Finite Element Simulation Research Articles

Investigations on mesh stiffness functions in three-dimensional spur and helical gear models. Definitions and numerical simulations

A definition of mesh stiffness as a scalar function connecting spur and helical three-dimensional pinions and gears is presented along with its conceptual limitations. Since it relies on global parameters namely, variations in torque and transmission errors, it can therefore be applied to the vast majority of the models found in the literature. In parallel, a multi-foundation (MF) model of mesh interface is introduced with the objective of being as accurate as three-dimensional finite element (FE) simulations for highly reduced computational costs. Numerous results on mesh stiffness and tooth contact conditions are presented for unmodified spur and helical gears. It is shown that the proposed mesh stiffness functions based on global parameters are sound and that the MF and FE results compare well, particularly when gear body deflections are limited. The contributions of off-line of action contacts, elastic couplings when several tooth pairs are loaded and axial deflections in helical gears are analysed. Finally, the notion of mesh stiffness function representative of the elasticity of a pinion-gear pair for static and dynamic conditions is examined.

Data-driven homogenisation of viscoelastic porous elastomers: feedforward versus knowledge-based neural networks

A computational framework is established to implement time-dependent data-driven surrogate constitutive models for the homogenised mechanical response of porous elastomers at large strains. The aim is to enhance the computational efficiency of multiscale analyses through the use of these surrogate models. To achieve this, explicit finite element (FE) simulations are conducted to predict the homogenised response of a cubic unit cell of a porous elastomer, using two different viscoelastic descriptions of the parent material, subject to pseudo-random, multiaxial, non-proportional histories of macroscopic strains. The histories of homogenised variables extracted from each set of FE predictions form a training dataset, which is used to train two different surrogate models, both relying on artificial neural networks (NNs). The first model predicts the increment in macroscopic stress over a simulation step, as a function of the macroscopic stress and strain at the beginning of the step, of the prescribed macroscopic strain increment, and of the corresponding time increment. The second model uses the same inputs and outputs but tests a knowledge-based modelling approach: it relies on the aid of an additional nonlinear elastic constitutive model, which is time- and path-independent and known a priori. This model represents an existing base of knowledge which is augmented and corrected by an NN after training on viscoelastic data. The data-driven surrogate model, therefore, learns the viscoelastic behaviour of the unit cell starting from knowledge of its elastic response. The two surrogate models are found to have comparable and very high accuracies at capturing the homogenised unit cell response to highly complex loading cases across a range of viscoelastic properties. Hyperparameter optimisation shows that the second, knowledge-based model requires a simpler NN and therefore incurs a smaller computational cost.

A one-step integrated forming and curing process for smart thin-walled fiber metal laminate structures with self-sensing functions

This study proposes and analyzes a novel one-step integrated forming and curing (IFC) process for thin-walled fiber metal laminates (FMLs) structures embedded with fiber Bragg grating (FBG) sensors, and have achieved both high-performance properties and self-sensing functions in the formed structures. A prototype machine and testing setup have been developed to validate the process's feasibility by manufacturing high-performance FMLs flat and curvature parts with effective self-sensing capabilities for real-time manufacturing and in-service monitoring. Numerical models considering curing-induced deformation and heat transfer during manufacturing have also been developed to support the analysis and validation of the self-monitoring capabilities of the intelligent FMLs parts. The results reveal that with proper control of pressure (e.g., 0.6 MPa) and time during forming and curing, high tensile and impact performance of FMLs can be maintained with embedded FBG, with less than a 3% loss. Additionally, the IFC process can effectively lead to an apparent reduction of springback deformation in the formed FMLs (more than 80%). The validation of the self-sensing function during the manufacturing process has been achieved by comparing the strain monitoring results with finite element (FE) simulation results during curing, with a minimum discrepancy of 2.0%. For the in-service self-sensing function, comparison between FE analysis and surface-fixed strain gauges during the compression instability test confirmed the efficacy of FBG sensors, with a minimum discrepancy of 4.3%. The results show that the proposed novel IFC process enables the successful manufacture of smart thin-walled FMLs parts with high shape accuracy and mechanical properties in a single step and holds significant promise for manufacturing self-sensing smart structures in the aerospace and aviation industries.

Analysis and Calculation of Cross-contact Force between Strands of Multi-layer Conductor

Abstract As a key component of the transmission line, the inter-layer cross-contact force of the internal strand is an important factor affecting the mechanical properties of the conductor. In this paper, the cross-contact characteristics between the strands of multi-layer conductors are analyzed. According to the relationship between the contact force and the contact distance between the strands, the finite element simulation of different material strands of different conductors at different cross angles is carried out. Through the analysis, it can be seen that the cross angle between the strands and the material of the strands have a significant impact on the contact force. Then, based on the existing Hertz contact theory model, the relationship between the contact force and the contact distance between the strands is modified, and the contact force and contact distance models suitable for different cross angles of the conductor strands are obtained, that is, the modified Hertz contact model. According to the simulation results, combined with the modified Hertz contact model, the contact force coefficient between the strands is fitted, and the calculation formula of contact force and contact displacement is proposed. The formula can be applied to the calculation of contact force at any intersection angle between strands. The calculation formula provides theoretical support for the accurate structural calculation of the conductor, which is helpful to the analysis and calculation of the contact friction between the strands.

A numerical conductive network model for investigating the strain-sensing response of graphene nanoplatelets-filled elastomeric strain sensors

Strain sensors have attracted great attentions for practical applications such as human-machine interface. It is challenging to model the electrical behavior of elastomeric strain sensors modified with nanomaterials. This study presents a finite element simulation to explore the piezoresistivity of graphene nanoplatelet (GNP)-filled elastomeric nanocomposites. The percolation network model is employed to determine the critical distance necessary for electrical percolation. The finite element percolation network model uses the Euclidian distance between GNPs distributed inside the representative volume element to calculate the resistivity. The influence of various parameters, including GNP alignment direction, aspect ratio, and volume fraction, on the resistivity changes of the nanocomposite is investigated. Results demonstrate that nearly 20% more tunneling distance is allowed for percolation of nanocomposite with 30% larger aspect ratio GNPs. Findings reveal that as the volume fraction of GNPs increases, the critical distance for the electrical percolation decreases significantly.

Structure optimization of transmission coil of wireless power transmission system for rail transit vehicles

Abstract To solve the transmission efficiency problem of traditional wireless energy systems applied to rail transit vehicles. In this paper, the key components of a wireless power transmission system, such as the transmission efficiency of the transmission coil and the poor anti-deviation ability of the coil, are studied. Firstly, this paper analyzes the traditional planar circular and square coil shapes, analyzes the magnetic field characteristics of the traditional transmission coil structures by ANSYS Maxwell simulation software, and obtains the advantages and disadvantages of different coil structures. According to the analysis structure, the coil structure is optimized and improved, and the coil structure form of the combined coil is put forward. Through the comparative analysis of finite element simulation software, it is attested that combined coil structure has a significant improvement in transmission efficiency and anti-deviation ability.

Linear viscoelasticity of anisotropic carbon fibers reinforced thermoplastics: From micromechanics to dynamic torsion experiments

The link between experimental characterization and the constitutive behavior of an anisotropic linear viscoelastic unidirectional carbon fiber-reinforced thermoplastic composite is explored using micromechanics modeling. Dynamic torsion tests were conducted at 1 Hz over a wide temperature range, from the glassy to the rubbery states of the polymeric matrix, on both the pure matrix and the composite, for various cutting angles relative to the fibers. A two-step modeling procedure in the frequency domain is presented to predict and validate the effective behavior of the composite. The first step involves FFT-based homogenization, which maps the microstructure and constituent behaviors to effective transversely isotropic viscoelastic properties. The second step consists of finite element simulations using the effective behavior calculated from homogenization as input to replicate the experiments. A comparison between experimental results and model predictions across the entire temperature range is performed. The modeling predictions show good accuracy at low temperatures, where the matrix is in the glassy state. At high temperatures, where the matrix is in the rubbery state, the predicted behavior becomes too soft. As the phase contrast increases and the ratio of matrix bulk modulus to shear modulus rises significantly, the impact of fiber arrangement on the effective properties becomes more pronounced.

Design and study of a novel rotary high-impact test device

Abstract Impact testing is an important means of evaluating an object’s ability to withstand impacts at specific peak accelerations. Currently, commonly used high-g impact testing devices, such as the Mach hammer and air cannon test devices, generally provide overloads ranging from 10, 000g to 30, 000 g, with a maximum of 50, 000 g. To meet the demand for high-overload impact collisions, this paper designs and studies a high-g long pulse width rotary impact test device with a detachable impact head. A finite element simulation model of the impact process was established by using finite element analysis software, and the dynamic response of the device was studied by changing the initial rotation speed and the target plate material. The results show that the overload of this rotary impact test device can reach more than 70, 000 g, and increasing the speed and hardness of the target plate material can improve the overload magnitude. This device and research method can provide theoretical support for high-overload impact testing.

Optimization of hydrogel extrusion printing process parameters based on numerical simulation

The printing quality of biological scaffold is not only affected by the fluidity of bio-ink but also by the printing process parameters, such as the size of the needle, printing height, extrusion speed, and printing speed. Therefore, optimizing the printing process parameters can further improve the molding quality of the biological scaffold. In this study, the printing and deposition process of sodium alginate hydrogel was modeled and analyzed based on the Herschel–Bulkley model by the finite element simulation method. The orthogonal experiment method, control variable method, and response surface method were used to design experiments, and the influences of different printing process parameters on the hydrogel deposition process were investigated. Finally, the optimal combination of printing process parameters was obtained by taking the molding degree and offset of the hydrogel line as optimization objectives. The results show that the strength relationship of the factors affecting the molding degree of the hydrogel line is as follows: printing height > needle diameter > printing speed > extrusion speed, and the strength relationship of the factors affecting the printing offset is as follows: printing height > needle diameter > extrusion speed > printing speed. The optimal combination of printing process parameters is d = 0.34 mm, H = 0.51 mm, v1 = 10 mm/s, and v2 = 7.91 mm/s. Compared with the printing experiment results of the hydrogel line molding degree under the optimal process parameters, the error range is within −11.55%–1.27%, which further demonstrates the reliability of the optimization method of hydrogel extrusion printing process parameters based on numerical simulation and response surface method.

Dynamic optimization design of thin plate structure based on surrogate model

Abstract To enhance dynamic optimization efficiency in traditional thin plate structures, surrogate models are integrated for structural dynamic size optimization, reducing dependence on high-precision finite element simulations. This paper focuses on optimizing the aluminum alloy sheet as the subject of research. The parameters of the specimen are optimized through sensitivity analysis, based on the comparison between the free mode Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA) results. The modified specimen undergoes validation under a four-edge clamped boundary condition. Subsequently, random vibration analysis is conducted to determine the root mean square (RMS) value of the acceleration response. Employing surrogate model technology, four models are constructed using parametric modeling and experimental design methods. These models are then compared for their fitting effectiveness. The results indicate that the RBF model exhibits the highest accuracy in fitting each response, effectively replacing dynamic simulation. Finally, the RBF combined with the NSGA-II method, optimizes the specimen’s structural size, resulting in a 21.6% reduction in mass and an 18.60% decrease in acceleration response. These outcomes demonstrate satisfactory optimization results, ensuring accuracy while enhancing the dynamic characteristics of the specimen structure. This research offers valuable insights for related engineering applications.

Fabrication and characterization of SiC-reinforced magnesium-matrix composites with honeycomb structures and anisotropic properties

This study presents a novel approach for fabricating SiC-reinforced magnesium matrix composites by combining digital light processing (DLP) with pressureless infiltration. Pre-oxidation of SiC powder enhanced its wettability with the magnesium alloy, enabling the near-net-shape fabrication of honeycomb Mg-based composites with precisely controlled SiC and Al2O3 powder ratios. The influence of varying ceramic content on the microstructure and compressive properties of the composites was investigated, revealing significant mechanical anisotropy. A combined approach utilizing fracture morphology analysis and finite element simulations elucidated the compressive behavior and failure mechanisms of the composites under different loading directions. This work not only offers a promising route for on-demand design and fabrication of Mg-based composites but also provides valuable insights into understanding the mechanical behavior of architected composites.

Hierarchical Ordered Mesoporous Sr2Bi4Ti5O18 Microflowers with Rich Oxygen Vacancies In Situ Assembled by Nanosheets for Piezo-Photocatalysis.

The Aurivillius phase layered perovskite ferroelectric material Sr2Bi4Ti5O18 (SBTO) exhibits spontaneous polarization and piezoelectric properties, which confer significant potential for piezo-photocatalysis. Its ability to enhance electron-hole separation while providing excellent fatigue resistance positions it as a promising candidate in this field. Defects were introduced to improve the structural polarization and photoelectrochemical properties of SBTO. SBTO nanocrystals, featuring a mixed structure of hierarchically ordered mesoporous microflowers and nanosheets, were successfully synthesized via the hydrothermal method. The SBTO sample synthesized at a lower hydrothermal temperature displayed optimal oxygen vacancy concentration and exhibited superior piezoelectric-photo synergistic degradation activity for organic pollutants. Additionally, corona polarization increases the macroscopic polarization of the SBTO photocatalyst, promoting the separation of photogenerated carriers. Finite element simulations confirmed that a single flower-like SBTO structure generates a higher piezoelectric potential compared to a sheet-like morphology. In conclusion, integrating self-assembled hierarchical structure design, ferroelectric polarization, and defect engineering forms an effective strategy for achieving high-performance SBTO-based layered perovskite piezo-photocatalysts.

A concise strategy for enhancing the performance of bio-based polyurethane aerogels using melamine-modified sodium alginate via Aza-Michael addition reaction

Bio-based waterborne polyurethane (PU) has garnered significant attention as a sustainable alternative petroleum-derived counterpart, offering environmentally friendly alternatives. In this work, a new approach is proposed to fabricate two kinds of composite aerogels of lowly/highly melamine-modified sodium alginate (SAML/SAMH) with methacrylate-terminated PU (SAML-PU and SAMH-PU) through dynamic covalent cross-linking via Aza-Michael addition reactions. We aim to improve the poor compatibility of polysaccharide and PU associated with traditional blending methods and impart the resulting aerogels with good biodegradability, compressive strength, thermal insulation, flame-retardant, and self-healing. Comprehensive characterizations, including Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy collectively demonstrate the successful derivatization of alginate and the effective synthesis of the Aza-Michael addition copolymer involving derivate alginate and PU. Substantial improvements in compressive strength and thermal properties are realized at comparable densities. Higher compressive strength, higher decomposition temperature and lower thermal conductivity are significantly achieved for SAML-PU (0.35 MPa, 410 °C and 0.024 W/m/K at 0.13 g/cm3) and SAMH-PU (0.58 MPa, 427 °C and 0.022 W/m/K at 0.12 g/cm3) compared to pristine PU foams (0.15 MPa, 330 °C and 0.031 W/m/K at 0.15 g/cm3). Additionally, molecular simulations of the Aza-Michael addition reaction and finite element simulations of aerogel thermal-insulation properties are conducted to corroborate experimental results. Notably, the dynamic polymers of SAML-PU and SAMH-PU exhibited excellent self-healing, recycling, biodegradability, and flame-retardant attributes. The elucidated preparation methodology and the exceptional performance and versatile applications of sodium alginate-based PU aerogels suggest a promising trajectory for future research endeavors and industrial implementation.

Design theory of self-centering column foot joint with dog bone weakened flange cover plate

Basing on the concept of post-earthquake repairability, plastic damage control, and self-centering, this study introduces a novel self-centering column foot joint with dog bone weakened flange cover plate (FCP) for prefabricated steel structure. The method and design theory for the target yield load and initial stiffness of the new joint were established. Parametric research was conducted using finite element simulation to assess the influence of the dog bone weakened FCP thickness, initial cable force, and axial compression ratio on the bearing performance of the new joint, thereby verifying the above method and theory. The results reveal the accuracy of the proposed method for determining the target yield load and initial stiffness, and provide practical design guidance for the new joint. The design theory values of the new joint and the simulation values demonstrate an error within 10%, which satisfies the engineering accuracy requirements. The corresponding procedures and suggestions for the design theory of this new joint were finally provided. Based on design theory, the overall plastic damage concentrates on the dog bone weakened FCP, successfully controlled by the new joint design, ensuring minimal damage to the main structure and demonstrating good bearing capacity and self-centering performance.

The investigation on the bending fatigue properties of Ti-6Al-4V lattice sandwich structures fabricated EB-PBF

In this study, lattice sandwich structures of Ti-6Al-4V alloy with simple cubic (SC) and rhombic dodecahedron (RD) unit cells were prepared by electron beam powder bed fusion (EB-PBF) technique. Through a combination of finite element simulation and experimental investigation, the effect of lattice cell shape and heat treatment on the bending fatigue performance of these lattice sandwich structures was studied. The results show that the underlying fatigue mechanism of the RD lattice sandwich structure is primarily dominated by cyclic ratcheting of the lattice. In contrast, for the SC lattice sandwich structure, the fatigue mechanism involves an interaction of cyclic ratcheting and fatigue crack initiation and propagation of the lattice. During the cyclic deformation process, the struts of the lattice unit cells in the SC lattice sandwich structure mainly undergo buckling deformation. Under the same bending deformation strain, the struts experience much higher stress in the SC lattice sandwich structure, making them more susceptible to crack initiation and resulting in a quick fatigue failure. Therefore, the fatigue performance of the RD lattice sandwich structure is significantly superior to that of the SC lattice sandwich structure. Heat treatment result in the enhanced plasticity of parent materials of the lattice sandwich structure, leading to improved resistance to cyclic strain accumulation during fatigue processes and an increase in fatigue strength.

Free vibration analysis of damaged laminated piezoelectric plates and composite plates with piezoelectric patch based on the Extended Layerwise Method

The dynamic analytical models for a laminated piezoelectric plate and a laminated composite plate with piezoelectric patch containing the delamination, transverse crack and debonding damages are established by the Extended Layerwise Method (XLWM). The virtual kinetic energy is introduced into Hamilton’s principle, so resulting in mass matrices and displacement-dependent second mode derivatives in the finite element (FE) governing equations. Then, the FE governing equations for the laminated piezoelectric plate, and the characteristic equations of natural frequencies for the laminated piezoelectric plate with delamination and transverse crack are derived. The coupling model of the laminated composite plate and the piezoelectric patch is established by the displacement continuity and internal force equilibrium conditions at the nodes of the contact area. Based on the degrees of freedom (DoFs) in contact, the final governing equations is deduced, followed by the analysis of free vibration responses for both plates with various damages. The accuracy of natural frequencies for each plate is verified by comparing the results with those of FE simulation by ANSYS.

Machine learning-based axial compressive capacity estimation of cold-formed steel build-up sections

To consider the highly nonlinear and complex buckling behaviour of various sections of cold-formed steel (CFS) built-up columns, experimental and finite element (FE) methods are commonly used for calculating their axial compressive capacity, although these methods are time-consuming and costly. This paper proposes machine learning (ML) methods to overcome the issues of traditional methods for predicting the maximum axial load capacity (MALC) of CFS built-up columns. A total of 3839 samples from more than 33 different types of sections were collected from 43 published papers, including 817 experimental data and 3,022 FE simulation data. A total of 15 characteristic parameters, such as the second moment of area, the radius of gyration, and the polar second moment of area, are considered when nine different ML models are trained. The robustness of these models was compared via the Monte Carlo simulation method, and the predicted results were compared with the calculated results from the current codes. The results show that the extreme gradient boosting (XGB) model has higher accuracy and smaller prediction errors in estimating the MALC. The proportion of data with a relative percentage error less than 10% in the prediction results of the AISI-DSM codes is 45.31%, whereas the XGB model achieves a proportion of 87.57%, and the results calculated from current codes tend to be more conservative, with a large deviation, which needs to be further considered.

A rate-dependent crack bridging model for dynamic fracture of CNT-reinforced polymers

Carbon nanotubes (CNTs) improve the fracture toughness of polymer-based matrix composites by bridging the crack growth path. This research presents a finite element (FE) rate-dependent crack bridging model of Mode-I dynamic crack growth in CNT-reinforced polymers accounting for rate of loading and rapid crack growth. Two distinct CNT bridging and matrix cracking damage mechanisms are taken into account in the fracture process zone (FPZ) accounting for the dissipation of fracture energy. A viscoelastic-viscoplastic material model is adapted for the matrix phase to capture the strain rate effects. The crack in the matrix phase is modeled using cohesive zone elements characterized by experimental data. A rate-dependent traction-separation law obtained from CNT pull-out simulation at relevant crack opening speeds is used to simulate the CNT bridging in the FPZ. Considering the given traction-separation law as a constitutive equation, the CNTs are replaced with non-linear spring elements to facilitate the FE simulation of crack bridging with numerous CNTs in the FPZ. The proposed rate-dependent FE model for crack bridging enables the study of the effect of key CNT factors such as length, orientation, waviness, volume fraction, and agglomeration on fracture energy dissipation at various crack speeds. The developed model can simultaneously consider the interactive effects of all CNT parameters which is useful for considering all processing-induced uncertainties in analyzing the effects of CNTs on the dynamic fracture toughness of nanocomposites.

Streamlined line-defect taper design for broadband and efficient mode coupling: connecting a silicon strip with a planar valley photonic crystal zigzag interface.

The integration of planar valley photonic crystal (VPC) interfaces into high-speed data communication chips markedly improves data rates and system robustness. This Letter presents a novel, to the best of our knowledge, edge coupler, termed the line-defect taper, which is crucial for efficient and broadband light delivery to planar VPC interfaces via silicon strip waveguides. The coupling performance of the line-defect taper is evaluated through full-wave three-dimensional finite-element simulations. The results demonstrate a -3 dB transmission bandwidth of 65.5 nm, covering 41.2% of the topological bandgap, and a -1 dB transmission bandwidth of 16.3 nm, accounting for 10.3%. With its compact design (only 3.6 µm in length), simplicity, and scalability, the line-defect taper is a promising candidate for integration into densely packed chips, highlighting its potential in advancing on-chip devices.

Ground tests for a future space experiment: Evaporation rates through a centimetric square chimney by vapor interferometry and simulation

In this paper, results of preparatory tests for a space experiment “Marangoni in Films” on board International Space Station are reported. The setup is thermalized at a setpoint temperature so that (thermal) Marangoni convection is exclusively a result of evaporative cooling of the film, here composed of a Hydrofluoroether (HFE)-7100, evaporating into nitrogen at a given setpoint pressure. The present paper is entirely devoted to the evaporation rates, whereas the Marangoni convection itself will be analyzed in future studies. Apart from the temperature and nitrogen pressure, various setpoints for the initial relative saturation in HFE-7100 vapor are explored. A special design of the test cell with a square chimney surrounding a square opening of the liquid layer permits to largely stabilize the evaporation rates during a longest-lasting middle stage (beyond the initial transients and the final film dry-out). In addition, it facilitates the use of vapor (digital-holographic) interferometry for measuring the evaporation rates, the results of which are compared with independent measurements by means of the pressure evolution within our sealed cell of a fixed volume. An excellent agreement is found before the final dry-out stage for all setpoint parameter combinations tested. The study is accompanied by numerical finite-element simulations in an axisymmetrized geometry, neglecting a possible influence of the Marangoni convection and verifying certain premises used in interferometric post-processing. Even if the simulation results might somewhat over-/underpredict in each particular case, the overall dependence of the evaporation rate on the setpoint parameters is well reproduced and the role of the buoyancy convection is thereby explored.