Finite Element Research Articles

Comparison of vibration values of rotating discs with variable parameters obtained by finite element analysis modeling with different machine learning algorithms

PurposeRotating functionally graded (FG) disks of variable thickness generates vibration. This study aims to analyze the vibration generated by the rotating disks using a finite element program and compare the results obtained with the regression methods.Design/methodology/approachTransverse vibration values of rotating FG disks with variable thickness were modeled using different regression methods. The accuracies of the obtained models are compared. In the context of comparing regression methods, multiple linear regression (MLR), extreme learning machine (ELM), artificial neural networks (ANNs) and radial basis function (RBF) were used in this study. The error graph between the observed value and the predicted value of each regression method was obtained. The error values of the regression methods used with scientific error measures were calculated.FindingsThe analysis of the transverse vibration of rotating FG disks with the finite element program is consistent with the studies in the literature. When the variables and vibration value determined on the disk are modeled with ELM, MLR, ANN and RBF regression methods, it is concluded that the most accurate model order is RBF, ANN, MLR and ELM.Originality/valueThere are studies on the vibration value of rotating discs in the literature, but there are very few studies on modeling. This study shows that ELM, MLR, ANN and RBF, which are machine learning methods, can be used in modeling the vibration value of rotating discs.

Performance of repair pre-damaged RC columns using steel straps tensioning techniques (SSTT) confinement: experimental data and modelling

PurposeA model that extends study parameters to predict repaired column behaviour is efficient. Three-dimensional nonlinear finite element models were created in ABAQUS to simulate steel strap confinement with inclusion of pre-damaged levels.Design/methodology/approachExperimental and analytical studies demonstrate that restored reinforced concrete (RC) columns usually crush at mid-height under axial compressions. Numerical models verified RC column load-deformation. Although some specimens have considerable column stiffness differences, a numerical model based on statistical analysis matches experimental test results.FindingsIt shows that, finite element model exhibited a tendency to overestimate the stiffness of the columns, with an average absolute error (AAE) of 23.1%. The validation results indicate that the AAE values for strength and ductility were 15.1% and 12.3%. It has been demonstrated that the combination of strength and ductility is capable of yielding predictions with an error rate of approximately 20%. A parametric study focused on finite element model-predicted load bearing capacity reduction.Originality/valueA numerical analysis employing finite element modelling has been formulated to investigate the behaviour of confined columns. The model underwent validation through comparison with the experimental results. The validated model is utilised to perform additional parametric investigations on the confined column.

COMPARATIVE ANALYSIS OF STRESS-STRAIN STATE OF SINGLE-ROOTED TEETH DURING INDIRECT RESTORATION OF THE CROWN WITH STUMP INLAYS OF DIFFERENT DESIGNS

The aim of our study on the biomechanics of the tooth inlay is to select the most efficient design of stump pin inlay for indirect restoration of single-rooted teeth. Materials and methods. To implement the aim of the study, the biomechanics research was conducted in the following four designs of stump inlays: 1 - traditional, 2 - with a single-stage change in the diameter of the pin along its length, 3 - with a two-stage change in the pin along its length, and 4 - with a single-stage change in the diameter of the pin and a cap in the crown of the tooth, covering the end of the root. The mathematical modeling was performed using the common software MSC NASTRAN for finite element analysis. The package, with the help of which the elastic three-dimensional models of the dentition are built and analyzed based on the finite element procedure, determines the displacement of each node of the finite element along the axis system, with three coordinates, normal and tangential stresses, as well as equivalent Huber-Mises stresses, which are calculated according to the well-known formula of deformable solid mechanics Results. The minimum values of equivalent stresses in both the pin inlay and the dentin of the root of the tooth at the level of the apical end of the pin inlay occur when using a pin inlay with a one-stage change in the diameter of the pin and a cap on the crown of the premolar. At the same time, the values of equivalent stress in dentin at the level of the apical end of the inlay pin are closest to the maximum values of equivalent stresses observed on the surface of the root of the tooth (differences do not exceed 10%). The maximum values of equivalent stresses in both the pin inlay and the dentin of the root of the tooth at the level of the apical end of the pin inlay occur when using a pin inlay of conventional design. In this case, the difference in the values of equivalent stresses in the pin compared to the inlay with a one-stage change in the diameter of the pin and a cap is 9%, and in the dentin at the level of the apical end of the inlay pin, the difference in stresses is 10%. The maximum values of equivalent stresses in both the dentin of the root of the tooth to be restored and the pin of the stump inlay occur when applying a traditionally used pin inlay. Among the various pin inlays considered, a stump inlay featuring a single-stage change in the diameter of the pin and a cap on the crown of the tooth to be restored demonstrates the highest efficiency, yielding the lowest equivalent stresses in the dentin of the tooth's root.

Numerical approximation for stochastic nonlinear fractional diffusion equation driven by rough noise

In this work, we are interested in building the fully discrete scheme for stochastic fractional diffusion equation driven by fractional Brownian sheet which is temporally and spatially fractional with Hurst parameters belonging to (0, 1/2]. We first provide the regularity of the solution. Then we employ the Wong-Zakai approximation to regularize the rough noise and discuss the convergence of the approximation. Next, the finite element and backward Euler convolution quadrature methods are used to discretize spatial and temporal operators for the obtained regularized equation, and the detailed error analyses are developed. Finally, some numerical examples are presented to confirm the theory.

Combining finite element analysis and reinforcement learning for optimal grip point planning of flexible components

Abstract Handling large flexible components is still a challenge in many industries. Examples include the handling of fibre-reinforced plastics or the assembly of industrial-scale electrolytic cells. Difficulties often arise in the design of suitable endeffectors. Inefficient gripping point design, i.e. the total number and positioning of grippers, can lead to increased stress and deflection of the component being handled. To counteract this, endeffectors are often oversized resulting in the use of more grippers than needed. Correspondingly, heavier moving masses imply longer handling times as well as higher energy consumption. This paper presents a process for planning and optimising gripping points for large flexible components. In addition to the shape of the component, actual dynamic loads of the handling path are also taken into account. The key element to the process is an optimisation algorithm based on reinforcement learning and trained using an finite element method (FEM) simulation. After computing a desirable starting configuration, the algorithm optimises the placement of gripper positions while aiming for a reduced total number. In addition, the optimisation has prescribed handling limits, such as physical and geometric constraints, that must not be exceeded. It was shown that the algorithm satisfactorily optimises the gripping points for dynamic loads for different materials and shapes. Furthermore, it has been shown that the computation of an initial configuration yields preferable results for simple components, yet requiring optimisation in the case of more complex shapes.

A numerical study of Mullins softening effects on mode I crack propagation in viscoelastic solids

This paper presents a finite element analysis of steady-state crack propagation in viscoelastic soft solids exhibiting Mullins softening. A cohesive-zone model is employed to simulate the localized processes at the tip of a Mode I crack in materials governed by viscoelastic behavior and damage-induced Mullins effects. The study numerically evaluates the intrinsic dissipation characteristics of typical rubber-like materials, focusing on the influence of key factors such as Mullins damage, relaxation modulus, and relaxation time. The impact of these factors on material toughening is examined, with particular emphasis on their role in crack propagation. The results reveal that crack propagation velocity is highly sensitive to the interplay between energy dissipation mechanisms. Specifically, Mullins damage parameters are shown to increase fracture toughness by raising the local energy release rate threshold at the crack tip. Additionally, the relaxation modulus enhances viscous dissipation, further elevating this threshold and subsequently reducing crack propagation velocity. Interestingly, an inverse relationship between relaxation time and crack propagation velocity is observed. The study provides a detailed analysis of the dissipation mechanisms at the crack tip, offering valuable insights for improving material toughness.

Modeling of reflected ultrasonic fields in composed samples

Ultrasonic nondestructive testing involves the study of propagation, reflection and refraction patterns of elastic waves excited by contact or non-contact piezoelectric transducers in the inspected object. The finite element modeling usually requires high computational costs and additional postprocessing to select individual waves from the total solution. When probing joints of homogeneous materials, such as turbine blades made of heat-resistant monocrystalline alloys, the joint boundary is low-contrast, and the reflected signals are relatively weak. This causes additional difficulties for their separation from the total wave field and correct interpretation of the information they bring. To solve this problem, explicit asymptotic representations for reflected and transmitted waves in a two-layer elastic half-space with a surface source are proposed in the present work, which allow fast parametric analysis. They can be used to analyze ultrasonic probing data, for example, to estimate the state of the junction zone or to determine the mutual orientation of the crystals’ principal axes.

Investigation of Electromagnetic Wave Propagation in Photonic-like Welded Materials Using the Finite Element Method

In this study, two identical and two dissimilar materials are conjoined by applying the friction welding method to yield various rods. This investigation’s primary focus entails examining the repercussions associated with the heat-affected zone (HAZ) arising from elevated temperatures at the welding interfaces on the propagation of electromagnetic (EM) waves within the resultant structures. The study incorporates the photonic crystal approach in conjunction with Maxwell’s equations, and the subsequent solution of the latter is executed using the finite element method. The subdivision of the structures into fifteen elements is predicated upon the assumption of the electromagnetic wave number of the m-th segment, km, of discrete segments. The finite element method is then administered to the HAZ regions of the structures, wherein the HAZ is discretised into one, three, and five elements, respectively.

Investigation into the sheet metal forming process using solid granules medium with graphite powder addition

ABSTRACT The solid granules medium sheet metal forming process uses loose particles instead of a rigid convex mold in the deep drawing process. This study focused on a mixed medium of solid granules with added graphite powder , establishing numerical models for four different proportions of graphite powder-solid granules mixtures. A finite element simulation of deep drawing was conducted using 08AL sheets. A deep drawing test shows that the thickness distribution curve closely aligns with the numerical simulation. By adding graphite powder to the solid granules medium, the lubrication conditions between the granules and the sheet metal can be modified, increasing the thickness in the fracture-prone areas of the cylindrical part. Utilizing this numerical model yields thickness distribution and deformation characteristics that closely resemble those observed in deep drawing tests, thereby contributing significantly to the optimization and advancement of this forming technology.

Failure Analysis of Girth Weld Cracking in Gas Transmission Pipelines Subjected to Ground Subsidence and Traffic Loads

Girth welds are weak points in pipelines, and failures occur frequently. In a gas transmission pipeline, a girth weld experienced cracking, prompting a failure analysis using experimental methods and finite element analysis (FEA). Experimental results showed that X-ray non-destructive testing (NDT) revealed cracks, porosity, and lack of fusion in the girth weld. However, the hardness and microstructure of the material showed no abnormalities. During operation, the pipeline experienced an increase in soil cover and was subjected to ground subsidence and vehicle loads. Finite element analysis was conducted on the defective girth weld under different conditions, including varying soil cover depths, different levels of subsidence, and varying vehicle loads, to examine the pipeline’s stress response. The results indicated that the combination of soil cover, subsidence, and vehicle loads led to pipeline failure, whereas none of these factors alone was sufficient to cause girth weld failure. To prevent such failures from occurring again, the following measures are recommended: strengthen on-site welding quality control of girth welds, conduct inspections for defects in girth welds of in-service pipelines, and promptly address any defects that exceed acceptable limits.

Experimental and multiscale analysis of volume fraction effects in tensile properties of recycled PLA-PDA/kenaf fiber 3D printing filament composites

Polylactic acid, a biodegradable thermoplastic derived from renewable sources, has notable environmental advantages and versatile properties. However, recycled PLA often experiences reduced mechanical strength and altered chemical composition due to the recycling process, limiting its suitability for 3D printing filament applications. Recognizing the inherent limitations of recycled PLA (rPLA), this research employs a unique method of coating rPLA with dopamine (DA) and reinforcing it with kenaf fibers (KF) at various weight fractions, introducing a novel multiscale modeling approach to address the challenges of interfacial bonding and tensile performance in recycled polymers. The methodology integrates experimental single filament tensile testing with multiscale finite element modeling to accurately predict the composite’s mechanical behavior across different scales. The findings reveal that a 5% kenaf fiber weight/volume fraction provides the optimal balance between tensile strength, stiffness, and toughness, achieving a significant 49.3% improvement over the unreinforced rPLA. However, increasing the kenaf fiber content beyond 5% leads to a decline in mechanical properties, attributed to higher fiber agglomeration and suboptimal fiber-matrix interactions. The novelty of this research lies in its combined use of PDA coating, natural kenaf fiber reinforcement, and advanced multiscale modeling to enhance and predict the performance of rPLA-PDA/kenaf composites, paving the way for sustainable, high-performance materials in 3D printing applications.

Analysis of the screw pile group subjected to combined V–H loading for energy application

ABSTRACT The present study investigates the behaviour of screw piles in very stiff clay under the combined vertical and horizontal loads using a three-dimensional finite element analysis. The soil is modelled using the Mohr–Coulomb elastic, perfectly plastic material, whereas the pile shaft and helices are modelled as a linear elastic material. This study examines the effect of the number of helices, helix diameter, inter-helix spacing, and pile spacing on the performance of screw piles under both vertical compression and lateral loads. The study shows that the effect of the number of helices is negligible under the combined load. The increase in the helix diameter (D h) improves the pile performance. The results also reveal that the optimum interhelix spacing is 3D h, and the optimum pile spacing is 2D h. Thus, the present study demonstrates that optimizing the geometry of the screw pile enhances its performance, making it suitable for offshore wind turbines.

Plane Wave Finite Element Method for the Dynamic Response of the Periodic Pile-Type Composite Ground Under a Harmonic Concentrated Load

In this study, a simplified model for the pile-type composite ground, namely, the periodic pile-type composite ground (PPCG) model is proposed. The PPCG in this study is assumed to be periodic in the horizontal directions and finite in the vertical direction. For investigation of the dynamic response of the PPCG to a harmonic concentrated load, a plane wave finite element (PWFE) method for the PPCG under the load is developed in this study. To develop the method, the concentrated load is decomposed into its wavenumber domain components by the 2D Fourier transform first. The response of the PPCG to a wavenumber domain load component is represented by a set of plane waves, and the variables associated with each plane wave are discretized via the FEM along the vertical direction of the PPCG. The finite element equations for each plane wave of the PPCG are developed via the virtual work principle. To obtain the overall dynamic response of the PPCG to the concentrated load by synthesizing the responses due to all load components effectively, the mode superposition method is used to construct the response of the PPCG to the load component, and the polar coordinate system-based inverse Fourier transform method is developed for the inversion of the 2D Fourier transform with respect to the wavenumber. With the developed method, some numerical results about the dynamic response of the PPCG to the concentrated load are presented.

Designing optimized geometry and fiber orientation of composites for dynamic tension via artificial intelligence

Machine learning is quickly becoming an invaluable tool for examining large databases to find patterns and predictions based on similar parameters tested in previous studies. A natural application of this subset of artificial intelligence revolves around material data sets where tests are repeated for basic studies (e.g. tension, compression, bending, or shear) and extrapolating the data for tests not yet considered. Dynamic testing and validation with machine learning is examined here, as a significant time and cost is required for understanding larger-sized specimens (cm scale and larger) especially when the samples are composite materials in tension. This is due in part to the challenges involved in ensuring failure at the region of interests for an anisotropic material and minimizing the number of repeated tests. In this study, the data sets were generated artificially via finite element analysis with failure, and a machine learning code applied to infer the shape of the tensile test coupon knowing only the failure and stress field. Then the algorithm was run to generate a library of ideal coupon geometries based on ply angle and area location of failure within the test specimen. The result is a highly efficient prediction algorithm that can create the ideal specimen shape for tensile testing at speeds orders of magnitude faster than comparable finite element codes.

Hypervelocity impact investigations of composite truss tubes for in orbit assembly risk assessment

As the number of orbital structures increases, so does the threat posed by micrometeoroid and orbital debris (MMOD) impacts. These impacts range from the ballistic range (less than 1.5 km/s) to exceeding 20 km/s and can significantly weaken space structures such as the International Space Station (ISS), leading to further risk as the debris shed could damage the in-orbit assembly field. Space structures, including the James Webb Space Telescope (JWST) and the in-space assembled telescope (ISAT), often employ fiber-matrix composites in various shapes and sizes. While the effects of hypervelocity impacts (HVI) on flat plate composites have been extensively studied, there is a notable lack of research on HVI of composite tubes. Understanding how MMOD impacts affect the integrity of individual truss members, as well as the structure as a whole is essential for assessing the condition of existing space structures and improving future designs. To replicate MMOD impacts, HVI investigations from 1 to over 3 km/s were conducted on a specialized two-stage light-gas gun, showing the transition from single inlet wall damage to cascading internal fragmentation inside the tube, leading to increased damage with increasing velocity. Our investigation focuses on the image analysis of the damage area and ejecta fragmentation in the carbon fiber reinforced polymer (CFRP) tubes, as well as quantifying the resulting hole diameter. This data is crucial for validating corresponding computational models. In this study we present three separate methods of characterizing HVI including: impedance matching through equations of state, a hybrid Lagrangian finite element (FE) model using LS-DYNA with smoothed particle hydrodynamics (SPH), and experimental investigations. All methods agree that HVI can cause nearly three times the amount of damage within a tube compared to similar conditions on a plate. Our findings help enhance our understanding of MMOD impact risks on existing structures and contribute to the development of systems with greater resilience to HVI.

Analysis of factors influencing Y-ring sealing under ultra-high-pressure, high-temperature and low-temperature conditions

Abstract To study the factors affecting the sealing performance of a Y-shaped sealing ring at the stem of a 140-MPa cage throttle valve under -46°25C and 180°C operating conditions, uniaxial tensile tests were conducted on polytetrafluoroethylene (PTFE) and its modified materials. Finite element simulation software was then used to perform a simulation study of the Y-shaped sealing ring. The finite element simulation software was used to perform a sensitivity analysis on the five most critical parameters of the Y-shaped sealing ring and to perform dimensional optimization by using the multi-island genetic algorithm. The results show that compared with 25°C, under a 180°C condition, the contact stress at both ends of the sealing lip decreases when the valve stem moves upward . Under the condition of -46°C, the contact stress at the sealing lip increases when the valve stem goes down, the contact stress at both ends of the sealing lip decreases when the valve stem goes up; and the impact of the stem movement speed on the maximum value of the Y-shaped sealing ring contact stress is small.The design dimensions that have the greatest influence on the maximum von Mises stress and the maximum contact stress of the inner lip of the Y-seal during stem movement are the width and the tip height of the lip, respectively. The optimum values of the design variables are determined and the feasibility of the theoretical design is verified by testing.

Enhancing Oxygen-Dissolving Capacity of Rotary Drum Food Waste Composting: Tumbling Process Optimization and Experimental Validation with Discrete and Finite Element Methods

An optimized tumbling process can significantly improve the oxygen dissolving capacity of composting and fertilizer quality: by increasing the fluffiness of the lower layer of the pile, localized anaerobic fermentation can be avoided, thereby enhancing compost quality. This paper presents a method for improving the oxygen dissolving capacity of rotary drum food waste composting through a combination of simulation optimization and experimental validation. First, the discrete element method was used to optimize the key parameters of the tumbling process. The response surface method was then employed to analyze the composting test results and determine the optimal conditions. To ensure the reliability of the equipment under this method, failure risk analysis was conducted using the finite element method. The simulation optimization results showed that with a rotary drum reactor speed of 3.5 r/min, a horizontal angle of inclination of 2.5°, a mixing blade angle of inclination of 43°, and a blade pitch of 580 mm, the fluffiness of the lower layer of the pile increased by 8.515%, achieving the best tumbling and indirectly enhancing oxygen dissolving capacity. The maximum deformation of the load-bearing components was only 0.0548 mm, and the minimum safety factor was 4.408 (≥1 is considered safe). A 14-day composting experiment was conducted to validate the optimized parameters. The results showed that the maximum temperature of the compost pile reached 68.34 °C (lasting 7 days), with the pH, moisture content, C/N ratio, humus substances, humic acid, and fulvic acid contents of the fertilizer all meeting or exceeding the levels recommended by Chinese national standards. These findings indicate that the optimized tumbling device effectively improved the stability and dissolved oxygen efficiency of food waste composting, providing valuable practical insights and a research foundation for enhancing oxygen efficiency in the composting of other organic wastes.

Thermal and irreversibility analysis of non-Newtonian fluid within trapezoidal cavity containing heated cylinder

In this article, the mixed convection transport of the Carreau fluid in the presence of a magnetic field and a heated circular cylinder within a trapezoidal cavity is examined. Finite element analysis is used via COMSOL Multiphysics software to simulate the two-dimensional flow. The heat equation is formulated by incorporating the effects of viscous dissipation and Joule heating. The upper and lower surfaces of the cavity are adiabatic, while the left and right sides are assumed to be cold. The temperature distribution and flow field within the cavity are visualized through the plotting of isotherms, streamlines, and total entropy generation. The graphical representations are performed to examine the impacts of physical parameters on temperature, flow field, and total entropy generation, including the Reynolds number , Weissenberg number ( 1.0 ≤ We ≤ 6.0 ) , Power law index ( 0.1 ≤ n ≤ 5.0 ) , Hartman number ( 1.0 ≤ M ≤ 50 ) , and Richardson number ( 0.2 ≤ Ri ≤ 5.0 ) and ( 0.2 ≤ Rc ≤ 0.8 ) . It is found that the Joule heating and Richardson number are the main reasons to increase the thermal performance within the cavity. The r ( 100 ≤ Re ≤ 500 ) ising values of power law index and Weissenberg numbers caused to reduce the velocity field, irreversible effects and circulation within cavity. While the entropy is augmented by elevating the Eckert and Hartmann numbers. Furthermore, heat transfer improved with the increased magnetic field and Eckert number.

Electromagnetic responses on microstructures of duplex stainless steels based on 3D cellular and electromagnetic sensor finite element models

Electromagnetic responses on microstructures of duplex stainless steels based on 3D cellular and electromagnetic sensor finite element models

A method for predicting thermal expansion coefficients of carbon fiber/epoxy composites with void defects

AbstractTo predict the coefficient of thermal expansion (CTE) of carbon fiber/epoxy resin composites with void defects comprehensively and accurately, a comprehensive study is carried out by integrating experiment, analytical model (ANM), and finite element model (FEM). The experiments on composites are conducted combining with Micro‐CT to provide geometric parameters and verification for ANM and FEM. An ANM considering void defects is established based on the Chamis model to investigate the influence of porosity, temperature and the ratio of modulus of the constituents of composites. A FEM is established to verify the ANM and reveal the mechanisms of the influence of void defects. The results show that the proposed ANM has high agreement with FEM and experiment. The longitudinal CTE decreases by 61.94% as the porosity increases from 0% to 20% at 60°C, and the same change of porosity results in a 15.62% decrease at 180°C. The transverse CTE is less susceptible to changes in porosity, showing reductions of 2.32% at 60°C and 3.33% at 180°C.Highlights An innovative model is proposed to predict CTE considering void defects. The glass transition temperature Tg of the resin has a significant effect on CTE. Void defects change the homogeneity of the original stress field of the matrix. The reduction of the longitudinal CTE caused by void defects is more significant.