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The Proton Exchange Membrane Fuel Cell (PEMFC) performances are strongly impacted by the compression of the Gas Diffusion Layer (GDL). Despite its fibrous microstructure, this material is usually considered as a continuous medium and characterized with uniform loading. However, the GDL is subjected to a heterogeneous compression onto rib/channel patterns in the fuel cell assembly. In the present study, a complex behavior of the GDL response is experimentally revealed when the material is loaded with a rib/channel pattern, compared to uniform compression. The tests are simulated by finite element modeling using a classical strain-dependent elastic law, using parameters fitted from uniform compression experiments. It is shown that the numerical results do not reproduce the effect of pattern observed experimentally. Hypotheses to interpret these results involve mechanisms at the fiber microscale including fiber fracture, cross-link breakage and fiber rearrangement, which are exacerbated by larger material deformation caused by the heterogeneous loading. • Unexpected impact of rib/channel patterns on GDL compression. • Experimental investigation of the effect of rib/channel width on GDL deformation. • Numerical study with classical model unable to reproduce experimental results. • Interpretations based on mechanisms at the fiber microscale. [ABSTRACT FROM AUTHOR]

Alumina-based multilayer laminates with layers of varied porosities and ceramic fiber reinforcements, which can be achieved by including paper-derived ceramic layers, are interesting candidates for chemically stable and thermal shock resistant materials. In order to investigate the complex sintering behavior of these laminates, the sintering of each alumina layer contained within a laminate, each one with its individual sintering anisotropy and sintering shrinkage, has to be considered separately. For this purpose, sintering curves are determined by dilatometry measurements, serving a consecutive examination by an analytical model. Modeling parameters specific to each layer, are applied in finite-element-type sintering simulations for symmetrical multilayer laminates. Differences in the sintering shrinkages may cause internal stresses at layer interfaces and, in turn, may influence the thermal and mechanical properties of multilayer laminates after sintering. Accordingly, the prediction of developing internal stresses within alumina-based multilayer laminates by the presented sintering simulations is a key aspect of this study. [Display omitted] • Individual laminates sintering dilatometry. • Anisotropic sintering assessment by analytic modeling. • Finite element simulation of multilayer laminates sintering. [ABSTRACT FROM AUTHOR]

Femoral deformities are highly prevalent in children with cerebral palsy (CP) and can have a severe impact on patients' gait abilities. While the mechanical stress regime within the distal femoral growth plate remains underexplored, understanding it is crucial given bone's adaptive response to mechanical stimuli. We quantified stresses at the distal femoral growth plate to deepen our understanding of the relationship between healthy and pathological gait patterns, internal loading, and femoral growth patterns. This study included three-dimensional motion capture data and magnetic resonance images of 13 typically developing children and twelve participants with cerebral palsy. Employing a multi-scale mechanobiological approach, integrating musculoskeletal simulations and subject-specific finite element analysis, we investigated the orientation of the distal femoral growth plate and the stresses within it. Limbs of participants with CP were grouped depending on their knee flexion kinematics during stance phase as this potentially changes the stresses induced by knee and patellofemoral joint contact forces. Despite similar growth plate orientation across groups, significant differences were observed in the shape and distribution of growth values. Higher growth rates were noted in the anterior compartment in CP limbs with high knee flexion while CP limbs with normal knee flexion showed high similarity to the group of healthy participants. Results indicate that the knee flexion angle during the stance phase is of high relevance for typical bone growth at the distal femur. The evaluated growth rates reveal plausible results, as long-term promoted growth in the anterior compartment leads to anterior bending of the femur which was confirmed for the group with high knee flexion through analyses of the femoral geometry. The framework for these multi-scale simulations has been made accessible on GitHub, empowering peers to conduct similar mechanobiological studies. Advancing our understanding of femoral bone development could ultimately support clinical decision-making. • Distal femoral growth plate stresses quantified with subject-specific simulations. • Large dataset of 50 femurs – 26 healthy, 24 femurs of participants with cerebral palsy. • Knee flexion angle is of high relevance for typical bone growth at the distal femur. • Workflow reveals plausible growth results supported by geometrical analysis. • Multi-scale workflow based on free software published on GitHub. [ABSTRACT FROM AUTHOR]

Paper, a porous-fibrous network, is made up of hydrophilic fibres, which are notably susceptible to deformations due to variations in moisture content. The response of paper sheets to full or partial wetting, based on the water-induced fibre swelling, has mostly been predicted in the past using highly idealised two-dimensional network geometries. The purpose of the present paper is to establish how precisely the two-stage process of determining effective hygro-expansivity under uniform wetting by a two-dimensional model followed by bending analysis using a continuum model predicts the curl of a fully three-dimensional network. In the present multi-scale modelling work, the moisture-induced homogenised sheet scale curl, derived from hygro-elastic deformations using non-uniform moisture profiles, is analysed based on an idealised non-woven three-dimensional fibrous network finite element model. First, the effective paper sheet swelling properties, derived computationally for the uniform wetting condition, are compared with analytically homogenised hygro-elastic properties. Whereas the analytically predicted elastic modulus has an inaccuracy of only ∼ 5%, the hygro-expansivity coefficient is over-predicted by roughly a third for a network with straight fibres. The difference is smaller if waviness of the fibres and wrap-around in the fibre bonds are taken into account. Fibre alignment turns out to have little influence. Subsequently, paper sheet curl predictions made by the analytical model are compared with that computed from the three-dimensional network model. The inaccuracy of the fully analytical model, based on the two-dimensional network description, relative to the fully detailed three-dimensional computational model with straight fibres is on the order of 40%–50%. The fidelity of the simple model is primarily constrained by the inaccuracy of the effective hygro-expansion coefficient. If the expansivity extracted from the three-dimensional simulations under uniform wetting is inserted, the inaccuracy drops to less than 10%. The continuum bending description hence performs adequately, provided it is based on a reliable estimation of the uniform expansion behaviour of the material. • Hygroscopic curl of paper sheets may be predicted using homogenised models. • We assess the accuracy of such predictions. • As a reference simulations of an idealised three-dimensional fibre network are used. • The predictions are accurate provided an accurate hygro-expansivity is used. • Two-dimensional network models may not be sufficient for this. [ABSTRACT FROM AUTHOR]

This paper presents a numerical comparison of finite-element methods resulting in local mass conservation at the element level for Poisson's problem, namely the primal hybrid and mixed methods. These formulations result in an indefinite system. Alternative formulations yielding a positive-definite system are obtained after hybridizing each method. The choice of approximation spaces yields methods with enhanced accuracy for the pressure variable, and results in systems with identical size and structure after static condensation. A regular pressure precision mixed formulation is also considered based on the classical RT k space. The simulations are accelerated using Open multi-processing (OMP) and Thread-Building Blocks (TBB) multithreading paradigms alongside either a coloring strategy or atomic operations ensuring a thread-safe execution. An additional parallel strategy is developed using C++ threads, which is based on the producer-consumer paradigm, and uses locks and semaphores as synchronization primitives. Numerical tests show the optimal parallel strategy for these finite-element formulations, and the computational performance of the methods are compared in terms of simulation time and approximation errors. Additional results are developed during the process. Numerical solvers often fail to find an accurate solution to the highly indefinite systems arising from finite-element formulations, and this paper documents a matrix ordering strategy to stabilize the resolution. A procedure to enable static condensation based on the introduction of piecewise constant functions that also fulfills Neumann's compatibility condition, and yet computes an average pressure per element is presented. • Numerical comparison of the mixed, primal hybrid, and other locally conservatives finite element methods. • Introduction of a twice hybridized primal hybrid method, yielding a positive definite matrix after static condensation. • Comparison of multi-threaded strategies and thread-safety mechanisms. • A numerical procedure to stabilize the linear system resolution for indefinite matrices is described. • A general procedure that enables static condensation and fulfills Neumann's compatibility condition. [ABSTRACT FROM AUTHOR]

Research laboratories worldwide use the spark plasma sintering (SPS) technique for sintering metallic and ceramic matrix composites. Typically, the SPS sintered parts are low circular cylinders (discs). The upscaling and industrialization of SPS technology face two challenges: the limitation of shaping non-cylindrical parts and the inhomogeneous sintering of large-sized products. This paper addresses these challenges in sintering axisymmetric shells within an SPS setup with improved thermal insulation. The paper considers the sintering of a 75 mm shell as a case study. The shell material is a zirconia-carbon nanotube composite. Finite element analysis revealed that homogeneous sintering of such a shell requires careful thermal insulation of the entire setup. Investigation of phases, microstructure, density, microhardness, and fracture toughness in the sintered shell showed a homogeneous structure and uniform properties. [ABSTRACT FROM AUTHOR]

• Nonlinear model for a bended piezoelectric semiconductor beam is established. • Differential quadrature method based iteration procedure is developed. • Nonlinearity of constitutive relation and non-uniformity of structure are focused. • Potential barriers and wells are realized through designing structures. In this paper, the effects of nonlinear constitutive relation on the electro-elastic coupling behaviors in non-uniform piezoelectric semiconductor beams are investigated. On the basis of three-dimensional theory for piezoelectric semiconductor and double power series, one-dimensional bending model is developed. In order to deal with the nonlinear problem, a differential quadrature method based iteration procedure is proposed. Comparing with the results from finite element method, the proposed method has good convergence and high accuracy. In numerical analysis, the effects of nonlinearity and non-uniformity in piezoelectric semiconductor are discussed thoroughly. It is found the introduction of nonlinearity induces the loss of symmetric for all electrical field quantities but little changes the mechanical quantities. While the reduction of width along the length direction produces larger mechanical and electrical responses. Importantly, the effects of nonlinearity on the electrical field quantities are more evident in a piezoelectric semiconductor beam with rapidly varied cross section. Besides, we designed the piezoelectric semiconductor beams subject to double shear forces and a beam with locally varied cross section. In the designed structures, the potential barriers and wells are realized, which provide new approaches adjusting the electro-elastic behaviors in piezoelectric semiconductors. The study in this paper could be the guidance designing high performance electronic devices. [ABSTRACT FROM AUTHOR]

In this paper, we present explicit expressions for conforming finite element function spaces, basis functions, and degrees of freedom on the pentatope (the 4-simplex) and tetrahedral prism elements. More generally, our objective is to construct high-order finite element function spaces that maintain conformity with infinite-dimensional spaces of a carefully chosen de Rham complex in four dimensions. This paper is a natural extension of the companion paper entitled "Conforming finite element function spaces in four dimensions, part I: Foundational principles and the tesseract" by Nigam and Williams (2024). In contrast to Part I, in this paper we focus on two of the most popular elements which do not possess a full tensor-product structure in all four coordinate directions. We note that these elements appear frequently in existing space-time finite element methods. In order to build our finite element spaces, we utilize powerful techniques from the recently developed 'Finite Element Exterior Calculus'. Subsequently, we translate our results into the well-known language of linear algebra (vectors and matrices) in order to facilitate implementation by scientists and engineers. [ABSTRACT FROM AUTHOR]

The stability, robustness, accuracy, and efficiency of space-time finite element methods crucially depend on the choice of approximation spaces for test and trial functions. This is especially true for high-order, mixed finite element methods which often must satisfy an inf-sup condition in order to ensure stability. With this in mind, the primary objective of this paper and a companion paper is to provide a wide range of explicitly stated, conforming, finite element spaces in four dimensions. In this paper, we construct explicit high-order conforming finite elements on 4-cubes (tesseracts); our construction uses tools from the recently developed 'Finite Element Exterior Calculus'. With a focus on practical implementation, we provide details including Piola-type transformations, and explicit expressions for the volumetric, facet, face, edge, and vertex degrees of freedom. In addition, we establish important theoretical properties, such as the exactness of the finite element sequences, and the unisolvence of the degrees of freedom. [ABSTRACT FROM AUTHOR]

This paper delves into the numerical analysis of the extended Fisher-Kolmogorov (EFK) equation within open bounded convex domains R ⊂ R d , where d ≤ 3. Two distinct finite element schemes are introduced, namely the semi-discrete and fully-discrete finite element approximations. The existence and uniqueness of solutions are established for both the semi-discrete and fully-discrete finite element approximations. Error bounds are investigated across different scenarios, including comparisons between the semi-discrete and exact solutions, as well as between the semi-discrete and fully-discrete solutions, along with the fully-discrete and exact solutions. An effective algorithm has been proposed to solve the nonlinear system resulting from the fully-discrete finite element approximation at each time step. The paper also provides computed numerical error results and showcases a variety of numerical experiments to further illustrate and support the findings. [ABSTRACT FROM AUTHOR]

This research proposes an Optimized Current chopping Control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements, comprising minimized torque ripple to reduce vibrations and acoustic noises, maximized output torque to enhance vehicle acceleration, and improved efficiency, which contributes to extending the EV's battery life. Therefore, an optimization problem is formulated and solved offline, incorporating a CCC-based SRM drive model. The control variables for this optimization problem are the switching angles of the SRM. A multi-objective function is chosen to combine three performance indices: torque ripple, average torque, and efficiency. The Harris Hawks Optimization (HHO) method is utilized in this paper to solve the optimization problem and find the optimal switching angles based on the selected objective function. HHO demonstrates a strong search capability that can effectively handle the nonlinear magnetization characteristics of SRMs. Constraints on the switching angles are also included in the optimization problem to control the phase current's RMS value and power consumption. The optimized switching angles are applied to a current chopping control (CCC) strategy and an asymmetric half-bridge converter to implement the proposed HHO-based CCC drive. Moreover, to demonstrate the effectiveness of the proposed HHO-based CCC drive, a comparative analysis based on simulations and experimental measurements is presented against other CCC approaches for SRM drives, including modified particle swarm algorithm (MPSO)-based CCC drives and analytical-based CCC drives. • A finite element analysis (FEA) software is utilized to determine the magnetic characteristics of SRMs accurately. • The obtained magnetic characteristics are then verified using a series of indirect experimental measurements to build an accurate four-phase 8/6 SRM model. • The Harris Hawks optimization (HHO) method is employed in this paper to find the optimal switching angles based on the selected objective function. • This research proposes an optimized current chopping control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements. • The proposed HHO-based CCC drive is validated and compared based on simulations and experimental measurements against other CCC approaches for SRM drives, including modified particle swarm algorithm(MPSO)-based CCC drives and analytical-based CCC drives. [ABSTRACT FROM AUTHOR]

A novel higher-order multi-scale computational approach for efficient nonlocal gradient elasticity simulation of composite materials is proposed in this paper. Based on the use of decoupling technique, raw fourth-order nonlocal gradient equations with periodically oscillatory coefficients are decoupled as the new second-order multi-scale equations for reducing the continuity requirements when implementing multi-scale simulation. Next, a novel macro-micro coupled multi-scale computational model with higher-order corrected terms is rigorously devised for high-resolution multi-scale and nonlocal analysis of composite materials via multi-scale asymptotic analysis. Then, the local error analysis of higher-order multi-scale solutions in the point-wise sense illustrates that establishing higher-order asymptotic corrected terms plays a vital role in investigating the micromechanical mechanisms. Moreover, a rigorous global error estimation with an explicit rate of higher-order multi-scale solutions is first derived in the energy norm sense. In addition, an efficient multi-scale numerical algorithm is presented to effectively simulate nonlocal gradient elasticity problems of composite materials based on finite element method (FEM). And we also derive the convergence estimation of the proposed numerical algorithm. Finally, numerical experiments are conducted to gauge the efficiency and accuracy of the proposed higher-order multi-scale method. This paper offers a unified higher-order two-scale computational framework for enabling nonlocal gradient elasticity behavior simulation of composite materials. [ABSTRACT FROM AUTHOR]

This paper designs, analyzes, and implements a finite element analysis for the simulation of the nonlinear advection-diffusion model. The key feature of the proposed work is to provide novel a priori error estimates in Bôchner norms L 2 (0 , T ; H 0 1 (Ω)) and L ∞ (0 , T ; H 0 1 (Ω)) simultaneously. To achieve the desired error estimates for both semidiscrete and fully discrete schemes, our idea is to introduce the Ritz projection operator that allows us to enforce the known estimates for P 1 and P 2 finite elements in the formulation of the desired results. Further, this paper establishes the stability, existence, and uniqueness in the precise normed spaces. Finally, we prove the fully discrete error estimates using the Backward Euler and Crank-Nicolson's schemes which are corroborated by numerical experiments to validate the developed theory on various domains for both schemes. To the best of author's knowledge, this is the first finite element simulation that provides the estimates in the L 2 Bôchner norm for any such types of time-dependent problems. [ABSTRACT FROM AUTHOR]

Grinding damage of hard and brittle materials has a direct impact on part strength and subsequent polishing efficiency. Damage suppression is one of the key research issues in hard and brittle material processing. Due to the uncertain damage evolution law, there is still a lack of optimization methods for the multi-step grinding process under given damage constraints. In this paper, the extended finite element method is used to establish a model between the prefabricated crack depth and final crack depth, which reveals the influence of various existing subsurface damages on crack propagation. It is found that only when the prefabricated crack depth is close to the indentation crack depth on the perfect surface, the final crack depth will be affected to some extent. To optimize the grinding process to achieve low damage, a semi-empirical model for predicting grinding damage is proposed which is suitable for process optimization and does not rely on some difficult-to-obtain parameters. Finally, based on the damage evolution law and prediction model, the core content of this paper is proposed, that is, a multi-step grinding process optimization method with variable grinding depth. This method can minimize the damage while ensuring the same processing efficiency, the damage depth is reduced by 25 %. The effectiveness of the optimization method and the correctness of the damage evolution law are proved by experiments. This method is suitable for engineering applications and has practical significance for understanding the damage evolution mechanism, which is helpful for the suppression of grinding damage and the optimization of the grinding process. • Reveal the evolution mechanism of various existing subsurface damage on crack propagation by XFEM. • Propose a semi-empirical model for grinding damage prediction suitable for process optimization. • Propose a multi-step grinding process optimization method for hard brittle materials with variable grinding depth. • Prove the effectiveness of the optimization method and the evolutionary model through experiments. [ABSTRACT FROM AUTHOR]

In this paper, further in-depth research on chip formation mechanism is conducted on the cutting of metallic glasses. The study of chips contributes to a better understanding of the machining nature of materials, which is of significant importance for improving product quality, reducing energy consumption, and resource utilization. This paper employs a combination of simulation and experimental methods, wihch not only analyzes the mechanism of chip formation in depth, but also investigates the time-varying characteristics of cutting forces. The results indicate that, when comparing simulation with experiments, the average error in cutting forces is 7.62%, and the chip morphology is also quite similar. Observations in the simulation show that as the cutting thickness increases from 7.96 μm to 23.87 μm, the free surface of the chip exhibits serrated features, and the main shear zone of the chip becomes clearer. Cutting forces exhibit periodic variations, with alternating peaks and valleys representing the formation of shear zones in the chip. In the experiment, observed chips displays a wrinkled free surface and a smooth non-free surface, with some chip edges exhibiting a burr phenomenon. By selecting appropriate machining parameters, the generation of secondary shear bands on the free surface was effectively reduced. By observing the chip morphology, it is found that the chip formation is accompanied by the material removal of plasticity and brittleness, which is the result of the combined action of heat, stress, and free volume. It should be considered to lower temperature to reduce the phenomenon of chip adhesion, providing guidance for further optimizing the cutting process of metallic glass. This paper can provide to readers further understanding of the chip formation mechanism in milling metal glass. • 2D finite element modeling was used to simulate the chip formation. • The shear zones appeared on the serrated chips. • The experimental results verified the accuracy of the simulation model. • The chips of BMG have smooth non-free surface and wrinkled free surface. • The serrated chips are the result of heat, stress, and free volume. [ABSTRACT FROM AUTHOR]

In order to solve the deficiencies of traditional board-level assembly CubeSat, such as low modularity, complex assembly process and poor scalability, a sandwich module assembly structure and method with no drive components is proposed, which can achieve quick connection and flexible assembly between modules. First, the proposed CubeSat standard module can be compatible with the standard interface of traditional CubeSat. The 4-in-1 interface of Mechanical-Electrical-Thermal-Data does not occupy the internal space of the standard module, and the electrical and thermal interfaces meet the requirements of CubeSat in-orbit work. Secondly, in order to improve the reliability of the connection between the modules, a plug-in connection scheme of the mechanical interface was designed. Finally, a genetic algorithm was used to optimize the interface size, so that it has better plug-in performance. The simulation results show that the performance of the male interface of titanium alloy material is the best, and the error between the finite element analysis and genetic algorithm results is less than 4.8 %, which is consistent with the actual tensile test results of the optimized prototype, and meets the mechanical requirements of the launch process and space orbit operation for CubeSat. The test results can guide production and provide a reference for subsequent engineering applications of CubeSat modular assembly. • In this paper, a standardized modular assembly method of CubeSat sandwich structure is designed. The assembly structure does not include driving parts, is simple in form, can be quickly connected, is flexible in assembly mode, and does not occupy the internal space of the standard module. • A standard 4-in-1 connection device was designed in this paper, including four interfaces: mechanical, electrical, thermal and data, which can achieve "plug and play". • This paper uses genetic algorithm to optimize the structure of the mechanical connection male joint, and obtains the optimal configuration of the male joint. This ensures the reliability, firmness and stability of mechanical connections, and meets the mechanical requirements of CubeSats during launch and in orbit. [ABSTRACT FROM AUTHOR]

This paper summarizes the effective components of computer-aided design and computer-aided manufacturing (CAD-CAM) resin composites that contribute to achieving greater mechanical properties and further development. In silico multi-scale analysis, in silico nonlinear dynamic finite element analysis (FEA), and artificial intelligence (AI) were used to explore the effective components of CAD-CAM resin composites. The effects of the filler diameter and silane coupling ratio on the mechanical properties of CAD-CAM resin composites have been clarified through multi-scale analysis. The effects of the filler contents, and filler and monomer compositions have been investigated by AI algorithms. The fracture behavior of CAD-CAM composite crown was analyzed using in silico non-linear dynamic FEA. The longevity of CAD-CAM composite crown was assessed through step-stress accelerating life testing (SSALT). As the filler diameter decreases, there is an increase in elastic moduli and compressive strengths at the macroscale. At the nanoscale, a decrease in the filler diameter results in a decrease in the maximum value of the maximum principal strain. When the silane coupling ratio decreases, there is a decrease in the elastic modulus and compressive strength. According to the exhaustive search and feature importance analysis based on the AI algorithm, the combination of certain components was narrowed down to achieve a flexural strength of 269.5 MPa. The in silico non-linear FEA successfully detected the sign of the initial crack of the CAD-CAM composite molar crown. The SSALT revealed that CAD-CAM resin composite molar crowns containing nanofillers with a high fraction of resin matrix demonstrated great longevity. This paper summarized the effective components of CAD-CAM resin composites for their further development. The integration of in vitro and in silico approaches will expedite the advancement of CAD-CAM resin composites, offering benefits such as time efficiency and reduction of material waste for researchers and manufacturers. • The effective components of CAD-CAM resin composites (RC) have been summarized. • A smaller filler and a high silane coupling ratio enhance the mechanical properties of CAD-CAM RC. • Non-linear FEA has detected the sign of the initial crack in the CAD-CAM composite crown. • AI has been utilized to narrow down the effective components that achieve high flexural strength. • CAD-CAM composite crowns with a high fraction of resin matrix demonstrate remarkable longevity. [ABSTRACT FROM AUTHOR]

CORC superconducting cable is a compact and flexible composite superconductor. It is widely used in large power systems because of its good flexibility and high engineering current density. In these applications, reducing the AC loss generated by the superconductor is a key factor in studying the electromagnetic field of the superconducting conductor, which affects the operational stability of the entire superconducting power device. Currently, the use of striated tape-wound cables not only allows for flexible wiring at design time but also effectively reduces AC losses. This technology has been widely used in large superconducting magnet equipment. In this paper, the finite element model of single superconducting tape and CORC superconducting cable is established based on the finite element idea. The electromagnetic properties and mechanical changes are numerically calculated by H-method. The results show that both the current density and the magnetic field of a single superconducting tape show a gradual penetration from the two sides to the center. The area of maximum current density and magnetic field distribution is at the tape boundary. The distribution of current density, magnetic field and Lorentz force of three-dimensional CORC superconducting cable is similar. All of them are gradually attenuated from the maximum value at the boundary to the center position. It is worth noting that the current density, magnetic field and Lorentz force of the striated superconducting cables are smaller than the values without striations. The calculation results of the finite element model in this paper show that the striations weaken the current density, magnetic field and Lorentz force of the CORC superconducting cable by about 8.77%, 16.21% and 9.23%. Moreover, the presence of striations can effectively reduce the AC loss of superconductors. [ABSTRACT FROM AUTHOR]

Hydrogen, as a clean energy carrier, presents a significant step toward sustainable energy solutions but faces challenges in storage due to its low energy density and high volatility. This study addresses the optimization of Type V hydrogen storage tanks by investigating the burst pressure performance of spherical, cylindrical, and toroidal shapes. Using finite element analysis (FEA) and first-order shear deformation theory, we examined how these geometries impact burst pressure outcomes across a range of composite materials and layup configurations. The materials tested included carbon T700/epoxy, Kevlar/epoxy, E-glass fiber/epoxy, and basalt/epoxy. Results demonstrate that the toroidal shape significantly outperforms spherical and cylindrical designs in stress distribution and burst pressure, with basalt/epoxy composites exhibiting superior burst pressure performance (12.7 MPa) compared to Kevlar/epoxy (10.8 MPa), E-glass fiber/epoxy (11.4 MPa), and carbon T700/epoxy (8.9 MPa). Kevlar/epoxy toroidal tanks outperform other materials in weight performance, having a structural performance index of 0.0305 Mpa.m3/kg and hydrogen density per unit mass of 0.0251 kg H 2 /kg. The stacking sequence [-45/45]s optimized stress distribution for the toroidal shape across all materials. The findings highlight that toroidal designs offer significant advantages for high-pressure hydrogen storage, providing efficient stress management and improved safety. This paper underlines the potential of toroidal vessels for enhancing hydrogen storage efficiency and emphasizes the importance of material selection and stacking sequences in achieving optimal burst pressure performance for international organization for standardization (ISO) certification. • Toroidal tanks show superior burst pressure over spherical and cylindrical designs. • The [-45/45]s stacking sequence optimizes stress distribution for toroidal tanks. • Basalt/epoxy composites outperform other materials in burst pressure performance. • Kevlar/epoxy toroidal tank outperforms others in weight performance. • Toroidal tanks offer efficient stress management and enhanced safety for hydrogen storage. [ABSTRACT FROM AUTHOR]

In this paper, we introduce two one-parameter families of quadratic polynomial enrichments designed to enhance the accuracy of the classical Crouzeix–Raviart finite element. These enrichments are realized by using weighted line integrals as enriched linear functionals and quadratic polynomial functions as enrichment functions. To validate the effectiveness of our approach, we conduct numerical experiments that confirm the improvement achieved by the proposed method. [ABSTRACT FROM AUTHOR]

This paper considers a new stabilized finite element method (FEM) of the Stokes equations based on Clément interpolation by the constrained quadrilateral nonconforming rotated Q 1 - Q 0 finite element pair. The stabilized term constructed in this method is quite different from those of the existing literature. This method not only has the same attractive computational properties as the conforming stabilized finite element method with local polynomial pressure projection, such as parameter-free, avoiding higher-order derivatives and edge-based date structure, but also guarantees the superclose and superconvergence results for the velocity and pressure. Finally, two numerical examples are supported to confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this paper, we develop and study a new mathematical model to describe the good functioning of the biodenitrification process, combining both the biological and the mechanical aspects, and taking into account the chemotaxis-phenomenon. The model is governed by a non-linear reaction-diffusion-advection system for the bacterial activity and the Darcy flow for the porous medium. We prove the existence and uniqueness of the solution and we carry out the numerical approximation of the model within a variational framework. We propose a full discrete system based on a finite element method and we perform numerical simulations both in 2D and 3D. [ABSTRACT FROM AUTHOR]

This paper introduces a linear version of the reduced multibody system transfer matrix method for studying the eigenvalue problems and steady-state responses of tree multibody systems. The core idea is to recursively transfer mechanical information between elements, utilizing a directed rooted tree to depict the system topology. Reduced transfer equations are provided for both spatial rigid and flexible bodies. For flexible bodies, the derivation is based on the dynamical equations from the finite element method and component mode synthesis. The effectiveness and numerical stability of this method is validated through three numerical examples. • A novel recursive method is introduced for eigenvalue problems and steady-state responses of tree multibody systems. • A directed rooted tree depicts information transfer in systems and presents a recursive algorithm. • Derivation for flexible bodies utilizes dynamical equations from the finite element method or component mode synthesis. • This recursive method is concise, highly structured, and highly programmable. [ABSTRACT FROM AUTHOR]

Lattice metamaterials, a class of structures utilized for geometric lightweighting and enhancing structural integrity, feature interconnected elements arranged in specific patterns. These patterns confer unique properties beneficial for improving stiffness, damping, energy absorption, and strength across various applications. However, computational simulation of lattice structures for design and optimization presents significant challenges due to nonlinear and elastic/inelastic effects like instabilities, contacts, rate-dependence, and plasticity. Current methods heavily rely on finite element analysis (FEA), yet they entail high computational complexity and do not fully align with experimental observations. Moreover, additive manufacturing (AM) technologies introduce additional computational complexity due to process-induced anisotropic behaviors. This paper proposes a computational model to construct an effective descriptor by integrating metamaterial topological information with AM conditions. This descriptor serves as a surrogate for FEA models. Additionally, a database is established to correlate the descriptor with experimentally acquired mechanical responses of additively manufactured metamaterials. The bidirectional operation of the envisaged descriptor fulfills two objectives: informing the mechanical response of novel metamaterial models and guiding design and AM processes based on desired outcomes. Model validation demonstrates significant concurrence between predicted and experimental results, evidencing the model's capability to capture inherent nonlinearity in both design and process. [ABSTRACT FROM AUTHOR]

The radial displacement of hydrogen storage composite overwrapped pressure vessel (COPV) is a key factor related to the collapse failure and burst pressure. However, there is still lack of effective method to monitor the radial displacement during the hydrostatic test and service process of the vessels. This paper proposed a method to measure the radial displacement based on fringe projection profilometry (FPP). Hydrostatic test with a composite overwrapped pressure vessel verifies the proposed method. The variation of displacement changing with inner pressures observed in the experiments is in agreement with that obtained from finite element analysis. Also Computed Tomography (CT) scanning is conducted and a widely spread micro defects is found in the composite layer of the cylinder. 78.9% of the total observed defects are small (<1000 mm2). In regions where large-sized defects (>1000 mm2) are concentrated, the total area of defects reaches 16,200 mm2. According to the statistical analysis, the strong correlation is found between the defects area and radial displacement. • Presented a novel method based on fringe projection profilometry (FPP) for monitoring the deformation of composite overwrapped pressure vessels (COPVs) during hydrostatic testing. • Employing 3D point clouds from FPP to reconstruct the cylinder and measure radial displacement. • The variation trend of radial displacement with pressure obtained by experiments is consistent with the finite element results. • Utilized Computed Tomography (CT) to detect and quantify micro delamination defects in the cylinders. • A significant correlation was found between the area of defects and radial displacement, while the relationship between the number of defects and radial displacement was less pronounced. [ABSTRACT FROM AUTHOR]

In this paper, two efficient two-grid finite element algorithms are proposed for solving two-dimensional nonlinear pseudo-parabolic integro-differential equations. Firstly, we obtain optimal error estimates of the fully discrete finite element method using a temporal-spatial error splitting technique in H 1 and L p norms. Then the two-grid technique to improve computation efficiency of the proposed finite element method. Error estimates in H 1 and L p norms of two-grid solutions are presented. Theoretical analysis shows that the two-grid algorithms maintain asymptotically optimal accuracy. Finally, numerical examples are provided to support our theoretical results and demonstrate the effectiveness of these methods. [ABSTRACT FROM AUTHOR]

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]

Atomic force microscope (AFM) is a powerful instrument for nanoscale measurement in different environments. Since high-resolution AFM measurements require avoiding external vibration interference, bulky vibration isolation platforms are commonly applied, which is a limitation for in-situ AFM measurements in some environments with small space and limited loads. For high-resolution imaging without bulky external vibration isolation, this paper presents a vibration isolation method for AFM with its internal z-axis (vertical) actuators moving the AFM probe. A piezoelectric actuator was used for z-axis actuation, and a flexural structure with low stiffness was designed to guide the z-axis motion and achieve vibration isolation. The low stiffness mechanically isolated the probe from floor vibrations at high frequencies. The parameters of the flexural structure were determined theoretically, and its performance was analyzed through finite element method. Finally, the prototype of the platform was machined and its vibration isolation performance was experimentally tested. The experimental results indicate that the vibrational isolation effect of the designed flexural structure is increased by 51 % in the z-axis in the frequency range 0.1–300 Hz and above 900 Hz compared to the original AFM structure. • A novel vibration isolation platform for AFM probe with flexure-based structure is proposed. • The flexure-based structure is designed based on a symmetric configuration. • The proposed vibration isolation platform has a simple and compact mechanical structure with 51 % higher vibration damping performance in z-axis. [ABSTRACT FROM AUTHOR]

Current design methods for flexure (or compliant) mechanisms regard stress as a secondary, limiting factor. This is remarkable because stress is also known as a useful design parameter. In this paper we propose the Stress And Geometry (STAGE) method, to design the geometry of a flexure mechanism together with a desired stress field. From this design, the stress-free to-be-fabricated geometry is computed using the inverse finite element method. To demonstrate the potential of the method, the geometry of the well-known crossed-flexure pivot is taken as example. We first show how this mechanism can be redesigned for the same functional geometry with various internal stresses. This results for a specific choice of stress field in a design of a crossed-flexure pivot with 23% lower peak stresses during motion as compared to the known designs, for a ± 45° rotation. We then present a second example, of a Folded Leaf Spring (FLS). With a parameter sweep the optimal stress field is calculated, showing a peak stress reduction of 28% during motion. This result was validated with an experiment, showing a normalized mean absolute error of 5.5% between experiment and theory. With a second experiment it was verified that the functional geometry of the FLS with internal stresses was equal to the one without internal stresses, with geometric deviations smaller than half the thickness of the flexures. • A method is proposed to design the geometry and stress of flexure mechanisms simultaneously. • The peak stress in a Crossed-Flexure Pivot has been reduced by 23% using the proposed method. • This stress reduction is achieved without changing the functional geometry of the mechanism. • Similarly, the peak stress in a Folded Leaf Spring has been reduced by 28%. • Empirical tests validate that the stresses are reduced without changing the functional geometry. • The fabrication method used in the article is proven in Industry (wire-EDM). [ABSTRACT FROM AUTHOR]

This paper reports the performance of different tool electrode structures in micropatterning of vertically aligned carbon nanotube (CNT) forests through dry micro-electro-discharge machining (μEDM). Micro cylindrical electrodes of tungsten with flat and hemispherically rounded tips were employed in this study. The rounded-tip electrode was shaped using a custom wet μEDM process. Both types of electrodes were used to pattern arrays of micro test slots at different depths and discharge voltages on a multi-walled CNT forest from which the resultant discharge gaps were experimentally characterized. The rounded-tip electrode showed a 2.1–2.4× reduction in the discharge gap with applied voltages of 15–20 V, suggesting its potential to improve the lateral resolution of the patterning process when compared with the flat-tip case. Finite element analysis of the process configuration with these two electrodes was conducted and showed good agreement with the improvement factors of the discharge gap experimentally observed. However, the process using the rounded-tip electrode resulted in larger variations on the bottom surfaces of the created patterns, while the use of the flat-tip electrode provided higher uniformity on these surfaces, revealing an apparent trade-off relationship between the discharge gap and the patterning uniformity for the two electrode types under the tested conditions. Elemental analysis of the processed CNT forest surfaces showed no detectable contamination from the electrodes onto the forest structures patterned using either electrode. [Display omitted] • Tool geometry affects precision in microplasma machining of carbon nanotube forest. • Flat- and rounded-tip electrodes contrast in their electrostatic behavior. • Discharge gap found to be 2.1–2.4 × smaller for round tip with 15–20 V of voltage. • Round tip yields tighter tolerance while flat tip offers higher surface uniformity. • Simulation reproduces the discharge gap ratio observed between two electrodes well. [ABSTRACT FROM AUTHOR]

In this paper, we mainly resort to a proper orthogonal decomposition (POD) method to study the reduced-dimension of unknown mixed finite element (MFE) solution coefficient vectors in the two-grid Crank-Nicolson MFE (TGCNMFE) method for the nonlinear wave equation and build a preserving accuracy reduced-dimension extrapolated TGCNMFE (RDETGCNMFE) method for the nonlinear wave equation. For this purpose, we first build a new TGCNMFE method for the nonlinear wave equation and demonstrate the existence, unconditional stability, and error estimates for the TGCNMFE solutions. From there, we build a preserving accuracy RDETGCNMFE method for the nonlinear wave equation by using the POD method to decrease the dimension of unknown TGCNMFE solution coefficient vectors and employ the matrix analysis to analyze the existence, unconditional stability, convergence, and errors for the RDETGCNMFE solutions. We finally make use of numerical experiments to verify our theoretical results and to show the advantages of RDETGCNMFE method. [ABSTRACT FROM AUTHOR]

This paper mainly focuses on the dimensionality reduction of unknown finite element (FE) solution coefficient vectors in two-grid Crank-Nicolson FE (TGCNFE) method for the spatial fractional nonlinear Allen-Cahn (SFNAC) equations. For this reason, a new TGCNFE method for the SFNAC equations is first established and the unconditional stability and convergence (errors) of TGCNFE solutions are demonstrated. Subsequently, the most important thing is to use a proper orthogonal decomposition to reduce the dimension of the unknown FE solution coefficient vectors of the TGCNFE method for the SFNAC equations and to construct a new reduced-dimension extrapolation TGCNFE (RDETGCNFE) method, and demonstrate the unconditional stability and errors of RDETGCNFE solutions. Finally, the correctness of the obtained theoretical results of unconditional stability and errors is validated by some numerical experiments. [ABSTRACT FROM AUTHOR]

This paper presents an inverse finite element (FE) approach aimed at estimating multi-layered human penile tissues. The inverse FE approach integrates experimental force–displacement and boundary deformation data of penile tissues with a developed FE model and uses new experimental data on human penile tissue. The experimental study encompasses whole organ plate-compression tests and individual layer tensile and compression tests, providing comprehensive insights into the tissue's mechanical behaviour. The biomechanical characterisation of penile tissue is of crucial significance for understanding its mechanical behaviour under various physiological and pathological conditions. The FE model is constructed using the realistic geometry of the penile segment and appropriate constitutive models for each tissue layer to leverage the accuracy and consistency of the model. Through systematic variation of tissue parameters in the inverse FE algorithm, simulations achieve the best match with both force–displacement and deformed boundary results obtained from the whole organ plate-compression tests. Test results from individual tissue layers are also utilised to assess the estimated parameters. The proposed inverse FE approach allows for the estimation of penile tissue parameters with high precision and reliability, shedding light on the mechanical properties of this complex biological organ. This work has applications not only in urology but also for researchers in various disciplines of biomechanics. As a result, our study contributes to advancing the understanding of human penile tissue mechanics whilst the methodology could also be applied to a range of other soft biological tissues. This research uses a multi-target inverse finite element (FE) approach for estimating the material parameters of human penile tissues. By integrating experimental data and a realistic FE model, this study achieves high-precision constitutive model parameter estimation, offering key insights into penile tissue mechanics under various loading conditions. The significance of this work lies in the use of this inverse FE approach for fresh-frozen human penile tissues, to identify the mechanical properties and constitutive models for both segregated tunica albuginea and corpus cavernosum as well as intact penile tissue segments. The study's scientific impact lies in its advancement of the understanding of human urological tissue mechanics, impacting researchers and clinicians alike. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper is devoted to a study of a history-dependent mixed hemivariational-variational inequality arising in contact mechanics. The contact problem concerns the deformation of a viscoelastic body with long memory, subject to a general friction law on one part of the boundary and a frictionless Signorini condition on another part of the boundary. The solution existence and uniqueness of the history-dependent mixed hemivariational-variational inequality based on a Lagrange multiplier approach are proved. Then, a fully discrete scheme is introduced and studied. The trapezoidal rule is used to approximate the integral in the history-dependent operator. For the spatial discretization, the linear finite elements are used to discretize the displacement field, and dual basis functions are used in the approximation of the Lagrange multiplier. Optimal order error estimates are derived for the displacement and the Lagrange multiplier under appropriate solution regularity assumptions. Numerical results are presented to illustrate the theoretical prediction of the convergence orders. [ABSTRACT FROM AUTHOR]

As a composite material, fibre reinforced polymer (FRP) has many uses. Incorporating FRP composite material enhances the reinforced concrete beams' (RCB) performance, properties and behaviour as external reinforcement. A summary of how different FRP influences the RCB properties should be studied. This review paper discusses the use of FRP to reinforce RCB and briefly describes the topic. Previous experimental studies and finite element analysis (FEA) results showed that RCB constructed with FRP significantly improved the axial load, load-deflection, ultimate load, crack propagation, stress-strain distribution, and failure mode of RCB. Since this FRP composite material has superior strength, force, mounting and anchoring properties, it can be used as an alternate exterior reinforcement in RCB. The structural behaviour and performance of RCB can be enhanced by utilising FRP composite material in civil and structural engineering, especially in building construction projects. [ABSTRACT FROM AUTHOR]

In this paper, a novel linearized second-order energy-stable fully discrete scheme for the nonlinear Benjamin-Bona-Mahony-Burgers (BBMB) equation is introduced, along with a superconvergence analysis of the conforming finite element method (FEM). Through skillful decomposition of the nonlinear term u ∇ ⋅ u , a new linearized second-order fully discrete scheme is developed. This scheme requires fewer iterations and exhibits higher computational efficiency compared to the nonlinear approach. Furthermore, it maintains energy stability, enabling direct numerical solution boundedness in the H 1 -norm, which represents an improvement over the L ∞ -norm boundedness reported in previous literature. Secondly, relying on this boundedness and the high-precision results of the bilinear element, we derive the unconditional error estimates for superclose and global superconvergence without any restrictions on the time step size Δ t and spatial mesh size h. Finally, numerical examples are presented to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes and analyzes a mixed variational formulation for the Navier-Stokes equations with variable viscosity that depends nonlinearly on the velocity gradient. Differently from previous works in which augmented terms are added to the formulation, here we employ a technique that had been previously applied to the stationary Boussinesq problem and the Navier-Stokes equations with constant viscosity. Firstly, a modified pseudostress tensor is introduced involving the diffusive and convective terms and the pressure. Secondly, by using the incompressibility condition, the pressure is eliminated, and the gradient of velocity is incorporated as an auxiliary unknown to handle the aforementioned nonlinearity. As a consequence, a Banach spaces-based formulation is obtained, which can be written as a perturbed twofold saddle point operator equation. We address the continuous and discrete solvabilities of this problem by linearizing the perturbation and employing a fixed-point approach along with a particular case of a known abstract theory. Given an integer ℓ ≥ 0 , feasible choices of finite element subspaces include discontinuous piecewise polynomials of degree ≤ ℓ for each entry of the velocity gradient, Raviart-Thomas spaces of order ℓ for the pseudostress, and discontinuous piecewise polynomials of degree ≤ ℓ for the velocity as well. Finally, optimal a priori error estimates are derived, and several numerical results confirming in general the theoretical rates of convergence, and illustrating the good performance of the scheme, are reported. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the superconvergent behavior of a two-grid finite element method (FEM) with 2-step backward differential formula (BDF2) for nonlinear dispersive wave equation. By introducing an auxiliary variable q = u t for the original variable u , the problem is transformed into a parabolic system. With the help of the combination technique of the interpolation and Ritz projection, the superclose and superconvergent estimates for the above two variables in H 1 -norm are obtained under the lower regularity of the exact solution compared with the standard Galerkin FEM. Finally, some numerical results are provided to show the correctness of the theoretical predictions and good performance of the proposed method. [ABSTRACT FROM AUTHOR]

This paper is contributed to explore how a Crank-Nicolson weak Galerkin finite element method (WG-FEM) addresses the singularly perturbed unsteady convection-diffusion equation with a nonlinear reaction term in 2D. The problem and some asymptotic behavior results are given for the exact solution and its derivatives with the parameter ε. These results are essential for proving the uniform convergence of the proposed WG-FEM. A tensor product Shishkin mesh featuring piece-wise discontinuous bilinear polynomials is employed to handle the layers for uniform convergence at different parameter values of ε. An error estimate ‖ u N − I N u ‖ W G is presented, where I N u denotes the vertex-edge-cell interpolation of the solution u , and ‖ ⋅ ‖ W G denotes the Weak Galerkin norm. The optimal uniform convergence order is demonstrated for semi-discrete and fully discrete schemes. Various numerical experiments are conducted to validate the optimal order of convergence demonstrated by the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we first investigate the well-posedness and regularity of mild solution to a stochastic active fluids model driven by the additive noise. A fully-discrete scheme is proposed for solving the given model, which is based on the finite element method for spatial discretization and the backward Euler method for temporal discretization. By overcoming the difficulty of error analysis caused by the discrete Laplacian operator, we obtain the convergence results of the developed scheme. Finally, some numerical examples are provided to validate the theoretical results and we also simulate the motion states of the active fluids. [ABSTRACT FROM AUTHOR]

Nonlocal problems involving fourth-order terms pose several difficulties such as numerical discretization and its related convergences analysis. In this paper, the well-posedness of the extended Fisher-Kolmogorov equation with nonlocal diffusion is first analyzed using the Faedo-Galerkin technique and the classical compactness arguments. Moreover, we adopt a BDF2 scheme for time discretization and a mixed Galerkin scheme for spatial discretization. Then, we derive the optimal order convergence rates of the fully discrete system. Finally, some numerical simulations and convergence results are provided to confirm the theoretical results and the accuracy of the proposed scheme. [ABSTRACT FROM AUTHOR]

This article introduces a unified mixed finite element framework based on a saddle-point formulation that applies to time-dependent fourth order linear and nonlinear problems with clamped, simply supported, and Cahn-Hilliard type boundary conditions. The classical mixed formulations lead to large matrix systems that demand huge storage and computational time making the schemes expensive, especially for the time-dependent problems. The proposed scheme circumvents this by employing biorthogonal basis functions that lead to sparse and positive-definite systems. The article discusses a mixed finite element method for the biharmonic problem and the time-dependent linear and nonlinear versions of the extended Fisher-Kolmogorov equations equipped with the aforementioned boundary conditions. The wellposedness of the scheme is discussed and a priori error estimates are presented for the semi-discrete and fully discrete finite element schemes. The numerical experiments validate the theoretical estimates derived in the paper. [ABSTRACT FROM AUTHOR]

• An exact matrix-form solution is proposed for analyzing multiple non-circular tunnels in layered media. • Generalized complex variable theory, conformal mapping and fast Fourier transform are used in derivation. • The proposed solution avoids complicated coefficient determinations and iterative algorithm. • Effects of elastic properties, tunnels' position, equivalent layer and the layer thickness surrounding tunnels are discussed. This paper presents a matrix-form complex variable method that can predict the stress and displacement field around multiple tunnels in layered media. The proposed matrix-form method avoids complicated coefficient determinations and iterative algorithm, which effectively improves the computation efficiency. Firstly, the expressions for the stress and displacement field are given under the generalized complex variable theory. The conformal mapping technique and fast Fourier transform algorithm are used to formulate the matrix-form expressions of boundary conditions. Considering the boundary conditions of the tunnels and soil interfaces, the global matrix solution for multiple tunnels in layered media are obtained by assembling the matrix solutions of all single layers. The present theory is verified by comparison with the existing literature, finite element analysis and field data in engineering practices, and several numerical examples are given to reveal the effects of elastic properties, tunnels' position, equivalent layer and the layer thickness surrounding tunnels. [ABSTRACT FROM AUTHOR]

• A hybrid method by integrating the advantages of frequency-wavenumber method and finite element method. • The entire process simulation from the source to the local terrain has been achieved. • Seismic response of mountains due to point dislocation source. • The crustal velocity structure and source parameters influence the seismic response. This paper proposes a hybrid method to analyze seismic responses from the source to complex terrain. The hybrid method is based on the domain reduction idea, dividing the overall model into global domain (including the source and propagation path) and local domain (including complex terrain). For the propagation of seismic wave fields in the global domain, a frequency-wavenumber method based on the exact dynamic stiffness matrix is adopted. For the local domain, the finite element method combined with the artificial boundary substructure method is used to analyze the seismic response of complex terrain. The advantage of this hybrid method is that the frequency-wavenumber method can accurately and efficiently calculate the three-component ground motion of the global large-scale model, while the finite element method has a variety of elements and constitutive models, which can finely simulate the local complex terrain. We take the Zigong Xishan Park site as the research object, and verify the correctness of the hybrid method. Based on this, we use the hybrid method to simulate the seismic response of the site, focusing on the propagation process of seismic waves on the mountain surface, the spatial distribution of peak ground displacement, and the effects of crustal velocity structure and source parameters on the seismic response of the mountain. The results show that the propagation of seismic waves and the distribution of peak ground displacement are closely related to changes in terrain, and the crustal velocity structure and source parameters have significant effects on the seismic response of the mountain. [ABSTRACT FROM AUTHOR]

• This manuscript firstly establishes a half vehicle-pavement-continuous beam bridge (VPCB) coupled system analytical model. • It is innovatively that the bridge and vehicle initial conditions are considered into analytical model. • The pavement road surface local deterioration is simulated by increasing the local roughness level of the road surface. At present, the highway bridge field is in a period of vigorous development, and the application of continuous beam bridges is becoming more extensive, so the related safety research is particularly important. However, there are few studies on the vehicle-bridge coupled interaction of continuous beam bridges, and the influence of pavement is not considered. In order to ensure that the theoretical research can better serve the engineering practice, it is urgent to establish a more refined and more complex vehicle-bridge coupled model. In this paper, a vehicle-pavement-continuous beam bridge (VPCB) coupled system model is established. A half-vehicle model is adopted, the pavement is simulated by a continuous and uniform spring damper, and the bridge is a three-span continuous beam bridge. The motion equation of VPCB system is established and deduced using D 'Alembert principle and modal superposition method. The dynamic responses of VPCB system are calculated by Newmark- β method. Here, the continuous beam bridge mode functions are fitted based on the modal vector of the continuous beam calculated by the finite element model. The correctness of the method is verified by existing literatures. The effects of bridge pavement, vehicle speed, bridge second span length, the pavement equivalent spring stiffness coefficient k p and damping coefficient c p , road roughness on VPCB system are studied. The results show that the pavement can reduce the bridge dynamic amplification factor (DAF) and the vehicle acceleration to improve the ride comfort. The dynamic responses of the vehicle and the bridge contain each other's natural frequencies. The responses of VPCB system increase with the vehicle velocity, the vehicle responses are more affected than the bridge responses. The pavement equivalent stiffness and damping coefficient has little effect on the system. The responses of vehicle and bridge increase with the increase of the bridge second span length. When the vehicle travels each span of the three-span continuous beam bridge, the time history curve of the pavement deformation under the tire resembles a sine wave. When the local roughness level of the road surface increases, the system responses at the deteriorated position suddenly increases, and the responses of the subsequent position will also be affected. The larger the roughness grade, the more obvious the responses increase. The effect on the system responses of the whole pavement damage is more significant than the local pavement damage. [ABSTRACT FROM AUTHOR]

In this paper, we consider a finite element approximation of an optimal control problem governed by a time fractional wave equation. We first prove the well-posedness and regularity of the optimal control problem. Furthermore, we discuss the fully discrete scheme and analyze its stability and a priori error estimate. Numerical experiments are given to illustrate the theoretical findings. • The weak solution to the time fractional wave equation is studied under low regular data. • The well-posedness and regularity of the optimal control problem are proven. • Numerical schemes exist the first-order and second-order accuracy in time and space respectively. [ABSTRACT FROM AUTHOR]

The contact quality between geometric features significantly affects the assembly accuracy and dynamic performance of mechanical products. However, accurate and efficient contact problem solving is currently a common challenge in the fields of tolerance analysis and tooth contact analysis (TCA). In this paper, a tolerance analysis method for gear mechanisms considering form deviations and elastic-plastic contact behaviors is proposed. Specifically, tolerance modeling of systematic and random deviations on tooth surfaces is represented by skin model shapes (SMS). Elastic-plastic contact behaviors including contact deformation, status, and stress distribution are modeled and calculated by a modified boundary element method (BEM). The accuracy and efficiency of this BEM algorithm are verified by comparing with the finite element method (FEM), indicating that the BEM can greatly improve the computational efficiency while maintaining high solution accuracy. A case study for a pair of spur gears demonstrates the significant effects of contact behaviors on transmission performance. This research provides an effective method to introduce mechanical contact behaviors in tolerance analysis of gear mechanisms. In addition, the contact simulation results can also be adopted in the analysis of vibration, reliability, and other aspects. • An accurate and efficient tolerance analysis method for gear mechanisms is proposed. • Real tooth surface topography and elastic-plastic contact behaviors are considered. • Systematic and random tooth surface deviations are represented by skin model shapes. • Elastic-plastic contact behaviors are modeled by a modified boundary element method. [ABSTRACT FROM AUTHOR]