. It consists of a two-step procedure. In particular, the first step makes use of finite element modeling based on classical 2D plate elements, whereas a refined layer-wise model based on Carrera Unified Formulation (CUF) is adopted to extract the 3D stress and strain fields in some critical regions that may have arbitrary dimensions. This approach allows dealing with large local areas, increasing the accuracy of the static solution, along with the possibility of embedding this technique in more complex procedures, such as the least-weight design of large heterogeneous complex assemblies, stiffness optimization, or localized progressive failure analysis. The numerical results shown in this paper want to assess the physical and numerical validity of the global/local approach. Particular attention is focused on the choice of the dimensions of the local area (patch) subjected to detailed refined analysis. Also, the convergence properties of the present hybrid FE model are discussed. The first examples deal with laminated composites. Then, the advantages of this methodology are further highlighted by considering free-edge problems and a complex wing structure. • Global to local 3D stress state analysis of composite structures. • Classical finite element software tool is coupled with layerwise CUF formulation. • The method can deal with failure onset mechanisms, including free-edge effects. • A full wing structure is analyzed. [ABSTRACT FROM AUTHOR]

This paper describes an advanced coupling method of finite element and discrete element called the Continuum-Discontinuum Element Method (CDEM). In this study, the Barton-Bandis model(BB model) for joint non-linear deformation is introduced into the CDEM to investigate the propagation of stress waves in jointed rock masses. The paper provides a detailed account of the development process of the BB model. Then, the developed model is utilized to simulate several representative cases of stress wave propagation in jointed rock masses, revealing the principles of stress wave propagation in jointed rock masses. The findings of this study demonstrate that the simulation results of the CDEM exhibit favorable consistency with experimental and theoretical results. This confirms the capability of the CDEM to accurately and effectively simulate stress wave propagation in jointed rock masses, thereby expanding the applicability of the CDEM. This research provides powerful support for further understanding and analysis of stress wave propagation problems in jointed rock masses. [ABSTRACT FROM AUTHOR]

Substantial compressive deformation occurs in the gas diffusion layer (GDL) under the pressure applied during the fuel cell assembly. The GDL deformation has a direct impact on the efficiency and performance of the fuel cell since it leads to the alteration of the GDL microstructure and porosity. This makes the accurate characterization of the GDL compressive behavior crucial for analyzing the fuel cell performance and its optimal design. In this paper, analytical, experimental, and numerical methods have been employed to comprehensively study the constitutive law of the GDL under compression. Starting from the recently developed stress-density relations, the constitutive stress-strain equations are derived for the GDL and the relation between the stress-density and stress-strain laws are revealed. Experimental compression tests have been performed on GDL samples and the capability of the proposed constitutive law in capturing the real behavior of the material has been proved. It has been observed that the simplifying assumption of constant zero Poisson's ratio in the through-plane direction made in many previous studies cannot accurately represent the GDL material behavior and a modification is proposed. The developed constitutive law has been successfully implemented in a finite element model of the GDL-bipolar plate assembly in the fuel cell structure and the variations of the GDL porosity, density, and through-plane Young's modulus and Poisson's ratio have been investigated for different vertical displacements of the bipolar plate. • The constitutive stress-strain constitutive laws are derived for the gas diffusion layer. • The relation between the stress-density and stress-strain constitutive laws are revealed. • The evolution of the GDL through-plane Poisson's ratio during deformation are explored for the first time. • The developed constitutive laws are successfully implemented in the finite element model. [ABSTRACT FROM AUTHOR]

• An atomistic–continuum multi-scale method is developed for nonlinear behavior of hetrogenous nano-materials. • The nucleation, migration, and elimination of dislocation as well as the dislocation-vacancy interaction are captured. • Effect of nano-scale void defects is modeled using the stress tensor and tangent modulus derived from atomistic RVE. • A statistical study is exerted to investigate the effect of influential parameters on the RVE mechanical behavior. • The mechanical behavior of nano-porous gold foam is studied during the compaction process. In this paper, an atomistic–continuum homogenization multiscale method is developed to study the nonlinear behavior of heterogeneous nanomaterials. The atomistic representative volume element (RVE) with vacancy and/or void defects are analyzed by employing the fully atomistic method, in which the nucleation, migration, and elimination of dislocation, as well as the dislocation-vacancy interaction, are captured. The coarse-scale material domain is modeled within the framework of the nonlinear finite element method, and the impression of nanoscale material defects is investigated by upscaling the stress tensor and tangent modulus from the atomistic RVE based on the Hill-Mandel principle. The principle of inter-scale kinematic compatibility is implemented using the periodic boundary condition. The mechanical behavior of atomistic RVE under various deformation modes is elucidated through stress – strain and dislocation density – strain curves. Due to the random nature of defects on the atomistic scale, a statistical procedure is exerted to numerically investigate the effect of influential parameters on the RVE mechanical behavior. Finally, the impression of vacancy and/or nanoscale void defects on the multiscale simulation of coarse-scale materials is illustrated in several numerical examples. The obtained results of the multiscale analysis is also verified with experimental data. Moreover, the compaction behavior of nanoporous gold foam is studied through the proposed multiscale method that highlights a good agreement with the fully atomistic analysis. [ABSTRACT FROM AUTHOR]

• A 3D finite element model is developed for an experimental PEM water electrolyzer. • Optimal levels of process parameters are obtained using the RSM tool. • PEM water electrolyzer shows different mechanical and electrochemical behavior under various bolt torques. • Bolt torque and cell voltage are the most influential factors for maximum performance from the PEMWE. Proton exchange membrane water electrolyzer (PEMWE), integrated with renewable energy sources, is promising in green hydrogen production with its compact system design, high efficiency, and high-purity hydrogen production capacity. Renewable hydrogen production from PEMWE depends significantly on operational factors. This study optimized the process variables affecting the PEM electrolysis cell performance using the response surface methodology (RSM) of the Design-Expert 13 software (trial version) at a fixed temperature of 80 °C. Water flow rate, cell voltage, and bolt torque were defined as the input factors of the model, while hydrogen flow rate and current were considered as the responses of the model. The statistical analysis showed that cell voltage, torque, and cell voltage-torque interaction significantly affected the current. Besides, it has been observed that the water flow rate plays a vital role in the hydrogen flow rate. The optimum conditions for green hydrogen production were a water flow rate of 2.45 mL/min, a cell voltage of 2.2 V, and a bolt torque of 10 Nm. In addition, a good match between the predicted and measured responses of the model was observed. This paper also includes finite element (FE) modeling and simulation of an experimental PEMWE. Based on the FE method, a three-dimensional simulation model of the PEMWE was established to investigate the effects of different bolt torques on the mechanical responses of the cell components. Numerical simulations were performed with a commercial code (ANSYS Mechanical). A pressure-sensitive film was placed instead of the catalyst-coated membrane (CCM) component of the single-cell PEMWE. The experimental results obtained from pressure-sensitive films were compared with the numerical results, and it was observed that the results were in agreement with each other. The maximum equivalent stress on the CCM for a bolt torque of 10 Nm is around 116.3 MPa. [ABSTRACT FROM AUTHOR]

A precise and cost-effective prediction tool for fluid-structure interaction (FSI) analysis is crucial for optimizing the structural design of tidal turbine blades. However, the high computational costs associated with fluid dynamic analysis pose a significant challenge, as the current lack of efficient FSI prediction methods hinders the advancement of cutting-edge tidal turbine designs. To address this issue, this paper proposes a novel consolidated framework that integrates deep learning convolutional neural networks (CNN) with blade element momentum (BEM) theory and finite element method (FEM) to perform deformation analysis of turbine blade structures. The proposed CNN-BEM-FEM integrated framework efficiently identifies the geometric features and predicts the hydrodynamic parameters of turbine blades and thus, achieving accurate assessments of the structural behavior of tidal turbines. The study applies two-step verification procedures to validate the prediction accuracy of the CNN-BEM-FEM framework and the result demonstrates excellent agreement with experimental tests for hydrodynamic performance and blade deformation. When compared with the static one-way FSI calculated by Ansys Workbench software, the computational efficiency of CNN-BEM-FEM framework increases by more than 18 times, with discrepancies in blade deformation and equivalent stress calculations generally less than 5 %. By applying the proposed method to predict the FSI performance of tidal turbine blades with various shear web structures, the practical applicability for composite turbine blade design is successfully demonstrated. The results underscore the potential of the CNN-BEM-FEM framework as an efficient and accurate prediction tool for optimizing the structural design of tidal turbine blades. • A high-efficient framework that combines CNN, BEM and FEM for tidal turbine rotor structural analysis is proposed. • Convolutional neural network (CNN) is used for identifying hydrodynamic performance of turbine blade section. • Blade element momentum (BEM) is for turbine prediction, while finite element method (FEM) is for structural analysis. • It shows great agreement with experiments, ensuring precise prediction of turbine blade deformations and hydrodynamics. • It outperforms benchmark software by more than 18 times, demonstrating exceptional computational efficiency. [ABSTRACT FROM AUTHOR]

Exploring the wave propagation in nano-waveguides enables the development of on-chip nano-resonators, leading innovative capabilities that enhance acoustics and micro-mechanics. This paper conducts a numerical investigation into the dynamic properties of periodic nano-waveguides. The Second Strain Gradient (SSG) elasticity, which captures the size effects, is used in the determination of the constitutive relations. The weak form including the element matrices is deduced by the Hamilton's principle. Furthermore, a finite element method, based on the periodic structure theory, is introduced to explore the free wave propagation by solving the eigenvalue problems. The stiffness hardening phenomenon manifested in the dispersion curves, band structures, and energy flow vector fields is discussed. The sensitivity of higher order parameters existing in the SSG theory is analyzed. The numerical investigation for wave propagation in the periodic nano-waveguides through the SSG theory is an innovative work, highlighting the significance of the proposed methodology in explaining the special dynamic characteristics of complex nano-waveguides. • Modeling of 3D nano-waveguides by second strain gradient theory. • Eigenvalue problems within 2D wave finite element method framework. • 2D wave motion properties in two different nano-waveguides. • Sensitivity of higher order parameters existing in second strain gradient elasticity. [ABSTRACT FROM AUTHOR]

As studies on the damage behaviors of composites during screw type blind riveting are notably absent, this paper seeks to fill this gap by combining experimental tests and numerical simulation methods. A three-dimensional finite element model was proposed, and the simulation results were obtained and validated by experimental data. The light microscope and scanning electron microscope were used to observe the stress state, axial deformation, damage modes, and damage distribution in two load-bearing regions at the initial contact and after installation. The results demonstrated that the preload showed a four-step "zero -steep rise -decline -steep rise" development during installation. The stress and deformation were concentrated in two circular zones, with the maximum axial stress component and deformation of 321 MPa and 0.046 mm, respectively. In two pressed zones, there were three failure modes, with out-plane matrix crushing being the most severe. In-plane matrix cracking damage is seen at a 45° direction in the first layer, with a damage index of 0.745. In addition, the effect of two geometric parameters of the sleeve on the blind head shape, load-bearing regions, and CFRP damage was investigated. The results would build confidence in reducing CFRP damage and enhancing joint integrity. [ABSTRACT FROM AUTHOR]

In this paper, the finite element method is utilized to evaluate the behavior of the armchair phosphorene nanotubes under the compressive loading. The energy equations of the molecular and structural mechanics are used to obtain the elemental properties. The critical compressive forces of various armchair phosphorene nanotubes are computed with clamped-clamped and clamped-free boundary conditions. Results show that the stability of armchair phosphorene nanotubes increases with increasing nanotube aspect ratio, particularly under clamped-clamped boundary conditions. Finally, the buckling mode shapes of armchair phosphorene nanotubes under different boundary conditions are compared. Our work offers valuable insights into how these nanotubes respond to mechanical stress, helps determine elemental properties, and investigates the effects of nanotube geometry and different boundary conditions on their stability. This knowledge has broad applications in fields like nanotechnology, materials science, and nanomechanics, advancing the understanding of nanoscale materials and their potential for various practical uses. The finite element method is utilized to evaluate the behavior of the armchair phosphorene nanotubes under the compressive loading. [Display omitted] • FE method is utilized to evaluate the behavior of the armchair PNTs under the compressive loading. • The elemental properties are obtained by the energy equations of the molecular and structural mechanics. • The buckling forces of the armchair PNTs with different radii and lengths are computed. • The stability of armchair PNTs increases by increasing the nanotube aspect ratio. • The clamped-clamped nanotubes are more stable than clamped-free ones. [ABSTRACT FROM AUTHOR]

• A train-cracked track slab coupled dynamic model is newly established by co-simulation technology. • The reliability of the proposed model is demonstrated by comparison with field measurement results. • The dynamic characteristic differences of the entire system with or without side cracks are revealed. • Several new insights into the dynamic stress of the slab with side-crack. The Ballastless track have been extensively implemented in high-speed railways. However, during the long-term operational process, degradation, such as side crack or defect phenomena produced on the slab inevitably, poses a threat to the stability and the durability of the track structure. Consequently, it is imperative to propose a dynamic approach that can effectively predict the impact of side-cracked slab (SCS) on the vehicle-track coupled system. This paper utilizes co-simulation technology to investigate the dynamic behavior of the slab with and without side crack. Firstly, the dynamic substructure of the finite element model of the SCS is obtained by eigenvalue analysis. Secondly, the SCS model has been applied to the classical vehicle-track coupled dynamic system, and the coupled dynamic model of the train-side cracked slab (TSCS) is established, which considers the multi-rigid-body vehicle subsystem, the flexible rail subsystem, the flexible SCS and subgrade foundation subsystem, and the wheel-rail nonlinear contact model. Later, the accuracy and reliability of the proposed model are verified by the comparison with field tests. Finally, the differences in the vibration characteristics of the vehicle and track structure with and without a side crack are compared and analyzed, and its dynamic stress of the slab as variable train speeds is revealed. The results indicate that the existence of a side crack will reduce the natural frequency of the slab, with a maximum decrease of 22.31%. Although the SCS has a minor effect on the vehicle responses, the existence of a side crack has a significant impact on the slab, especially on the root mean square (RMS) of the vibration acceleration of the slab, with a maximum difference of 74.10% laterally and an increase of 55.16% vertically. Meanwhile, the train speed remarkably affects the crack tip dynamic stress of the SCS, with a maximum increase of 76.07% in the longitudinal direction, 50.34% in the lateral direction and 49.09% in the vertical direction. Higher train speeds will further exacerbate crack propagation under long-term train loading. This study may contribute to the dynamic modeling of TSCS systems and the maintenance of the slab ballastless track. [ABSTRACT FROM AUTHOR]

• Establish a relationship between bite depth and residual collapse strength. • Determine the critical depth of slip bite by calculating the extrusion force. • Propose a new simulation methodology to test slip ultimate bearing capacity. • Carry out indoor tests to test the ultimate load-bearing capacity of the slip. • Optimal design of slip structure based on casing damage and ultimate bearing capacity. The packer's slips indent the inner wall of the casing, leaving a series of marks between the teeth of the slips and the inner wall of the casing. Excessive bite depth can result in damage to the inner wall of the casing, potentially leading to failure. To minimize damage to the inner wall of the casing and improve the ultimate bearing capacity of the slip, a three-dimensional finite element analysis model of the slips is developed and validated through laboratory experiments. The optimization objective is to minimize casing damage and maximize bearing capacity. This paper examines the correlation between the residual collapse strength of the casing and the maximum depth of slips penetrating the inner wall. It determines the critical depth value by calculating the extrusion force endured by the inner wall of the casing as an optimization evaluation index. At the same time, the optimal structural parameters of the slips were determined through numerical simulation and orthogonal experiments. These parameters include a 90° dental angle, a 21° inner cone angle, a 219 mm outer diameter, and a 6.5 mm tooth pitch. The research results indicate that the equivalent stress of the improved slip has decreased by 8.66 %. The equivalent stress on the inner wall of the casing has been reduced by 9.34 %, and the maximum tooth mark depth of the casing has decreased by 30.48 %. Furthermore, the ultimate bearing capacity of the slip has increased by 2.24 times. Research has shown that the improved slip not only reduces damage to the inner wall of the casing and minimizes stress concentration on the slip, but also increases the ultimate bearing capacity of the slip. The research results can serve as a reference for the study and application of packers. [ABSTRACT FROM AUTHOR]

• Residual stresses and deformations of I-section curved beams with different curvatures were measured using the cutting strip and novel 3D scanning methods, respectively. • Welding process of the I-section curved beam was precisely simulated using the finite element method. • Effects of the welding sequence, welding speed, and curvature on the residual mechanical properties of the welded I-section curved beams were investigated. • Reasonable welding sequences, welding speeds, and curvatures of the I-section curved beams were recommended. This paper presents an experimental and numerical investigation on welding-induced residual stresses and deformations of in-plane curved welded I-section steel beams. Two welded curved beams with different curvatures were investigated. After welding the curved beam, the residual deformations were measured by a 3D scanner. The residual stresses were subsequently obtained through a high-precision sectioning method. The effects of curvature on the magnitude and distributions of residual deformations and stresses at the specific sections were analysed with the test results. It was found that the residual deformation gradually increased from the weld region to both ends of the flange plate, and the torsion in the web plate became severe with a decrease in curvature of the curved beam. Moreover, the welding process of the curved beam was simulated using the finite element (FE) method. The developed FE model was validated against the test results, and thereafter, parametric analyses were conducted to assess the influence of welding sequence, welding speed, and curvatures of the curved beam on the welding residual stresses and deformations. The numerical results demonstrated that the residual stresses and deformations were significantly influenced by welding speeds, but the influence from curvature of the curved beam was relatively small. Finally, a reasonable welding sequence, welding speed, and curvature of the curved beams were recommended. [ABSTRACT FROM AUTHOR]

• A spline finite strip formulation for shear buckling analysis of thin-walled cross section is developed. • Decomposition of buckling modes into pure local, distortional and global buckling stress of thin-walled members subjected to shear edge stresses is presented. • The influence of flange and web stiffeners, different end conditions and interaction of flexural and shear stresses on pure buckling modes are evaluated. The direct strength method (DSM) design for shear incorporates the elastic shear buckling stress of the cross-section to evaluate the ultimate shear capacity of thin-walled members. To calculate the shear buckling stress using the finite strip method (FSM), the shape functions for longitudinal interpolation are an issue, while capturing the phase change of displacements along the plate strip. This paper presents a novel constrained spline finite strip method (cSFSM) that eliminates the phase change of displacements. Although constrained buckling analysis for shear stresses is reported in the literature based on FSM, the present study is unique in determining pure buckling stresses for simply supported members subjected to shear edge stress. The formulation also provides an accurate representation of the variation of shear stress along the longitudinal and transverse directions of the plate. Hence, coarse discretization of cross-section is sufficient to obtain the accurate shear buckling stress. The formulation is demonstrated on channel sections with lips subjected to shear edge stresses, and elastic buckling stresses are compared with results available in the literature and also with the finite element method (FEM). Illustrative examples are presented on lipped channel members with different end conditions and longitudinal stiffeners on flanges and webs, to calculate the pure elastic buckling stresses under shear edge stresses. The calculation of buckling stresses for members subjected to longitudinal variation of shear and flexural stresses is also presented to calculate coupled and uncoupled buckling stresses. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) is being increasingly used in structural applications due to its high strength-to-weight ratio, ease of construction and versatility. The performance of CFS structures in fire has received signification recent attention, but the fracture behaviour of thin-walled CFS at elevated temperatures, which is fundamental to the fire response of the key components, like connections has yet to be extensively studied; this is therefore the subject of the present paper. First, using experimental data on cold-formed grade S280GD+Z275 steel at elevated temperatures from the literature, damaged true stress-strain curves considering the post-necking behaviour are determined. Then, a fracture prediction approach, implemented in the finite element analysis software Abaqus and considering ductile damage and a damage evolution law is calibrated and validated against the experimental data. Finally, the applicability of the proposed approach to different types of CFS material, including high-strength CFS, is assessed. The results show that the proposed model can accurately predict the fracture behaviour of CFS at elevated temperatures. • Description of post-necking damaged true stress-strain behaviour of cold-formed steel using weighted average method. • Proposal of empirical formula for determining suitable values for weighting factor. • FE modelling of fracture in cold-formed steel coupons at elevated temperatures. • Validation of developed FE models against existing coupon tests covering a range of grades and temperatures. [ABSTRACT FROM AUTHOR]

In this paper, a novel numerical simulation approach based on the finite element method for dynamically modeling the excavation process of shield tunneling is proposed, with the shield-ground interactions well captured. This method is capable of mimicking the alternating modes of advancing and stopping of a shield boring machine during underground construction, with the important effects of the cutterhead rotation and slurry support pressure considered. Under the cutting action, the soil at the excavation face would experience irreversible deformation and damage, such that additional support needs to be provided by the cutterhead blades and slurry to maintain stability. The impacts of key construction parameters are examined, including cutterhead rotary speed, advance rate, and slurry support pressure, on shield tunneling operations and ground responses. The numerical model is rigorously validated against physical model experiments. This work provides useful insights into the mechanistic processes in the stratum during shield tunneling, including the spatiotemporal evolution of ground deformation patterns and stress redistributions. The results offer valuable guidance for optimizing shield tunneling operations and enhancing tunneling safety and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, the Variational Iteration Method (VIM) or Extended Kantorovich Method (EKM) is formulated for the first time for flexible porous functionally graded (PFGM) plates with different boundary conditions and geometric nonlinearity according to the theory of Theodore von Karman. Its accuracy and efficiency are demonstrated. The plate is subjected to a uniform transversal load and temperature field. The displacement field of the plate is approximated based on the classical plate theory (CTP) or Kirchhoff's plate theory. The governing equations are derived using Hamilton's principle. Modified Coupled Stress Theory (MCST) is used to account for size-dependent effects. The material properties vary with thickness and are temperature dependent. Four porosity distribution patterns are considered in this study. Several examples are solved to demonstrate the proposed algorithm. The results obtained are compared with solutions obtained by the Bubnov-Galerkin Method (BGM) in higher approximations, the Finite Difference Method (FDM) of second order accuracy, as well as with results obtained by the Finite Element Method (FEM) of other authors. The results include an analysis of the effect of size dependent parameters, porosity type pattern, porosity index, functionally graded index, temperature field and different types of boundary conditions on the stress–strain state and bending deflection of plates. [ABSTRACT FROM AUTHOR]

Non-directional rafting of γ' phases in high generation nickel-based single crystal superalloys happens when the alloys are thermally exposed at high temperatures, but so far the reason remains unclear. The microstructures and internal stress fields of a 4th generation single crystal superalloy during thermal exposure at 1100 ℃ and 950 ℃ are investigated using transmission electron microscopy and finite element analysis. It is found that the non-directional rafting of γ' phases occurs after 1100 ℃/200 h and 950 ℃/500 h thermal exposures. The γ' phases are mainly rodlike shape in the space after thermal exposures and a small quantity of γ' rafts exist as well. The elastic strain energy gradient in γ matrix caused by the inhomogeneity of matrix channel width in the alloy is most likely the driving force for the non-directional rafting. Additionally, dislocations are observed only after the thermal exposure process at 1100 ℃. The effect of dislocations on non-directional rafting during thermal exposure is discussed in detail in the paper. • TEM and finite element analysis are used to study non-directional rafting of γ'. • γ' phases are mainly rodlike spatially after thermal exposure at high temperature. • It is found that dislocations are unnecessary for the non-directional rafting. • Elastic strain energy is larger in narrower γ matrix channel at high temperature. • Elastic strain energy gradient in matrix probably causes non-directional rafting. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on based the universal morphology of recycled coarse aggregates in reality, an idealized model of recycled coarse aggregates was prepared using stones. Axial compressive strength tests were conducted on prism-shaped specimens of Modeled Recycled Coarse Aggregate Concrete (MRCAC), which were prepared with different old cement mortar coverages and aggregate arrangements. Through comparison with experimental data, the reliability of the finite element analysis model was determined. It was found that the arrangement of MRCA had a significant impact on the failure characteristics and elastic modulus of MRCAC. Thus, different arrangement modes affected the stress distribution within the specimens, resulting in significantly different axial compressive strength. • Studied the influence of aggregate arrangement on the stress characteristics of MRCAC. • Studied the influence of old cement mortar on the mechanical properties of MRCAC under different internal force transmissions. • Revealed the influence characteristics of old mortar on the stress-strain relationship in recycled concrete. [ABSTRACT FROM AUTHOR]

In this paper, J -integral and T* -integral in elastic–plastic fracture are computed by the quadrature element method (QEM). Since high stress gradients exist in the immediate vicinity of the crack front, computing these integrals accurately is not a trivial task. The QEM facilitates the construction of arbitrarily high-order elements, which effectively capture the stress gradients, making it particularly suitable for this computation. After performing an elastoplastic stress–strain analysis of the fracture problem, the stress and deformation states are further formulated to compute the integrals. The integrals are formulated in several forms, including the contour and domain forms, as well as the incremental and total forms. Classical numerical examples are solved to demonstrate the effectiveness and high accuracy of the method. Overall, the equivalent domain integral (EDI) form outperforms the contour integral form because errors at the local contour have less effect on the integral. Moreover, the QEM yields more accurate solutions than the popular finite element method (FEM) that employs low-order finite elements and shares the same number of degrees of freedom. Additionally, it is found that the EDI form solution is not very sensitive to the specific type of the S function. Therefore, a linear function is suggested for convenience. [ABSTRACT FROM AUTHOR]

The battery-pack system of electric vehicles is prone to collide with low obstacles on the road, causing battery short circuits and even explosions. It poses a great safety threat to passengers and drivers. The honeycomb structure's high energy absorption and lightweight properties have made it a popular choice in the automotive industry. This paper designs different bio-inspired honeycomb structures to a battery-pack system of electric vehicles to improve the crashworthiness performance. The effects of different bio-inspired honeycomb structures on the crashworthiness of a battery-pack system during frontal impact are analyzed based on a nonlinear finite element model. First, the geometric parameters of seven different bio-inspired honeycomb individual units are described. The overall structure of the honeycomb is applied to a battery-pack system. Second, the nonlinear finite element model of a battery-pack system and honeycomb structures are established and verified. Then, collision simulations are conducted. The deformation and the maximum stress of a battery-pack's bottom shell are computed. The energy absorbed by the honeycomb structures during frontal impact are investigated. The results indicate that the proposed bio-inspired honeycomb structure mimicking grass stems improves the safety performance of battery-pack systems most. Finally, a parametric design is carried out on the bio-inspired honeycomb structure. The effects of wall thicknesses and the number of replacement hexagons on the crashworthiness performance are analyzed. The honeycomb structure preforms best when thickness is 1 mm and the number of replacement hexagons is 2 and 4. The optimized bio-inspired honeycomb structure reduces the deformation of the battery-pack' bottom shell by up to 30%, and maximum stress by 10%. • The deformation, maximum stress, and energy absorption are investigated. • The effects of seven bio-inspired honeycomb structures are analyzed. • Parametric design is carried out to further improve the crashworthiness performance. • The deformation of the bottom shell can be reduced by up to 30%. [ABSTRACT FROM AUTHOR]

Due to the multi-functional requirements, more and more multi-dimensional functionally graded structures are reported, while their thermo-mechanical performances are still unclear. This paper aims at theoretically examining the thermo-mechanical behaviors of two-dimensional functionally graded (2D-FG) microbeam excited by a moving load. The formulation is established in the framework of the modified couple stress theory in combination with Hamilton's principle, and this problem is numerically solved through the finite element method (FEM). The material properties of the 2D-FG microbeam are treated as temperature-dependent parameters that vary smoothly along with both the axial and thickness directions, and three different thermal loads including the uniform, linear, and nonlinear temperature rises are taken into account. Both the fundamental frequency and the dynamic transverse deflection are analyzed with consideration of different axial and thickness gradient indexes, thermal load types, temperature rise amplitudes, and small scale parameters. The conclusion obtained in this paper can serve as a guideline for assessing the thermal performance of microstructures subjected to a moving load. • A two-dimensional functionally graded (2D-FG) microbeam under moving load is modeled. • 2D-FG material properties are treated as temperature-dependent parameters. • Influences of uniform, linear and nonlinear temperature rises are compared. • Coupling effect of temperature rise and moving load on the dynamic deflection is analyzed. [ABSTRACT FROM AUTHOR]

• The heterogeneous aggregate expansion rooted from fast neutron was considered. • Radiation-induced damage yields significant stiffness degradation. • Combined effect of neutron radiation, lateral stress ratio and strain rate was investigated. • Failure mechanism of radiation-induced concrete under biaxial compression was revealed. • Formulas of biaxial compression strength for radiation-induced concretes were derived. As a good shielding material, heavyweight concrete is largely utilized for building the Concrete Biological Shielding (CBS) wall of the commercial nuclear power plant, and is often subjected to the biaxial loadings with a strain rate possibly varying from 10−5s−1 to 10−2s−1. This paper assesses the combined effects of the lateral stress and the strain rate on the compressive strength of radiation-induced heavyweight concrete on the example of serpentine concrete. For this goal, a 3-dimensional rectangular numerical concrete specimen containing special aggregates and ITZs was firstly established. Exposed to neutrons of different fluences, the initial damages caused by the fast neutron were assessed by a thermal-mechanical approach. Then, a series of static and dynamic biaxial compressive tests on the rectangular specimens having initial damages of different degrees were carried out by finite element analysis via ABAQUS. The failure modes, the crack patterns, and the ultimate compressive strengths of the pre-irradiated serpentine concrete were obtained numerically. Finally, based on the numerical results and the classical "Kupfer-Gerstle" ("K-G") criterion, this paper derives the biaxial strength criterion of the radiation-induced heavyweight concrete undergoing both lateral stress and strain rate. Through the formula, it was found that the fast neutron fluence of high level reduces significantly the biaxial compressive strength of the heavyweight concrete. Besides, if the heavyweight concrete undergoes additionally lateral stress and the strain rate, the biaxial compressive strength could be enhanced. The enhancement effect was maximized at the lateral stress ratio of 0.5 and the strain rate of 10−2s−1. The current numerical approach was developed with a potential application to the lifetime extension of the heavyweight concrete infrastructures used in commercial nuclear reactors. [Display omitted] [ABSTRACT FROM AUTHOR]

• A stress-based evolutionary topology optimization framework via XIGA is proposed. • Geometric boundaries of optimized design explicitly expressed as B-spline. • Satisfactory stress accuracy along the structural boundaries is guaranteed by XIGA. • No need for fine meshing to achieve clear strength design with smooth boundaries. • Structural boundary control points of the strength design can be directly edited to further improve strength performance. This paper presents a novel approach to stress-based topology optimization that employs NURBS representations of explicit geometric boundaries to address stress minimization and stress-constrained problems. The proposed methodology is compatible with CAD systems and utilizes Extended IsoGeometric Analysis (XIGA) to ensure an accurate representation of stress field in the evolving structure. A p -norm aggregation scheme is used to measure global stress levels, and the aggregated stress constraint is augmented to the objective (compliance) via a Lagrange multiplier in stress-constrained problems. The proposed approach introduces a novel and efficient Lagrange multiplier trail strategy aimed at reducing computational costs. Additionally, a normalization scheme and a partial differential equation filter are presented to stabilize the highly nonlinear stress-based optimization. Validation studies demonstrate the effectiveness and characteristics of the proposed approach. Moreover, control points of the structural design can be directly edited to further improve strength performance. Comparative studies show clear advantages of the proposed methodology in terms of computational efficiency compared to other Finite element analysis (FEA)-based optimization methods. Overall, this paper presents a practical and novel approach that addresses the limitations of existing FEA-based optimization methods in terms of accuracy, flexibility, and degree of freedom (DOF) cost, and makes a significant contribution to the field of stress-based topology optimization. Graphical abstract [Display omitted] [ABSTRACT FROM AUTHOR]

• Level-set method is applied for stress-based topology optimization of plate problems. • Solving optimization problems with arbitrarily complex geometries and boundaries. • A stabilized least-squares method is applied for solving level-set-based equations. • The shape derivatives, adjoint method, and p -norm aggregation function are used. In this paper, we present a stress-based topology optimization of plate structures by using a finite element level-set (LS) method. Since stress constraints are independent with LS-based design variables, the singularity phenomenon arising in topology optimization under stress constraints can be resolved without using any relaxation technique. The finite element method is used for solving LS-based equations of design variables and the state and adjoint equations of plate structures with arbitrary complex geometries and boundaries of the design domain. To obtain stable finite element solutions without any oscillation, both unsteady LS convection-diffusion equation and LS re-initialization convection-reaction equation are solved using a stabilized least-squares finite element method. [ABSTRACT FROM AUTHOR]

• The LCF tests of notched specimens under three temperatures after different degrees of initial overload treatment was conducted. • The initial overloads could significantly improve the crack initiation life, but could also introduce damage near the notch surface, especially for large overload situations. • The LCF life model considering the sensitivity of overload induced residual stress can give a more accurate prediction. • A recommendation to improve the fatigue life of GH4169 alloy by initial overload was given through comprehensive experimental results and finite element model analysis. In this paper, the effect of initial overload on the low cycle fatigue life of GH4169 alloy at different temperatures was studied. The plate specimen with a central hole was designed to perform low cycle fatigue tests at 20 °C, 500 °C and 650 °C with variable initial overloads. Results showed that the subsequent crack propagation rate depended on both overload ratio and following test temperature, and excessive overload treatment would also damage the surface or internal grains of the specimens through fracture characteristics under SEM. A finite element model was adopted to analyze the residual stress and stress-strain field at the edge of the central hole. Then, the stress and strain data were input to three strain-based model to predict the fatigue life of GH4169 alloy considering residual and mean stresses. Based on the combination of the experimental results and model prediction, the suggestion to improve the fatigue life of GH4169 alloy by initial overload can be put forward as following: a single initial overload makes the maximum local stress reach 90 %–93.5 % of the true ultimate stress of the material, so as to maximize its fatigue life. [ABSTRACT FROM AUTHOR]

Although extensive experimental and numerical studies have been conducted on the axial performance of steel tube and sandwiched concrete jacketed CFST columns, contableurations with outer square tubes and inner circular CFST components are rarely found. This paper investigates the axial performance of square steel tube and sandwiched concrete jacketed circular CFST columns, examining the effects of outer steel ratio and sandwiched concrete strength on failure patterns, relative load-strain curves, and load-bearing capacity. The analysis of ultimate compressive capacity confirmed the effective confinement provided by the outer square steel tube. Based on the experimental results, a finite element model was established to further study the working mechanism of retrofitted columns. The load on components, distribution of longitudinal stress and transverse constraint stress on concrete revealed that the inner concrete experiences dual confinement effects from both inner and outer steel tubes, with the constraint of the outer square steel tube becoming significant only during the load dropping phase. Furthermore, a simple equation was proposed for predicting the axial compressive load-bearing capacity of retrofitted columns using superposition methods and design codes. Comparison results demonstrated good agreement between experimental and calculated values. • The axial performance of circular CFST columns strengthened with square steel tube and sandwiched concrete jackets was investigated. • The outer tube thickness had a greater impact on the compressive strength of retrofitted columns compared to the sandwiched concrete strength. • A finite element model was established to study the force mechanism of axially-loaded circular CFST columns strengthened with square STSCJ. • An equation was proposed to calculate the axial compressive capacity of retrofitted columns based on the superposition methods and design codes. [ABSTRACT FROM AUTHOR]

Microscale beam-like structures are standard components of micromechanical systems in many devices. However, the small dimensionality affects their deformation characteristics and leads to misinterpretations of the results. Presenting such size dependency is possible with advanced continuum descriptions via introducing additional variables compared to the classical one. Hence, the problems where contact occurs require the readjustment of boundary conditions considering these extra parameters. That burdens the already challenging task of contact problem calculations and restricts most demonstration examples to two-dimensional problems and geometrical linearity. The resolution of the imposed restrictions within finite element modeling further emphasizes the usage of advanced media in design and facilitates its application to various problems, which is the aim of this paper. The delivery of that task is as follows. Firstly, we present the kinematics and material descriptions for the micropolar media. The authors propose to use a newly developed continuum-based micropolar beam formulation to avoid an overwhelming computational burden and, at the same time, deal with nonlinear stress–strain relations. Secondly, the work develops a contact approach within the micropolar theory from two-dimensional to three-dimensional elasticity, although the contact is considered frictionless. Finally, it compares two existing contact formulations, including the developed one, for the contact beam problems, using the examples of two collinear sliding beams' bending. • Presented two known contact formulations within the micropolar theory. • Developed one of the contact approaches to three-dimensional elasticity. • Considered a practical problem of bending two-layered cantilever beam.. [ABSTRACT FROM AUTHOR]

In this paper, a strain gradient thermoelastic problem is studied from the numerical point of view. The heat conduction is modeled by using the type II thermal law and the second gradient of the thermal displacement is also included in the set of independent constitutive variables. An existence and uniqueness result is recalled. Then, the fully discrete approximations are introduced by using the implicit Euler scheme and the finite element method. A discrete stability property and a main a priori error estimates results are proved. Then, some numerical simulations are performed, including some issues as the numerical convergence of the approximations, the effect of two possible dissipative terms (second- and fourth-order) or a comparison with the type II strain gradient thermoelasticity. [ABSTRACT FROM AUTHOR]

Piezo stack energy harvesting from railway vibrations shows substantial potential for powering wireless sensor networks responsible for monitoring railway infrastructure. Nevertheless, assuring the safety and durability of these energy harvesters in the condition of the dynamically fluctuating railway vibrations remains a considerable challenge. In this paper, we present two innovative protection methods designed for piezo stack energy harvesters with a frequency up-conversion mechanism. These methods involve the incorporation of ring-type and circular stoppers within the resonant system and the utilisation of proposed impact protection components within the impact system. Two distinct harvesters incorporating the proposed protection components, Harvester Types I and II, are designed to align with their respective operating acceleration targets, which are determined based on the amplitudes of railway vibration acceleration. Finite element modelling is used to guide the design process, involving the evaluation and selection of various design parameters aligned with the acceleration target and stress limits. The protection mechanisms' effectiveness and impact on energy harvesting performance have been validated through experimental testing under measured rail vibration signals, and their performance has been further assessed through stress analyses. Harvester Type I operates seamlessly within a 5 g threshold, effectively mitigating the increase in maximum output acceleration and stress beyond this limit. In contrast, Harvester Type II efficiently dissipates excess energy, enabling the harvester to operate at a 15 g acceleration while reducing the rate of acceleration and stress growth. The results demonstrate that both proposed harvesters provide effective protection from unexpected railway vibration overloads. This research makes a significant impact on the practical, real-world implementation of piezo stack energy harvesters operating within the dynamic environment of railway vibrations. [Display omitted] • Two strategies are proposed to protect energy harvesters with frequency up-conversion from mechanical overload. • Harvester Types I and II are developed to incorporate the proposed strategies considering the railway requirements. • FEM modelling is developed to evaluate and determine the design parameters. • Experiments are carried out to assess the protection mechanism and energy harvesting performance of the harvesters. • The proposed harvesters can provide effective protection from unexpected railway vibration overloads. [ABSTRACT FROM AUTHOR]

The vertical uplifting response of suction caisson plays a pivotal role in the ability of the jacket foundation to resist the large moment. Although the macro element model, which encapsulates generalized load and displacement relationships in a unified element, is widely utilized to simulate foundation responses, a macro element model tailored for suction caissons considering project-specific foundation geometries and site-specific soil stress-strain curves is currently underdeveloped. This paper addresses this gap by constructing a macro element model for the uplift response of suction caisson. This goal is achieved by deriving the macro element model via up-scaling soil stress-strain relations. Firstly, finite element analyses (FEA), with a verified undrained hyperbolic soil model, are adopted to obtain macro responses of the uplifting suction caisson in undrained clays. Subsequently, using the same hyperbolic hardening relationship and associated flow rules as the constitutive model of soils, an elasto-plastic macro element model for suction caisson subjected to uplift loads is established. The macro model is then calibrated against the computed caisson responses from FEA, leading to the establishment of a scaling law between the parameters of the macro element model and that of the soil constitutive model. Finally, the constructed macro element model undergoes validation against numerical results and centrifuge test outcomes. The assessment affirms that the proposed macro element model, developed via the up-scaling strategy, can effectively represent test responses and serve as a practical alternative to advanced FEA solutions, providing an efficient and reliable design procedure. • Macro-element (ME) model of vertically loaded suction caisson is investigated. • ME model is established via up-scaling soil stress-strain relations. • Project-specific soil properties and foundation geometries are considered. • ME model serves as a practical alternative to FEA solutions. [ABSTRACT FROM AUTHOR]

This paper presents the experimental and numerical results of an ongoing research project on the use of thermal break systems (TBSs) in internally insulated reinforced concrete (RC) structures. A new TBS, which combines steel profiles and U-shaped steel bars, is introduced and tested under monotonic loading to determine its horizontal and vertical shear capacities. The test results confirmed the appropriateness of SLABE-TBS for use in exterior wall–slab joints that demand high ductility or energy absorption despite the failure mode by concrete punching. The tested joints exhibited load-carrying capacities of 190.2 and 120.5 kN/m under horizontal and vertical loading, respectively. On the other hand, the finite element analysis performed using LS-DYNA software confirmed the significance of the U-shaped steel bars of the SLABE-TBS in improving the joint's shear capacity. However, incorporating the steel bars in the SLABE unit can reduce the equivalent stresses in the adjacent steel profiles by 33 %. • A new thermal break system (SLABE-ZN) for exterior wall–slab joints was proposed. • The tested exterior joints equipped with SLABE-ZN exhibited stable behavior under horizontal and vertical loading. • Incorporating steel bars in the SLABE unit can reduce the equivalent stresses in adjacent steel profiles by 33 %. • The contribution of the U-steel bars was approximately 30 % and 21 % under horizontal and vertical loading, respectively. • Decreasing the insulation thickness by 10 mm accounts for a 7 % increase in the load-carrying capacity of the SLABE system. [ABSTRACT FROM AUTHOR]

In this paper, a composite column using carbon fibre reinforced plastics and polyvinyl chloride composite tube (CFRP-PVC) to constrain coral aggregate seawater sea-sand concrete (CSSC) was proposed, and CFRP was pasted on the inner and outer walls of the PVC tube. To investigate the effects of the number of CFRP layers and void defects on the axial compression performance of PVC tubes, six specimens were made for axial compression loading tests and finite element parameter analysis. The results indicate that due to PVC improving the integrity of CFRP, PVC tube provide a stress transfer path for CFRP, placing CSSC in a triaxial compression state. When both the inner and outer walls of the tube are pasted with CFRP, brittle failure of CFRP-PVC tube can be effectively avoided and have relatively superior mechanical properties. In the same situation, when one layer of CFRP is pasted on the inner wall of the tube, it has better ductility and bearing capacity. When two layers of CFRP are pasted on the outer wall of the tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defect only has a significant impact on ductility. A finite element model of CFRP-PVC confined CSSC columns considering Hashin damage criterion was established based on ABAQUS, accurately predicting the failure process and CFRP damage morphology of test columns under axial load. Parameter analysis shows that when the confinement coefficient of CFRP-PVC confined CSSC columns is less than 0.3 and the height-diameter ratio is greater than 15, the load-displacement curve will lose the strengthening stage, and increasing the number of outer CFRP layers will slightly increase the stiffness of the strengthening stage. A bearing capacity calculation method suitable for CFRP-PVC confined CSSC was proposed based on the model of steel tube confined concrete, with an error of 1.2%. ● CFRP-PVC tube confined coral aggregate seawater sea-sand concrete (CSSC) column was proposed. ● The axial compression test was conducted to explore the mechanical properties of CFRP-PVC confined CSSC columns. ● The finite element models of the CFRP-PVC confined CSSC column were established to conduct parametric investigation. ● The axial strength calculation method of CFRP-PVC confined CSSC columns was proposed considering the CFRP-PVC tube restraint efficiency. [ABSTRACT FROM AUTHOR]

In nanotechnology, flexoelectric solids exhibit notable electrical polarization induced by internal strain gradients, rendering them promising for various applications. However, inherent material imperfections are inevitable. Particularly within flexoelectric solids, substantial strain gradients exist in proximity to internal defects, resulting in localized concentration of electrical polarization and potential structural failure. Among the various defect types, circular-shaped inhomogeneity is prevalent. This paper comprehensively investigates the plane strain problem on cylindrical inhomogeneities within flexoelectric solids. The full-field analytical solution is derived for this problem for the first time. Given that flexoelectric theory encompasses pure strain gradient elasticity theory, the strain gradient elasticity solution for plane strain cylindrical inhomogeneities is also established for the first time. This study reveals that the stiffness and size of the inhomogeneity, along with the loading ratio in two directions, exert a noteworthy influence on the local electromechanical coupling behavior near the inhomogeneity. Finally, the mixed finite element method is utilized to approximate the solution numerically, and the close agreement between the finite element results and the analytical solution demonstrates this study's reliability and rigor. Therefore, this investigation imparts valuable insights into examining defects in flexoelectric solids and serves as a foundation for studying more intricate defect typologies. • The exact solution for flexoelectric cylindrical inhomogeneities is derived. • The inhomogeneity stiffness influences stress and polarization concentration. • Effects of loading conditions and inhomogeneity sizes are investigated. • A mixed finite element method is used for comparison with analytical results. [ABSTRACT FROM AUTHOR]

Virtual-real Fusion is a technology that enables rapid integration of physical information and decision-making through visualization and interaction. By combining with the field of ship structure design, this technology is applied to improve the competitiveness of enterprises. In this paper, a method of virtual-real interaction and symbiosis between engineering analysis and physical scenarios is proposed, aiming to enhance the design and evaluation of hull structures. Initially, the establishment of a high-fidelity digital twin model is ensured to be consistent with the physical scene, paired with a collision detection mechanism consistent with the physical scene, which plays a key role in the correlation of loads and boundary conditions for subsequent real-time numerical simulations. Secondly, measured data from physical sensors are used to drive virtual scenes to ensure that computers understand and reproduce specific physical phenomena. Subsequently, the real-time numerical simulation data is filtered and transformed. At the same time, engineers can explore finite element analysis results on-site through virtual reality visualization technology to track the mechanical interactions between physical components, thereby reducing spatial and logical misunderstandings and enabling collaboration with other departments. Finally, a prototype system with basic functions is developed. A case study focusing on mechanical experiment of ship structures is carried out, which demonstrates the practicability of the proposed method. • Acquire load data from the real environment and simulate deformation and stress of the structure in real time. • Carry out analysis and model modification of virtual reality-assisted interaction. • Configure a physical sensor network for real-time acquisition of virtual-reality fusion field data. • Enable real-time interaction and decision-making between virtual and physical objects. [ABSTRACT FROM AUTHOR]