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The all-vanadium flow battery (VFB) is a promising candidate for long-duration energy storage. Flow field design is deemed as a critical approach to realize high power density operation for VFBs. However, conventional graphite bipolar plates still face mechanical limitations for practical stack uses, so there is an urgent need to explore alternative design strategies. Herein, a carbon paper based serpentine flow field (SFF) design is proposed for high power density VFB operation, which simultaneously reduces pressure drop and concentration polarization. Finite element analyses firstly compare different SFF designs and reveal effectively reduced pressure drop and promoted flow velocity across the electrode for 100 % SFF design. Subsequently, the 100 % SFF design presents significantly reduced concentration polarization at 200 mA cm−2 and 85 % SOC, which outperforms non-flow field and other SFF designs. Moreover, the full cell experiments demonstrate an enhanced voltage efficiency of 83.6 % at 200 mA cm−2 along with higher discharge capacity. By further coupling 100 % SFF with Bi catalyst, the VFB cell finally proves to deliver a 79 % voltage efficiency at 300 mA cm−2 and stably operate over 1000 cycles, which highlights the great potential of proposed design strategy to realize high power density VFB operations. • A carbon paper based flow field design strategy is proposed for VFBs. • Simulation results present reduced pressure drop and concentration polarization. • The flow cell with 100 % SFF delivers a voltage efficiency of 83.6 % at 200 mA cm−2. • Long-term cycling stability over 1000 cycles is realized by proposed design. [ABSTRACT FROM AUTHOR]

As a basic mechanical component, the sealing ring is widely used in industrial, aerospatial, and other fields. In this study, an elastic metal C-shaped sealing ring with a wave structure was taken as an example, and its performance was analyzed theoretically and measured experimentally. First, an experimental study was performed on the C-ring seal. The proposed method for experimental measurement of the contact stress of the C-ring seal involved innovative use of a universal electronic testing machine and pressure sensitive paper, in conjunction with the hue⁻saturation⁻brightness (HSB) method. Based on the discoloration of the pressure sensitive paper after contact stress, computer software was used for analysis, the discoloration was digitized, and the contact stress was established. Second, a theoretical calculation model of the C-ring seal was established using ANSYS software, and a finite element theoretical calculation of the mechanical properties of the sealing ring was established. Finally, the contact stress results were compared with the model calculation results of the C-ring seal. The error between the two was small (4.8%), which proved the validity of the calculation model and the scientificity of the experimental method.

The insulation status of oil-impregnated paper (OIP) bushings directly indicates their operational condition. Damp defects constitute the primary factor contributing to the deterioration of oil-paper insulation. In this paper, the overall moisture distribution of capacitor cores with three damp defects (steady-state, transient, anzd tail moisture damp defect) and its effect on the electric field were studied. A moisture diffusion model for OIP bushing was established based on Finite Element Method (FEM) software, and it was also verified by moisture diffusion experiments. Then, the overall moisture distribution of the capacitor core under three damp defects was investigated. The findings indicate significant variation in the overall moisture distribution of the capacitor core influenced by factors such as aluminum foil and temperature. Furthermore, the relative permittivity of the oilimpregnated paper was computed. Subsequently, the impact of various moisture-induced defects on the electric field was determined. Simulation results unveiled distortion in the electric field of each electrode within the capacitor core. Specifically, the electric field of the zero electrode increased, while that of the outermost electrode decreased in all three damp defect scenarios. The conclusions drawn can thus be used for intelligent operation and condition assessment of OIP bushings. [ABSTRACT FROM AUTHOR]

The disc-cutter is a finishing tool for the ultrasonic-cutting of paper honeycomb-core material. The cutting state directly affects the machining accuracy and surface quality of the workpiece. The cutting force is an important physical quantity and the cause of ultrasonic cutting defects of the honeycomb-core material. Due to differences in the mechanical properties and cutting performance of honeycomb-core materials and commonly used metal materials, existing metal-cutting-force models cannot be applied to the calculation of ultrasonic cutting forces in the processing of honeycomb-core materials. In response to this problem—combined with actual working conditions using the ABAQUS finite element analysis software—a finite element simulation model of the ultrasonic vibration-assisted cutting force of the disc-cutter on the honeycomb-core material was established, and the cutting curves and values were obtained. The experiment of ultrasonic vibration cutting of the disc-cutter proves that from the surface morphology of the honeycomb core, the milling-width has the greatest influence on the cutting force, and the cutting-depth has the smallest influence on the cutting force. The maximum error between the cutting force experimental results and the finite element simulation results under the same cutting conditions was 13.2%, which means that the established cutting-force finite element model is more accurate and can be used to predict the cutting in honeycomb ultrasonic vibration-assisted cutting-force value. Finally, based on the response surface method, a three-dimensional cutting force prediction model of the ultrasonic cutting honeycomb core of the disc-cutter was established by using the simulation model data. The results of this study can provide a useful basis for the improvement of cutting performance and processing efficiency in the processing of paper honeycomb-core materials.

Purpose : Finite element analysis is frequently used for lumbar spine biomechanical analysis. The primary scope of this work is to illustrate, using finite element analysis, how the biomechanical behavior of the transforaminal lumbar interbody fusion (TLIF), along with a novel combination of the interspinous process device (IPD) and pedicle screws, improves lumbar spine stability. Methods : In this study, unilateral pedicle screw fixation (UPSF) and bilateral pedicle screw fixation (BPSF) were used. Four FE models were developed using ANSYS software, as follows: (1) Intact model; (2) TLIF with "U"-shaped Coflex-F IPD (UCF); (3) TLIF with Coflex-F and UPSF (UCF + UPSF); (4) TLIF with Coflex-F and BPSF (UCF + BPSF). The intact model was subjected to four pure moments (10 Nm), and the results were validated with previous literature data. The intact model results correlated well with the literature data, and the model was validated. Three surgical models were subjected to 7.5 Nm four pure moments, flexion (FL), extension (ET), lateral bending (LB), and axial rotation (AR) and a 280N follower load. Results : The surgical model results were compared with the intact model. The comprehensive analysis results show the UCF + BPSF surgical model gave a good advantage on range of motion, cage stress, Coflex-F stress and endplate stress compared among the two models. Conclusion : This study proposes that the UCF + BPSF system helps to reduce the stress on the implant and adjacent endplates and gives very good stability to the lumbar spine under the various static loading conditions., (© 2023 S. Meganathan et al., published by Sciendo.)

The converter transformer epoxy impregnated paper bushing is a multi-media electrical equipment, and the main materials include the internal conductor, the external conductor, transformer oil, SF6 gas, the air inside internal conductor, the main insulation material epoxy impregnated paper, sheath, and fittings. In actual operating, the converter transformer bushing is undertaken by the harmonic current with large number of high harmonics and the temperature distribution of the epoxy impregnated paper converter transformer bushings under actual current waveform needs to be researched. What's more, the temperature distribution of the epoxy impregnated paper converter transformer bushings is affected by several factors and to provide basis for the optimization of bushings it's necessary to research about the impact of these factors on the temperature distribution of the epoxy impregnated paper converter transformer bushings. In this paper, on the basis of our previous paper [8], the 3-D temperature distribution of the 400 kV epoxy impregnated paper converter transformer bushing under actual current waveform with large number of harmonics has been simulated by using the computational fluid dynamics (CFD) and finite element method (FEM) analysis. The temperature distribution regularity of the 400 kV converter transformer bushing under different influencing factors has been computed and analyzed. The dissipation structure of the bushing has been optimized and the DC steady-state electric field distribution of the 400 kV converter transformer bushing has been obtained considering the temperature gradient in epoxy impregnated paper. [ABSTRACT FROM PUBLISHER]

The influence of nonuniform aging has not been considered in the prediction of the frequency domain spectroscopy (FDS) of the transformer oil-paper insulation (OPI) when using the finite element method (FEM). Given this issue, the modified simulation model was constructed based on the XY model and FEM. In the current work, the dielectric response property of the pressboards with different aging conditions in the modified model was characterized by its dielectric response parameters measured in the lab. Then the modified simulation model constructed in a 3-D system would be applied to study the effect of both nonuniform aging and the axial geometry on the FDS of OPI. Finally, the feasibility of the proposed models was verified by comparing the measured FDS and the predicted FDS. This article is expected to provide a model for predicting the FDS of the transformer OPI including the effect of nonuniform aging. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the beneficial reuse of paper mill sludge as landfill cover and bottom liner material in municipal solid waste landfills. For this purpose, two-dimensional finite element analyses of a typical landfill geometry were carried out using PLAXIS finite element program. The results of the analyses were evaluated in terms of displacement and factor of safety (FS) values, and compared with those of the compacted clay. The results of this study showed that, vertical and lateral displacements of the landfill slightly increased while the FS of the landfill slopes decreased with increasing surface loading. However, for all the cases studied, lower vertical and lateral displacements and higher FS values were obtained for the landfills with paper mill sludge as the cover and bottom liner material in comparison to those of the compacted clay. Besides, for all the cases studied, FS values greater than 1.5 were obtained, indicating that the landfill slopes were stable under the proposed loadings and landfill cover and bottom liner materials. Based on these results, it can be stated that the paper mill sludge examined in this paper has geotechnical properties that are desirable for a landfill cover and bottom liner material for use as a substitute of compacted clay in municipal solid waste landfills. [ABSTRACT FROM AUTHOR]

Computational models of the brain have become the gold standard in biomechanics to understand, predict, and mitigate traumatic brain injuries. Many models have been created and evaluated with limited experimental data and without accounting for subject-specific morphometry of the specimens in the dataset. Recent advancements in the measurement of brain motion using sonomicrometry allow for a comprehensive evaluation of brain model biofidelity using a high-rate, rotational brain motion dataset. In this study, four methods were used to determine the best technique to compare nodal displacement to experimental brain motion, including a new morphing method to match subject-specific inner skull geometry. Three finite element brain models were evaluated in this study: the isotropic GHBMC and SIMon models, as well as an anisotropic model with explicitly embedded axons (UVA-EAM). Using a weighted cross-correlation score (between 0 and 1), the anisotropic model yielded the highest average scores across specimens and loading conditions ranging from 0.53 to 0.63, followed by the isotropic GHBMC with average scores ranging from 0.46 to 0.58, and then the SIMon model with average scores ranging from 0.36 to 0.51. The choice of comparison method did not significantly affect the cross-correlation score, and differences of global strain up to 0.1 were found for the morphed geometry relative to baseline models. The morphed or scaled geometry is recommended when evaluating computational brain models to capture the subject-specific skull geometry of the experimental specimens., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The corrugated compensators are important components in the piping system, absorbing mechanical deformation flexibly. To reduce the risk of the piping system with corrugated compensators and improve the safety and stability of industrial equipment, condition monitoring and fault diagnosis of bellows is necessary. However, the stress monitoring method of corrugated compensators with limited localized sensors lack real-time and full-domain sensing. Therefore, this paper proposes a digital twin construction method for global mechanical response sensing of corrugated compensators, combining Gaussian process regression in machine learning and finite element analysis. The sensing data of three types of displacements are used as the associated information of a finite element model with 19,800 elements and its digital twin. The results show that the values of performance metrics correlation of determination R2 and standardized average leave-one-out cross-validation CVavg of the digital twin satisfy the recommended threshold, which indicates that the digital twin has excellent predictive performance. The single prediction time of the digital twin is 0.76% of the time spent on finite element analysis, and the prediction result has good consistency with the true response under dynamic input, indicating that the digital twin can achieve fast and accurate stress field prediction. The important state information hidden in the multi-source data obtained by limited sensors is effectively mined to achieve the real-time prediction of the stress field. This paper provides a new approach for intelligent sensing and feedback of corrugated compensators in the piping system. [ABSTRACT FROM AUTHOR]