Finite Element Numerical Simulation Research Articles

The effect of RAP content on fatigue damage property of hot reclaimed asphalt mixtures.

The fatigue property of the recycled mixture affects the structural design of recycled pavement. In order to explore the effect of different reclaimed asphalt pavement (RAP) content on the fatigue properties of recycled mixtures, the fatigue properties of recycled mixtures were analyzed through an indoor fatigue test and finite element numerical simulation. Based on the phenomenological method and the dissipated energy theory, the fatigue properties of recycled mixtures with different RAP contents were analyzed and the fatigue damage of the mixtures were also studies under various strain levels. Based on the finite element numerical model of fatigue damage, the stress distribution and internal damage field distribution of trabecular specimens under different temperatures, strain levels and RAP contents were analyzed. The results showed that the anti-fatigue level of the mixture decreased as the RAP content was increased. The relative change rate of dissipated energy for different types of mixtures showed a two-stage change rule with the change of load times, that is, the value is large and decreasing, and the value is small and stable. The correlation between the plateau value (PV) and the fatigue life was established under the double logarithm coordinates, which could better analyze the influence law of the RAP content on the fatigue performance of the recycled mixture. Under different temperatures, strain levels, and RAP contents, the stress at the bottom of trabecular specimen and the overall damage field were mainly generated at the upper part under compressive stress and the bottom under tensile stress, and the damage field distribution area accounted for a small part of the whole specimen. According to the test results and fatigue damage distribution, it is recommended that the content of recycled aggregate in recycled asphalt mixtures be less than 30% to ensure good performance. The research results have important practical significance for the improvement of fatigue performance and engineering application of recycled mixtures.

Thermal insulation performance of buildings with phase-change energy-storage wall structures

Considering that improving the energy efficiency of buildings is crucial to achieving China's carbon neutrality goal, the application of phase-change energy-storage (PCES) technology could be considered a practical and feasible approach. Currently, the heat transfer characteristics of PCES walls and their influence mechanisms on the indoor building environment are the key issues to be solved in this field. Based on gypsum-based phase-change materials (PCMs), outdoor, indoor and central PCES walls are designed in this study. Unsteady heat transfer experiments, finite element numerical simulations and energy consumption analyses were used to study the thermal behaviour of PCES walls, and the thermal insulation performance of the buildings utilizing these wall structures were assessed. The results show that the maximum temperature of inner surface of wall with PCMs applying at the interior side is reduced by 0.6 °C, and the maximum temperature lag is reduced by 0.8 h. The results also prove that buildings employing this PCES walls as envelope have a reduction of annual cooling energy consumption about 7.6%, and a reduction of annual carbon dioxide emissions by about 2%, comparing with conventional buildings. Thus, these results suggest that the use of PCES walls can effectively enhance the thermal insulation performance of buildings in summer. This research could provide an innovative idea for the design of PCES walls, which is of significance for the application of PCES walls in severe cold regions.

Stability analysis and support scheme design of the landslide behind Yang Erping's house in Zuopo Village

The stability of the landslide behind Yang'erpingfang, Zuopo Village, Luluo Town, Xingtai County is calculated and analyzed using the strength reduction method with MIDAS GTS finite element numerical simulation software, based on the treatment of Zhuwenping landslide in Bai'an Township, Xingtai County.

Existence analysis of solutions to the linear Schrödinger Kirchhoff Poisson equation based on interrupted finite elements

Abstract In this paper, we firstly explore the existence of solutions to the following linear Schrödinger Kirchhoff Poisson equation with critical exponential growth on the full space □3 by using the discontinuous finite element (DG) as well as the principle of centralized compactness: { − ( a + b ∫ □ 3 | ∇ u | 2 ) Δ u + V ( x ) u + φ u - 1 2 u Δ ( u 2 ) = K ( x ) u p − 2 u , x ∈ □ 3 − Δ φ = u 2 , x ∈ □ 3 \left\{ {\matrix{{ - \left( {a + b\int_{{\square^3}} {{{\left| {\nabla u} \right|}^2}} } \right)\Delta u + V\left( x \right)u + \phi u - {1 \over 2}u\Delta \left( {{u^2}} \right) = K\left( x \right){u^{p - 2}}u,} & {x \in {\square^3}} \cr { - \Delta \phi = {u^2},} & {x \in {\square^3}} \cr } } \right. , x ∈. Secondly, we make reasonable assumptions on the V, K , f functions of the equation, and use the principle of variational division to firstly obtain the corresponding energy generalization of this equation, and then we prove the corresponding generalizations of the equation satisfy the (C) c conditions. Finally, the existence of the solution of the equation is obtained by numerical simulation and then by using the Yamaji Lemma. The results show that the error of the finite element solution of the linear Schrödinger Kirchhoff Poisson equation in the spatial direction P1 reaches the optimal estimation under the L 2 -parameter in an intermittent finite element numerical simulation environment, i.e., it is proved that there exist at least 1 and 3 positive solutions to the problem. The paper achieves rich research results which are informative for the solution of this class of linear differential equations.

Research on the suppression method of sensor impact vibration parasitic effects in surface reflection pressure measurement.

Ground reflection pressure plays a crucial role in evaluating the destructive power of ammunition explosions. Accurately measuring this pressure is essential for assessing ammunition's destructive capability and guiding ammunition design. In this study, a theoretical analysis of the parasitic effect of shock and vibration was conducted and COMSOL was employed for performing a multi-physics finite element numerical simulation analysis to elucidate the attenuation characteristics of stress waves in commonly used shock- and vibration-resistant materials. Furthermore, a device was designed using aluminum foam and polytetrafluoroethylene to mitigate the parasitic effects on the ground reflection pressure sensor. Experimental testing was conducted to validate the device's effectiveness. The results demonstrated that the device successfully reduced the intensity of stress waves reaching the ground reflection pressure sensor, with a relative attenuation rate of 29.6% in peak stress values. The sensor measurements obtained with the suppression device exhibited smoother curves and higher signal-to-noise ratios, significantly improving the reliability of the measurement results. Our study holds considerable engineering application value in enhancing the accuracy of shock wave pressure measurements in explosive fields.

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.

Study on Failure Energy per Unit Area of Concrete Specimens Based on Minimum Energy Dissipation Theory.

In order to study the strength change of concrete specimens under different loading conditions, based on the principle of minimum energy dissipation, the damage energy per unit area of concrete was studied. By using finite element numerical simulation software for concrete specimens with different failure modes of tension, pressure, bending and torsion, a double-broken line damage constitutive model is adopted. The failure forms of concrete specimens under different loading conditions, as well as the failure area and failure energy of each specimen during loading, are simulated and analyzed. The failure energy per unit area under different failure modes was quantitively calculated, the relationship between the failure area and failure energy consumption under different failure modes was analyzed. The results show that, under different failure modes, the failure area of concrete specimens is different, the energy consumed during failure is different, and the strength is different. However, no matter how the failure mode changes during the failure process, the failure energy W per unit area remains constant and fluctuates in the range of 2.0~6.0 mJ/cm2, which is related to the physical properties of concrete itself.

Parameter inversion method for target plate constitutive model based on BP neural network

In this paper, a neural network-based inversion method that can be used to streamline the acquisition of polymethyl methacrylate (PMMA) material constitutive model parameters for explosive cutting simulations is presented. This approach mitigates the need for multiple tests, a requirement of traditional methods. Initially, three categories of the damage, penetration depth, impact fracture thickness and spallation damage thickness, were distinguished and quantified by cutting the14 mm PMMA target plate with a 2.5 mm wide linear shaped charge, and the adjustment interval for the constitutive model parameters could be determined by combining the explosive cutting experiment data and the empirical parameters of the Johnson Holmquist Ceramics (JH-2) constitutive model. Subsequently, the numerical simulations of the cutting process of the performed target plate tests were carried out using LS-DYNA, and a dataset of target plate damage incorporating the three types of damage data was amassed. Ultimately, a neural network model correlating the parameters of the PMMA target plate constitutive model with the damage data was developed and trained using the plate damage dataset, and several supplementary experiments as well as finite element numerical simulations involving a 4.2 mm wide linear shaped charge cutting a 19 mm PMMA target plate were conducted. The numerical results displayed minimal variance from the experimental results in terms of fracture characteristics and damage data, suggesting that the inverted JH-2 constitutive model parameters can be effectively applied to PMMA target plate explosive cutting simulations. The parameter inversion method allows for the acquisition of more accurate material constitutive model parameters with fewer experiments and will be beneficial for further theoretical studies and practical applications of target plates in the future.

Coexistence and Coevolution of Wrinkle and Ridge Patterns in the Film-Substrate System by Uniaxial Compression.

Homogeneous wrinkles and localized patterns are ubiquitous in nature and are useful for a wide range of practical applications. Although various strain-driven surface instability modes have been extensively investigated in the past decades, understanding the coexistence, coevolution, and interaction of wrinkles and localized patterns is still a great challenge. Here, we report on the formation and evolution of coexisting wrinkle and ridge patterns in metal films deposited on poly(dimethylsiloxane) (PDMS) substrates by uniaxial compression. It is found that the evolving surface patterns show unique features of morphological transition from stages I to III: namely, transition from localized ridges to coexisting wrinkles and ridges, and finally to sinusoidal-like structures, as the compression increases. Based on the compressive strain-driven surface instability theory and finite element numerical simulation, the morphological features, transition behaviors, and underlying mechanisms of such complex patterns are investigated in detail, and the changes of amplitude and wavelength versus the strain are consistent with our experiments. This work could promote a better understanding of the effect of strain localization and the interaction of multiple surface patterns in hard film-soft substrate systems.

A hybrid modeling method of fatigue crack growth for gas turbine blades under combined high and low cycle fatigue loadings

Fatigue crack is one of the major faults of the gas turbine blades. Previous modeling studies on fatigue crack growth of blades mainly focus on a single numerical or analytical approach considering different sizes of cracks under various fatigue loadings. However, the actual crack propagation process is time-varying. The iteration and update of the model are necessary to evaluate the fatigue life of blades precisely. This paper proposes a hybrid modeling method to study blade crack growth under combined high and low cycle fatigue (CCF) loadings. The method emphasizes the combination and interaction between the finite element (FE) numerical simulation and the analytical calculation based on the fracture mechanics model. The current crack propagation length of the blade FE model is calculated from the crack growth rate obtained by the stress intensity factor (SIF) range according to Paris law. Then, a new SIF range is resolved from the FE model with the updated crack length. The proposed method is verified by the first-stage compressor blade from an in-service gas turbine. Results show that the crack growth is faster using the proposed hybrid modeling method than the traditional method. The update of the SIF range under CCF loadings cannot be ignored when predicting the fatigue life of the blade. Also, a sensitivity analysis is carried out. Suggestions are given on how to set the crack extension length at each stage during modeling, especially when the blade approaches failure.

Paleotectonic Stress and Present Geostress Fields and Their Implications for Coalbed Methane Exploitation: A Case Study from Dahebian Block, Liupanshui Coalfield, Guizhou, China

The macroscopic structural fractures (joints) and geostress distribution characteristics of coal reservoirs are important factors affecting the exploitation of coalbed methane (CBM). In this study, the joints in the sedimentary strata of the Dahebian block in Liupanshui area, Guizhou Province were investigated. Directional coal samples were collected for observation and statistical analysis of coal microfractures, the paleotectonic stress fields of the study area were reconstructed, and the tectonic evolution was elucidated. The geostress distribution characteristics of the target coal seam (coal seam No. 11, P3l) in the study area were analyzed using the finite element numerical simulation method. The results indicate that the structural evolution of the Dahebian syncline in the study area can be divided into two stages. The Late Jurassic–Early Cretaceous stage (Early Yanshanian) is the first stage. Affected by the sinistral strike slip of the Weining–Ziyun–Luodian (WZL) fault zone, the derived stress field in the study area exhibits maximum principal stress (σ1) in the NEE–SWW direction. The Late Cretaceous stage (Late Yanshanian) is the second stage. Affected by the dextral strike slip of the WZL fault zone, the derived stress field exhibits σ1 in the NNW–SSE direction. The folds and faults formed in the first stage were modified by the structural deformation in the second stage. The dominant strikes of joints in the sedimentary strata are found to be in the NW–NNW (300°–360°) and NE (30°–60°) directions, with dip angles mostly ranging from 60° to 90°. The dominant strikes of coal microfractures are in the NW (285°–304°) and NE (43°–53°) directions. The distribution of geostress in the study area is characterized by high levels of geostress in the syncline center, decreasing towards the surrounding periphery. The overall trend of the geostress contour line is similar to the shape of the syncline and is influenced by folds and faults. The σ1 of coal seam No. 11 is vertical stress. The prediction results show that the joint density of coal seam No. 11 in the block is 36–50 joints/m, and the shape of the joint density contour line is also affected by the axial direction of the Dahebian syncline and the surrounding faults. The variation in coal seam joint density and the control effect of geostress on joints opening or closing affects the permeability of coal reservoirs. The study results provide significant guidance for the exploitation of CBM.

Retracted: Three-Dimensional Finite Element Numerical Simulation and Analysis of Solid-State Processing of Metal Material

Retracted: Three-Dimensional Finite Element Numerical Simulation and Analysis of Solid-State Processing of Metal Material

Finite Element Formulation and Computation of Superplastic Metal Forming Processes with Optimized Rate of Deformation Control

Superplastic forming (SPF) is a material forming technique that uses superplastic exceptional elongations and deformation characteristics to form superplastic materials into certain shapes. The combination of superplastic forming with diffusion bonding (SPF/DB) gives rise to an almost unlimited extension of superplastic forming since more integral lightweight cellular structural components can be manufactured. This paper discusses numerical modelling of the mechanism of superplasticity in metallic materials. The SPF computational method based on the finite element technique augmented with the controlling rate of deformations is developed to examine a range of design or operating conditions leading to more economical forming processes. The non-Newtonian ‘viscous flow’ material is used to model the constitutive of superplastic material during the forming period. The contact mechanics between the sheet material and the mold surface and the intersheet material contact mechanics are imposed using the penalty control method, in which the sticking contact boundary conditions are employed. The space discretization is carried out using the membrane element under plane strain and axisymmetric flow stress conditions, while the implicit time integration technique is utilized to follow the shape changes of the formed sheet material. The validation of the SPF finite element formulation was performed by comparing it with the available analytical solution of Hydraulic Free Bulging of Thin strips. The SPF of a hemispherical dome made of 7475 aluminum sheet alloy was performed to demonstrate the forming process as well as to validate the results obtained between the SPF finite element numerical simulation and the experimental results. The SPF/DB of the multicell component section is considered in the final part.

Floating column mechanism experimental investigation in historic timber buildings subjected to decay for seismic resilience

SummaryTraditional wooden structures are characterized by the presence of a column base that seems to be floated above the foundation stone. This study used pseudo‐static experiments to assess the seismic performance of flat pendulum floating resting columns, focusing on the decay and repair of the wood frame (WF). First, an artificial method was used to simulate fungal decay damage of column‐foot joints, and filling reinforcement was applied to the decayed column‐foot joints, and second, according to the design method in the Sung dynasty architecture, the Ying‐tsaofa‐shih (building standards). This study presents the findings of pseudo‐static tests that were conducted at Yangzhou University. Three 1:3.52 scaled specimen WFs with flat‐pendulum‐floating‐shelf (FPFS)‐typed (Ping‐bai‐fu‐ge) columns, i.e., non‐damaged WF (named after NT), considering the damaged WF (named after DF) and strengthening damaged WF (named after DR) with one‐way straight mortise‐tenon joints (OWSMT) joints were made and subjected to cyclic lateral loads during testing. The properties of the WFs with FPFS columns, such as the failure mode, hysteretic and envelope curves, strength and stiffness deterioration, and energy dissipation, have been studied. Finally, the effects of additional damage and reinforcement measures on the seismic performance of WFs are analyzed and compared with the finite element numerical simulation results. This research shows that damage to the column foot decreases the WF's seismic performance, although filler reinforcement may increase it. The foot and mortise joints are interconnected and interact in the wood frame's seismic stressing mechanism. Foot decay reduces the seismic performance of the foot joint, hence increasing the seismic energy dissipation activity of the mortise joints.

Numerical Simulation of Impact Effect on Stability of Transmission Tower Foundation

The impact effect can cause structural damage to a transmission tower’s foundation and affect its overall stability. In order to study the influence of the impact effect on the stability of transmission tower foundations, a three-dimensional finite element numerical simulation method was used to investigate the variations in the extent of damage, displacement, and inclination degree of a transmission tower foundation under different impact velocities, impact durations, impactor shapes, and impact locations. The results show that as the impact velocity increases, the damage value of the transmission tower foundation continuously increases, and the damaged area expands. The lateral displacement value increases continuously with the duration of the impact effect, and the variation in lateral displacement follows a linear function distribution. The inclination degree of the transmission tower foundation increases continuously with increased impact duration and can lead to overturning failure. A smaller impact contact area results in a larger compressive damage value for the transmission tower foundation, and different impact contact areas lead to different modes of failure for the transmission tower foundation. The damage value and damaged area of the transmission tower foundation vary with the location of the impact. By comparing the deformation of the transmission tower foundation before and after reinforcement, it is evident that the reinforcement design can significantly improve the deformation resistance and anti-overturning capacity of the transmission tower foundation.

Ultra-broadband high-efficiency cross-polarization conversion and amplitude-phase manipulable multi-functional wavefront manipulation based on terahertz metasurface

Drawing upon the physical phenomenon of polarization transformation, this paper proposes an ultra-broadband, high-efficiency linear polarization converter composed of a metallic grating, an L-shaped metallic patch, and a dielectric substrate. The polarization conversion properties have been scrutinized using the finite element numerical simulation software CST. The computational outcomes reveal that the polarization converter operates within the frequency range of 0.5 THz to 1.8 THz, exhibiting a relative bandwidth of 113%, a transmission coefficient exceeding 0.87, a polarization conversion efficiency approaching 100%, and a phase coverage spanning 360°. Furthermore, a Fabry–Perot interference model was established utilizing Matlab to corroborate the concurrence between the theoretical analysis and the numerical findings. The polarization converter metasurface amalgamates both phase and transmission amplitude variations to accomplish not only a two-dimensional focusing lens operating between 1.55 THz and 1.65 THz, but also a spatial imaging capability utilizing transmission amplitude variation within the 0.5 THz to 1.15 THz range. The outcomes demonstrate that the devised metasurface exhibits ultra-broadband and high transmission efficacy, thus providing novel insights for the versatility of terahertz wave polarization and phase manipulation.

Flexural–torsional buckling of steel circular arches with I-section under central concentrated load in elevated-temperature environment

This article reports the fire resistance experiments conducted on I-section circular steel arches, as well as the observed out-of-plane flexural–torsional buckling (FTB) behavior and in-depth finite element numerical simulation results. The test was carried out using a large fire test furnace to provide a real fire environment with a nonuniform temperature field. A specially designed loading device allowed for unconstrained out-of-plane deformation of the specimens inside the furnace, thereby achieving effective load conditions and noncoupled response of the components. Numerical analyses were performed using a combination of the general codes Fluent and Abaqus, with the former used for heat transfer analyses, and a structural FE model including the loading device and complex geometric imperfections was established based on the measured data. Thus, accurate simulation of the out-of-plane behavior of the steel arches at elevated temperature was achieved. On this basis, an in-depth parametric study was carried out to investigate the effects of temperature field variations, load ratio (LR), and geometric imperfection. The analysis results show that FTB occurs at nonuniform temperatures for the arches under concentrated load, and the difference in temperature distribution in fire has a minimal effect on the FTB behavior. LR is negatively correlated with critical temperature; the smaller the LR, the more significant the weakening of critical loads by fire. The effect of initial geometrical imperfections on FTB at elevated temperatures is similar to that at ambient temperatures, and the effect on the critical temperature of FTB can almost be ignored when the imperfection amplitude is less than S/400.

Prediction of the Productivity Ratio of Perforated Wells Using Least Squares Support Vector Machine with Particle Swarm Optimization

The productivity ratio is a vital metric for assessing the efficiency of perforated completions. Accurate and rapid prediction of this ratio is essential for optimizing the perforation design. In this study, we propose a novel approach that combines three-dimensional finite element numerical simulation and machine learning techniques to predict the productivity ratio of perforated wells. Initially, we obtain the productivity ratio of perforated wells under various perforation parameters using three-dimensional finite element numerical simulation. This generates a sample set for machine learning. Subsequently, we employ the least squares support vector machine (LSSVM) algorithm to establish a prediction model for the productivity ratio of perforated wells. To optimize the parameters of the LSSVM algorithm, we utilize the particle swarm optimization (PSO) algorithm. We compare our proposed PSO-LSSVM model with that established based on other parameter optimization methods and machine learning algorithms, such as Grid search-LSSVM, PSO-ANN, and PSO-RF. Our results demonstrate that the PSO-LSSVM model exhibits rapid convergence, high prediction accuracy, and strong generalization ability in predicting the productivity ratio of perforated wells. This research provides a valuable reference and guidance for optimizing perforation design. Additionally, it offers new insights into predicting the productivity of complex completions.

Mechanical performance investigation on fiber strengthened recycled iron tailings concrete

Recycled aggregate concrete has received much attention in recent years. Using tailings sand in concrete can save natural resources and create environmentally friendly building materials. Simultaneously, adding iron tailings can compensate for the loss of strength caused by recycled aggregates and enhance performance. The mechanical properties of recycled aggregate concrete with iron tailings and prepared concrete specimens with iron tailings sand content of 0%, 25%, 50%, 75%, and 100% were studied. Mechanical tests are conducted to evaluate the performance with the assistance of PVA fibers. The patterns of change in numerical values such as compressive strength, flexural strength, and peak strain of recycled concrete specimens are tested and analyzed, and the experiment's effectiveness is demonstrated through finite element numerical simulation. The results show that when the TRAC content is 50%, the working performance of recycled concrete reaches its peak; When the TRAC content exceeds 50%, the positive effect of tailings sand on the performance of concrete decreases; The strength of TRAC concrete increases with the increase of PVA fiber content; Improving the replacement rate of recycled iron tailings aggregate can increase the peak strain of the specimen under cyclic loading, and the stress-strain curve calculated by finite element software is consistent with the experimental results.

Brazilian splitting experiment and finite element simulation analysis of the influence of bedding loading angle on shale fracture mode

During the diagenetic processes of compaction and cementation, shale forms multiple beddings, significantly effecting the rock anisotropy. Therefore, it is important to study the effect of bedding on the mechanical properties of shale to guide fracturing engineering. To study the failure mode and fracture morphology of shale with bedding planes under different bedding dip angles, Brazilian disc splitting tests and finite element numerical simulations are performed for shale samples and the results are compared. (1) The bedding angle has a significant effect on the failure mode and tensile strength of shale, and the tensile strength tends to increase with increasing bedding angle. (2) The failure modes of shale under different bedding dip angles can be divided into three types: tensile failure along the bedding plane; comprehensive shear and tensile failure of the matrix and the bedding plane; and matrix tensile failure. (3) The direction of secondary cracks is mostly perpendicular to the bedding plane, and a smaller angle between the load application direction and the bedding direction results in a larger number of generated cracks with more complex shapes. (4) When the loading angle of the bedding is 30°, the tensile strength is low and the matrix and the bedding plane are comprehensively destroyed by shear and tension, resulting in a more complex joint mesh; conversely, when the bedding angle is greater than 60°, the tensile strength increases and the complexity of the seam mesh decreases. These findings can provide guidance for the selection of the bedding angle and the design of fracturing schemes in fracturing engineering.