Finite Element Simulation Model Research Articles

Shape measurement by using multicore optical fiber sensor with asymmetric dual cores

Abstract Shape measurement by using multicore optical fiber sensor has attracted more attention in many fields due to the good consistency of the fiber cores. Three symmetrically arranged cores in multicore fiber are usually used for reconstructing shape by calculating the bending vectors, which will not be achieved when one of the cores is damaged or occupied in actual application. A shape measurement method using multicore optical fiber sensor with asymmetric dual cores is proposed in this paper. Based on analyzing the principle of shape reconstruction and the geometric relationship of asymmetric dual cores in multicore fiber sensor, the bending vector is decomposed. The mathematical expressions for bending curvature and orientation of asymmetric dual cores are derived. The two dimensional (2D) and three dimensional (3D) shape reconstruction results both in finite element modelling simulation and shape measurement experiment based on optical frequency domain reflectometry have shown that the proposed method using multicore fiber sensor with asymmetric dual cores is able to achieve shape measurement, and its performance is comparable and even equivalent to the traditional method by using three symmetrically arranged cores. In the experiment, the maximum relative errors of 2D and 3D reconstructed shapes are 2.653% and 5.139%, respectively. The proposed method, which only needs asymmetric dual cores in the multicore optical fiber sensor for shape reconstruction, will be conducive to solve the limitation of multicore optical fiber sensors in shape measurement applications.

EXTH-74. COOLING GLIOBLASTOMA WITH A NEURAL IMPLANT

Abstract Survival rates for glioblastoma (GBM) patients are low due to the difficulty in eradicating all tumor cells, leading to frequent recurrence. This recurrence is frequently within 2-cm from the original site. Studies indicate that supra-total resection improves survival, and non-destructive local therapies show promise in preventing GBM recurrence. Our research demonstrates that non-freezing, ‘cytostatic’ hypothermia is effective against GBM in rats and can be scaled to pig models. This method, unlike ablative cryogenic hypothermia, safely inhibits GBM growth without damaging healthy tissue. Using in vitro culture models and in vivo rat models via a Peltier device, we tested cytostatic hypothermia. This was followed by finite-element modeling (FEM) to simulate bioheat transfer in human and pig brains. The system consists of a neural implant with a multiprobe array, a Peltier chip, a water block, and an artificial internal circulation system with a piezoelectric pump. In vitro tests identified a cytostatic window of 20–25°C. Miniature Peltier devices were fabricated to achieve this in rats to inhibit GBM growth and extend survival. Rats whose tumors received cytostatic levels of hypothermia survived their full study period. FEM simulations confirmed that multiprobe arrays could cool brain tissue to 25°C without significantly raising skin temperature. Portable systems were successfully fabricated and tested in pigs, achieving safe target temperatures with minimal EEG and OCTA changes. Our findings suggest that cytostatic hypothermia can be scaled to larger animals and made implantable and portable, offering a promising non-destructive approach to halting GBM growth and prolonging survival, moving closer to becoming a viable treatment option for patients with GBM.

Frequency Range Optimization for Linear Viscoelastic Characterization of Burger's Model

The linear viscoelastic behavior of materials is represented using mechanical models of choice, which are further utilized in different numerical investigations, such as finite element simulations and discrete element simulations. Burger's model is one of the widely adopted mechanical models and remains highly favored in contemporary research due to its multiple advantages. Specifically, it excels in representing long-term creep and stress relaxation behavior in a relatively simplified manner. Accurate identification of the long-term behavior for the viscoelastic material, particularly asphalt concrete, is crucial, as it serves as a key indicator of asphalt pavement performance over its service life. However, past research studies show that the parameters of Burger's model should be back-calculated from experimental data only within a limited range of frequency, otherwise, the parameters fail to represent the true material behavior. To the best of the authors’ knowledge, there is no approach for researchers to obtain the critical frequency range in which the experiments should be performed. Therefore, this study proposes a novel framework to find the critical frequency range to obtain appropriate model parameters of Burger's model, to better characterize the viscoelastic behavior of the materials. To examine the framework, asphalt concrete mixtures are used as examples in this study. Necessary laboratory tests including complex modulus tests and stress relaxation tests, are performed on two distinctive types of asphalt concrete mixtures. The generalized Maxwell model with different number of Maxwell chains are used to evaluate the performance of Burger's model. Furthermore, since commercially available finite element packages generally do not have a direct built-in Burger's model, the article shows a way of implementing Burger's model in finite element simulation. The simulations corresponding to the laboratory tests are carried out in both frequency domain and time domain to thoroughly evaluate the performance of Burger's model. The optimal frequency range of 0.1-20 Hz for the examined mixtures is found to significantly improve the accuracy of the descriptive master curve. The results also suggest that the generalized Maxwell model requires a minimum of four Maxwell chains to maintain good performance in accurately characterizing the behavior of asphalt mixtures. However, adding more Maxwell chains beyond a critical limit may not provide significant benefits. Finite element simulations demonstrate that the stress relaxation behavior predicted by the obtained Burger's model parameters aligns more closely with experimental data over longer time intervals. This makes Burger's model a strong choice for aiding in the design of simulations for studies focused on the long-term behavior of materials.

Design and study of a novel rotary high-impact test device

Abstract Impact testing is an important means of evaluating an object’s ability to withstand impacts at specific peak accelerations. Currently, commonly used high-g impact testing devices, such as the Mach hammer and air cannon test devices, generally provide overloads ranging from 10, 000g to 30, 000 g, with a maximum of 50, 000 g. To meet the demand for high-overload impact collisions, this paper designs and studies a high-g long pulse width rotary impact test device with a detachable impact head. A finite element simulation model of the impact process was established by using finite element analysis software, and the dynamic response of the device was studied by changing the initial rotation speed and the target plate material. The results show that the overload of this rotary impact test device can reach more than 70, 000 g, and increasing the speed and hardness of the target plate material can improve the overload magnitude. This device and research method can provide theoretical support for high-overload impact testing.

Study on the Mechanical Behavior of Top-Chord-Free Vierendeel-Truss Composite Slabs

A top-chord-free Vierendeel-truss composite slab (TVCS) comprises a concrete slab, several vertical webs, and a steel bottom chord. In this study, static tests and finite element analyses were conducted based on an actual project to investigate the deformation, crack characteristics, ultimate bearing capacity, and failure mode of the composite slab. The findings indicated that the loading process of this type of floor can be divided into elastic, elastoplastic, and failure stages. The section stress distribution in the elastic stage was further analyzed. The crack development pattern exhibited a fine density in the pure bending sections of the concrete slabs, while demonstrating good overall flexural bearing capacity and ductility for the composite slab. Experimental results were compared with the ANSYS finite element model simulation to validate the accuracy of the simulation. Parametric analysis was conducted to assess the impact of concrete strength, steel strength, vertical web width, and distance ratios on the mechanical characteristics of the composite slab. By introducing an adjustment coefficient for the vertical web distance ratio, a revised calculation formula for flexural bearing capacity was proposed, which aligned well with the finite element analysis.

Heat transfer and electromagnetic property investigation on the hot air quartz fiber/PTFE capillary/epoxy resin anti/de‐icing composites

AbstractTo achieve the wave‐transparent and anti/de‐icing requirements of electromagnetic functional structural components on the windward surface of the aircraft, the PTFE capillary hot air tubes were pre‐buried inside the quartz fiber cloth and the hot air anti/de‐icing quartz fiber/PTFE capillary/epoxy resin (QF/PTFE/EP) composite components was prepared to that met the wave‐transparent performance. A multi‐field coupled numerical finite element simulation model was established, and the anti/de‐icing performance of the QF/PTFE/EP composite with different built‐in tube diameters were investigated by combining experiments and simulations under different hot air temperatures and pressures. The feasibility of hot air anti/de‐icing was verified through anti/de‐icing experiments and numerical simulation. The electromagnetic transmittance of the prepared hot air anti/de‐icing QF/PTFE/EP composite components was tested to characterize the effect on the stealth performance of the aircraft under the service environment. The experimental results demonstrated that with 5 mm tube pitch and hot air of 60°C ± 1°C, the surface temperature of the component with three tube diameters could reach more than 10°C. Furthermore, the decrease in the transmittance of the hot air anti/de‐icing QF/PTFE/EP composite components caused by different incidence angles and two polarization modes was less than 3%.Highlights The hot air QF/PTFE/EP anti/de‐icing composite components were fabricated. The heat transfer, anti/de‐icing, and electromagnetic transmittance performance of the hot air QF/PTFE/EP anti/de‐icing QF/PTFE/EP components were investigated. The experimental and simulation results verified the hot air anti/de‐icing QF/PTFE/EP components met the requirement of aircraft anti/de‐icing and wave transmission.

Surrogated modelling for structural reliability and safety assessments of high-strength concrete beams with industrial and recycled steel fibers

As a secondary material recycled from tyres, Recycled Steel Fibre Reinforced Concrete (RSF) aims to replace industrial steel fibres (ISF) to improve concrete matrix‘s severability, fracture toughness, and residual tensile stress. Despite the increasing attention on the mechanical properties of this material, RSF concrete’s influence on structural component strength is still neglected due to a lack of sufficient and reliable experimental data. This study looks into existing Crack mouth opening displacement (CMOD) experiment results of both types of steel fibre reinforced concrete beams together with nonlinear finite element model (FEM) simulations using the RILEM TC 162-TDF crack damage model(CDP) proposed for ISF in ABAQUS. Meanwhile, an additional parameter analysis of the experimental data related to shear capacity also examines the shear span ratio, fibre content, and fibre type of the two types of fibre reinforced concrete beams. Moreover, Kriging surrogate models (KSM) and Sobol global sensitivity analysis have been conducted. For the reference concrete beams with a fibre content of 0.4 %, the prediction accuracy ratios of ultimate strength, corresponding displacement, and stiffness between the FEM and the experiment results are 98 %, 88 %, and 100 %, respectively. This paper has been proved that the CMOD-based CDP model effectively elucidates the shear contribution of different steel fibres, which can be used in structural analysis of ISF or RSF concrete for structure components. Utilizing FEMs, a series of modified flexural strength prediction formulas based on TR63 standards are proposed to enhance structural applications with ISF and RSF. Moreover, the prediction ability of the proposed formulas is validated using the results of 183 real flexural capacity experiments of ISF reinforced concrete beams, achieving an improved R² value of 0.97.

Smart composite structural insulated panels (CSIPs) with embedded piezoelectric sensors for damage localization

Coastal communities face increasing vulnerability to natural disasters, necessitating resilient construction solutions. This study presents the development of smart composite structural insulated panels (CSIPs) embedded with piezoelectric sensors for damage localization in hurricane and tornado-prone areas. Experimental studies, such as four-point bending and in-panel compression tests, were conducted to analyse the shock response and failure modes of these smart CSIPs. Material characterization informs the development of finite element models for simulation, enhancing structural design. By integrating structural health monitoring capabilities, these smart CSIPs enable continuous tracking of their response to environmental factors, improving longevity and durability. Shock identification and localization in smart CSIPs are successfully demonstrated through numerical simulations and experimental validation, showcasing the potential step towards self-resilient structures in coastal regions. This novel approach provides real-time information on structural integrity, paving the way for improved safety and predictive maintenance of buildings and infrastructure utilizing CSIPs.

Seismic evaluation of steel beam-column connection equipped by circular slit dampers

AbstractThis study evaluates metallic yield dampers, specifically slit steel dampers, for protecting steel beam-to-column connections during seismic events. Finite element model simulations were conducted for the damper and its connection. Analysis of circular parameters, like the radius slot, showed that appropriately sized slit dampers exhibit advantageous seismic behavior. Moment-rotation, hysteresis curves, and plastic stresses comparisons indicate efficient energy absorption. The maximum moment was 25% lower than conventional samples. The slit steel damper model with a ductility factor of 3.5 allows significant plastic deformation before potential failure. Results emphasize the slit damper's potential for optimal performance in steel frames, suggesting its use for efficient energy absorption.

Simulation and experimental thermal analysis of ultrasonic vibration-assisted high-efficiency deep grinding of γ-TiAl blade tenon

Gamma titanium-aluminum intermetallic compounds (γ-TiAl) have attracted considerable attention in the aerospace industry because of their outstanding thermal stability and broad range of properties. To analyze the grinding temperature during high-efficiency deep grinding (HEDG) and ultrasonic vibration-assisted high-efficiency deep grinding (UVHEDG) of γ-TiAl materials, both an analytical thermal model and a finite element simulation model were developed. Subsequent comparison trials between HEDG and UVHEDG were conducted to validate the accuracy of the simulation. The results show that the final prediction error can be effectively maintained within 15 %, and the temperature measurement curve fits well when an ultrasonic heat influence factor is incorporated into the 3D finite element model. The introduction of ultrasonic vibrations into the HEDG reduced the maximum grinding temperature by 39.1 %, effectively preventing grinding burns. The highest temperature consistently occurred in the top zone of the blade tenon tooth due to different heat conduction paths caused by the complex profile. This led to a 32.4 % and 31.9 % reduction in the grinding temperature in the bottom zone under HEDG and UVHEDG, respectively. The surface roughness of the machined blade tenon tooth reached 0.664 μm at the top and 0.721 μm at the bottom under UVHEDG, whereas it was 0.735 μm and 0.843 μm under HEDG.

A frequency-domain finite element model for simulating high temperature superconductors using the J-A and T-A formulations

Abstract The AC losses, the current density and the magnetic field are important variables to design devices made of High Temperature Superconductors (HTS). These variables are often numerically computed using a transient finite element analysis even though the interest may lay in the steady-state regime of the device. The need for solving time-dependent variables has led to improve the computation time with efficient finite element models (FEM) relying on different formulations. These transient FEM are computationally slow and demanding in terms of resources. In the present work, an alternative path is taken with the development of a frequency-domain FEM using a phasor representation to alleviate the computation burden. This model does not have the versatility of the transient models. However, it can generate the initial steady-state conditions for a subsequent transient analysis. It is perfectly adapted to study the steady-state regime of HTS devices operated in AC conditions. In this phasor modelling approach, the Root Mean Square (RMS) resistivity of the superconductor is introduced. It is subsequently approximated by an exponential function introducing a factor to ease its implementation in the commercial software COMSOL Multiphysics with the most recent and fastest formulations T-A and J-A. The case studies encompass single BSCCO and REBCO tapes as well as a CORC cable or specifically, in the present work, a CORT (Conductor on Round Tube). The results of the time- and frequency-domain FEM simulations are compared against experimental data. The comparison of the models' results is carried out comparing the current density distributions as well as the AC losses. The comparison against experimental data is only conducted on the AC losses. In the present case, it is used to quantify thoroughly the accuracy of the numerical results compared to the measurements. A reasonable agreement between those results and the experimental data was found. 

Design optimization of a phase-change capacitive sensor for irreversible temperature threshold monitoring and its eco-friendly and wireless implementation

Monitoring the temperature of perishable goods during transport and storage is essential to prevent waste and maintain product quality. Exploiting the unique property of phase-change materials (PCM), altering their physical state at specific temperatures, we optimize a capacitive sensor design based on a copper on polyimide interdigitated spiral (IDE) structure coated with a PCM to irreversibly detect temperature thresholds. The effect of the sensor dimensioning on its response is analyzed using a finite element model simulation. The model predicted up to 51% capacitance variation for optimal coverage of the PCM after spreading over the IDE, which was validated experimentally within a 5% error. Two melting concepts utilizing the spreading or the removal of the melted PCM over the IDE are investigated based on a capillary retention mechanism to maintain sensor sensitivity under inclination. Finally, an eco-friendly implementation of the capacitive structure and its wireless operation at 460 MHz is demonstrated on paper with a printed zinc transducer passivated with beeswax and covered with jojoba oil. Melting of the oil at a threshold temperature of 12.3 °C resulted in an irreversible shift in resonance frequency of 14 MHz. This study provides guidelines for the design and implementation of irreversible temperature monitoring capacitive sensors.

Study on the sealing performance of 105MPa conical core BOP in the fully sealed state

Achieving full sealing is a technical challenge in the simulation, manufacturing, and experimentation of annular anti-spray seals. Based on Yeoh rubber constitutive model and large deformation theory, the finite element simulation model of 105 MPa annular blowout prev conical core seal was established, the stress distribution and contact pressure law of the core under different working pressures and full sealing conditions were analyzed, the full sealing state simulation of 105 MPa annular blowout prev core was realized, and the sealing performance of the core was evaluated. The results show that the conical core can meet the sealing requirements at 105 MPa. The high stress of the conical rubber core of 323 MPa appears at the joint of the inner wall of the rubber core and the back of the support bar and the joint of the upper and lower convex of the support bar. The high stress of 892 MPa appeared in the neck and back of the upper plate and the rear area of the lower plate. When the piston operating pressure is constant, with the increase of the working pressure, the overall stress of the rubber core increases, which is easy to cause the fatigue failure of the rubber core.

Performance Evaluation of a Bioinspired Geomagnetic Sensor and Its Application for Geomagnetic Navigation in Simulated Environment.

For geomagnetic navigation technology, taking inspiration from nature and leveraging the principle of animals' utilization of the geomagnetic field for long-distance navigation, and employing biomimetic technology to develop higher-precision geomagnetic sensors and more advanced navigation strategies, has emerged as a new trend. Based on the two widely acknowledged biological magnetic induction mechanisms, we have designed a bioinspired weak magnetic vector (BWMV) sensor and integrated it with neural networks to achieve geomagnetic matching navigation. In this paper, we assess the performance of the BWMV sensor through finite element model simulation. The result validates its high measurement accuracy and outstanding adaptability to installation errors with the assistance of specially trained neural networks. Furthermore, we have enhanced the bioinspired geomagnetic navigation algorithm and proposed a more advanced search strategy to adapt to navigation under the condition of no prior geomagnetic map. A simulated geomagnetic navigation platform was constructed based on the finite element model to simulate the navigation of the BWMV sensor in geomagnetic environments. The simulated navigation experiment verified that the proposed search strategy applied to the BWMV sensor can achieve high-precision navigation. This study proposes a novel approach for the research of bioinspired geomagnetic navigation technology, which holds great development prospects.

Experimental study on the acoustic properties of monofilament fabrics

The traditional machining perforated sound absorption structure has high processing cost and inconvenient installation and disassembly, so that how to efficiently and economically manufacture submillimeter micropores still remains a challenge. In this study, a kind of flexible microporous sound absorbing material was obtained by weaving a polymer artificial fiber covered with ethylene polyester fiber, and the relationship between the sound absorption performance of the curtain and the porosity of the pass and fabric was obtained through the finite element simulation model and impedance tube experiment. The mechanism parameters of wide-band flexible microporous material with high sound absorption performance are obtained, which guide the design of a kind of sound absorption material with lower production cost and easy installation and disassembly.

Integrated detection for open and closed surface fatigue cracks utilizing scanning laser source-induced Rayleigh wave fields with self-reference peak-to-peak features

In this study, the integrated detection method for open and closed surface fatigue cracks is investigated. Firstly, the finite element simulation models are established to investigate the interaction between scanning laser source-induced Rayleigh waves and open and closed surface fatigue cracks, and the laser ultrasonic detection experiments are conducted for fatigue specimens containing fatigue cracks in different states. The simulation and experimental results indicate that the variation patterns in the peak-to-peak values of Rayleigh waves with horizontal scanning positions for open and closed cracks exhibit both similarities and differences. Subsequently, an integrated detection method based on self-referenced peak-to-peak features is proposed, which utilizes the similarities and differences to detect and distinguish open and closed cracks, respectively. Furthermore, this proposed method is experimentally validated, indicating that it can achieve accurate integrated imaging of open and closed cracks that have a high degree of agreement with the SEM images of the cracks. Additionally, the proposed method achieves a detection error of 2 % for the vertical lengths of the fatigue cracks. This study can provide guidance for integrated real-time detection of open and closed surface fatigue cracks of mechanical components in service.

Finite Element Simulations of Effective Stimulated Volume in Rat Brain Optoelectronic Stimulation

Abstract This study presents a finite element model (FEM) simulation of optoelectronic stimulation in the rat brain, designed to investigate the effects of this emerging neural stimulation technique. A detailed 3D model of the rat brain and an equivalent circuit representation of the organic semiconductor-based stimulation device was used to simulate the subdural application of optoelectronic stimuli to the rat brain. The model is based on realistic electrode geometries and material properties. The stimulated brain volume is approximately 38 mm3 with a maximal stimulation depth of 2.6 mm. Our results indicate that optoelectronic stimulation can achieve targeted activation of cortical neurons. Further studies will focus on optimizing device parameters, exploring long-term effects, and expand this approach for specific neural bioelectronics to fully exploit its potential in clinical applications.

Finite Element Model Calibration with Surrogate Model-Based Bayesian Updating: A Case Study of Motor FEM Model

This paper introduces an advanced methodology for the calibration of Finite Element Models (FEM) utilizing a surrogate model-based Bayesian updating framework. The approach is exemplified through a case study on motor design, where precise FEM calibration is essential for predicting and optimizing motor performance. Traditional calibration techniques are often computationally expensive due to the iterative nature of the simulation process. To mitigate this, the proposed method integrates surrogate models to approximate FEM simulations, significantly reducing the computational burden without sacrificing accuracy. Bayesian updating is then employed to iteratively refine the surrogate model by incorporating new data, thereby enhancing prediction accuracy. This dual approach not only accelerates the calibration process but also ensures a high level of precision, making it highly suitable for complex engineering applications requiring both efficiency and reliability. The case study underscores the effectiveness of this methodology, demonstrating its potential to streamline the design process in motor development and other FEM-dependent engineering fields. The findings suggest that the surrogate model-based Bayesian updating approach achieves robust calibration with significantly fewer simulations, thereby optimizing both time and computational resources.

Numerical and machine learning models for concentrically and eccentrically loaded CFST columns confined with FRP wraps

AbstractPrevious research largely concentrated on predicting load‐carrying capacities of concrete‐filled steel tubes (CFST) confined with fiber‐reinforced polymer (FRP) wraps under pure concentric loads, neglecting the more complex failure mechanisms that occur under real‐life eccentric loading conditions. This study, therefore, employs both finite element modeling (FEM) and machine learning methods to accurately predict the load‐bearing capacities under both concentric and eccentric loading conditions. This research analyzed a comprehensive dataset comprising 128 experimental tests and an equivalent number of FEM simulations designed to evaluate their eccentric performance. These models have been thoroughly generated and validated against existing literature. Additionally, the developed ML models, particularly a hybrid deep learning model, demonstrated significant predictive accuracy, with an average R2 value of 0.969 across all model folds. Partial dependence analysis further highlighted the significant influence of concrete strength and the interactive effects of steel tube area and FRP wrap thickness on the load‐carrying capacity of the columns. Furthermore, to enhance cost‐efficiency and resource management compared with traditional laboratory testing, a user‐friendly graphical user interface (GUI) has been developed and hosted on an open‐source platform such as GitHub. This interface supports real‐time, precise predictive capabilities and promotes a collaborative environment for ongoing model refinement and improvement.

Optimization of Clamping and Conveying Parameters for Spinach Orderly Harvesting with Low Damage by Simulation and Experiment

The leaves of spinach are delicate and easily injured during harvesting. To reduce the spinach damage rate and increase the conveyance success rate, an orderly harvester was designed and manufactured, and the key conveying parameters of the harvester were optimized by simulation and experiments. The compression damage stress of spinach was determined by compression tests. Then, a finite element simulation model for spinach clamping was established, and the influence of different clamping heights on the spinach deformation and equivalent stress were simulated and analyzed. Finally, response surface Box–Behnken experiments were conducted to optimize the combinations of the twisting angle, clamping distance, and height difference. The results of the compression tests showed that the compression damage stresses of spinach leaves, stems, and their connection points were 8.04 × 10−2 MPa, 7.85 × 10−2 MPa, and 11.63 × 10−2 MPa, respectively. The optimal clamping height of spinach for orderly conveyance was obtained to be 20 mm according to the finite element simulation. The response surface experimental results indicated that the significance order of factors affecting the extrusion force was the clamping distance, the height difference, and the twisting angle. The significance order of factors affecting the conveyance success rate was the clamping distance, the twisting angle, and the height difference. The optimal parameter combination was ae twisting angle of 60°, clamping distance of 24 mm, and a height difference of 20 cm. The experimental validation of the optimization results from the finite element simulation and response surface tests demonstrated that the extrusion force and conveyance success rate were 2.37 N and 94%, respectively, with a conveying damage rate of 3% for spinach, meeting the requirements for the low-damage and orderly harvesting of spinach.