Multiphysics Finite Element Method Research Articles

A novel flexural damping channel magnetorheological damper with high effective magnetic field coverage and experimental verification of damping performance

Abstract Conventional magnetorheological dampers (MRDs) have limitations owing to their low effective magnetic field coverage, and improving MRD structures is a common approach to address this issue. However, many existing MRD designs have limitations such as large radial dimensions and high coil power consumption. Therefore, this paper transformed the conventional damping channel into the flexural damping channel to increase the effective magnetic field coverage of the MRD based on the conventionalstructure. And then, the pressure drop model was utilized to preliminarily determine the structural parameters of the new MRD. Subsequently, a multi-physics coupling finite element method (FEM) analysis model was constructed to accurately determine the structural parameters, ensuring that the novel flexural damping channel (NFDC) MRD increases the output peak damping force while reducing the radial dimension and input power. Furthermore, the damping force variable range is stabilized when the excitation current is zero (field-off). Finally, a large number of vibration tests were conducted on both the conventional and NFDC MRDs, and it was found that the NFDC MRD has better vibration energy dissipation capacity and higher output peak damping force while maintaining a basically same field-off damping force variable range compared with the conventional MRD. The above process not only proved that the NFDC MRD possesses excellent output damping capability and working condition adaptability, but also validated the operational effectiveness of employing the multi-physics coupling analysis method to design the NFDC MRD.

The impact of various curing methods on the curing process of polymer-fiber composites analyzed using analytical approach

Ti/Gf/Cf represents a novel form of hybrid fiber metal laminates (HFMLs) that successfully blend the benefits of titanium alloy, glass fiber reinforced plastic (GFRP), and carbon fiber reinforced plastic (CFRP). These materials have garnered attention in the field of engineering due to their exceptional levels of stiffness, strength, and shear resistance. The quality of HFMLs during the curing process was significantly impacted by the chosen curing method. Moreover, the use of multiple types of fibers complicated the optimization of curing parameters in HFMLs. A comprehensive study was conducted using a multi-physics field coupling finite element method to investigate the impact of various curing methods on the development of temperature distribution, curing degree, and curing stress in HFMLs during the curing process. By integrating thermal transmission equations, curing kinetics, and viscoelastic mechanical models, a detailed curing simulation model was established. Increasing the cooling rate from 1 °C to 5 °C was shown to raise the maximum curing stress by 4.7 MPa. Additionally, higher curing temperatures were found to induce internal curing stress due to variations in thermal properties. Insufficient insulation times were observed to exacerbate non-uniform temperature distribution and curing degree fields in HFMLs, potentially leading to increased internal stress. To mitigate the generation of large residual stress, it is recommended to lower the heating and cooling rates, reduce curing temperatures, and extend the insulation time appropriately during the curing process of HFMLs. The primary goal of this research was to accurately predict the evolution of curing parameters in HFMLs under different curing regimes, which were impacted by the chosen curing method. The results of the study demonstrated that rapid changes in temperature during heating and cooling stages can lead to uneven curing, resulting in the accumulation of residual stress within the laminates.

Modeling for neurosurgical laser interstitial thermal therapy with and without intracranial recording electrodes

Laser thermal ablation has become a prominent neurosurgical treatment approach, but in epilepsy patients it cannot currently be safely implemented with intracranial recording electrodes that are used to study interictal or epileptiform activity. There is a pressing need for computational models of laser interstitial thermal therapy (LITT) with and without intracranial electrodes to enhance the efficacy and safety of optical neurotherapies. In this paper, we aimed to build a biophysical bioheat and ray optics model to study the effects of laser heating in the brain, with and without intracranial electrodes in the vicinity of the ablation zone during the LITT procedure. COMSOL Multiphysics finite element method (FEM) solver software was used to create a bioheat thermal model of brain tissue, with and without blood flow incorporation via Penne's model, to model neural tissue response to laser heating. We report that the close placement of intracranial electrodes can increase the maximum temperature of the brain tissue volume as well as impact the necrosis region volume if the electrodes are placed too closely to the laser coupled diffuse fiber tip. The model shows that an electrode displacement of 4 mm could be considered a safe distance of intracranial electrode placement away from the LITT probe treatment area. This work, for the first time, models the impact of intracranially implanted recording electrodes during LITT, which could improve the understanding of the LITT treatment procedure on the brain's neural networks a sufficient safe distance to the implanted intracranial recording electrodes. We recommend modeling safe distances for placing the electrodes with respect to the infrared laser coupled diffuse fiber tip.

Analysis of conductive filament heat transfer in TiO2-based RRAM device

Abstract Resistive random access memory (RRAM) has developed into a new type of non-volatile memory that has attracted much attention for its high density and low power; TiO2 has been studied to make RRAM because of its high conductivity. Based on the COMSOL Multiphysics finite element method and domain decomposition method, an electrically-thermally coupled model of TiO2-based RRAM with oxygen vacancy (Vo) conduction mechanism is constructed, the formation and cutting process of RESET and SET conductive filament (CF) under different voltages is simulated. Moreover, the characteristics of the internal temperature distribution of the CF are explored. The results show that the RESET process is more sensitive to heat changes, the transverse direction thermal value of the CF is more obvious than the longitudinal direction, and the rate of change is faster. Additionally, the electric field induces the migration of the Vo in filament, which affects the enthalpy change of the device’s heat transfer and resistive properties. This is an important reference for a deeper understanding of the switching behavior of RRAM devices and the control mechanisms for thermal studies.

A New Multiphysics Finite Element Method for a Biot Model with Secondary Consolidation

A New Multiphysics Finite Element Method for a Biot Model with Secondary Consolidation

Attenuation characteristics of concrete using smart aggregate transducers: Experiments and numerical simulations of P-wave propagation

Concrete is a highly heterogeneous construction material. Waves that propagate through concrete face significant reflection, scattering, and attenuation issues. Understanding the behavior of waves as they propagate through concrete and arrive at a sensor has generated much attention, especially for developing real-world field applications. In this study, a predictive model of attenuated P-wave propagation using Rayleigh damping is presented. The method used frequency excitations ranging from 20 to 200 kHz and smart aggregates (SAs) were embedded in a concrete specimen to excite and receive P-waves. Moreover, 10 distances were marked opposite the exciter at two propagation paths. In the simulations and experiments, signal processing methods were utilized to extract the first arrival packet for calculating amplitude attenuation. The P-wave damping coefficient was modeled using the multi-physical finite element method, and the results of the predictive model were compared with the experimental results. A discussion on the utilization of frequency-dependent attenuation coefficients was conducted to explore potential P-wave attenuation factors and their respective contributions to the overall attenuation. Numerical studies have demonstrated a strong correlation with the experiments when an appropriate level of material damping coefficient was considered. By enhancing the overall comprehension of the P-wave damping coefficient and attenuation characteristics within concrete, damage detection techniques based on P-waves can be improved.

Multirate Time Iterative Scheme with Multiphysics Finite Element Method for a Nonlinear Poroelasticity

Multirate Time Iterative Scheme with Multiphysics Finite Element Method for a Nonlinear Poroelasticity

Combined FEM and phase field method for reliability design of forward degradation in SiC bipolar device

The reliability of 4H-SiC bipolar devices is compromised by the expansion of single Shockley stacking faults (SSFs) during forward-current operation. Because SSF expansion is governed by multiphysical aspects, including electrical, thermal, and stress states, analysis of the mounted structure is important for improving power module design. We propose a practical design method that analyzes the critical condition due to SSF expansion using a combined method with a multiphysical finite element method (FEM) and phase field model based on the time-dependent Ginzburg–Landau equation. In preliminary studies, the thermal deformation of the demonstration module and the variation of threshold current of a bar-shaped SSF were verified from experimental and reference data. Estimating the SSF expansion rate on the constructed response surface under the mutiphysical inputs from FEM, the proposed design method can be used effectively in the design process by changing the various design variables.

Heat behavior and axial temperature distribution of a Ti-6Al-4V alloy in a superconducting induction heater with a controllable magnet structure

Ti-6Al-4V (TC4) metal billets can usually be preheated by gases, resistance furnaces, and conventional induction heater powered by alternating current. However, the disadvantages of these heating methods are long heating time and small skin depths. The novel superconducting induction heater has several advantages in terms of heating quality, heating efficiency, heating time and axial temperature control. It has gained successful commercial application in the large aluminum extrusion industry in 2021. However, no studies on TC4 heating behavior using a superconducting induction heater have been reported, and no studies on uniform and gradient temperature characteristics of TC4 in superconducting induction heater. The uniform temperature distribution of TC4 is helpful to reduce the heating residual stress of forgings. The gradient temperature distribution of TC4 billet can obtain different properties in different parts of the same TC4 billet, which is suitable for manufacturing functionally graded materials. In this study, a high-temperature superconducting (HTS) direct-current (DC) induction furnace was firstly used to perform heating experiments for TC4 metal billets of 1250 mm length and 220 mm diameter. The application of the superconducting magnet for induction heating allows for high-power and fast heating of the TC4 billet at an extremely low frequency (4 Hz). The HTS induction heater technology has the advantages of high penetration depth, high energy efficiency (>82%), high heating uniformity, and controllable temperature distribution. Additionally, it improves the metal heating quality and reduces the heating cost. The 10 identical iron pieces of superconducting magnet on both sides of the iron core can be adjusted independently. The gradient and uniform temperature distributions of the thermally optimized TC4 billets were experimentally determined using adjustable electromagnetic heating power. Subsequently, the heating behavior of TC4 billets was modeled and compared using the numerical multiphysical finite element method; the results obtained using this method are in agreement with the experimental results. An expert database has been established for the heating strategy of TC4 billets. The optimized axial temperature distribution was analyzed for three different TC4 billet diameters (Φ220, Φ300, and Φ446 mm). The obtained gradient and uniform axial temperature distributions had an error of less than ±3 °C, and the adjustable difference at two-ends temperature of TC4 billets was in the range 10–100 °C/m. Finally, the maximum thermal stress on the TC4 billet during heating also was analyzed. The results of this study will be useful of the novel HTS induction heater application for TC4 billet heating, and axial temperature control. The uniform temperature distribution control will reduce the heating residual stress of forgings. The gradient temperature distribution of TC4 billet is suitable for manufacturing functionally graded materials.

A multiphysics-based artificial neural networks model for atherosclerosis

Atherosclerosis is a medical condition involving the hardening and/or thickening of arteries' walls. Mathematical multi-physics models have been developed to predict the development of atherosclerosis under different conditions. However, these models are typically computationally expensive. In this study, we used machine learning techniques, particularly artificial neural networks (ANN), to enhance the computational efficiency of these models. A database of multi-physics Finite Element Method (FEM) simulations was created and used for training and validating an ANN model. The model is capable of quick and accurate prediction of atherosclerosis development. A remarkable computational gain is obtained using the ANN model compared to the original FEM simulations.

Enhanced near-field radiation of acoustic-actuated antennas using embedded magnetoelectric composites

Acoustic-actuated antennas operate at the acoustic wave resonance rather than electromagnetic (EM) wave resonance and thus show a significant superiority for the miniaturization of antennas. This paper designs a new acoustic-actuated antenna using embedded magnetoelectric (ME) composites, to improve the radiations of ME antennas through the enhanced strain transfer at the interfaces between different phases. The performance of the ME antenna is examined through a multiphysics finite element method with considering the nonlinear magnetostrictive model. Then, three optimum schemes are proposed for the improvement of the ME antenna, which are also verified by the simulation results. It has been demonstrated that the EM radiations of the embedded ME composite are effectively improved by changing its sizes or configuration. Due to the magnetic flux and stress concentration effects, the maximum |E| and |H| radiations are respectively enhanced by 88 % and 97 % via using a trapezoidal magnetostrictive layer. The effects of magnetic bias and pre-stress indicate that near-field radiations of the ME antennas with fixed dimensions can be enhanced by external multi-physics fields. This simulation may facilitate the understanding of nonlinear CME behavior as well as provide a basis for the design of tunable ME antennas.

Promoting CO2 Dynamic Activation via Micro-Engineering Technology for Enhancing Electrochemical CO2 Reduction.

Optimizing the coordination structure and microscopic reaction environment of isolated metal sites is promising for boosting catalytic activity for electrocatalytic CO2 reduction reaction (CO2 RR) but is still challenging to achieve. Herein, a newly electrostatic induced self-assembly strategy for encapsulating isolated Ni-C3 N1 moiety into hollow nano-reactor as I-Ni SA/NHCRs is developed, which achievesFECO of 94.91% at -0.80V, the CO partial current density of ≈-15.35mA cm-2 , superior to that with outer Ni-C2 N2 moiety (94.47%, ≈-12.06mA cm-2 ), or without hollow structure (92.30%, ≈-5.39mA cm-2 ), and high FECO of ≈98.41% at 100mA cm-2 in flow cell. COMSOL multiphysics finite-element method and density functional theory (DFT) calculation illustrate that the excellent activity for I-Ni SA/NHCRs should be attributed to the structure-enhanced kinetics process caused by its hollow nano-reactor structure and unique Ni-C3 N1 moiety, which can enrich electron on Ni sites and positively shift d-band center to the Fermi level to accelerate the adsorption and activation of CO2 molecule and *COOH formation. Meanwhile, this strategy also successfully steers the design of encapsulating isolated iron and cobalt sites into nano-reactor, while I-Ni SA/NHCRs-based zinc-CO2 battery assembled with a peak power density of 2.54mW cm--2 is achieved.

Composite Mould Design with Multiphysics FEM Computations Guidance

Composite moulds constitute an attractive alternative to classical metallic moulds when used for components fabricated by processes such as Resin Transfer Moulding (RTM). However, there are many factors that have to be accounted for if a correct design of the moulds is sought after. In this paper, the Finite Element Method (FEM) is used to help in the design of the mould. To do so, a thermo-electrical simulation has been performed through MSC-Marc in the preheating phase in order to ensure that the mould is able to be heated, through the Joule’s effect, according to the thermal cycle specified under operating conditions. Mean temperatures of 120 °C and 100 °C are predicted for the lower and upper semi-mould parts, respectively. Additionally, a thermo-electrical-mechanical calculation has been completed with MSC-Marc to calculate the tensile state along the system during the preheating stage. For the filling phase, the filling process itself has been simulated through RTM-Worx. Both the uniform- and non-uniform temperature distribution approaches have been used to assess the resulting effect. It has been found that this piece of software cannot model the temperature dependency of the resin and a numerical trick must have been applied in the second case to overcome it. Results have been found to be very dependent on the approach, the filling time being 73% greater when modelling a non-uniform temperature distribution. The correct behaviour of the mould during the filling stage, as a consequence of the filling pressure, has been also proved with a specific mechanical analysis conducted with MSC-Marc. Finally, the thermo-elastic response of the mould during the curing stage has been numerically assessed. This analysis has been made through MSC-Marc, paying special attention to the curing of the resin and the exothermic reaction that takes place. For the sake of accuracy, a user subroutine to include specific curing laws has been used. Material properties employed are also described in detail following a modified version of the Scott model, with curing properties extracted from experiments. All these detailed calculations have been the cornerstone to designing the composite mould and have also unveiled some capabilities that were missed in the commercial codes employed. Future versions of these commercial codes will have to deal with these weak points but, as a whole, the Finite Element Method is shown to be an appropriate tool for helping in the design of composite moulds.

Multiphysics finite element method for a nonlinear poroelasticity model with finite strain

Multiphysics finite element method for a nonlinear poroelasticity model with finite strain

Characterization of a Thermoacoustic-based Pulsed High Power Microwave Detector Chain.

Detection of microwave-induced thermoacoustic (TA) wave generation was evaluated as a potential technique for detection of high power microwave (HPM) directed energy exposure. Even when HPM is employed for counter-materiel effects, incidental but still potentially harmful personnel exposure is possible. Real-time detection of ongoing exposure with potentially unknown time and frequency domain characteristics is a critical first step in preventing acute health effects by alerting and then enabling the timely use of electromagnetic frequency energy shielding, such as structures and vehicles. Leveraging the TA effect as a field interaction mechanism, a lossy dielectric polymer subjected to pulsed HPM was tested using a planar sample geometry with thin film piezoelectric sensors used to capture the resulting TA output. The piezoelectric signal was analyzed in both the time and frequency domain to determine empirical relationships between incident microwave beam properties and signal components. This analysis was coupled with an empirically-based single term Cole-Cole model approximation fit for the complex permittivity. The results were used to identify appropriate signal conditioning and processing techniques needed to convert the TA response into a useful form for personnel exposure applications. These results also served as a comparison point for multi-physics finite element method computational modeling of the electromagnetic response of a simplified three-layer tissue model.

A two-level multiphysics finite element method for a nonlinear poroelasticity model

In this paper, we propose a two-level multiphysics finite element method for a nonlinear poroelasticity model. To clearly reveal the multiphysics processes and overcome the “locking phenomenon”, we reformulate the original fluid-solid coupled problem into a fluid-fluid coupled problem–a generalized nonlinear Stokes problem coupled with a diffusion problem. To reduce the cost of computation, we propose two fully discrete coupling and decoupling two-level multiphysics finite element methods and use the backward Euler method for time variable of the reformulated nonlinear poroelasticity model. In computation, the generalized nonlinear poroelasticity (Stokes in Algorithm 2) problem is solved by using the Newton iterative method on a coarse mesh, then a linearized poroelasticity problem is solved on a fine mesh by using the solution of the coarse mesh. Then, we give the stability analysis and error estimates of the proposed methods. Finally, we show some numerical examples to verify the theoretical results–overcoming “locking phenomenon” and reducing the computational cost. • It is the first time to propose a two-level multiphysics finite element method for the nonlinear poroelasticity model. • The optimal order error estimate of the proposed two-level method is given. • To reduce the cost of computation, a poroelasticity problem is solved by using the Newton method on a coarse mesh.

Strongly Coupled Electromagnetic–Mechanical Problem With Analytical Solution

Strongly coupled electromagnetic–mechanical (ME) problems are presently very relevant for academic research and industrial technology and product development. Although the algorithm basis for such coupled simulations is rather extensive and available in numerous publications, verification of the obtained results is very difficult and relies mainly on expensive, tedious, and time-consuming measurements. The main reason for this is an evident deficiency of reference examples with analytical solutions (ASs) in the available literature. To mitigate the problem, this article defines two strongly coupled electromagnetic–ME problems and presents their AS in detail. The obtained ASs were cross-validated by comparing them against an in-house developed multiphysics finite element method (FEM) solver and an excellent agreement between the two was found.

Multiphysics mixed finite element method with Nitsche's technique for Stokes‐poroelasticity problem

AbstractIn this article, we propose a multiphysics mixed finite element method with Nitsche's technique for Stokes‐poroelasticity problem. Firstly, we reformulate the poroelasticity part of the original problem by introducing two pseudo‐pressures to into a “fluid–fluid” coupled problem so that we can use the classical stable finite element pairs to deal with this problem conveniently. Then, we prove the existence and uniqueness of weak solution of the reformulated problem. And we use Nitsche's technique to approximate the coupling condition at the interface to propose a loosely‐coupled time‐stepping method to solve three subproblems at each time step–a Stokes problem, a generalized Stokes problem and a mixed diffusion problem. And the proposed method does not require any restriction on the choice of the discrete approximation spaces on each side of the interface provided that appropriate quadrature methods are adopted. Also, we give the stability analysis and error estimates of the loosely‐coupled time‐stepping method. Finally, we give the numerical tests to show that the proposed numerical method has a good stability and no “locking” phenomenon.

MetaFEM: A generic FEM solver by meta-expressions

Current multi-physics Finite Element Method (FEM) solvers are complex systems in terms of both their mathematical complexity and lines of code. This paper proposes a skeleton generic FEM solver, named MetaFEM, in total about 6,000 lines of Julia code, which translates generic input Partial Differential Equation (PDE) weak forms into corresponding GPU-accelerated simulations with a grammar similar to FEniCS or FreeFEM. Two novel approaches differentiate MetaFEM from the common solvers: (1) the FEM kernel is based on an original theory/algorithm which explicitly processes meta-expressions, as the name suggests, and (2) the symbolic engine is a rule-based Computer Algebra System (CAS), i.e., the equations are rewritten/derived according to a set of rewriting rules instead of going through completely fixed routines, supporting easy customization by developers. Example cases in thermal conduction, linear elasticity and incompressible flow are presented to demonstrate utility.

Cell mechanics in an ultrasonic standing wave

Diseases like cancer are known to cause functional changes to the cell, which are reflected in structural and material properties of the cell. Looking at cell's response to the exposure to an acoustic field is one way to measure these mechanical properties. In contrast to the dynamic nature of acoustic fields, the mechanical properties of cells are mostly examined in a static configuration, rendering the mechanics of a cell in an acoustic field largely misunderstood. We built multiphysics finite element method models for a prokaryotic (gram-negative bacteria) and a eukaryotic (mammalian) cell in an acoustic standing wave, and we use the models to compute the forces on the two cell types.