Finite Element Method Model Research Articles

Refinement of Finite Element Method Analysis Model of Pressurized Water Reactor Nuclear Fuel Spacer Grid Based on Experimental Data

A Finite Element Method (FEM) analysis of the nuclear fuel spacer grid was conducted to assess the strength of components for the safety of nuclear power plants. The fuel assembly consists of fuel rods, upper end-fitting, lower end-fitting, guide tubes, and spacer grids. Spacer grids play a critical role in maintaining the proper spacing between fuel rods within a fuel assembly and ensuring smooth coolant flow. This role becomes particularly crucial during unforeseen emergencies, such as seismic loads, where minimizing deformation caused by external forces is essential. Therefore, this study proposes FEM models of spacer grids, mesh refinement of models, and analysis of the stiffness of the spacer grids concerning the presence or absence of pellet and clad. The results revealed significantly lower shear stiffness compared to normal stiffness, indicating potential vulnerability of the fuel assembly to large loads such as those experienced during seismic events.

Stress Concentration Factors of CHS-to-CFRHS Y-Joints Under Axial Tension Loading

A CHS-to-CFRHS Y-joint that consists of a circular hollow section (CHS) brace and a concrete-filled rectangular hollow section (CFRHS) chord by welding has a simple and smooth weld profile that saves time and cost for the fabrication of CHS-to-CFRHS Y-joints and leads to a superior fatigue performance, compared with other welded tubular joints. This investigation presented an analysis of the stress concentration factors (SCFs) of CHS-to-CFRHS Y-joints subjected to axial tension loading of the brace. First, a finite element (FE) modelling method, which was validated with the experimental results cited in the reference, was utilised to establish the FE models of CHS-to-CFRHS Y-joints. Then, a parametric analysis was conducted to investigate the influences of the significant non-dimensional geometric parameters on the SCFs of CHS-to-CFRHS Y-joints. It is found that the intersection angle of the brace and chord has an important influence on the magnitudes of the SCF values. An increase in the intersection angle of the brace and chord will increase the values of the SCFs at the 60° location and saddle. The values of the SCFs at the 60° location and saddle reach the maximum value when the intersection angle of the brace and chord reaches 90°. Furthermore, on the basis of the large database of the SCF results, empirical design equations were established to calculate the SCFs at the crown toe, 60° location and saddle via multiple regression analysis. A safety factor was applied to the empirical design equations to ensure safe and reliable results of SCF calculations for the fatigue design of CHS-to-CFRHS Y-joints in a composite truss structure. Ultimately, a comparative analysis of SCFs was conducted with the FE models of welded tubular joints with rectangular hollow section (RHS) chords and CFRHS chords. The results reveal that infilling concrete in the chord leads to a reduction in SCFs along the weld profile of more than 11% on average, and the peak SCF decreases by more than 15%.

Prediction and optimization of composite shell with cutout under hydrostatic pressure via deep neural networks

Composite cylindrical shells with openings represent an innovative primary structural configuration for submersibles, effectively enhancing their structural performance and, consequently, their endurance capabilities. Under hydrostatic pressure conditions, it is essential to optimize the structural design parameters to improve the buckling load and static strength margins of composite cylindrical shells with openings. However, the stress state around openings is highly complex, making simulation and computational analysis challenging and time-intensive. Therefore, leveraging advanced computational methods to assist in structural design is imperative. This study presents an experimental study on the hydrostatic pressure bearing performance of filament-wound composite shells. Based on the experimental results, an accurate finite element method (FEM) model has been established. This study has developed a data-rich framework, generating a synthetic dataset of strength performance under hydrostatic pressure through 16,996 FEM analysis. Subsequently, machine learning (ML) models have been established to predict strength performance. This study presents the validation of the superiority of Deep Neural Network (DNN) models in predicting structural strength under hydrostatic pressure, and evaluates the prediction error. Additionally, for the first time, the DNN model is applied to estimate the structural performance under hydrostatic pressure, with optimization achieved through the integration of a genetic algorithm. The introducing of DNN greatly accelerates the computational speed compared to full FEM-based optimization procedures. By optimizing representative long and short shell models separately, it is demonstrated that ML-based optimization can replace full FEM-based procedures, facilitating preliminary structural design optimization and offering more efficient design solutions.

Finite Element Simulation of Hot Rolling for Large-Scale AISI 430 Ferritic Stainless-Steel Slabs Using Industrial Rolling Schedules-Part 1: Set-Up, Optimization, and Validation of Numerical Model.

A growing need to reduce the environmental impact and cost of manufacturing stainless steels has led to the development of ferritic stainless steel as an alternative to austenitic and duplex steels. The development of new stainless steels involves the optimization of their hot rolling processes, with the aim of minimizing the occurrence of defects and improving productivity. In this context, numerical simulation using the finite element method (FEM) is presented as a key tool to reduce the time and cost associated with traditional trial-and-error optimization methods. Previous work oriented towards the simulation of stainless steels has been focused on the study of small samples, on the performance of laboratory-scale tests, and on the use of 2D FEM models. In this study, a three-dimensional FEM model is proposed to simulate the hot rolling process of large-scale AISI 430 ferritic stainless-steel slabs using an industrial rolling schedule employed in the actual manufacturing process of flat products. Model optimization is performed in order to reduce the computational cost of the simulations, based on the simulation of the first pass of the hot rolling process of AISI 430 stainless steel. The results show that model optimization reduces the computational time by 90.2% without compromising the accuracy of the results. Thus, it was found that the results for thickness and rolling load showed a good correlation with the experimental values. In addition, the simulations performed allowed for the analysis of the distribution of temperature and effective plastic strain.

A Finite Element Method orthotropic multi-yield elastic-inelastic model of a wood-adhesive-steel composite

Composite elements made of wood reinforced by adhesively inter-layered steel lamina can be employed as structural elements in building engineering, thanks to their favorable ratios of strength and stiffness to mass and their ductility. The mechanical response of such composite, under loading, can be predicted by employing a Finite Element Method with a proper model of each material. In this work, the Finite Element Method model is formulated within the theories of Continuum Mechanics and irreversible thermodynamics of deformation, finite strains hypothesis, and kinematics of large displacements. For the wood material constituent an orthotropic elastic–plastic-damage constitutive law is adopted, to address the effects of irreversible strains, formulated by a multi-surface yield, both for plasticity and damage, where each yield surface operates disjointedly each other, at the level of stress–strain component. The validity of the proposed model and its computational technique is revealed by analyzing the stress–strain path until the failure of a composite element. Thus, the numerical results are compared with the experimental data obtained in a tension test of that composite element. The proposed model adequately represents the mechanical behavior of the composite.

Experimental and Modeling Study for the Solar-Driven CO2 Electrochemical Reduction to CO

With the rising levels of atmospheric CO2, electrochemistry shows great promise in decarbonizing industrial processes by converting CO2 into valuable products through scalable and sustainable technologies. In this framework, the present study investigates the solar-driven CO2 reduction toward carbon monoxide, achieved by the integration between the electrochemical reactor and dye-sensitized solar cells (DSSCs), both in experimental and modeling perspectives. COMSOL® Multiphysics 6.3 was used to develop a detailed finite element method model of the electrochemical cell integrated with a photovoltaic module, validated with the experimental results that demonstrated a strong correlation. A 2D model was designed, incorporating cathode and anode regions divided by an ion-exchange membrane. The model includes platinum foil and silver nanoparticles as catalysts for the oxygen evolution reaction and CO2 reduction reaction, respectively. Integration with the fundamental equations of the DSSCs was simulated to analyze the solar-driven CO2 reduction behavior under solar irradiance variations, offering a valuable tool for optimizing operating conditions and predicting the device performance under different environmental conditions. The integrated device successfully produces CO with a faradaic efficiency of 73.85% at a current density of J = 3.35 mA/cm2 under 1 sun illumination, with the result validated and reproduced by the mathematical model. Under reduced illumination conditions of 0.8 and 0.6 suns, faradaic efficiencies of 68.5% and 64.1% were achieved, respectively.

Interphase investigation of modified McLachlan model and the 3D finite element method for electrical conductivity.

This paper explores the electrical conductivity interphase of Ag/Epoxy composite using modified McLachlan theory and 3D finite element composite model through experimental verification. The model characteristic presents conductivity as a dynamic function influenced by particle content, particle electrical properties, electrical properties transition, and an exponent. This model was meticulously crafted, considering the intricate interplay between the polymer matrix and silver particles, the tunnelling distance between adjacent silver particles, and the interphase regions around particles. This model has proven its mettle through rigorous analysis of experimental results and the impact of various parameters on conductivity. The predictions have shown impressive alignment with the experimental data, highlighting the crucial roles played by the parameters in the conductivity of silver composites where the percolation threshold reached 6vol % of filler loading. The experimental study demonstrated that the electrical conductivity was 3.84×10-1S/cm for micro-sized particles and 1.32×10-2S/cm for nano-sized particles. Notably, a large tunnelling distance drastically reduces conductivity, while higher and slighter surface energies of the polymer matrix and filler enhance conductivity. Furthermore, a thin interphase yields minimal conductivity, whereas a thick interphase and low waviness improve conductivity. The McLachlan-modified model falls slightly short in accuracy compared to the 3D finite element method models. Adjustments to the equations can enhance its alignment with experimental data.

Failure and Degradation Mechanisms of Steel Pipelines: Analysis and Development of Effective Preventive Strategies.

The increasing challenges related to the reliability and durability of steel pipeline infrastructure necessitate a detailed understanding of degradation and failure mechanisms. This study focuses on selective corrosion and erosion as critical factors, analyzing their impact on pipeline integrity using advanced methods, including macroscopic analysis, corrosion testing, microscopic examination, tensile strength testing, and finite element method (FEM) modeling. Selective corrosion in the heat-affected zones (HAZs) of longitudinal welds was identified as the dominant degradation mechanism, with pit depths reaching up to 6 mm, leading to tensile strength reductions of 30%. FEM analysis showed that material loss exceeding 8 mm in weld areas under standard operating pressure (16 bar) induces critical stress levels, risking pipeline failure. Erosion was found to exacerbate selective corrosion, accelerating degradation in high-stress zones. Practical recommendations include the use of corrosion-resistant materials, such as duplex steels, and implementing integrated monitoring strategies combining non-destructive testing with FEM-based predictive modeling. These insights contribute to developing robust preventive measures to ensure the safety and longevity of pipeline infrastructure.

Inverse engineering stress-dependent resilient moduli of cement-treated base materials in asphalt pavements using falling weight deflectometer

ABSTRACT Cement-treated aggregates (CTA) and cement-treated soils (CTS) are prevalent materials for road base and subbase layers. These materials have stress-dependent resilient moduli. This study introduces a novel inverse engineering approach for determining the stress-dependent resilient moduli of cement-treated base materials. Unlike traditional methods requiring complex triaxial tests, this approach utilises falling weight deflectometer (FWD) data from asphalt pavements. It involves creating a pavement finite element method (FEM) model that combines the viscoelastic asphalt layers. An artificial neural network (ANN) model is trained using the FEM-generated dataset ( R 2 > 0.99). The nonlinear parameters are effectively determined by integrating the ANN model with a genetic algorithm (GA) for solution optimisation, thereby eliminating the need for triaxial tests. Results show that the inverse engineering approach accurately and efficiently predicts the stress-dependent resilient modulus of pavement base layers ( R 2 > 0.98). The nonlinear parameters obtained from the model are comparable to the laboratory values. Specifically, the CTA is more resilient and can withstand higher stresses without permanent deformation. Additionally, both CTA and CTS demonstrate similar sensitivity to bulk stresses, while the CTS exhibits a greater response to shear stresses compared to CTA.

Deformation of Threaded Metal – Composite Couplings Under the Action of Gas-Dynamic Loads

The combination of metal and composite in threaded couplings increases the reliability of the structure operating under conditions of intensive internal pressure. Strength analysis of threaded metal – composite couplings based on the application of modern finite element modeling methods at the stage of design documentation development allows to create more efficient structures that better meet the operational requirements. The strength of threaded couplings of cylindrical shells made of composite material and metal under the action of gas-dynamic internal pressure is analyzed in this paper. A methodology for numerical study of the problem in Ansys / Explicit Dynamics software package is proposed. Detailed modeling of threaded couplings is used. The developed model takes into account the following: dependence of material properties on ambient temperature; nonlinear relations between the components of stress and strain tensors in metal elements, orthotropic properties of composite materials; peculiarities of contact interaction in the zones of threaded couplings of prefabricated shell elements made of different materials. The stress state of a cylindrical structure with a central shell made of carbon fiber-reinforced plastic or fiberglass and with steel shells at the edges, loaded with gas-dynamic internal pressure with a maximum value of 20 MPa at a maximum ambient temperature of 100 °С was studied. It was obtained that plastic deformations are concentrated on the edges of the threaded couplings of steel shells. At the same time, the magnitude of plastic coupling deformations with the inner metal shell is an order of magnitude higher than for couplings with the outer metal shell. The magnitude of plastic deformations in couplings with an inner metal shell is twice less when using fiberglass than when using carbon fiber reinforced plastic. Localization of critical stresses was observed only in metal shells at threaded couplings. In this case, in the thread zone they are within the elasticity limits, and the stress state of the FRP shell is not critical. No local material failure was observed in the structure.

Numerical study of the asynchronous excitation effect of Boumerdes’ earthquake on a bridge behavior

This paper represents the numerical analysis of asynchronous excitation effects on a bridge response due to the Boumerdes earthquake, using the finite element method in modeling, and the Newmark method for dynamic response analysis. The influence of the time delay of excitation between the supports on the response of structure is investigated and study how these variations can affect structural behaviour during seismic events. The dynamic displacements, normal, and shear forces and bending moments are computed through detailed simulations. The obtained results show that due to the non-uniformity in the earthquake excitation, changes in qualitative and quantitative features of dynamic displacements of the bridges. This will consequently subject the bridges to increased displacements hence compromising their structural safety and integrity. In fact, the analysis also underlines that, due to non-uniform seismic forces, the distribution of normal and shear efforts, along with bending moments, gives important concentrations of stresses that were underestimated under uniform loading conditions. From these observations, one underlines the importance of non-uniform distribution of seismic loading during bridge design or evaluation. It provides useful data to the engineers and designers who will implement the improvement in the seismic resistance of bridge structures in earthquake areas.

Asymmetric Hairpin Winding Design for Losses Reduction with Thermal Analysis for an Electric Vehicle Case Study

The asymmetric design of hairpin windings is known as a method for reducing AC losses in electric motors, especially at high frequencies. However, the design of the asymmetric winding is very critical to obtaining the best benefit regarding the efficiency and the thermal performance of the motor. Compared to the state-of-the-art in this paper, deep investigations are carried out to obtain the optimum design of the asymmetric hairpin windings while still employing a conventional manufacturing method. An analytical model is developed to speed up the investigation process, and the results of the analytical model are validated with a finite element method (FEM) model. The conclusions from the analytical investigation are considered in the design of an electric vehicle (EV) motor. The performance of the motor is studied for two different driving profiles to validate the rules of the asymmetric windings design and check the degree of dependency of the design of asymmetric windings on the application. It is proved that using asymmetric design reduces motor losses and improves thermal performance.

Modeling of Creep in Refractory Lining in Anode Baking Furnaces

Refractory flue walls in anode baking furnaces are exposed to harsh conditions during operation, affecting the structural properties of the material. The flue walls in industrial furnaces degrade over time to the point where they no longer perform as intended and must be replaced. Earlier studies of spent refractory lining from anode baking furnaces have shown considerable densification of the flue wall bricks, where the densification varies significantly from the anode side to the flue side of the brick. The observed densification is proposed to be caused by high-temperature creep, and the aim of this work was to determine whether the uneven densification across the brick could be modeled using a finite element method (FEM) implementing high-temperature steady-state creep. Finite element modeling was used to model steady-state creep for a material similar to that used in the baking furnace. Thermal and physical parameters and boundary conditions were chosen to simulate the conditions in an anode baking furnace. Refractory samples of pristine and spent lining from the baking furnace were also analyzed with X-ray computed tomography (CT), with a reduction in the porosity confirming the densification during operation. The FEM modeling demonstrated that high-temperature creep could explain the observed densification in the spent flue walls. The present findings may be useful in relation to increasing the lifetime of industrial flue walls.

Effect of Load-Bearing Wall Material on Building Dynamic Properties.

Nowadays, more and more buildings are being constructed from various types of modern materials. Many works have been written about these materials, which primarily focus on the influence of their properties on the thermal and acoustic insulation of, for example, building walls. However, there are very few publications analyzing the influence of construction materials on the dynamic properties of building structures and their vibration behavior. Yet, vibrations are dangerous for building structures. In the analysis of dynamic issues, the dynamic properties of objects should primarily be taken into account because the dynamic response of a building depends on the values of these parameters. This article focuses on numerically determining and analyzing the impact of load-bearing wall construction material on building dynamic properties-natural vibration frequencies and mode shapes. Seven building construction materials were considered, and then nine variants of building load-bearing walls made from these materials were analyzed. The analyses were carried out on the example of a low-rise administrative building structure. The building was modeled using the finite element method (FEM) with three-dimensional (3D) model analysis. Three variants of 3D FEM models were proposed, validated, and compared. A notable impact of load-bearing wall material properties on the natural frequencies and mode shapes of building structures was found. Two issues could be mentioned as the main new contributions of this paper: numerical analysis and comparing the effect of various building construction materials on dynamic building properties and the proposition and validation of various approaches to 3D FEM building load-bearing wall modeling. The findings of this research are of important significance and should be taken into account when constructing buildings subjected to dynamic loading or analyzing the possible harmful effects of various types of vibrations on buildings.

Relaxation Modeling of Unidirectional Carbon Fiber Reinforced Polymer Composites Before and After UV-C Exposure

Carbon fiber-reinforced polymers (CFRPs) are widely used in aerospace for their lightweight and high-performance characteristics. This study examines the long-term viscoelastic behavior of CFRP after UV-C exposure, simulating low Earth orbit conditions. The viscoelastic properties of the polymer were evaluated using dynamic mechanical analysis and the time-temperature superposition principle on both unexposed and UV-C-exposed samples. After UV-C exposure, the polymer’s instantaneous modulus decreased by about 15%. Over a 32-year period, the modulus of the unexposed resin is expected to degrade to approximately 25% of its initial value, while the exposed resin drops to around 15%. These experimental results were incorporated into finite element method models of a unidirectional CFRP representative volume element. The simulations showed that UV-C exposure caused only a slight reduction in the CFRP’s axial relaxation coefficient along the fiber’s axis, with no significant time-dependent degradation, as the fiber dominates this behavior. In contrast, the axial relaxation coefficient perpendicular to the fiber’s axis, as well as the off-diagonal and shear relaxation coefficients, showed more notable changes, with an approximate 10% reduction in their initial values after UV-C exposure. Over 32 years, degradation became much more severe, with differences between the pre- and post-exposure coefficient values reaching up to nearly 60%.

The model of mechanical stress dependence of 2D magnetic permeability of grain-oriented electrical steel sheets adaptable for finite element-based modeling

The paper presents the model of stress dependence of 2D relative magnetic permeability of anisotropic, grain-oriented M120‒27s electrical steel suitable for finite element method modeling. The proposed model was developed based on experimental results acquired using the measuring setup with a testing yoke equipped with a Cardan gyroscopic mechanism and hydraulic press. In the presented model, parameters of the tensor description of 2D relative magnetic permeability were chosen during the feature selection process and identified during differential evolution optimization. The good quality of the proposed model was quantitatively confirmed by the R-squared coefficient, which exceeds 0.997 for all plots of the 2D relative magnetic permeability tensor.

Evaluation of thermal parameters with geothermal energy recovery from a cold climate municipal solid waste landfill

This study presents finite element method (FEM) modeling with COMSOL Multiphysics to estimate the thermal properties of a waste landfill through back-analysis of temperature responses from buried thermistors during a full-scale multi-week active thermal response test. Field tests were conducted at the Loraas MSW landfill in Saskatoon, Canada, using instrumented equipment, including a vertical borehole heat exchanger and thermistor strings. The test consisted of two phases: a heat injection test during the summer and a heat extraction test in the winter. The study focused on a landfill 25 m deep, observing temperature changes at various depths over time. The effect of heat generation rate (HGR) on landfill temperature was investigated. Thermal conductivity and volumetric heat capacity increase with depth, with close alignment between summer and winter results, validating the tests. This research enhances the understanding of thermal parameters in MSW landfills by combining field tests and numerical modeling, offering insights into landfill behavior in cold climates. These findings hold significance for optimizing geothermal energy recovery from such landfills, calibrating thermal parameters for coupled models in landfills, and improving waste management practices.

Multi-parameter coupling modeling method and hybrid mechanism of concrete-encased CFST hybrid structures

Concrete-encased concrete-filled steel tubular (CFST) hybrid structures consist of encased CFST components and reinforced concrete (RC) encasement, posing unique challenges related to their hybrid mechanisms and coupling effects. This study addresses these issues by proposing an automatic and efficient Finite Element (FE) modeling method, which accounts for multiple constitutive models of confined concrete, meticulous grid division and reasonable interaction. The FE modeling method was packaged with a user-friendly graphical interface in the software ‘Auto CECFST’, which has been shared on GitHub(https://github.com/CECFST/Auto-CECFST.git). The modeling method has been verified by test results on the strength, stiffness and deformation capacity. Utilizing the refined FE modeling method, 7776 FE models are generated based on an orthogonal combination of 7 critical parameters of concrete-encased CFST hybrid structures. To accurately define failure modes, stress ratio (φ) was proposed to achieve quantitative analysis on the failure mode, followed by a comprehensive investigation into the full-range analysis of the hybrid mechanism of two components. Moreover, further exploration focused on multi-parameter coupling effects of critical mechanism characteristics, including strength, stiffness, and deformation capacity, elucidating the hybrid mechanism and mechanical similarities between single and multi-chord structures. Based on the above analysis, the balance of strength and deformation ability could be achieved by certain parameter ranges. Finally, available strength and stiffness calculation methods are validated against experimental and FE results under three typical failure modes, revealing the advantages and limitations of calculation methods on the basis of mechanics and data statistics, which provides a basis for security structural design.

Method of Finite Element Model Updating for Identifying the Parameters of Modified Johnson–Cook Constitutive Equation

Method of Finite Element Model Updating for Identifying the Parameters of Modified Johnson–Cook Constitutive Equation

Local-distortional-global buckling interaction os lipped channel steel cold-formed columns

It is well-established that axially loaded thin-walled steel cold-formed members are susceptible to elastic buckling. This has been a focal point of numerous research studies, leading to insights into various buckling interaction cases, including local-global (LG), local-distortional (LD), distortional-global (DG), and local-distortional-global (LDG) interactions. This investigation specifically focuses on the triple buckling interaction LDG, building upon the authors' previously proposed design solution for LD buckling interaction. The study was conducted using experimental and finite element method (FEM) column results, creating a comprehensive database to validate the proposed solutions. The first research step involved verifying the accuracy of the shell FEM model by calibrating with experimental results of lipped channel (LC) columns developing the LDG buckling. Once the FEM model's accuracy was confirmed, a parametric study was conducted to support the development of the proposed LDG design solution for LC columns. The proposed design equations adhere to the core principle of the direct strength method, capable of incorporating all single buckling modes (L, D, and G) and their combinations (LG, LD, and LDG). Comparisons were made using LRFD-based reliability analysis, which confirmed that the proposed solution is reliable, easy to apply, and aligns with the usual design principles and parameters found in current codes and standards for steel cold-formed structures. Additionally, DG and LDG design approaches from other authors are mentioned and discussed in the context of the findings of the present investigation.