Finite Element Calculations Research Articles

Influence of thermo-mechanical loads on variable stiffness composite beams: a comprehensive study using semi-analytical and finite element approaches

This study investigates the stability and vibration characteristics of variable stiffness laminated composite (VSLC) beams subjected to thermo-mechanical loadings. A semi-analytical model is developed to determine the buckling and vibration characteristics of variable stiffness composite beams. The model employs a displacement-based Ritz approach to derive the matrix representation of the governing equations. Modified constitutive relations are derived to account for the Poisson effects that arise due to the development of zero-stress conditions in the width direction of beams. The material properties and temperature variations are assumed to be constant across the thickness of the beam. Moreover, finite element calculations are carried out using commercial software ABAQUS in conjunction with a MATLAB-generated input file, which is utilized to capture fiber angle variations within the beam. Numerical results are obtained to elucidate the effect of slenderness ratio, modulus of elasticity ratio, boundary conditions, number of layers, and ply-sequence on the free vibration and instability characteristics of VSLC beams subjected to mechanical loadings and thermal environments. This study underscores the crucial importance of taking these factors into account for precise and dependable design and analysis of such composite beams in engineering applications.

A Kriging Surrogate Model for Ball Grid Array Electronic Packaging With Stochastic Material and Geometrical Parameters

Abstract Ball grid arrays (BGAs) offer significant advantages in the automotive industry, such as their small size and high integration density, making them a promising electronic packaging approach. However, the operating environment of automobiles is more complex compared to other applications, primarily due to vibrations generated by power engines and oscillations caused by pavement roughness. The resonant frequencies of electronic packaging structures play a crucial role in system reliability and safety. However, accurately describing the implicit relationship between system resonant frequencies and material and geometrical parameters can be challenging. A Kriging surrogate model (KSM) is proposed by the combination of the Latin Hypercube stochastic sampling with finite element computation. Four different BGA configurations are established with either the initial values in the deterministic model or the specified sampling interval ranges in the stochastic model. The results of the finite element model (FEM) for BGA electronic packaging are validated and demonstrate qualitative agreement with published literature. The impacts of material and geometrical parameters on the resonant frequencies are investigated and compared. The mean, maximum, minimum, and variance are recorded based on a large database of stochastic samples. The feasibility of KSM for the resonant frequency prediction of BGA is confirmed by its satisfactory accuracy and computational efficiency.

Effects of CO2 Geosequestration on Opalinus Clay

CO2 geosequestration is an important contributor to United Nations Sustainable Development Goal 13, i.e., Climate Action, which states a global Net-Zero CO2 emissions by 2050. A potential impact of CO2 geosequestration in depleted oil and gas reservoirs is the variations in induced pressure across the caprocks, which can lead to significant local variations in CO2 saturation. A detailed understanding of the relationship between the pressure gradient across the caprock and local CO2 concentration is of utmost importance for assessing the potential of CO2 geosequestration. Achieving this through experimental techniques is extremely difficult, and thus, we employ a coupled Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) based solver to mimic sub-critical CO2 injection in Opalinus Clay under various pressure gradients across the sample. The geomechanical and multiphase flow modelling utilising Darcy Law helps evaluate local variations in CO2 concentration in Opalinus Clay. Well-validated numerical results indicate favourable sub-critical CO2 geosequestration under a positive pressure gradient across Opalinus Clay. In the absence of a positive pressure gradient, a peak CO2 concentration of 5% has been recorded, which increases substantially (above 90%) as the pressure gradient across the sample increases.

Numerical Study on Hydrodynamic Performance of a Pitching Hydrofoil with Chordwise and Spanwise Deformation

The hydrofoil plays a crucial role in tidal current energy (TCE) devices, such as horizontal-axis turbines (HATs), vertical-axis turbines (VATs), and oscillating hydrofoils. This study delves into the numerical investigation of passive chordwise and spanwise deformations and the hydrodynamic performance of a deformable hydrofoil. Three-dimensional (3D) coupled fluid–structure interaction (FSI) simulations were conducted using the ANSYS Workbench platform, integrating computational fluid dynamics (CFD) and finite element analysis (FEA). The simulation involved a deformable hydrofoil undergoing pitching motion with varying elastic moduli. The study scrutinizes the impact of elastic modulus on hydrofoil deformation, pressure distribution, flow structure, and hydrodynamic performance. Coefficients of lift, drag, torque, as well as their hysteresis areas and intensities, were defined to assess the hydrodynamic performance. The analysis of the correlation between pressure distribution and deformation elucidates the FSI mechanism. Additionally, the study investigated the 3D effects based on the flow structure around the hydrofoil. Discrepancies in pressure distribution along the spanwise direction result from these 3D effects. Consequently, different chordwise deformations of cross-sections along the spanwise direction were observed, contributing to spanwise deformation. The pressure difference between upper and lower surfaces diminished with increasing deformation. Peak values and fluctuations of lift, drag, and torque decreased. This study provides insights for selecting an appropriate elastic modulus for hydrofoils used in TCE devices.

Experimental and numerical investigation on the hydroelastic response of barge and KVLCC2 ship

In this paper, the hydroelasticity of two segmented ship models (Barge and KVLCC2) is investigated by experimental and numerical methods. A two-way Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) coupled method is adopted and further validated its accuracy against experimental results. The current approach emphasizes the overall convergence between two solvers, maintaining a strongly coupled manner to comprehensively address the fluid-structure interaction phenomenon, including the added mass effect. A series of experiments of a segmented Barge and KVLCC2 under various wave conditions were firstly conducted. The motions of the models are measured and the displacement Response Amplitude Operators (RAOs) are calculated. The CFD-FEA coupled method is demonstrated in agreement with experimental results by comparing the numerical prediction with the tank test results in terms of motion, affirming the validity and robustness. Finally, the hydroelastic response is discussed and investigated.

A novel locally resonance metamaterial cylindrical shell with tower-shaped lattice for broadband vibration suppression

Vibration issues in cylindrical shells are prevalent in engineering applications and can significantly impact the operational performance of systems. To address these challenges, this paper designs a novel local resonance tower structure, and establishes an analytical model to investigate vibration characteristics of the metamaterial cylindrical shell. Based on the model, a gradient design strategy is proposed to improve vibration suppression properties over a wide frequency range. Firstly, the governing equations of the cylindrical shell are derived and the dispersion analysis is conducted to predict the bandgap boundaries using the extended plane wave expansion (EPWE) method. Then, for a finite-period metamaterial cylindrical shell with specific boundary conditions, the frequency response of the structure is obtained by finite element calculations to show the bandgap behavior. The results of these two methods are basically the same. In addition, the effects of frequency spacing, damping and array period on the vibration characteristics are considered comprehensively. The results show that a wider and more stable attenuation range can be obtained by reasonably adjusting these three parameters. Finally, the comparison between experimental and numerical calculations verify that the tower structure is effective, and that the proposed design strategy can broaden the vibration attenuation region.

Design and Analysis of 5-DOF Compact Electromagnetic Levitation Actuator for Lens Control of Laser Cutting Machine.

In laser beam processing, the angle or offset between the auxiliary gas and the laser beam axis have been proved to be two new process optimization parameters for improving cutting speed and quality. However, a traditional electromechanical actuator cannot achieve high-speed and high-precision motion control with a compact structure. This paper proposes a magnetic levitation actuator which could realize the 5-DOF motion control of a lens using six groups of differential electromagnets. At first, the nonlinear characteristic of a magnetic driving force was analyzed by establishing an analytical model and finite element calculation. Then, the dynamic model of the magnetic levitation actuator was established using the Taylor series. And the mathematical relationship between the detected distance and five-degree-of-freedom was determined. Next, the centralized control system based on PID control was designed. Finally, a driving test was carried out to verify the five-degrees-of-freedom motion of the proposed electromagnetic levitation actuator. The results show it can achieve a stable levitation and precision positioning with a desired command motion. It also proves that the proposed magnetic levitation actuator has the potential application in an off-axis laser cutting machine tool.

Mechanism analysis of the abnormal head-cover vibration of an ultra-high-head pump-turbine operating in pump mode by CFD and FEM

ABSTRACT Hydraulic excitation causes abnormal head-cover vibration in some pump-turbines, particularly as design heads continue to rise. Pump-turbines with heads exceeding 600 m have reported such vibrations in pump mode, and it is urgent to reveal the reasons. A study was conducted on a head-cover of a pump-turbine with a maximum head of 660 m by 3D computational fluid dynamics (CFD) and finite element method (FEM) numerical simulations to investigate the hydraulic excitation source and vibration mechanism. Results show that the intensive vibration is related to the coincidence of frequency and mode between abnormal pressure pulsations with frequency 6–8f n and the low-order wet mode of the head-cover. A new flow pattern termed the rolling vortex was discovered in the vaneless space under high-head pumping conditions. The 6–8f n pressure pulsations result from the interaction between rolling vortices and guide-vanes, similar to the rotor-stator interaction. The flow mechanism of the rolling vortices is that the outflow velocity near the hub at the runner outlet is higher than that near the shroud, due to the positive blade lean angle and the X-shape distorted blades. Suppressing rolling vortices may help eliminate the abnormal head-cover vibration, which will be attempted in further study.

Thermal analysis of fire effects on fire doors using the finite element method

The goal of this paper is to use the finite element method and computer simulation to prove the effectiveness in assessing the fire resistance of building construction elements, specifically on the example of the fire resistance of fire doors. For that purpose, data from the building where fire doors with defined characteristics were installed were used. For simulation purposes, numerical modelling with thermal and structural analysis will be used. In this way, the parameters of the temperature distribution on the fire door and the contact material due to fire will be obtained, as well as the distribution of strain and stresses, which will indicate the fire resistance of the used structure. Computer simulation with numerical modelling offers a number of advantages both in the speed of providing results of a larger number of variants of the simulation model and in the accuracy of the results obtained once the model is calibrated. Also, the mentioned type of predicting the effect of fire can be applied to other elements of the structure of the construction object, which can significantly influence the decision-making that will prevent the negative consequences of the occurrence of a possible fire.

Relationship between Ambient Temperature and Reasonable Heat Dissipation Coefficient of Mass Concrete Pouring Blocks.

In engineering practice, similar surface insulation measures are typically applied to different parts of mass concrete surfaces. However, this can lead to cracking at the edges of the concrete surface or the wastage of insulation materials. In comparison to flat surfaces, the edges of mass concrete structures dissipate heat more rapidly, leading to more pronounced stress concentration phenomena. Therefore, reinforced insulation measures are necessary. To reduce energy consumption and enhance overall insulation effectiveness, it is essential to study the specific insulation requirements of both the flat surfaces and edges of concrete separately and implement targeted surface insulation measures. Taking the bridge abutment planned for pouring in Nanjing City as the research object, this study established a finite element model to explore the effects of different ambient temperatures and different surface heat dissipation coefficients on the early-age temperature and stress fields of different parts of the abutment's surface. Based on simulation results, reasonable heat dissipation coefficients that meet the requirements for crack prevention on both the structure's plane and edges under different ambient temperatures were obtained. The results indicate that under the same conditions, the reasonable heat dissipation coefficient at the edges was smaller than that on the flat surfaces, indicating the need for stronger insulation measures at the edges. Finally, mathematical models correlating ambient temperature with reasonable heat dissipation coefficients for the structure's plane and edges at these temperatures were established, with high data correlation and determination coefficients (R2) of 0.95 and 0.92. The mathematical models were validated, and the results from finite element calculations were found to be consistent with those from the mathematical models, validating the accuracy of the mathematical models. The conclusions drawn can provide references for the insulation of similar engineering concrete planes and edges.

Preliminary Analysis of Beam Position Monitor Accuracy

The beam position is the most important reference basis for the operation of synchrotron radiation light sources, particularly for commissioning the first-turn injection of fourth-generation light sources. To improve the accuracy of the beam position measurement, we analyzed methods for calculating the beam position, and a finite element calculation and the stretched wire calibration system were used to demonstrate the procedure. We proved the relationship between the coverage range, fitting order, scanning step size, and accuracy both theoretically and experimentally, which can provide a basis for selecting the appropriate fitting order for different operation stages of the accelerator. It was proved that the accuracy of beam position calculations using simplified polynomial coefficients is comparable to those without a simplified one, which can save resources for reading electronic processing. The testing results of a batch of beam position monitors (BPMs) were in good agreement with the finite element calculation results, and the small difference between the manufactured BPMs also proved that quality control was performed well, and it benefited from button sorting.

High fidelity FEM based on deep learning for arbitrary composite material structure

Due to the outstanding performance, composite materials are widely used and analyzing their properties and designing them based on performance has become a crucial task in the field of many manufacturing industries. Composite materials possess complex multiscale structures, and traditional fine-scale finite element modeling and analysis may lead to severe computational resource challenges. To overcome this difficulty, breakthroughs in key technologies of multiscale accelerated analysis algorithms are required. In this study, an innovative approach based on artificial intelligence and multiscale finite element method is presented. This approach involves partitioning the entire composite material structure into coarse grids that resemble homogenous structures of similar size, providing results consistent to fine-grid finite element analysis. By utilizing CNN for image feature recognition and employing the CGAN adversarial method, coarse-grid equivalent stiffness matrices and multiscale shape functions from completely random microstructures of composite materials can be obtained. Consequently, this enables a rapid response process from microstructure to low-resolution grid to high-resolution physical field, with remarkably accurate physical field results. Moreover, compared to traditional fine-grid finite element methods, this approach significantly reduces memory usage and computation time. This method is applicable to composite materials with varying shaped inclusions, different component properties, and diverse geometric distributions, allowing these materials to perform high-fidelity finite element calculations on coarse grids and predict their mechanical behavior. Furthermore, this breakthrough opens avenues for accelerating the optimization design of composite materials with diverse mechanical functionalities, by employing a bottom-up approach.

Modal analysis of honeycomb panel satellite structure based on MSC Apex

Modal analysis plays an important role in the process of Satellite structure development. In this paper, the honeycomb sandwich plate and the satellite structure are taken as the research objects, and the corresponding finite element models are established. The analysis results of the actual modeling of honeycomb plate and the equivalent modeling of sandwich sandwich plate are obtained, and the fundamental frequency deviation of the whole satellite structure is discussed when the equivalent correction coefficient γ of honeycomb plate is different. The results show that the maximum relative error of the modal frequency between the equivalent method of sandwich sandwich plate and the actual modeling is 2.8%. Therefore, the equivalent method can be applied to large-scale finite element analysis and calculation, and the calculation efficiency can be improved. When the value of γ is 0.4∼0.6, the vibration modes of the whole satellite structure are basically consistent, and the maximum fundamental frequency difference is 10%. The results can evaluate the accuracy of the sandwich sandwich plate equivalent method for satellite mechanical analysis.

Optimal computation of integrals in the Half-Space Matching method for modal simulation of SHM/NDE in 3D elastic plate

Simulating structural health monitoring (SHM) or nondestructive evaluation (NDE) methods based on elastic guided waves (GW) is very helpful to handle their complexity (co-existence of several GW modes, frequency dependence of wavespeed) and to further design optimal methods of inspection offering high sensitivity to the sought flaws. The half-space matching (HSM) method has been established for the development of a model that hybridizes local finite element (FE) computations for GW scattering by a flaw, with a modal semi-analytical model for GW radiation and propagation in flawless plate-like structures. Highly oscillatory Integral formulae appear in the HSM method that radiate the scattered field away from the FE zone as the superimposition of modal contributions, which computation can be time-consuming. The present work is concerned with their optimal computation. Integral of this form can be efficiently computed under the far-field approximation but this classical technique fails at predicting accurately wavefields at relatively short distances (small number of wavelengths). The method developed herein relies on the complexification of the integrals to be computed and on specific deformation of integration paths in the complex plane, as detailed in the paper. It allows the evaluation of the integrals without approximation other than that of numerical quadratures, ensuring high accuracy while offering high computing performances. It indifferently applies in the far-field and in the near-field. The method of computation is validated by comparing its predictions with a reference solution of GW scattering. Its computational performances are also demonstrated, compared to those of the standard computation of the HSM integral formulae.

Study on electric pulse-assisted plastic deformation behavior of 5182-O aluminum alloy

Plastic model-based neural networks are emerging phenomenological models with excellent calibration accuracy and interpretability of parameters, and they do not significantly increase the finite element calculation time of neural network models with a simple structure optimized by the algorithm. Because aluminum and magnesium have low ductility at room temperature, complex components made from these alloys need to be forged at high temperatures. In comparison with traditional thermoforming, advanced current-assisted processing provides energy savings, efficiency and green production. Experimental and constitutive modeling are carried out in this study to investigate the coupling effects of electrical pulse, temperature, strain rate, and strain on flow behavior and ductile fracture. It has been shown that electric pulses induce Joule heating effects and electroplastic effects, which reduce deformation resistance and improve formability. Electrical pulses suppress negative strain rate effects caused by dynamic strain aging, which is the main reason for the non-monotonic relationship between temperature and strain rate. The behavior of plasticity and fracture initiation can be described by simulations based on a neural network-based evolving plasticity model that incorporates stress states, current density, temperature, and strain rates.

Research on the calculation method of grinding temperature field of spiral bevel gear based on generative machining

At present, the process parameter setting of spiral bevel gear grinding is mainly based on an empirical method, and the tooth surface temperature is difficult to estimate effectively during grinding, which may lead to excessive tooth surface temperature and surface burn caused by improper selection of process parameters. Aiming at the above problems, this paper presents a method for calculating the temperature field of spiral bevel gear forming based on a combination of analytical and numerical methods. The motion equation of spiral bevel gear grinding is derived based on the method of tooth surface development. The time-varying heat flow calculation method in tooth surface grinding was developed through the discrete and two-dimensional contact zone. The time-varying temperature field analysis method of spiral bevel gear forming is developed using the time-varying heat flow and finite element calculation method. The related research can realize the temperature prediction of grinding tooth surfaces and provide the basis for improving grinding technology.

Failure pattern in ceramic metallic target under ballistic impact

The ballistic resistance and failure pattern of a bi-layer alumina 99.5% - aluminium alloy 1100-H12 target against steel 4340 ogival nosed projectile has been explored in the present experimental cum numerical study. In the experimental investigation, damage induced in the ceramic layer has been quantified in terms of number of cracks developed and failure zone dimensions. The resultant damage in the backing layer has been studied with variation in the bulge and perforation hole in the backing layer with the varying incidence velocity. The discussion of the experimental results has been further followed by three dimensional finite element computations using ABAQUS/Explicit finite code to investigate the behaviour of different types of bi-layer targets under multi-hit projectile impact. The JH-2 constitutive model has been used to reproduce the behaviour of alumina 99.5% and JC constitutive model has been used for steel 4340 and aluminium alloy 1100-H12. The total energy dissipation has been noted to be of lesser magnitude in case of sub-sequential impact in comparison to simultaneous impact of two projectiles. The distance between the impact points of two projectiles also effected the ballistic resistance of bi-layer target. The ballistic resistance of single tile ceramic front layer and four tile ceramic of equivalent area found to be dependent upon the boundary conditions provided to the target.

Modelling of aero-mechanical response of wind turbine blade with damages by computational fluid dynamics, finite element analysis and Bayesian network

Computational Fluid Dynamics and Finite Element Analysis structural models are developed for generation of large datasets of high-fidelity aerodynamic loading, displacement and stress for the NREL 5 MW wind turbine blade. Based on the datasets, analysis of structural responses of the turbine blade and their possible shifts with respect to a change in the operating conditions, e.g. rotor plane tilting and yawing, are performed. A Bayesian Network model is trained to produce ranges of values and likelihoods of occurrence of abnormal structural response or the most likely damage in the blade from inputs of operating conditions. The numerical analysis showed that yawing and tilting of rotor plane has very strong influence on the performance of a wind turbine. The out-of-plane bending is the dominant mode of the rotor blade while twisting and other complex modes of displacement could be more significant during some operating conditions such as at high tilt and yaw angles. The Bayesian Network is capable of computing probability mass functions of mechanical stress or displacement of the blade given a rotor rotation speed and a type of damage or vice versa, identifying a type of damage given a measured stress distribution level.

A finite element model of human hindfoot and its application in supramalleolar osteotomy

BackgroundThe majority of the ankle osteoarthritis cases are posttraumatic and affect younger patients with a longer projected life span. Hence, joint-preserving surgery, such as supramalleolar osteotomy becomes popular among young patients, especially those with asymmetric arthritis due to alignment deformities. However, there is a lack of biomechanical studies on postoperative evaluation of stress at ankle joints. We aimed to construct a verifiable finite element model of the human hindfoot, and to explore the effect of different osteotomy parameters on the treatment of varus ankle arthritis. MethodsThe bones of the hindfoot are reconstructed using normal CT tomography data from healthy volunteers, while the cartilages and ligaments are determined from the literature. The finite element calculation results are compared with the weight-bearing CT (WBCT) data to validate the model. By setting different model parameters, such as the osteotomy height (L) and the osteotomy distraction distance (h), the effects of different surgical parameters on the contact stress of the ankle joint surface are compared. FindingsThe alignment and the deformation of hindfoot bones as determined by the finite element analysis aligns closely with the data obtained from WBCT. The maximum contact stress of the ankle joint surface calculated by this model increases with the increase of the varus angle. The maximum contact stresses as a function of the L and h of the ankle joint surface are determined. InterpretationThe relationship between surgical parameters and stress at the ankle joint in our study could further help guiding the planning of the supramalleolar osteotomy according to the varus/valgus alignment of the patients.

The method for design of combined electromagnetic shield for overhead power lines magnetic field

Aim. Development of the method of designing a combined electromagnetic shield, consisting of active and passive parts, to improve the effectiveness of reduction of industrial frequency magnetic field created by two-circuit overhead power lines in residential buildings. Methodology. The problem of design of combined electromagnetic shield including robust system of active shielding and electromagnetic passive shield of initial magnetic field solved based on of the multi-criteria two-player antagonistic game. The game payoff vector calculated based on the finite element calculations system COMSOL Muliphysics. The game solution calculated based on the particles multiswarm optimization algorithms. During the design of combined electromagnetic shields spatial location coordinates of shielding winding, the currents and phases in the shielding winding of active shielding, geometric dimensions and thickness of the electromagnetic passive shield are calculated. Results. The results of theoretical and experimental studies of combined electromagnetic passive and active shielding of magnetic field in residential building from power transmission line with a «Barrel» type arrangement of wires presented. Originality. For the first time the method of designing a combined electromagnetic shield, consisting of active and passive parts, for more effective reduction of the magnetic field of industrial frequency created by two-circuit overhead power lines in residential buildings is developed. Practical value. Based on results of calculated and experimental study the shielding efficiency of the initial magnetic field determined that shielding factors whith only electromagnetic passive shield is more 2 units, whith only active shield is more 4 units and with combined electromagnetic passive and active shield is more 10 units. It is shown the possibility to reduce the level of magnetic field induction in residential building from power transmission line with a «Barrel» type arrangement of wires by means of a combined electromagnetic passive and active shielding with single compensating winding to 0.5 μT level safe for the population. References 53, figures 15.