Multiphysics Finite Element Analysis Research Articles

Generalization of crack growth mechanisms under isothermal and thermomechanical fatigue by COD and ERR parameters

An experimental-computational study of the crack opening displacement (COD) was performed to evaluate the ability of this parameter through the hysteresis loop area and energy release rate (ERR) to characterise fatigue crack growth under isothermal and thermomechanical conditions. To this end, a range of experimental crack growth tests were carried out including isothermal fatigue (IF), creep-fatigue interaction (CFI), in-phase (IP), and out-of-phase (OOP) thermomechanical fatigue (TMF). The crack growth experimental results in terms of COD and ERR were interpreted based on multi-physics finite element analyses of the stress–strain and displacement fields performed by incorporating Maxwell 3D, Fluent, and the transient structural modules of ANSYS. As a result of measurements and computations, the COD on the outer surface of the SENT specimen at the location of the original notch was found to be directly related to the crack tip opening displacement (CTOD). To gain insight into the fatigue crack growth mechanism operating under isothermal and TMF conditions, the fracture surfaces of all the tested specimens were examined using a scanning electron microscope to compare the morphology and changes in the dominant failure mechanisms. It was found that propagating cracks under isothermal and thermomechanical conditions interact with the microstructure of the material, and supporting fractography evidenced subtle differences in fracture mechanisms in terms of COD and ERR parameters. The relationship between the experimentally determined energy release rate and degradation function in the fatigue phase-field fracture methodology is discussed.

Multiphysics Simulation of In-Service Welding and Induction Preheating: Part 2

In-service welding simulations were carried out using a multiphysics finite element analysis (FEA). Calculated data as temperature and thermal cycles were validated by comparing them with experimental welding results carried out in a carbon steel pipe attached to a water loop. Two in-service welding cases were tested using the GMAW-P process with and without the assistance of induction preheating. The molten zone of weld macrographs and the simulated models were matched with excellent accuracy. The great agreement between the simulation and experimental molten zone generated a maximum error in the peak temperature of 1%, while in the cooling curve, the error was about 10% at lower temperatures. A higher hardness zone appeared in the weld’s toe within the CGHAZ, where the maximum induction preheating temperature achieved was 90°C with a power of 35 kW. Induction preheating reduced the maximum hardness from 390 HV to 339 HV.

Topology Optimization of a Switched Reluctance Machine by Electromagnetic-Structural Multiphysics Finite Element Analysis

Topology Optimization of a Switched Reluctance Machine by Electromagnetic-Structural Multiphysics Finite Element Analysis

Dynamic modeling and experimental study of multi-coil composite core energy harvester

To improve the output performance and working bandwidth of the magnetic levitation energy harvester, a new structure of multi-coil composite core energy harvester was proposed and verified by numerical simulation and experiment. Firstly, the working mechanism of the energy harvester was analyzed. The dynamics model and COMSOL Multiphysics finite element analysis model were established to study the influence of magnetic field and coil position on the output characteristics of the energy harvester. Then, an experimental platform was built to verify the proposed new energy harvester, and the influence of coil position on the output power of the energy harvester was explored. Three kinds of coil thicknesses, two kinds of coil winding directions, six kinds of coil connection modes and two kinds of magnet distribution experiments were designed. Finally, the influence of suspended core mass on output performance was analyzed, and the energy harvester with or without magnetic liquid was tested by sweeping frequency to evaluate its output performance. The experimental results show that the magnetic field near the coil can be enhanced effectively, and the output performance of the whole system can be improved by the magnet mutual repulsion energy harvester with coil connection mode CM1 in a consistent coil direction. With the increase of composite core mass, the output voltage and power of the energy harvester also increase, but the peak frequency decreases. Compared with the energy harvester without magnetic liquid, the output power performance of the designed multi-coil composite core energy harvester is significantly improved by 29%, and the frequency bandwidth growth rate is 73%. The normalized power density can reach 134.26 μWcm−3g−2. The new structure of the multi-coil composite core provides important reference significance for designing a more efficient magnetic levitation energy harvester.

Multiphysics Simulation of In-Service Welding and Induction Preheating: Part 1

A finite element model was developed using a multiphysics finite element analysis (FEA) coupling heat transfer, fluid flow, and electromagnetic heating. Part 1 presents the software implementation and model equations beside the mesh setting and modeling approach to simulate circumferential welding of Type B sleeve repair. The simulation was divided into four steps running sequentially for each physic solved in the model. Induction preheating was simulated and validated by comparing simulated temperature with experimental measurements. The multiphysics model differs from the usual simulations present in the literature, expressing more reliability in the results and making way for more-complete modeling for in-service applications.

Numerical simulation for electric field intensity and jet space of the quadratic spiral spinneret with auxiliary electrode

To produce a high quality electrostatic spinneret with low voltage requirements, low energy consumption, and narrow fiber diameter distribution, the mechanical model of the spinning unit of the fractal spiral spinneret was established by using the quadratic fractal spiral parametric equation. The established fractal spiral electrostatic spinning model was imported into COMSOL Multiphysics finite element analysis software, mesh division was performed on the model, multiple spinning units were combined to form the array spinneret, and the optimal parameters of the fractal structure were optimized. However, there are still two sides of the field intensity other than the middle field intensity of the high situation. In order to equalize the field intensity, we used the spinneret properties of the same disc auxiliary electrode and quadratic fractal spiral spinneret in a linear arrangement, and the auxiliary electrode and spinneret distance and spinneret radius of the two important parameters to optimize the simulation, resulting in obtaining a more uniform field intensity distribution of the quadratic fractal spiral spinneret electrospinning equipment. Based on the calculation of the fractional dimension of the Von Koch curve, the fractional dimension of the quadratic fractal spinneret was 1.77. The critical field intensity of the system was calculated to be 2.13 × 106 V/m, and the jet space was 1.22–3.13 mm. The optimized quadratic fractal spinneret model with auxiliary electrode faced the receiving plate in the range of 60° from the left to the right of the spinning sites, –5 to 5 sites, which may emit the spinning jet.

DLP printing of BT/HA nanocomposite ceramic scaffolds using low refractive index BT crystals

Biological piezoelectric materials have significant potential for bone repair and energy harvesting owing to their excellent biocompatibility and piezoelectric effect. The BaTiO3/Ca10(PO4)6(OH)2 (BT/HA) composite material is an outstanding representative of biological piezoelectric materials, which has not been individually designed using digital light processing (DLP) 3D printing because of the large difference in the refractive index of its components. Therefore, in this work, double-sided-tooth plate-like BT crystals with high curvature were prepared via a hydrothermal process, and BT/HA ceramic slurries were grinded out using dispersed intermittent ball milling scheme, and BT/HA nanocomposite ceramic scaffolds were fabricated by DLP 3D printing technology. The nanostructure, dielectric properties, and piezoelectric energy harvesting performance of the BT/HA nanocomposite ceramic scaffolds were evaluated. The influences of different morphologies and contents for BT on the piezoelectric potential and stress distribution were analyzed based on a multi-physics coupling finite element simulation. The cell proliferation and adhesion abilities were investigated also. The BT/HA nanocomposite ceramic scaffolds present excellent dielectric properties, cell proliferation and adhesion abilities, and an open circuit voltage of 8 V during piezoelectric energy harvesting. The material properties and multi-physics coupling finite element analysis imply that the double-sided-tooth plate-like BT plays an important role for the fastness structure and electric field distribution in the BT/HA nanocomposite. Thus, this work provides a strategy for the application of the customized BT/HA nanocomposite ceramic scaffolds in new-generation orthopedic implants and biological energy harvesting.

Analysis of underwater acoustic propagation induced by structural vibration in arctic ocean environment based on hybrid FEM-WSM solver

This paper investigates the underwater acoustic propagation characteristics induced by structural vibrations in the arctic ocean environment. For this purpose, a hybrid solver based on the finite element method (FEM) and the wave superposition method (WSM) is proposed. Leveraging the unique strengths of each method, the FEM is employed to perform structural-acoustic coupling analysis, while the WSM is used to analyze underwater acoustic propagation in the arctic ocean environment. In addition, the truncated singular value decomposition (TSVD) technique is introduced to mitigate the ill-conditioned effects of the Green's function matrix provided by the WSM. Numerical results demonstrate the accuracy and efficiency of the proposed solver in comparison to COMSOL Multiphysics finite element analysis software. Furthermore, the influence of sound speed stratification and ice layer thickness on the underwater acoustic propagation characteristics is numerically investigated in detail. These findings may provide valuable insights for the application of underwater acoustic communication and ocean exploration in the Arctic region.

A laterally excited bulk acoustic resonator with scattering vias in electrodes

Laterally excited bulk acoustic resonators (XBARs) using interdigital electrodes are currently limited in potential 5G applications due to the accompanied spurious modes and small capacitance. This Letter presents an XBAR with scattering vias in electrodes, named SV-BAR. The non-parallel boundaries thoroughly disrupt the coherent formation of standing waves in the lateral direction, thereby suppressing the higher-order spurious modes. The duty factor of SV-BAR is optimized as 0.5 using COMSOL Multiphysics finite element analysis for the 50 Ω impedance matching. The SV-BAR is fabricated using a 390 nm Z-cut LiNbO3 on an insulator substrate and exhibits an impressive ratio of Zp/Zs near 64.5 dB, a Kt2 of 21.80% at 4.762 GHz, as well as a large value f · Bode_Qmax · Kt2 (3.43 × 1011). The measured temperature coefficient of frequency is −69.8 ppm/°C, which can be compensated using SiO2 thin films. The SV-BAR provides an effective solution for high-performance radio frequency filters for 5G communication.

Intelligent Shape Decoding of a Soft Optical Waveguide Sensor

Optical waveguides create interesting opportunities in the area of soft sensing and electronic skins due to their potential for high flexibility, quick response time, and compactness. The loss or change of light intensities inside a waveguide can be measured and converted into useful sensing feedback such as strain or shape sensing. Compared to other approaches such as those based on microelectromechanical system modules or flexible conductors, the entire sensor state can be characterized by fewer sensing nodes and less encumbering wiring, allowing greater scalability. Herein, simple light‐emitting diodes (LEDs) and photodetectors (PDs) combined with an intelligent shape decoding framework are utilized to enable 3D shape sensing of a self‐contained flexible substrate. Multiphysics finite element analysis is leveraged to optimize the PDs/LEDs layout and enrich ground‐truth data from sparse to dense points for model training. The mapping from light intensities to overall sensor shape is achieved with an autoregression‐based model that considers temporal continuity and spatial locality. The sensing framework is evaluated on an A5‐sized flexible sensor prototype and a fish‐shaped prototype, where sensing accuracy (RMSE = 0.27 mm) and repeatability (Δ light intensity <0.31% over 1000 cycles) are tested underwater.

Design, Modeling, and Analysis of a Compact-External Electromagnetic Pumping System for Pool-Type Liquid Metal-Cooled Fast Reactors

Current pool-type Liquid Metal-Cooled Fast Reactors (LMCFRs), either under development or operational, immerse main reactor components in the primary coolant, (i.e. sodium), that includes heat exchangers, shielding structures, and pumping systems. Proposed main pumping systems, for some reactors that are under development, use electromagnetic pumps (EMPs) for primary coolant circulation. Annular linear induction pumps (ALIPs) are the preferred type since they are known for their advantages over mechanical centrifugal pumps (MCPs) when used to circulate liquid metals. This is due to ALIPs’ absence of moving parts such as shafts and impellers, seals and bearings, auxiliary lubrication systems, and simplicity of flow and pressure control mechanism. The immersion of reactor components in the primary sodium in the reactor vessel minimizes the likelihood of radioactive coolant leakage and loss of coolant accidents. However, since there is only one access point to reactor components, the immersion of ALIPs prevents additional potential advantages. Online pump inspection and replacement, reduction of negative effects on pump components due to the high temperature and radiation environment, an additional heat removal mechanism for self-cooled ALIPs, and simple decommissioning procedures are some possible advantages. This paper discusses a study conducted to investigate the possibility of using large EMPs, ALIP type, that are located outside the reactor vessel and connected in parallel, instead of in vessel sodium immersed ones for pool-type LMCFRs. The large, outside-vessel EMP idea is tested on a liquid metal-cooled test reactor design using an experimentally validated multiphysics finite element analysis tool. Specifically, the steady state reactor’s primary circuit cooling and pressure requirements are used to design two, in-vessel ALIPs and then two outside-vessel ALIPs. The two pumping systems are compared in terms of their geometries, performance characteristics, and impact on overall reactor design. It is found that the outside-vessel EMP design provides the same performance requirements and offers additional advantages compared to the in-vessel pump with only minimal reactor vessel modification and a slight drop in efficiency.

Electromagnetic noise analysis of servomotor used in secondary water supply equipment

The servo motor has the characteristics of high precision, high speed and stable operation, but it will produce large electromagnetic noise in the process of using, which will affect the user experience. Based on the ANSYS multi-physics finite element analysis platform, this paper studies the electrical noise characteristics of servo motors used in a secondary water supply equipment under different speed conditions. The time and space distribution characteristics of the radial electromagnetic force acting on the motor stator are obtained by electromagnetic field analysis and modal analysis respectively. The natural frequency of the motor structure modal mode can also be obtained from these analyses. The causes of large electromagnetic noise were analyzed from the aspects of radial electromagnetic force and structural mode, and the position distribution of large vibration on the motor is obtained by harmonic response analysis. On this basis, the sound pressure level distribution of servo electromagnetic noise at different frequencies is obtained through acoustic simulation, which has referential significance for noise prediction and shell noise reduction optimization of related servo motors.

A Lamb wave magnetoelectric antenna design for implantable devices

A 400 MHz magnetoelectric (ME) Lamb wave antenna design to function in the medical implant communication service band is proposed. The antenna employs a heterostructure of piezoelectric and magnetostrictive membranes to acoustically excite standing shear bulk wave and radiate as a magnetic dipole. Multiphysics finite element analysis simulations are performed for transmission and reception modes. In these simulations, three aspects are investigated: piezoelectricity, micromagnetic precession, and magnetic dipole radiation. An experimental demonstration of the antenna is also conducted and shows mechanical resonance with a Q-factor of 500 and ME coupling. These results indicate that the design can be operated in zero-order antisymmetric (A0) mode as a tunable oscillator or sensor. This ME approach provides a solution to the miniaturization problem of traditional current-based implantable antennas.

Impact of microannulus on the efficiency of heat transfer in the bottomhole

To ensure feasible power generation from closed-loop geothermal wells, deeper wells are required to reach higher temperature zones. However, weak bonding between cement and casing or cement and formation may allow formation of a small gap (known as microannulus), which could have a negative effect on the heat extraction rate and consequently compromises the entire investment. Previous projects have reported that the output temperatures were significantly lower than the expected values, and the cause is believed to be cement debonding. This study aims to develop a reliable simulation model to demonstrate the impact of microannulus in closed-loop geothermal systems. Multi-physics finite element analysis is used to construct models with and without microannulus. The microannulus is modeled based on real cement evaluation logs, with gaps varying between a few micrometers to few millimeters. In extreme cases, the presence of microannulus is found to decrease the geothermal power by more than 35%. Furthermore, the possibility of heat loss containment is investigated by a sensitivity study of wellbore parameters. These sensitivity analyses demonstrate that cement and geothermal fluids with higher thermal conductivity can improve but cannot compensate the presence of microannuli. The results also highlight the importance of proper cementing design to ensure wellbore integrity and avoid geothermal power loss.

On the Correct Generation of a Single Sound Mode in a Duct with Flow in COMSOL Multiphysics

The paper considers the statement of a single-mode sound generation in a duct with flow in the COMSOL Multiphysics finite element analysis software. Verification of the COMSOL Multiphysics solution is based on a comparison with the analytical solution of a single-mode propagation in an annular duct with uniform flow. The verified statement of a single-mode generation in COMSOL Multiphysics is then used to predict the noise of a JT15D turbofan engine in the far field. The results of computations are compared with JT15D static test data and known numerical simulation results.

In situ consolidation of carbon fiber PAEK via laser-assisted automated fiber placement

Automated fiber placement (AFP) of thermosetting composites has been one of the leading manufacturing techniques for aerospace structures over the last decade. Thermoplastic composites (TPCs) offer several advantages including a high toughness, recyclability, weldability, and potential for rapid out-of-autoclave manufacturing. High-power heating sources and flexible compaction rollers can be used to melt and consolidate TPC tapes via AFP to form large structures in a layer-by-layer manner as used in additive manufacturing. This paper investigates the in-situ consolidation AFP of TPC tapes (ICAT) toward their process optimization and revealing mechanisms that govern the ICAT process. To this end, a laser-assisted AFP system was utilized to fabricate short beam strength samples from carbon fiber reinforced low-melt polyaryletherketone (LM-PAEK™) at various processing parameters. Analysis of results revealed how ICAT process parameters affect interlaminar bonding, crystallinity, and void content in manufactured parts. Multiphysics finite element analysis (FEA) was also carried out to reveal mechanisms that control void, crystallinity, and bonding in ICAT. Finally, a comparison of post-fracture specimens made via ICAT with traditional compression molding was used to explain the underlying failure mechanisms in ICAT coupons. This study shows that at AFP rates of up to 0.15 m/s, high interlaminar shear strengths, up to 60 MPa, are possible to achieve with low void content (<1%) and high crystallinity (>20%), proving that ICAT is potentially a viable process for manufacturing the next generation of aerospace composites.

Frontal Polymerization in Short-Fiber-Reinforced Thermoset Composites

Frontal polymerization (FP) has recently been introduced as a faster, more energy-efficient manufacturing process for high-performance thermoset composites. This numerical study focuses on the FP-based manufacturing of short-fiber-reinforced polymeric matrix composites. The investigation involves a combination of multiphysics finite element analyses and analytical predictions. The developed model is also applied to a short-fiber composite with spatially varying fiber orientation obtained from a sample produced by vacuum injection method. The results show how the steady-state front velocity and inclination angle depend on the fiber orientation angle and volume fraction. Analytical expressions are derived to capture that dependence and show excellent agreement with the numerical steady-state results. Simulations of FP in short-fiber composites based on experimental distributions of the fiber orientation indicate the feasibility of FP in samples prepared by injection molding.

Multiscale and multiphysics FEA simulation and materials optimization for laser ultrasound transducers

The relationship between the nanocomposite design and the laser ultrasound transducer (LUT) characteristics was investigated through simulations in multiple scale levels for material behavior, device response, and acoustic wave propagation in media. First, the effects of the nanoparticle size and concentration on the effective properties of composites were quantitatively investigated with the finite element analysis (FEA) method. Second, the effective properties of the nanocomposite were assigned to the layer, which is modeled as a homogeneous material, in the FEA for the LUT simulating the energy conversion from the incident laser to the acoustic wave. Finally, the ultrasound propagation in the water was calculated by a theoretical wave propagation model. The FEA-based prediction was compared with the experimental data in the literature and a theoretical analysis for LUT based on Thermal-Acoustic coupling. As a result, the ultrasound waves on the transducer surface and at a distance in the water could be predicted. Based on the hierarchically integrated prediction procedure, the optimal conditions of the photoacoustic nanocomposites were investigated through the parametric study with the particle size and concentration as variables. The results guide the material designs optimized for different device characteristics, such as high pressure and broad bandwidth.

Planar ultrasonic transducer based on a metasurface piezoelectric ring array for subwavelength acoustic focusing in water

The development of a new ultrasonic transducer capable of improved focusing performance has become a necessity to overcome the limitations of conventional ultrasonic transducer technology. In this study, we designed and optimized a metasurface piezoelectric ring device, and using multiphysics finite element analysis, we examined the performance of a planar ultrasonic transducer consisting of this device, a matching layer, a backing layer, and housing in producing a needle-like subwavelength focusing beam in water. For practical experiments, a metasurface piezoelectric ring device was fabricated using a laser ablation process. Subsequently, using a pulse-echo test, we found that the − 6 dB bandwidth of a planar ultrasonic transducer with a center frequency of 1.0 MHz was 37.5%. In addition, the results of an ultrasonic-focusing performance test showed that the full width at half-maximum of the axial subwavelength focusing beam was 0.78λ, and the full lateral width at half-maximum of the subwavelength lateral focusing beam was 7.03λ at a distance of 10.89λ. The needle-like focused ultrasonic beam technology implemented with a piezoelectric ring array based new planar ultrasound transducer is expected to be used in high-resolution imaging devices or medical ultrasound focusing devices in the future.

Seismic assessment of corroded concrete bridges using incremental modal pushover analysis

An efficient yet accurate procedure was developed for the seismic assessment of reinforced concrete (RC) bridges subject to chloride-induced corrosion. The procedure involves using incremental modal pushover analysis to assess corroded bridges as an alternative and less computationally demanding approach to non-linear dynamic analysis. A multi-physics finite-element analysis is performed to evaluate the effects of chloride-induced corrosion on bridge columns. In doing so, chloride ingress in concrete is numerically simulated as a diffusion process by considering the effects of temperature, humidity, corrosion-induced cover cracking and concrete aging. The estimated chloride concentration is then employed to evaluate the corrosion current density, from which the effects of corrosion on reinforcement, cracked cover concrete, confinement and plastic hinge length can be determined for subsequent non-linear static analysis. A case study of a typical bridge structure is presented. The proposed procedure can be used to assess the seismic performance of irregular RC bridges exposed to severe corrosive environments.