Numerical Finite Element Method Research Articles

Application of machine learning for film thickness prediction in elliptical EHL contact with varying entrainment angle

This contribution demonstrates the potential of machine learning (ML) algorithms in predicting elastohydrodynamic lubrication (EHL) film thickness in elliptical contact with varying direction of lubricant entrainment, ranging from wide to slender elliptical configurations. The input parameters pertain to worm gear contacts, which are characterized by slender-like elliptical contact between a steel and a soft metal component. The study encompasses generating a database using numerical Finite Element Method (FEM) simulations, training artificial neural network (ANN) models, and evaluating their performance in terms of bias and variance. Key outcomes include the successful training of the ANN models, detailed analysis of the impact of tailored architecture on the ANN models' performance, and the superiority of the ANN compared to other ML regression algorithms. The study further identifies key input parameters that influence prediction accuracy and introduces a strategic dataset augmentation procedure to increase local and overall prediction accuracy. This strategic dataset augmentation enhances model robustness and precision while providing insights for expanding databases collaboratively. It holds potential for broader applications of ML for performance prediction of tribological contacts, thus paving the way for advanced ML models that consider additional factors and collaborative databases refined by multiple research groups.

Microwave Ablation Therapy for Hepatocellular Carcinoma: The Effect of Metabolic Heat on Temperature Distribution

Hepatocellular carcinoma is the main cause of liver cancer and one of the most occurring cancers worldwide. Microwave Ablation (MWA) is a method to destroy cancer cells by heating tumors above 50°C. Cancerous tissues can have high metabolic heat rates and affect temperature gain and distribution in thermal therapies. This research clarifies the metabolic heat effects in MWA therapy of liver cancer. Using Pennes Bioheat transfer equation with finite element numerical method, this research simulates temperature distribution with metabolic heat value ranging from 368,1 W/m3 to 29000 W/m3. The heat generated by metabolic heat is lower than the MWA heat source. However, the temperature increase should be considered as it can increase healthy surrounding tissue temperature to dangerous levels.

Analytical Solution of the Two-Dimensional Steady-State Seepage Field of a Seepage Anisotropy Pit Considering the Free Surface

An anisotropic foundation pit steady-state seepage field under a suspended waterproof curtain support considering the position of the free surface is studied analytically, and an analytical solution for the free surface position is given. The head distribution in the three zones is expressed as a series solution using the separation of variables method, and the explicit solution for the extent of the seepage field in each zone is obtained by combining the continuity condition between zones and the series orthogonality condition. The free surface position is determined according to the condition that the total head of the free surface is equal to the position head. A comparison of the calculation results of the analytical method and the indoor test and finite element analysis results verifies the correctness of the analytical solution, and the analytical method has more calculation efficiency than the finite element numerical method. Employing the aforementioned methods to analyze the influence parameters of the free surface position, the results show that drawdown increases as the ratio of the vertical permeability coefficient to the horizontal permeability coefficient increases; the greater the ratio of pit width to depth, the more significant the drawdown, but when the ratio continues to exceed 1.5, the drawdown is negligible.

НЕЛИНЕЙНАЯ ДЕФОРМАЦИОННАЯ МОДЕЛЬ СП 63.13330 В СТАДИЙНОЙ ПОСТАНОВКЕ

Normative documents in the field of reinforcement of reinforced concrete structures and the design of prefabricated monolithic structures fairly prescribe consideration of the initial stressstrain state of structures before reinforcement. The calculation can be performed using a normalized nonlinear deformed model according to SP 63.13330. At the same time, it does not explicitly provide for a calculation in several stages. The aim of the study is to develop a calculation method based on a normalized nonlinear deformation model in a staged formulation with minimal differences from the provisions of SP 63.13330. To achieve the goal, the following tasks are set: development of a calculation method, implementation of the method in the form of a universal program and verification of the developed program. The article presents a universal nonlinear deformation model in a staged formulation, which allows, within the framework of certain ratios, to calculate the strength and crack resistance of structural sections at an unlimited number of work stages, taking into account reinforcement, prestressing, initial stresses and cyclic loading (unloading and reloading). The method is implemented as a program in the Python programming language and verified on full-scale and numerical (finite element method) experiments. If we assume the initial stresses and deformations to be zero and calculate in one stage, then the proposed model is reduced to the SP 63.13330 model. For this reason, changing the norms according to the proposed method will not affect the current algorithms for calculating structures in one stage, however, it will significantly increase the scope of the model for calculating prefabricated monolithic, steel-reinforced concrete and reinforced structures. In addition, the accuracy of calculations of prestressed structures will increase, and it will be possible to calculate the cyclic loading of the section.

The thermal conductivity properties of porous materials based on TPMS

In this study, the effective thermal conductivity of materials based on a porous TPMS structure is investigated. The resulting structure is similar to a matrix and consists of identical pore cells that are strictly periodic in all directions. These pores have several characteristic sizes, and by altering them, materials with predictable effective thermal conductivity can be created. This work investigated materials based on Triply Periodic Minimal Surface (TPMS) of Schwarz P, Schoen IWP and Neovius. The calculation of thermophysical properties was performed using the numerical finite element method in the Ansys software package. Heat transfer in the structures was studied both with and without considering air. The empirical coefficient “n” for the Aivazov–Domashnev formula is expressed analytically. This relationship allows for the creation of materials with predictable thermophysical properties, taking into account the thermal conductivity of non-porous materials. The results of numerical modeling are validated by analytical Austin’s models and experimental data. The samples for the experimental study were made using additive technologies from PETG, ABS, PLA plastic and photopolymer resin. The study has scientific and applied significance, since a method is proposed for predicting the thermal conductivity of materials with an ordered structure. Several solid-state samples of elementary cells were made publicly available for designing materials with predictable thermal conductivity. The novelty of the work lies in obtaining the dependence of effective thermal conductivity on the geometric parameters of the ordered structure for materials with thermal conductivity in a wide range from 0.12 to 400 W/(m°C).

Fatigue Life Data Fusion Method of Different Stress Ratios Based on Strain Energy Density.

To accurately evaluate the probabilistic characteristics of the fatigue properties of materials with small sample data under different stress ratios, a data fusion method for torsional fatigue life under different stress ratios is proposed based on the energy method. A finite element numerical modeling method is used to calculate the fatigue strain energy density during fatigue damage. Torsional fatigue tests under different stresses and stress ratios are carried out to obtain a database for research. Based on the test data, the Wt-Nf curves under a single stress ratio and different stress ratios are calculated. The reliability of the models is illustrated by the scatter band diagram. More than 85% of points are within ±2 scatter bands, indicating that the fatigue life under different stress ratios can be represented by the same Wt-Nf curve. Furthermore, P-Wt-Nf prediction models are established to consider the probability characteristics. According to the homogeneity of the Wt-Nf model under different stress ratios, we can fuse the fatigue life data under different stress ratios and different strain energy densities. This data fusion method can expand the small sample test data and reduce the dispersion of the test data between different stress ratios. Compared with the pre-fusion data, the standard deviations of the post-fusion data are reduced by a maximum of 21.5% for the smooth specimens and 38.5% for the notched specimens. And more accurate P-Wt-Nf curves can be obtained to respond to the probabilistic properties of the data.

Influence of Subsoil and Building Material Properties on Mine-Induced Soil–Structure Interaction Effect

Soil–structure interaction (SSI) refers to the dynamic interaction between a structure and the surrounding soil on which it rests. The behavior of the soil can significantly affect the response of the building structure. In the context of civil engineering and structural analysis, SSI becomes particularly important when considering the response of structures to dynamic loads such as earthquakes or so-called paraseismic loads, e.g., mining tremors. Several factors contribute to SSI. Soil and building structure material properties, foundation type, and loading conditions are the most important parameters. The article concerns SSI in the case of mining rock bursts in Poland. The influence of changes in site material conditions and building material properties on the SSI phenomenon was investigated. A few variants of different properties of typical construction materials (brick, reinforced concrete, and cellular concrete) in the case of selected representative building structure were considered. The subsoil material properties from the wide range were also taken into account. Numerical three-dimensional finite element method (FEM) analysis was applied. The adopted models of the soil-structure system were verified by data from in situ experimental vibration measurements. A significant influence of the subgrade material and the building structure material on the SSI was demonstrated.

Complex variable solution for ground deformation responses considering the grouting pressure of shallow shield

During shield tunneling in shallow strata, ground deformation is highly sensitive to grouting pressure response. Excessive grouting pressure can cause ground uplift, and an excessively low grouting pressure can cause excessive ground settlement, affecting the surrounding environment. Current studies seldom analyze the influence of shield excavation on ground deformation when the grouting pressure is considered. To ensure micro-disturbance of the surrounding environment during shield tunneling, this study presents a complex variable analysis method for analyzing the influence of grouting pressure on surface settlement. This solution maps the semi-infinite strata outside the segment into circular domains by introducing a complex function conformal mapping method. The nonuniform convergence deformation pattern BC-4 was introduced as the boundary condition for the displacement around the tunnel. The Laurent series expansion of the analytical function considering the grouting pressure in the circular domain was substituted into each boundary condition to solve the analytical function. Subsequently, the accuracy of the analytical method was verified by combining it with a finite element numerical method. Finally, the influence of grouting pressure on ground deformation under different working conditions was analyzed through parameterization. This analytical method can provide a theoretical basis for controlling grouting pressure parameters in shield tunnels.

6σ Robust Lightweight Design of the GIL/GIS Bus Based on Co‐Simulation of Insulation, Current Flow, and Mechanical Stress

GIL/GIS bus is widely used in the field of power transmission and distribution, and the demand for lightweight is becoming more and more prominent. To reduce the weight of the bus and ensure the safety and reliability of the structure, a new 6σ robust design method of the GIL/GIS bus based on electric‐thermal‐mechanical co‐simulation is proposed. Taking a 550 kV/5000A bus as the initial structure, considering the uncertainty of product size and performance, a 6σ robust lightweight model of bus insulation electric field strength, current temperature rise, and mechanical stress multi‐performance co‐simulation is established. The finite element numerical calculation method is used to calculate and analyze the performance parameters of the bus. The Kriging surrogate model is used to form the response surface, and the optimal bus structure is obtained by genetic algorithm. The results show that after the robustness optimization, the performance of the bus meets the design requirements, the weight per meter decreased from 65.11 to 39.12 kg, and the lightweight effect is remarkable. Compared with the traditional deterministic optimization design, the reliability of the structure is improved. The new method of the GIL/GIS bus lightweight design proposed in this study has high feasibility and application prospects, which can provide new ideas for the development of gas‐insulated electrical equipment. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Thermal analysis with high accuracy of multi-beam mask fabrication

For a 7 nm technology node and beyond, multi-beam mask fabrication based on charged particles has attracted attention widely and shows great advantages in terms of throughput. However, the heating effect during mask writing is a serious problem and makes deformation error. To address this issue, an accurate analysis of heating with multi-beam writing is necessary. In this study, the thermal effects of electron beams on a mask during writing time (exposure time and nonexposure time) were simulated with a finite element numerical method. The variation in the temperature field with two writing paths (S-shaped and E-shaped) was analyzed. A comparative analysis of the mask’s deformation under different writing paths was conducted. Numerical research shows that the thermal analysis method in this study provides a guide for optimizing the process parameters of mask fabrication.

Numerical analysis of a pressure distribution field and fluid flow velocity vectors near cumulative perforation holes

Relevance. The need to determine a reliable pressure distribution field and fluid filtration velocity vectors inside the perforation hole and the reservoir rock surrounding it. Aim. On the basis of numerical finite element modeling of the fluid flow inside the perforation holes and its filtration in the surrounding reservoir rock, to reveal the patterns of pressure distribution and fluid filtration vectors in the perforation hole, on its walls and in the near-wellbore zone. Objects. Near-wellbore zone of a limestone reservoir of one of the oil fields in the south of the Perm Region, including perforations. Methods. Numerical finite element method for calculating the flow and filtration of liquid in the near-wellbore zone, taking into account the geometry of perforation holes. Results. The paper considers the main relationships used in numerical simulation of fluid flow and filtration in the ANSYS finite element modeling software package. The authors have developed the finite element scheme of the near-wellbore zone, including cumulative perforation holes and taking into account their geometric parameters, as well as the fact that inside the holes the fluid flow is modeled in open space using the Navier–Stokes equations, and in the surrounding reservoir rock based on the filtration equations and Darcy's law. Numerical calculations were carried out, on the basis of which the distribution of pressure, flow velocities and fluid filtration inside the holes and in the near-wellbore zone as a whole was obtained. Calculations were made with varying pressure in the well (or pressure drawdown), as well as for different values of reservoir permeability. The calculation results showed that for the actual drawdown values of 10 MPa and the reservoir permeability of 50 mD, the value of pressure change inside the perforation holes will not exceed 0.01 MPa, i.e. it can be assumed that it practically does not change inside the hole. It is noted that the maximum value of the filtration rate corresponds to the top of the perforation holes and then its value decreases as it approaches the borehole wall. It is concluded that in further modeling of the stress-strain state of the near-wellbore zone, taking into account the holes of cumulative perforation on the surface of the holes, it is permissible to set a constant pressure value equal to the pressure in the well, and not logarithmic or any other distribution of it.

Mathematical Modeling and Econometric Analysis of Composite Fuel Combustion Process

In this article, the process of combustion of composite fuel is studied. Particles of hydrocarbon fuel were taken as the object of research. The analysis of the combustion process is carried out on the basis of mathematical modeling. The created mathematical model was solved by the numerical method of finite elements using the Elcut program, and a computer model was developed. The results obtained on the basis of the numerical method were compared with the experimental results, as well as an econometric analysis and forecast based on the regression model. A comparison of the results obtained by the finite element method using the Elcut program with experimental data shows that the error is on average 5% and indicates the physical validity of the equations and boundary conditions (1)-(7) for the mathematical modeling of the considered tasks and use of the Elcut program for numerical calculations.

SR-M−GAN: A generative model for high-fidelity stress fields prediction of the composite bolted joints

Predicting the stress fields induced by composite bolted joints constitutes a valuable research endeavor aimed at enhancing the structural integrity of equipment in the aerospace and maritime fields. The stress field characteristics of composite bolted joints may undergo changes due to potential mechanical behaviors, such as damage, constitutive relationships and so on, which exhibit complexity and pose challenges for prediction. Nevertheless, modeling the intricate stress field distribution directly from experimental data poses a formidable challenge, necessitating a substantial investment in materials and resources. Traditional finite element numerical methods have the capability to model the distribution of the stress fields. However, to obtain a high-fidelity solution of this distribution, it is imperative to generate a fine-grid mesh and allocate the significant computational resources. The incorporation of computational techniques in coarse −grid would enhance the efficiency of computations, but these approaches compromise the accuracy of the calculations. In this paper, an innovative deep learning framework is introduced. The network named as the SR-M−GAN is drew inspiration from the conditional generative adversarial network (cGAN) used in the image super-resolution. The primary aim of SR-M−GAN is to mitigate the intrinsic trade-off between result fidelity and computational complexity. The model proposed in this paper effectively reconstructs high-fidelity stress field data from calculations on coarse grids and exhibits excellent reconstruction metrics. Simultaneously, the model only incurs additional computational costs during the deployment of the network model and training. When compared to experimental data, the model continues to demonstrate superior performance in both accuracy and computational efficiency. Therefore, this method offers a high-fidelity data augmentation approach for stress analysis in composite bolted joints, laying the groundwork for large-scale analysis of stress field characteristics in composite bolted joints.

Ramalan Kestabilan Cerun yang Diperkukuhkan Menggunakan Cerucuk Menggunakan Model Sistem Inferens Neuro-Fuzzy Adaptif (ANFIS)

Predictive analysis using artificial intelligence (AI) has transformed the landscape of forecasting analysis in various research fields. The advancements in AI modelling algorithms have enhanced decision-making, trend identification, and process optimization. In geotechnical engineering, AI assists in predicting soil behaviour, structural stability, and slope stability. The AI model discussed in this paper is the Adaptive Neuro-Fuzzy Inference System (ANFIS). In this study, the ANFIS model predicts slope stability by examining the Factor of Safety (FOS) value. Slope stability analyses reinforced with continuous bored pile walls generated by the numerical computation of the finite element method (FEM) in two dimensions (2D) and three dimensions (3D) are compared with the predictions of the ANFIS model. The numerical FEM computations employ PLAXIS 2D and PLAXIS 3D software. Meanwhile, the ANFIS model is designed within the MATLAB software platform involving 112 data samples. With six input pile parameters and one output, the finding shows that the ANFIS model can learn complex non-linear data and accurately predict the output. This is supported by the R² values of 0.9771 and 0.9965 from comparing the forecasting output with the 2D and 3D FEM outputs, respectively. Meanwhile, the low RMSE values of 0.0187 and 0.0180 each confirm this.

FIRE DESIGN OF STEEL MEMBER BY COMPONENT‐BASED FINITE ELEMENT METHOD

AbstractThe Component‐Based Finite Element Method (CBFEM) is the quite commonly used method to analyse and design connections of steel structures. It is the combination of the analytical component method and the numerical Finite Element Method (FEM). In this paper, the CBFEM is applied to analyse steel beams and columns at elevated temperature. The main objective of this study is to verify the CBFEM for predicting the resistance of steel members at elevated temperatures.

Seismic Response Analysis of Multi Span Hyperbolic Brick Arch Thin Shell Structure

The research objective is to investigate the multi-span hyperbolic brick arch thin-shell structure located in Changleyuan, Baoji City, Shaanxi Province. The study utilizes on-site dynamic testing and finite element numerical simulation methods to analyze the dynamic characteristics of the thin-shell structure and its seismic response under various seismic waves and directions. The simulation results indicate the following findings: Vertical earthquakes cause more severe damage to structures compared to horizontal earthquakes. Bidirectional seismic excitation has a greater impact on the structure than unidirectional and three-dimensional seismic excitation. The obtained results provide a scientific basis for the seismic protection, reinforcement, and repair of this multi-span double-curved brick arch thin-shell structure.

Reshaping force for deformed casing repairing with hydraulic rolling reshaper and its influencing factors

Hydraulic rolling reshaper is an advanced reshaping tool to solve the problem of casing deformation, which has been widely used in recent years. When it is used for well repair operation, the reshaping force provided by ground devices is generally determined by experience. However, too large reshaping force may destroy the deformed casing, and too small reshaping force may also prolong the construction period and affect the repairing effect. In this paper, based on Hertz contact theory and elastic-plastic theory, combined with the process parameters of shaping, and considering the structural characteristics of the deformed casing and reshaper, we propose a mathematical model for calculating the reshaping force required for repairing deformed casing by hydraulic rolling reshaper. Meanwhile, the finite element model and numerical method of hydraulic rolling reshaper repairing deformed casing are established by using the finite element method, and the reliability of the mathematical model is verified by several examples. On this basis, the control variable method is used to investigate the influence of each parameter on the reshaping force, and the influence degree of each parameter is explored by orthogonal simulation test and Pearson correlation analysis. The research results not only provide an important theoretical basis for the prediction of reshaping force in on-site construction, but also provide a reference for the subsequent improvement of the shaping process.

Preliminary design and evaluation method for the seismic isolation layer of a shield tunnel

Theoretical analyses and numerical simulations, proposed to increase the efficiency of tunnel seismic isolation measures, are too complex for solving practical problems. Herein, a simplified design method for a tunnel isolation layer is developed for preliminary calculations of the required physical parameters based on the surrounding rock conditions and seismic isolation performance. The internal force response of a shield tunnel in homogeneous ground before and after the installation of a seismic isolation layer is determined using the proposed method, considering the coupled effect of the isolation layer and surrounding rock by calculating the equivalent elastic modulus. The effectiveness of the derived method is verified using wave function expansion and finite element numerical simulation methods. The results obtained using the simplified design formulae are consistent with those obtained using the wave function expansion method. Furthermore, the effects of the seismic wave frequency, surrounding rock type, elastic modulus, and thickness of the seismic isolation layer on the seismic isolation effect are examined via parametric analysis. The proposed method could be applied to preliminary design and evaluation of seismic isolation layers for shield tunnels with different surrounding rock types.

High forward thrust metasurface beam-riding sail.

The radiation pressure force and torque on a one-dimensional bi-grating composed of a Si-SiO2 high contrast binary metagrating is analyzed for the purpose of stable beam riding whereupon a high power laser having an expanding Gaussian irradiance distribution propels the grating in outer space, free from gravitational forces. The binary metagrating structure has been simultaneously optimized to afford high forward thrust, and corrective restoring forces and torques in the event of small linear and angular disturbances. We demonstrate that stability may be enhanced at the expense of forward thrust. The validity of our metamaterial findings is reinforced owing to good agreements between finite-difference time-domain and finite element numerical methods. To reduce mass and enhance forward acceleration this laser-driven sail was designed to be free of a stabilizing boom.

A standard calibration method based on a symmetric resistance network matrix for galvanic logging instruments.

An increasing number of measurement electrodes have been designed to satisfy the demand for high-resolution detection using galvanic logging technology in complex formations. The forward modeling response analysis of logging tools has important guiding significance in the design of galvanic logging tools. Based on a three-dimensional finite element numerical simulation method, we established a forward model of galvanic multi-electrodes in a complex formation. We also designed a symmetrical resistance network model of the formation with equivalent resistance between two electrodes. A symmetrical resistance network was derived using the balanced bridge method. The asymmetrical admittance matrix was extended to a symmetrical extended admittance matrix to realize a convenient calculation of the equivalent symmetrical resistance network in complex formations. Verification of the microcolumn-focused logging tool, with nine electrodes in a simulated standard well, and an evaluation of the degree of invasion in an actual oil well indicate that this calibration method can improve the measurement accuracy of galvanic logging instruments.