Finite Element Simulation Research Articles

Experimental and Finite Element Investigations to Study the Temperature Distribution at the Orthotic Boot–Skin Interface

Abstract Orthotic walker boots, commonly used for lower limb injuries, have been linked to discomfort due to increased skin temperatures, which can result in excessive sweating and skin problems. This research investigates the boot–skin temperature variation at the posterior and anterior sections of the leg after wearing an orthotic boot for an extended period. The temperature distribution at the orthotic boot–skin interface was studied using experimental measurements and finite element simulations. The temperature data were collected from eight male participants using 12 thermistors judiciously placed around the shank. The participants wore an orthotic boot for 60 min while sitting idle, and the temperature rises in the anterior and posterior regions of the leg were recorded. An average temperature rise of 2.3 °C ± 0.7 °C in the anterior region and 2.5 °C ± 0.6 °C in the posterior region was observed. These findings corroborate with the finite element simulations, which demonstrated similar temperature rise of 2.2 °C ± 0.4 °C and 2.4 °C ± 0.5 °C in the anterior and posterior regions, respectively. A statistical analysis using the seven-point Bedford scale for thermal sensation showed that the temperature rise in the posterior region was statistically significant (p = 0.022), with a higher increase noted in the posterior region compared to the anterior. The finite element simulations presented here can be used as an optimization tool to study the use of new materials and design modifications to reduce thermal discomfort in orthotic devices and exoskeletons.

A Bifunctional Shear-Thickened Composite Electrolyte Toward High-Safety Lithium Metal Batteries.

Lithium metal batteries (LMBs) are limited in practical applications due to safety issues resulting from uncontrolled dendrite growth and mechanical abuse. Herein, a bifunctional gel shear-thickened electrolyte (STE) is developed to simultaneously prevent lithium dendrite growth and improve impact protection by dispersing hydroxyl-rich fumed silica in a conventional liquid electrolyte (LE). STE in Li||Cu cells enabled a lower overpotential for Li deposition compared to that using LE. Li|STE|Li cells stably cycled 1200h, while Li|LE|Li cells only survived for 200h, which is attributed to STE promoting the formation of the stable inorganic-rich SEI. Li|STE|LFP full cells achieved capacity retention of 77% after 200 cycles, much higher than LE-containing cells (54%@200 cycles). In addition, the superior protection performance of STE-containing pouch cells is verified by in-situ monitoring with digital image correlation technology and theoretical analysis with finite element simulation. Compared with the pouch cell without STE, the maximum principal strain and plastic strain of the STE-containing pouch cell are reduced by 80% and 62.5%, respectively, which benefits from the non-Newtonian fluid behavior of STE under impact loading. This work confirmed the great potential of the bifunctional gel electrolyte for enhancing the electrochemical performance and safety of LMBs.

Study on the Engineering Characteristics of Alluvial Silty Sand Embankment Under Vehicle Loads

This article takes alluvial silty sand in the alluvial plain area as the research object. Through a combination of theoretical analysis, finite element simulation, and on-site testing, the engineering characteristics of alluvial silty sand under traffic loads, as well as the feasibility of using alluvial silty sand as roadbed filling material in practical engineering, are systematically expounded on for the first time. The research results indicate that the influence of vehicle speed on the distribution and depth of dynamic stress is relatively small, while the moisture content (optimal 7.8%) and compaction degree (>94%) are the key factors determining the performance of the roadbed. Specifically, the displacement at the top of the roadbed varies with changes in moisture content. An increase in compaction degree is beneficial for reducing settlement and enhancing the stability of the roadbed. Through comparative analysis of finite element simulation and on-site testing, it was found that although the initial settlement of alluvial silt filling is large, the settlement rate is fast and can stabilize in a short period of time. Its long-term performance can still meet engineering requirements. Research has shown that alluvial silt can be used as an economical and reasonable roadbed filling material, but in practical applications, strict control of moisture content and compaction degree is required to optimize roadbed performance.

Enhanced Attenuation of Train-Induced Vibrations in Metro Superstructures via Radial Metastructures Embedded in Trackbeds

As urban density increases with more buildings constructed above complex metro transportation lines, the metro systems are characterized by higher speeds, increased line density, increased travel frequency, and sometimes shallow burial depths. The severe vibrations induced by metro operations significantly affect the life quality of residents. Traditional vibration attenuation structures, such as active measures (e.g. floating slabs and resilient rail pads) and passive methods (e.g. open trenches and soft-filled barriers), often fall short in addressing low-frequency vibrations and are limited in scalability. This paper introduces a novel approach using metamaterials with unique properties that can be engineered to cater for specific needs. It presents the design and evaluation of a radially periodic vibration-attenuation structure embedded within metro trackbeds, termed a metastructure barrier. This barrier consists of alternating layers of two materials arranged in a periodic pattern. The theoretical dispersion relation to identify the bandgaps is derived using transfer matrix method (TMM) and spectra element method (SEM), followed by finite element simulations to evaluate efficacy of the structure in attenuating vertical ground vibrations. The result indicates a substantial reduction in radial wave transmission within the 0–400[Formula: see text]Hz range, particularly effective at 0–100[Formula: see text]Hz, which is the target design frequency. Additionally, the paper considers practical aspects such as a hybrid structure incorporating another two floating slab track types, and the desirable number of layers in the barrier design for real-world scenarios. By applying the vibration data from a specific section of Beijing Subway, effectiveness of this metastructure is confirmed. With its customizable design and robust vibration attenuation capabilities, this metastructure offers a promising solution for mitigating train-induced vibrations in both metro renovation and new urban construction projects.

Promoting Electrochemical Reversibility: Concave versus Convex Electrodes.

The importance of electrode shape, alongside electrode size, as key factors in controlling the reversibility or otherwise of electrochemical responses, is recognized at the microscopic level but is explored here via finite-element simulation on the macroscopic scale. Reduced overpotential is seen for concave surfaces relative to flat or convex surfaces, providing an unexplored avenue for the design and fabrication of electrodes, including composites for diverse applications where enhanced reversibility is desirable, such as in sensors and battery materials where the promotion of electrocatalytic responses is important.

Enhancing Precision in Arc Welding Simulations: A Comprehensive Study of the Ellipsoidal Heat Source Model

Arc welding is a complex multiphysics mitigation process, and the related finite element simulation requires significant computational resources for multiphysics modeling to determine the temperature distributions in engineering problems accurately. Engineers and researchers aim to achieve reliable results from finite element analysis while minimizing computational costs. This research extensively studies the application of conventional ellipsoidal heat source formulation to obtain improved temperature distribution during arc welding for practical applications. The ellipsoidal heat source model, which artificially modifies the coefficient of thermal conductivity in the welding pool area to simulate stirring effects, is proven to be scientifically valid by comparing its results with those of COMSOL’s multiphysics arc welding analyses. The findings from finite element analyses demonstrate that the temperature fields generated using the modified ellipsoidal approach exhibit strong agreement with those obtained from multiphysics simulations, especially within the core regions of the weld pool. The method can easily be implemented in all different welding methods in which a stirring effect is formed by either electromagnetic or buoyancy-driven flows in the weld pool area. Furthermore, the method offers computational efficiency without sacrificing accuracy, making it suitable for industrial applications where multiphysics modeling is not feasible but reliable thermal and structural predictions are essential.

Fatigue assessment of offshore tubular joints: stress concentration factor vs. detailed finite element method using stress influence matrix

ABSTRACT In this work, two hotspot stress estimation methods were compared in prediction of the fatigue damage level of tubular joints of jacket-supported offshore wind turbines (OWT). The first method is the stress concentration factor (SCF) method, which uses empirical functions to determine eight hotspot stresses (HSSs) along the brace-chord weld interface of each tubular joint. The second method is the stress influence matrix (SIM) method, which is based on a single realization of detailed finite element simulation of tubular joints, determining HSSs through matrix multiplication and linear stress extrapolation. After determined HSSs, fatigue damage is computed using the rainflow counting and S-N curve. Two complete fatigue damage analysis processes for the tubular joints (TJs) of OWT were proposed. Furthermore, an implementation study involving TJ1-TJ5 of the reference NREL 5 MW OWT was presented. The results through comparison indicate that the SIM-incorporated fatigue assessment procedure that considers an extended number of hotspots on the inner or outer wall of the joint member could lead to a more precise fatigue analysis. The SIM-incorporated fatigue assessment procedure provides an optimal and less conservative solution for FLS design in view of the fact that the discrepancy between the SCF- and SIM-incorporated fatigue procedures increases with the joint elevation level.

Predictive Modeling of Activated Tungsten Inert Gas Welding in Grade 91 Steel Using Finite Element Method and Experimental Techniques

Grade 91 steel, a ferritic‐martensitic alloy, is commonly used in thermal power and nuclear plants due to its high‐temperature, high‐pressure performance. This study analyzes the thermal and mechanical behaviour of activated tungsten inert gas (A‐TIG) welding on 4 mm‐thick Grade 91 steel using an in‐house developed oxide flux. Transient temperatures are recorded at multiple locations during welding. X‐ray diffraction is used to evaluate residual stress, with peak tensile stress near the heat‐affected zone reaching 471 MPa. The A‐TIG process yields deep penetration and narrow weld beads due to high heat intensity. A finite element simulation incorporating a combined heat source model (conical and double ellipsoidal) is used to predict temperature, stress, and distortion. Longitudinal distortion predictions are compared with experimental results, showing good agreement. Distortion analysis using various theories confirms the accuracy of the simulation. Phase transformations from ferrite to austenite and then to martensite are included in the model, enhancing prediction accuracy. The combined model with large deformation and phase transformation effects provides results closely matching experimental data for both thermal and mechanical responses.

Study on the Approach to Obtaining Mechanical Properties Using Digital Image Correlation Technology

Accurate mechanical property parameters constitute an indispensable guarantee for the accuracy of finite element simulations. Traditionally, uniaxial tensile tests are instrumental in acquiring the stress–strain data of materials during elongation, thereby facilitating the determination of the materials’ mechanical property parameters. By capitalizing on the digital image correlation (DIC) non-contact optical measurement technique, the entire test can be comprehensively documented using high-speed cameras. Subsequently, through in-depth analysis and meticulous numerical computations enabled by computer vision technology, the complete strain evolution of the specimen throughout the test can be precisely obtained. In this study, a comparison was made between the application of strain gauges and DIC testing systems for measuring the strain alterations during the tensile testing of 316L stainless steel, which serves as the material for the primary circuit pipelines of pressurized water reactor (PWR) nuclear power plants (NPPs). The data procured from these two methods were utilized as material mechanical parameters for finite element simulations, and a numerical simulation of the uniaxial tensile test was executed. The results reveal that, within the measuring range of the strain gauge, the DIC method generates measurement outcomes that are virtually identical to those obtained by strain gauges. Given its wider measurement range, the DIC method can be effectively adopted in the process of obtaining material mechanical parameters for finite element simulations.

A Novel Ultrasonic Sampling Penetrator for Lunar Water Ice in the Lunar Permanent Shadow Exploration Mission

This paper presents an ultrasonic sampling penetrator with a staggered-impact mode, which has been developed for the extraction of lunar water ice. A comparison of this penetrator with existing drilling and sampling equipment reveals its effectiveness in minimizing disturbance to the in situ state of lunar water ice. This is due to the interleaved impact penetration sampling method, which preserves the original stratigraphic information of lunar water ice. The ultrasonic sampling penetrator utilizes a single piezoelectric stack to generate the staggered-impact motion required for the sampler. Finite element simulation methods are employed for the structural design, with modal analysis and modal degeneracy carried out. The combined utilization of harmonic response analysis and transient analysis is instrumental in attaining the staggered-impact motion. The design parameters were then used to fabricate a prototype and construct a test platform, and the design’s correctness was verified by the experimental results. In future sampling of lunar water ice at the International Lunar Research Station, the utilization of the ultrasonic sampling penetrator is recommended.

Integration of Pavement Finite Element simulation with Digital Twin: Current Practices, Emerging Trends, and Future Enablers

Integration of Pavement Finite Element simulation with Digital Twin: Current Practices, Emerging Trends, and Future Enablers

A Trimming Strategy for Mass Defects in Hemispherical Resonators Based on Multi-Harmonic Analysis

This study investigates the impact of etching trimming parameters on the multiple harmonics of the mass distribution in hemispherical resonators and proposes a novel 1st harmonic trimming scheme. As mass balancing technology advances, the extension of identification and trimming from frequency split to multiple harmonics remains a challenge. Initially, a multi-harmonic identification scheme based on spurious mode detection was established, considering the influence of the first three harmonics of the mass distribution on the dynamic characteristics of hemispherical resonators. Finite element method modeling and analysis revealed that common structural geometric errors significantly introduce the 1st harmonic. By integrating a rectangular pulse function into the mass distribution function to simulate etching grooves, spectral analysis revealed that groove depth and width determine the amplitude and gradient of introduced harmonics. This research introduces an innovative discrete trimming scheme aimed at addressing the frequency split and mode mismatch issues associated with traditional single-point trimming of the 1st harmonic. By decomposing the trimming task into primary and auxiliary etching grooves, the 4th harmonic introduced by the primary etching is compensated by the secondary 4th harmonic introduced by the auxiliary etching, achieving decoupling of the 1st harmonic from frequency split during the trimming process. The scheme was verified through finite element simulations and experimental testing. Results demonstrate that, for a similar reduction in the 1st harmonic, the variation in frequency split during the discrete trimming process is only 11% of that observed in single-point trimming, facilitating efficient and low-damage trimming of the 1st harmonic.

TLP-Supported NREL 5MW Floating Offshore Wind Turbine Tower Vibration Reduction Under Aligned and Misaligned Wind-Wave Excitations

This paper presents a numerical study on the structural vibrations of a TLP-supported NREL 5MW wind turbine equipped with a tuned vibration absorber (TVA) in the nacelle. The analysis was focused on tower bending deflections and was conducted using a reference OpenFAST V3.5.3 dedicated wind turbine modelling software and a finite element simulation framework based on Comsol Multiphysics V6.3 which was newly developed for this study. The obtained four-degree-of-freedom (4-DOF) tower bending model was transferred using modal decomposition to the MATLAB/Simulink R2020b environment, where a 2-DOF TLP surge/sway model and a bidirectional (2-DOF) TVA model were embedded. The wind field was approximated by a Weibull distribution of velocities (8.86 m/s mean, 4.63 m/s standard deviation). It was combined with the wave actions simulated using a Bretschneider spectrum with a significant height of 2.5 m and a peak period of 8.1 s. The TVA model used was either the standard NREL reference 20-ton passive TVA, a 10-ton passive, or a 10-ton controlled TVA (the latter two tuned to the tower’s first bending mode). The controlled TVA utilised a magnetorheological (MR) damper, either operating independently (forming a semi-active MR-TVA) or simultaneously with a force actuator, forming, in this case, a hybrid H-MR-TVA. Both aligned and 45°/90° misaligned wind–wave excitations were examined to investigate the performance of a 10-ton real-time controlled (H-)MR-TVA operating with less working space. In aligned conditions, the semi-active and hybrid MR-TVA solutions demonstrated superior tower vibration mitigation, reducing maximum tower deflections by 11.2% compared to the reference TVA and by 14.9% with regard to the structure without TVA. The reduction in root-mean-square deflection reached up to 4.2%/2.9%, respectively, for the critical along-the-waves direction, while the TVA stroke reduction reached 18.6%. For misaligned excitations, the tower deflection was reduced by 4.3%/4.8% concerning the reference 20-ton TVA, while the stroke was reduced by 22.2%/34.4% (for 45°/90° misalignment, respectively). It is concluded that the implementation of the 10-ton real-time controlled (H-)MR-TVA is a promising alternative to the reference 20-ton passive TVA regarding tower deflection minimisation and TVA stroke reduction for the critical along-the-waves direction. The current research results may be used to design a full-scale semi-active or hybrid TVA system serving a TLP-supported floating offshore wind turbine structure.

Finite Element Simulation of Biomechanical Effects on Periodontal Ligaments During Maxillary Arch Expansion with Thermoformed Aligners

Purpose: This paper investigates the biomechanical effect of thermoformed aligners equipped with complementary biomechanical attachments (CBAs) on periodontal ligaments (PDLs) during the expansion process of the maxillary arch. The analysis was conducted using advanced simulations based on the finite element method (FEM). Methods: High-resolution 3D CAD models were created for four tooth types: canine, first premolar, second premolar, and first molar. Additional 3D models were developed for aligners, CBAs, and PDLs. These were integrated into a comprehensive FEM model to simulate clinical rehabilitation scenarios. Validation was achieved through comparative analysis with empirical medical data. Results: The FEM simulations revealed the following: for canine, the displacement was 0.134 mm with a maximum stress of 4.822 KPa in the amelocemental junction. For the first premolar, the displacement was 0.132 mm at a maximum stress of 3.273 KPa in the amelocemental junction. The second premolar had a displacement of 0.129 mm and a stress of 1.358 KPa at 1 mm from the amelocemental junction; and first molar had a displacement of 0.124 mm and a maximum stress of 2.440 KPa. Conclusions: The inclusion of CBAs significantly reduced tooth tipping during maxillary arch expansion. Among the models tested, the vestibular CBA demonstrated superior performance, delivering optimal tooth movement when combined with thermoformed aligners. Significance: FEM techniques provide a robust and cost-effective alternative to in vivo experimentation, offering precise and reliable insights into the biomechanical efficacy of CBAs in thermoformed aligners. This approach minimizes experimental variability and accelerates the evaluation of innovative orthodontic configurations.

Numerical investigation of mold filling in vulcanizing of green tire using finite element method

AbstractThe present study investigates the mold‐filling problem during the curing and shaping of green tires using finite element simulation. A novel optimization method for designing air vents in tire molds based on gas flow fields is proposed. The research focuses on addressing the air accumulation issue in the tire molding process to ensure the quality and efficiency of the curing and molding. Additionally, the study thoroughly analyzes the impact of key factors such as shear heat generation, temperature variation, dynamic viscosity, and degree of curing on the quality of tire shaping. Experimental validation and simulation improvement were carried out by making a resin model. Compared with the traditional design scheme, the new design scheme effectively reduces the number of exhaust holes (by 81.2%) while meeting the exhaust requirements. This study addresses the air accumulation problem in tire molding, offering theoretical and practical guidance to improve mold design and production efficiency.Highlights The influence of key factors on tire molding quality is revealed. Optimized mold plan reduces the number of vents while meeting requirements. Simulation simplifies the mold process, providing new ideas of vent design.

A Temperature Field Simulation of the Pressure Quenching Process of 18Cr2Ni2MoVNbA Gears

In this paper, gears made of 18Cr2Ni2MoVNbA steel were taken as the research object, and their cooling curves under different flow rate conditions were determined. By calculating the corresponding heat transfer coefficients, a finite element simulation method was used to study the temperature field distribution law of different flow rate combinations on the gears in the cooling process of pressure quenching. The results show that among the four representative flow combinations, the working condition 1 (A + (A − b − c) + (A − b − c)) has the smallest temperature difference between the inner and outer gears, and can better reduce the temperature difference between the inner and outer parts. Furthermore, in the pressure quenching process of gears, the appropriate extension of the quenching time can keep the quenched gear with a lower average temperature, while promoting the martensitic transformation on the surface of the workpiece. Comparing the simulation results with the experimental data, the reliability of the pressure-quenching temperature field model is verified, which can provide theoretical guidance for the optimization of the pressure quenching process.

Achieving high-speed smooth motion for stick-slip piezoelectric motors with impact-enhanced driving mode

Abstract Stick-slip piezoelectric motors (SSPEMs) are widely regarded as promising candidates for precision positioning systems due to their compact structures and simple driving modes. However, challenges inherent to conventional SSPEMs, including backward motion and instability, seriously limit the output speed of SSPEMs at high driving frequencies. Inspired by the driving principle of impact inertial piezoelectric motors (IIPEM), this paper proposes an impact-enhanced driving mode that enables SSPEMs with smoother ripple motion and improved driving frequencies compared to conventional driving modes. The proposed driving mode utilizes the parasitic motion of the compliant mechanism (CM) and the inertia of the driving foot to generate larger force to the mover at high driving frequencies, so that the backward motion can be eliminated and the output performance can be improved at high frequency. To validate the proposed driving mode, an SSPEM with modified triangular configured CM (TCCM) is carefully designed by analytical models and finite element simulation. A prototype is then fabricated for validation. Experimental results show that the backward motion is eliminated when the driving frequency exceeds 800 Hz. Comparative results further highlight the advantages of the impact-enhanced driving mode, achieving a maximum driving frequency of 1800 Hz and a peak velocity of 38.19 mm/s. The proposed impact-enhanced driving mode offers a universal and effective solution for SSPEMs with parasitic-motion CMs, significantly improving speed, accuracy, and high-frequency one-step stability.

Modeling and Multi-field Simulation of a Self-Protecting Squeeze-Shear Magnetorheological Brake

Traditional magnetorheological (MR) brakes are widely applied in high-precision systems but face challenges such as insufficient torque and strict safety requirements. These brakes are unable to maintain their braking state after an emergency shutdown, limiting their use in high-safety environments. This study aims to improve both braking torque and safety by designing a multi-disc MR brake incorporating a self-protection mechanism and a wavy disc surface, which operates in a combined squeeze-shear mode. A mathematical model for braking torque was developed using the Bingham model and slab method. Finite element simulations were conducted to analyze the electromagnetic and thermal fields of the designed brake. The relationship between braking torque and current was also established through advanced optimization techniques. Simulation results demonstrate that the braking torque reaches a peak of 182.7 Nm under a current of 4A. During continuous braking at 4A for 40 s, the temperatures of all components remained within permissible limits.

Experimental evaluation and FE simulation of the asymmetrical rolling process of bimetal rods

PurposeRoll-formed products that are custom-made provide flexible and effective answers for various aerospace uses. The purpose of this study is experimental tests and finite element (FE) simulation of the asymmetrical rolling process of bimetal rods.Design/methodology/approachBimetal rods are fabricated using horizontal core-filling casting equipment (the inner layer is of aluminum [Al] and the outer layer is of copper [Cu]). Al and Cu materials undergo tension testing to obtain true stress–true strain curves. An asymmetric rolling machine is used to experimentally roll the bimetal rods. In addition, ABAQUS software is used to conduct FE simulation of the bimetal rod rolling process.FindingsA comparison is conducted between the experimental and numerical results to examine the geometric parameters of the bimetal rod after asymmetric rolling. In addition, an investigation is carried out into the impact of various reductions on the geometric dimensions of the rod’s cross-section, the curvature radius and the contact force between the rolls and the bimetal rod within a range of rotational velocities of the rollers. One of the most important results shows the decrease in the rod’s radius of curvature after rolling shows a correlation with the increase in the reduction of rod cross-section.Originality/valueThe bimetallic rod is fabricated using a horizontal core-filling casting device and subsequently tested via an asymmetric rolling test on an asymmetric rolling machine.

Three-dimensional magneto-thermal analytical model for planar induction heater of nonmagnetic conducting materials considering transverse finite length effects

Purpose This paper aims to present a three-dimensional nonlinear magneto-thermal analytical model for a planar permanent-magnet induction heater, enabling the evaluation of the spatiotemporal temperature distribution in a non-magnetic conducting plate. The coupled 3D magneto-thermal problem is formulated using the sub-domain method, image theory and the equivalent thermal network. Design/methodology/approach The 3D magneto-thermal problem is solved through a nonlinear coupling between an electromagnetic analytical model and a transient thermal analysis. The electromagnetic model is derived by solving the three-dimensional Maxwell equations in Cartesian coordinates. First, the analytical expression for the heating power is determined for an infinitely wide conducting plate using a hybrid formulation. Then, the method of images is applied to account for finite-width extremity effects. The thermal model is obtained using the equivalent thermal network method. To analyze the accuracy of the magneto-thermal model, the analytical results are compared with those obtained from the 3D finite element (FE) multiphysics simulation. Findings The obtained results show the accuracy of the proposed magneto-thermal model, even for geometries with a very strong 3D edge effects. The analytical model directly takes into account the magnetic edge effects, the transverse finite width of the conducting plate, the reaction field and the temperature-dependent nonlinearity of the physical properties, without using correction factors. The use of a direct formulation of induced currents in the conducting part allowed us to determine a new analytical expression for the heating power. The magneto-thermal analytical model shows a good compromise between accuracy and computation time. Practical implications The proposed magneto-thermal model significantly reduces computation time compared to 3D FE simulations, making it a robust tool for the quick and accurate optimization and design of planar permanent-magnet induction heater systems. Originality/value A new 3D magneto-thermal analytical model for determining the spatiotemporal temperature distribution on a planar heater has been developed. This model accounts for magnetic edge effects, the finite width of the workpiece and the reaction field, while improving computation time thanks to the new analytical expression for the heating power derived from a hybrid formulation.