Axisymmetric Finite Element Method Research Articles

Numerical investigation of punch-through mitigation in stiff-over-soft clays using skirted spudcan

Punch-through failure, a critical issue in offshore engineering, occurs when a foundation penetrates through strong-over-weak soil layers. This paper presents a study on the effectiveness of skirt addition to spudcans in addressing punch-through failure through numerical simulations using the axisymmetric Particle Finite Element Method (PFEM). The validity of the PFEM is verified by simulating a spudcan penetration centrifuge test. Subsequently, PFEM simulations are conducted to analyse the penetration behaviour of both generic and skirted spudcans in stiff-over-soft clays. Results from the simulations reveal the bearing responses of spudcans as they penetrate into clays, elucidate associated failure mechanisms, and underscore the significant of considering the spudcan-driving process in estimating punch-through failure mitigation. Findings indicate that, the skirt effectively mitigates punch-through failure by increasing plug height in the lower soft layer, thus reducing the rate of bearing capacity reduction. Furthermore, critical factors such as skirt length, upper layer thickness, lower layer strength gradient, and the strength ratio between lower and upper layers are assessed through comprehensive parametric studies to evaluate the efficacy of skirted spudcans in mitigating punch-through failure, with eventual goal to provide essential guidance for practical design considerations in offshore foundation systems.

Finite element modeling in heat and mass transfer of potato slice dehydration, nonisotropic shrinkage kinetics using arbitrary Lagrangian–Eulerian algorithm and artificial neural network

AbstractThe present study optimized the drying temperature (50–80°C) for potato slices based on color, texture, and visual observations. At an optimized temperature (60°C), a 2D axisymmetric finite element method (FEM) was developed in COMSOL Multiphysics to predict the heat and mass transfer (HMT) in a disk‐shaped potato slice. The nonisotropic shrinkage was predicted for the potato slice by the arbitrary Lagrangian–Eulerian approach. The experimental dehydration results revealed that axial shrinkage (27.44%) was 2.5 times higher than radial shrinkage (67.39%). The simulated outcomes based on FEM revealed the realistic visualization of spatial heat transfer, moisture migration, and nonisotropic slice deformation. The predicted moisture content, surface temperature, and shrinkage properties were in good agreement with the experimental results. The shrinkage behavior was further validated using artificial neural network (ANN) to simulate the slice shrinkage. Results showed that both the COMSOL and ANN approaches can precisely predict the shrinkage‐dependent HMT model. The ANN model outperformed the COMSOL determined by mean absolute error, mean square error (MSE), root MSE, and Chi‐square (χ2) values. The successful application of the presented approach for determining dehydration characteristics may have potential for quality assessment and management of different fruits and vegetables.Practical applicationsThis journal article explores the practical industrial applications of combining finite element method (FEM)‐based heat and mass transfer model and artificial neural networks (ANNs) to improve the efficiency and quality of food drying processes. FEM is employed to simulate and predict the realistic visualization of heat and mass transfer phenomena along with non‐isotropic shrinkage, while ANN serves as a data‐driven modeling tool for process control and prediction. The integration of these two technologies offers significant advantages in the food industry, including quantification of precise temperature and moisture content, as well as to monitor the drying process of various food products, reduced energy consumption, and time.

A modified sonic black hole structure for improving and broadening sound absorption

In order to improve and broaden the absorption performance of Sonic Black Hole (SBH), we propose a modified SBH structure with micro-perforated panels which is embedded the multiple resonator cavities, and investigate the sound absorption effect of the structure. Characteristics of acoustic streaming effects are embodied in sound pressure and flow velocity distribution. Further, proposed SBH structure can achieve high sound absorption under 6.0 kHz. Based on the symmetry of the structure, the Two-dimensional axisymmetric Finite Element Method (FEM) model is proposed to study the sound absorption mechanism, which shows that the change of flow velocity gradient of acoustic medium leads to the loss of acoustic energy inside the structure. By discussion on acoustic streaming effects of different frequencies, the resonator cavity and micro-perforated panels contributes more to the sound absorption performance at low frequencies, and SBH produces a sound absorption advantage at high frequencies.The theoretical calculation and simulation result match and prove the correctness of the sound streaming effect. Sound absorption tests by acoustic impedance tube confirm that the proposed structure can maintain a sound absorption coefficient of over 0.5 in the range of 0.05–6.0 kHz. The combination of micro-perforated panels and SBH structure is widely applicable to muffler design and has good application prospects.

Nanoindentation test of a DLC coated high-speed steel substrate using a two-dimensional axisymmetric finite element method

Diamond-Like Carbon is a thin coating that has high hardness, chemical inertia and low coefficient of friction characteristics that can improve the performance of cutting tools and mechanical components. To identify the characteristics of this film it is important to carry out mechanical tests, such as nanoindentation, which can provide important information in understanding and improving coating techniques and, when combined with the finite element method, leads to more detailed results of material behavior during testing. Considering this, the present work aimed to study and apply a nanoindentation test simulation of a Diamond-Like Carbon coated high-speed steel specimen. The results of the indenter penetration versus load were compared with experimental data seeking correlation of the model. A great proximity was observed between the experimental results and the results obtained in the simulation. When comparing the final indentation force, a proximity of 93.9 % and 95.5 % was found for the model with only one indentation and with partial indentations, respectively, thus validating the created model. The impact of modifying the indenter tip radius for the partial indentation method was also evaluated. The tip radius variation did not have a significant impact on the results of final indentation force and material hardness. The material hardness was also obtained in the simulation, which was equal to the experimental: 9.25 GPa.

Numerical modeling of phase prediction and geometry evolution of micro-drilling using single pulse laser

Due to high production capability, long laser pulses are preferred over ultrashort pulses during Laser-based machining. To reduce metallurgical defects, viz. heat-affected zone, recast layer, and micro-cracks, it is essential to analyze the causes of these defects and to derive the remedies. Generally, an extensive experimental investigation is carried out for the same. The experimental analysis is time-consuming, tedious, and requires high capital investment. Therefore, in this work, a two-dimensional axisymmetric transient finite element method (FEM) based numerical model of Laser-material interaction was developed to explore the temperature evolution, phase change, and geometry evolution with the help of coupled heat transfer and deformed mesh. The heat transfer module was implemented by considering the phase change using the apparent heat capacity method. The model was duly validated for the evolution and geometry of the Laser-drilled hole. The model was found in agreement with the experimental results, with a percentage deviation of 12% in the prediction of the responses. The numerical model will help to predict the temperate evolution and hydrodynamic behavior of the material during the laser-material interaction. This, in turn, will help to mitigate the metallurgical defects.

Photo-thermo-mechanical model for laser hair removal simulation using multiphysics coupling of light transport, heat transfer, and mechanical deformation (case study)

The mathematical model has become one of the tools for prediction to assist physicians and specialists with hair laser removal in dermatology. This paper proposes a model that comprehensively predicts optical, thermal, and mechanical responses within the skin during laser hair removal to determine optimal therapeutic conditions and prevent skin tissue damage. This research highlighted developing a mathematical model using multiple physics of light transport, heat transfer, and mechanical deformation. The present mathematical model is resolved using the 2D axisymmetric finite element method (FEM) with optical, thermal, and mechanical properties to characterize the laser intensity, temperature distribution, mechanical stress, and displacements within skin tissue. The comparison of the simulated results in laser wavelengths of 595 nm, 800 nm, and 1064 nm is also provided. The results revealed that laser deposition with skin tissue depends on the wavelength and optical diffusion coefficient. Applying the 1064 nm performs the best treatment outcome for hair laser removal. In contrast, 595 nm and 800 nm might lead to adverse pain sensations. The high temperature caused an increase in mechanical stress and displacement. The results of this study indicate that laser therapy has certain limitations that must be considered.

Optical properties and conductivity of biased GaAs quantum dots

We report the intraband optical absorption influence on the tunneling currents in biased gallium arsenide quantum dots. The energy levels and tunneling times are calculated using a complex eigenvalue formalism through an axisymmetrical two-dimensional finite element method. The absorption coefficient and the relative change of the refractive index are evaluated by taking into account a variable intraband relaxation time. A field-invariable relaxation, as it was often assumed by previous theoretical models, cannot be justifiable even for moderate electric fields. On the one hand, our work shows that the electron escape probability and implicitly the tunneling current may be controlled by the resonant optical field. Optically switching the QDs from lower to higher conductivity states is shown to be feasible. On the other hand, at high values of the electric field the tunneling-related electronic linewidth broadening blue-shifts and enlarges the absorption peaks, thus reducing the resonant nature of the intraband transitions.

The Mitigation of Eddy-Current Losses in Ferromagnetic Samples Produced by Laser Powder Bed Fusion

We study the use of topology optimization in the design of low-loss ferromagnetic core structures for additively manufactured electrical machines. The test case was a simple toroid core with a primary and a secondary winding. A 2D axisymmetric finite element method model was implemented for the toroid, and the core topology was optimized for minimum losses and maximum secondary flux linkage. The optimized core was then modified for additive manufacturing, and test samples were built via laser powder bed fusion. The B-H characteristics and losses of the core were measured in several operation points. The losses were compared against an additively manufactured solid core, a laminated core, and an additively manufactured core with evenly placed air gaps (i.e., grooves). The results show that the losses in the topology-optimized core are on the same level as the losses in the laminated core and considerably smaller than those in the solid core, which is a considerable improvement to previous published works.

Thickness evaluation of hollow nonmagnetic cylinders utilizing a motional eddy current

This paper presents a way to calculate the shell thickness of nonmagnetic hollow cylinders for nondestructive applications. Aluminum cylinders with a solid structure and with a hollow structure are considered. The motion component of the induced eddy currents in a conductive cylinder is utilized to evaluate the shell thickness of hollow conductive cylinders at various frequencies and at variable speeds. One axisymmetric excitation coil and two axisymmetric pickup coils with antiserial connection are used. An analytical method using an axisymmetric computational model is developed for a parametric analysis of solid and hollow cylinder structures and shell thickness calculations, in which Fourier series are utilized. A 2D axisymmetric finite element method is also performed for a comparison with the results of the analytical method. The measurements at variable speeds and at various frequencies are presented with various hollow aluminum cylinders. The high linearity of the induced voltage versus the speed curve makes it possible to calculate the shell thickness of nonmagnetic hollow cylinders at different speeds.

Transient heat transfer in a horizontal well in hot dry rock – Model, solution, and response surfaces for practical inputs

This article presents a solution to the geothermal problem of transient heat production from hot dry rocks using a horizontal well. Dimensionless forms of the governing equations are derived, including conduction in the rock, convection between the wellbore rock and the fluid, and advection and conduction in the fluid along the well. Ten model material and geometric parameters are reduced to three dimensionless parameters: α=4LDSt is the ratio of the rate of heat storage in the fluid to the rate the heat convection to the fluid from the rock, β=1Pe is the ratio of the rate of conductive versus advective heat transfer in the fluid, and γ=2LDBi is the ratio of heat convection to the rock from the fluid to the rate of heat depletion in the rock. An axisymmetric finite element method (FEM) program is developed and yields the solution for the temperature of the rock mass and fluid over time. For physically meaningful inputs, analysis indicates that the effect of β is negligible, that combinations of very large α and very low γ (and vice versa) do not occur, and that all other things being equal, increasing α or decreasing γ leads to higher fluid outlet temperatures. System response at different times and dimensionless temperature are captured in contour plots for values of α and γ spanning practical injection rates, well geometries and fluid and rock properties. Power law response surface models are fitted using model outputs at discrete intervals and provide a means to accurately and rapidly compute the temperature-time histories of practical geothermal systems.

Bidirectional Beam Propagation Method Based on Axi-Symmetric Full-Vectorial Finite Element Method

We first present a bidirectional beam propagation method (BiBPM) based on axially symmetric full-vectorial finite element method (Axi-FVFEM). The Axi-FVFEM based BiBPM is a more versatile method than previous scalar BiBPM for axi-symmetric structure. It has potential to offer more efficient analysis than widely used FEM or finite difference based techniques, especially for a large scale waveguide such as a long periodic structure. An air gap in an axi-symmetric waveguide and a fibre Bragg grating (FBG) are analyzed using the Axi-FVFEM based BiBPM for numerical validation, and we compare the numerical results with those of a 3D finite-difference time-domain (FDTD) method and a modal-based method.

Three-dimensional free flexural vibrations of fluid-filled functionally graded circular cylindrical shell with curvilinear radius variation

The three-dimensional free flexural vibrations of functionally graded circular cylindrical shell with curvilinear radius variation fully or partially filled with incompressible and inviscid fluid are investigated for the first time using a coupled axisymmetric solid-fluid hierarchical finite element method based on curved elements. Curved edges are described exactly by means of blending functions. The method is used in conjunction with the three-dimensional elasticity theory and Laplace’s equation to obtain the governing equations. The material properties follow the power law distribution in the thickness direction. The effectiveness of the method is illustrated using examples of clamped-free and clamped-guided functionally graded circular cylindrical shells with quadratic and cubic radius variations. The method is validated through convergence test and comparison study. New results for the cycle frequencies of the lowest two flexural modes are presented, which may serve as benchmarks for future studies. Moreover, the effects of several geometrical and mechanical parameters on the cycle frequencies, modal deflections, and modal hydrodynamic pressures are explored.

C-FLEX Advanced Finite Element Analysis Program for Flexible Pavement Analysis and Design

The U.S. Army Engineer Research and Development Center (ERDC) of the U.S. Army Corps of Engineers has initiated an effort to modernize the Department of Defense (DOD) pavement design and evaluation procedures initially developed in the 1950s. Flexible pavement analyses and evaluations are currently performed based on the elastic layered WESLEA and WESDEF software programs. To modernize the current pavement design and evaluation procedures used by the DOD, an advanced axisymmetric Finite Element Method (FEM) based analysis program, named C-FLEX, was developed and is introduced in this paper. The C-FLEX program is designed to feature accurate material models for all pavement layers with the capability to model the cross-anisotropic and nonlinear elastic properties of unbound base/subbase and subgrade layers, the viscoelastic behavior of the asphalt mixture, as well as mechanical reinforcement using geosynthetics in flexible pavements. The FEM formulation in C-FLEX and the program architecture and implementation details are introduced and discussed in this paper. The different analysis schemes and proper models used to characterize the cross-anisotropy and stress-dependent material nonlinearity are also described in detail. The viscoelastic analysis scheme and the geosynthetic characterization are currently under development and so are not included in this paper. Furthermore, two conventional flexible pavements with different layer properties are analyzed to verify the solutions and reliability of the C-FLEX program. Based on this development effort with ERDC, the C-FLEX program is envisioned to eventually serve as the flexible pavement analysis engine for the DOD’s new mechanistic design and evaluation platform.

Characterization of Lime and Polymer Treated Ultra-Soft Clay Soils Using the Modified Vane Shear and Correlating the Shear Strengths to the Electrical Resistivity and CIGMAT Miniature Penetrometer for Nondestructive Field Tests

With the growth in construction along the coastal regions, ports and offshore deepwater sea beds, ultra soft clay soils are encountered and are affecting the performance of the pipelines and other anchor systems placed in it. In this study, untreated and treated ultra-soft clay soils shear strengths were quantified using the modified vane shear device and correlated the shear strength to the CIGMAT miniature penetrometer penetration and electrical resisitivity. The ultra-soft clay soils were prepared by varying the bentonite content from 2 to 10%. The soil with 10% bentonite was treated with 2–10% lime and with 1–10% polymer separately to enhance the shear strength. The shear strength, pH, CIGMAT miniature penetrometer and electrical resistivity were used to characterize the untreated and treated ultra-soft clay soils. Untreated soft soil strength varied from 0.01 to 0.17 kPa when the bentonite content in the ultra-soft clay soil was increased from 2 to 10%. With 2% lime treatment the shear strength of 10% bentonite soil was increased to 0.27 kPa. Adding 10% lime to the 10% bentonite ultra-soft soil reduced the shear strength to 0.15 kPa. With 10% polymer treatment, the shear strength was increased by 45 times to 6.8 kPa for the 10% bentonite ultra-soft soil. The CIGMAT miniature penetrometer penetration varied linearly with the shear strength of the untreated ultra-soft clay soils and treated ultra-soft clay soils with 10% bentonite. pH was almost constant for untreated ultra-soft clay soils while it increased by 22% and 35% for the 10% lime and 10% polymer treated ultra-soft clay soilss respectively. Relative electrical resistivity decreased by 246% when the bentonite content was increased from 2 to 10% in the ultra-soft clay soils. Addition of 10% of lime to the ultra-soft clay soil with 10% of bentonite content decreased the relative electrical resistivity by 171%. Addition of 10% of polymer to the ultra-soft clay soil with 10% of bentonite content reduced the relative electrical resistivity by 545%. Power law, linear and Vipulanandan correlation models were used to predict the shear strength-resistivity relationship for the untreated, lime-treated and polymer-treated ultra-soft clay soils respectively. In addition, linear model was used to predict the water content relationship with electrical resistivity for the untreated and treated ultra-soft clay soils. The CIGMAT miniature penetrometer was modeled using 3-D axisymmetric finite element method, which predicted the penetration of CIGMAT penetrometer that agreed well with the experimental results of the untreated and treated ultra-soft clay soils. The CIGMAT miniature penetrometer penetration and the electrical resisitivity monitoring are two non-destructive methods that can be easily adopted in the field and the property correlations can be used to determine the shear strength of the ultra-soft caly soils in the field.

Analysis of expansion within a pressure inflated section of a simplified urethral model

Abstract A new inflatable sensor-actuator system is being developed to analyze the in-vivo biomechanical properties of the urethra of a male human. It could provide decision-aids to urologists while treating issues like urethral strictures. Models that could simulate the biomechanical variations of the urethra are important to evaluate the capabilities of the system under development. For the initial study, a simplified axisymmetric Finite Element Method ‘tube’ model was generated. To simulate an ideal inflating actuator (balloon) within this urethra model, a pressure was applied on the inner wall of the tube. From the region over which the pressure was applied, ‘sensor’ measurements were taken from the ‘top’ plane, ‘middle’ plane and a plane lying between these two. The resulting pressure-circumference and pressure-(wall) thickness responses at these measurement planes were determined. A hyperelastic response attributable to biological tissues was obtained. It was found that the resultant circumferential extension and thickness varies at different planes during the actuator inflation. After inflating at the highest chosen pressure, from the initial inner circumference of 25mm, final extensions ranging 45mm to 63mm for the peripheral plane were obtained. Similarly, extensions ranging from 48mm to 68mm were obtained for the other two planes. The pressure-circumference response at the plane lying on the periphery of the inflated region was found to be less compliant than the plane in the center for the model. A range of biomechanical responses were able to be achieved by performing a parametric variation for the chosen mathematical model and geometry in consideration. The study indicates that a larger dataset can be generated to further model a variety of urethral biomechanical responses. These initial simulations provide important information for identification tasks related to the current development. The results show that simulations could be a prospective way to test new sensors prior to real experiments.

Simulation of hot air infrared‐assisted green peas drying using finite element method

AbstractThe objective of this study was to simulate the drying kinetics of green peas in a hot‐air infrared‐assisted dryer using an appropriate finite element method (FEM). To achieve the aim of the study, the axisymmetric FEM with the Galerkin approach was employed to model and predict the drying behavior. One of the key physical properties required for the modeling was to determine the effective moisture diffusivity obtained from previous study on green peas drying in a lab‐scale hot‐air infrared‐assisted dryer. To compare the simulated moisture transfer results with those of experiments several experiments consisting of combination of main factors namely drying air temperatures (30°C, 40°C, and 50°C), infrared power intensity (0 as a control, 0.2, 0.4, and 0.6 W cm−2), and drying air flow velocity (0.5, 1, and 1.5 ms−1) were conducted in three replications. The predicted average moisture contents by the proposed mathematical model showed reasonably a good agreement with the experimental data (maximum error value: RMSE = 2.18 and MARE = 5.08%). The simulation was also compared by two‐dimensional FEM. The results demonstrated that the accuracy of the axisymmetric FEM was higher than two‐dimensional FEM. Based on the results, the developed FEM model has reasonable accuracy and can be applied to provide more information on the dynamics of moisture movement without running any experiments. Furthermore, the useful information about optimum design of industrial dryers and drying behavior can be achieved by simulation of the drying process.Practical ApplicationsFood security is an important issue for every developing country. Fruits are a major source of nutrients that widely used as fresh or processed. Drying process is widely used to improve the security, quality, shelf time, and also the packaging and transportation of the foodstuff. Design of dryer requires a high degree of attention. The useful information about optimum design of dryer and drying behavior can be achieved by simulation of the drying process. In this study, the finite element method is used to model and simulate the drying process of green peas (Pisum sativum L.). Green peas are one of the ancient cultivated and nutritious popular vegetables with a most useful amount of fiber that enjoy the antioxidant and anti‐inflammatory benefits.

HTS Transformer’s Partial Discharges Raised by Floating Particles and Nitrogen Bubbles

Presence of defects, conducting particles, nonconducting particles, and nitrogen gas bubbles in the insulation system of high-temperature superconducting (HTS) transformers, mainly inside the liquid nitrogen as its major insulation, can create local field enhancement and consequently partial discharges which eventually lead to the catastrophic failure of the transformer. In this paper, two-dimensional (2D) axisymmetric finite element method (FEM) modeling via COMSOL Multiphysics software has been utilized for the investigation of the impact of size and shape of conducting particles and nitrogen gas bubbles on partial discharge (PD) activities in liquid nitrogen. Conducting particles of various shapes and the nitrogen bubbles are studied for PD generation. The results have been analyzed and compared. This can be employed for HTS transformer efficiently and PD free insulation design to enhance its insulation life.

3-D Integral Formulation for Thin Electromagnetic Shells Coupled with an External Circuit

The aim of this article is to present a hybrid integral formulation for modelling structures made by conductors and thin electromagnetic shell models. Based on the principle of shell elements, the proposed method provides a solution to various problems without meshing the air regions, and at the same time helps to take care of the skin effect. By integrating the system of circuit equations, the method presented in this paper can also model the conductor structures. In addition, the equations describing the interaction between the conductors and the thin shell are also developed. Finally, the formulation is validated via an axisymmetric finite element method and the obtained results are compared with those implemented from another shell formulation.

Stress analysis of functionally graded saturated porous rotating thick truncated cone

In this article, static response of functionally graded saturated porous rotating truncated cone is investigated for the first time. Three different patterns are considered for porosity distribution along with the thickness of the cone, which are symmetric nonlinear, nonlinear asymmetric and uniform distributions. The relationship between stress and strain is based on the Biot constitutive law instead of simple Hook’s law. 2D axisymmetric elasticity theory and finite element method based on Rayleigh-Ritz energy formulation are used to model the problem. The effect of various parameters such as: rotational velocity, porosity and Skempton coefficients, semi vertex angle of the cone, different boundary conditions and different distribution of porosity on displacements and stresses of the cone has been investigated.

Finite element modeling of material removal rate in micro-EDM process with and without ultrasonic vibration

PurposeThis research explores the finite element modeling of the crater and material removal rate (MRR) in micro-electrical discharge machining (micro-EDM) with and without vibration of the workpiece. The application of workpiece vibration in the micro-EDM process improved flushing efficiency and enhanced material removal rate (MRR).Design/methodology/approachIn this work, the two-dimensional axisymmetric finite element method (FEM) has been developed to predict the shape of the crater with and without vibration. The temperature distribution on the workpiece surface with and without vibration has been obtained in the form of the contour plot.FindingsThe MRR obtained from the numerical model revealed that there was an enhancement in MRR in micro-EDM with vibration as compared to without vibration. The effect of process parameters on MRR in micro-EDM with and without is also presented in this work.Originality/valueIn this work, the two-dimensional axisymmetric FEM model has been developed to predict the shape of the crater with and without vibration.