Results Of Numerical Analysis Research Articles

Effect of Undercut Bolt Anchor Depth on Failure Cone Geometry: A Numerical FEM Analysis and Experimental Verification

This study examined the influence of the effective embedment depth hef of undercut anchors and the diameter of their heads on the formation of the so-called cone failure angle α. Cone failure formation during simulated anchor pull-out tests was analyzed numerically using the Finite Element Method (FEM) with the ABAQUS software and the XFEM algorithm. The analysis was conducted for three sizes of undercut anchor heads and four embedment depths. The numerical analysis results were compared with field test results obtained during pull-out tests of anchors installed in a rock medium (sandstone). Good agreement was observed between the numerical and field test results. The results of the numerical study are highly consistent with those obtained during the field survey. Moreover, they align closely with findings from previous numerical studies conducted by members of the research team, as presented in earlier publications. For the assumed simulation and field test conditions (sedimentary rocks, gray sandstone), no clear correlation was found between the embedment depth or the anchor head diameter and the value of the cone failure angle in the initial phase of the failure zone development. This result contrasts with certain findings reported in the literature. Many existing studies on anchor bolts focus on material properties or load-bearing capacity, but lack an in-depth analysis of how anchor depth influences the geometry of the failure cone. This research addresses that gap, providing valuable insights with practical implications for design codes and safety evaluations.

Evolutionary Game Analysis of Complex Networks in Enterprise Green Technology Innovation From a Prospect Theory Perspective

ABSTRACTGreen technological innovation in enterprises is a key driving force for achieving sustainable development and industrial transformation. However, how enterprises formulate effective innovation strategies by integrating subjective factors with objective market conditions within complex industrial networks remains an area requiring further exploration. This study aims to construct a complex network evolution model based on prospect theory and examines how subjective factors, such as reference points, risk preferences, and loss aversion, influence the adoption of green technology innovation in different network environments. It further explores how network characteristics, including topology, size, and node degree, affect the diffusion of innovation. Numerical analysis results indicate that in scale‐free networks, lowering reference points for enterprise gains, reducing loss aversion, increasing risk preference, expanding network size, and raising average node degree generally promote higher adoption of green technology innovation. In small‐world networks, the dependence on reference points is relatively lower, risk preference and average node degree demonstrate more complex impacts. Additionally, a moderate rewiring probability can enhance green technology innovation adoption in small‐world networks. These findings provide new insights and practical implications for understanding the driving mechanisms of green technological innovation in enterprises. They further emphasize the importance of government interventions tailored to the specific characteristics of industrial networks to effectively facilitate the diffusion of green technological innovation.

Analysis and Verification of a Slope Steering Model of TRVs in Hilly and Mountainous Environments

Compared to wheeled vehicles, tracked robotic vehicles have less ground pressure, greater traction adhesion, and stronger climbing and obstacle crossing capabilities, making them suitable for agricultural production in hilly areas. Good steering performance directly relates to the mobility performance and operating efficiency of tracked robotic vehicles. Affected by the ground slope, the ground pressure distribution of the vehicle’s two tracks is uneven, leading to changes in its steering performance. Therefore, analyzing and researching the steering performance of a tracked robotic vehicle under sloped conditions is of great significance. This study establishes a slope steering model for tracked robotic vehicles based on a ground pressure model of the multi-peak varying amplitude cosine distribution and the shearing displacement relationship between the track and the ground, and analyzes the impact of vehicle structural parameters, road surface parameters, and steering parameters on steering performance. To verify the proposed theoretical model, multi-body dynamics software is utilized for simulation modeling and analysis. Turning tests on different slopes are conducted on a “soil–machine–crop” integrated experimental platform. The relative error between the numerical analysis results and the virtual simulation software’s results is less than 12%, and the relative error between the numerical analysis results and the experimental results is less than 10.3%; the good consistency between the theoretical results and the simulation’s results and the experimental results indicates that the model is, indeed, correct and effective. The established steering model can provide a theoretical basis for the design and control of new steering mechanisms for agricultural tracked robotic vehicles.

A state‐variable‐preserving method for the efficient modelling of inverter‐based resources in parallel EMT simulation

AbstractThe aggregation models of renewable energy power stations are difficult to apply to the stability research of the fault inside the station or the oscillation analysis between the station and the grid‐side system, and the high dimensional characteristics of their detailed model will pose an enormous challenge to the simulation efficiency. To alleviate the contradiction between accuracy and efficiency, this paper proposes a state‐variable‐preserving method to efficiently model inverter‐based resources and a node tearing method to realize parallel simulation of the renewable energy power station consisting of inverter‐based resources. The state‐variable‐preserving model uses discrete state space expression to eliminate the internal nodes on the basis of preserving the original variables of the generation unit and reduces the solving scale of the generation station. The node tearing method reduces the solving complexity of the associated variables, which is more consistent with the topology characteristic that different power generation clusters are interconnected by the same bus. In the case study, the results of numerical accuracy analysis and numerical stability analysis of a photovoltaic power plant verify the reliability of the proposed method, and its simulation efficiency is verified by changing the scale of the photovoltaic power plant.

Enhancement of Aeroengine Combustion Chamber Air Cooling Holes Design for Emission Reduction and Pattern Factor Control

The results of a comprehensive numerical analysis of temperature uniformity and NOx and CO emission predictions in an aeroengine annular combustor liner, conducted by geometrical modifications through design changes in primary cooling air, including effusion cooling holes, are shown in the paper. A total of five geometric configurations were studied using computational fluid dynamics (CFD) simulations in ANSYS CFX. The adopted combustion model was sort of a combination of the finite-rate (i.e., chemistry, chemical processes) and eddy dissipation model (FRC/EDM). Further, the combustion of liquid kerosene (C10H22) with air, subsequent to the evaporation of fuel droplets, was simulated, and the Rosin-Rammler droplet size distribution was used in spray modeling for accurate depiction of fuel atomization. Both thermal and prompt formation mechanisms of NOx were considered, while k-ε model for turbulence was adapted to capture the nature of emission. An annular combustion chamber of realistic dimensions with a double radial air swirler was modelled in 3D CAD to undertake this study for good, tangible results. Built contour plots allowed to analyze the temperature distribution and NOx concentration along the axis from the center of the injector. Charts on the pattern factor, temperature, and NOx and CO concentrations at the outlet of the combustor served as performance metrics. The simulation was implemented with a two-step chemical kinetics scheme for kerosene combustion with the P1 radiation model, which would give an accurate thermal radiation prediction. One of the major objectives of this research is to compare the CFD results at the combustor outlet with gas dynamic and thermodynamic calculations that have been carried out using AxStream software at the Department of Aeroengine Design, Kharkiv Aviation Institute. It is important to emphasize that the mean deviation of gas dynamic results obtained from AxStream and CFD simulation results was found to be insignificant, hence the CFD approach has been validated. The results testify that redesigning the combustor liner, especially in the design related to primary and effusion cooling holes, drastically reduced NOx and CO emissions. Also, these design modifications have helped in reducing or improving temperature uniformity at the combustor outlet, either way enhancing combustion efficiency and performance.

Aeroelasticity Analysis of Turbine Blade with Asymmetric Outlet Pressure

Elements of high-power steam turbines are subjected to significant unsteady loads, in particular, rotor blades of the last stages. These loads can, in some cases, cause self-excited oscillations, which are extremely dangerous and have a negative impact on the efficiency and service life of the blade cascade. Therefore, when designing new or modernizing existing steam turbine stages, it is recommended to study the aeroelastic characteristics of the blades. The paper presents the results of numerical analysis of the aeroelastic characteristics of the rotor blade cascade of the last stage of a 380 MW steam turbine, taking into account the asymmetric pressure distribution behind the stage. The pressure distribution is caused by the influence of the exhaust hood and was obtained experimentally. The analysis used a proven numerical method for simultaneously solving the coupled problem of unsteady aerodynamics and elastic oscillations of blades, which allows predicting the amplitude-frequency spectrum of unsteady loads and blade oscillations in a viscous gas flow. The modeling results are presented in the form of displacements of the peripheral blade section and aerodynamic forces acting on this section, as well as their spectra. Also, the dependence of the aeroelasticity coefficient on the inter-blade phase angle of oscillation was obtained. The results of the calculations showed the absence of flutter and self-oscillations according to the first natural form of blade oscillations in the partial mode of operation of a steam turbine. The analysis of the results did not reveal a significant effect of the pressure asymmetry at the outlet of the cascade, due to the significant difference between the excitation frequencies caused by the non-uniformity and the natural frequencies of blade oscillations.

An Analytical Subthreshold I–V Model of SiC Double Gate JFETs

ABSTRACTSiC double gate (DG) junction field effect transistor (JFET) is promising for low‐noise and high‐temperature electronics. Existing studies indicate that JFETs can be considered a special case of MOSFETs when the oxide layer thickness approaches zero. In this article, we exploited the structural similarity between the DG JFETs and the DG MOSFETs. By obtaining the 2D Poisson's equation for the DG MOSFETs and deriving the limits, we developed a model for calculating the channel current of SiC DG JFETs in the subthreshold region. The model is derived from device physics, requiring no fitting parameters and offering relatively low computational complexity. The results indicate that, whether for enhancement mode or depletion mode JFETs, the calculated values of this model are in good agreement with the 2D numerical analysis results obtained from Silvaco Atlas. Moreover, for enhancement mode JFETs, even when significant short‐channel effects occur, the subthreshold current can still be well predicted. In addition, the model displays predictive capability for the depletion‐mode JFETs.

Нестационарные структурные изменения в ВТСП композитах при воздействии фемтосекундных лазерных импульсов высокой интенсивности

The paper presents the results of experimental study and numerical analysis of defect formation processes in superconducting YBa2Cu3O7-x films on Hastelloy substrate under the influence of ultrashort laser radiation. The aim of the work is to develop a technique for numerical analysis and calibration of modes of exposure to high intensity femtosecond laser pulses to create systems of controlled defects in HTS composites. The processes of defect formation under the influence from 1 (single mode) to 20 (multiple mode) laser pulses on one point with a frequency of 10 Hz and duration of 2 ps were considered. The laser beam focusing radii were 1.5 and 3 μm. The dependences of the defect diameter and depth on the laser radiation energy in a wide range have been studied and the peculiarities of defect formation in the multiple mode have been shown. The physical processes occurring under the influence of laser radiation in different focusing modes are demonstrated. The proposed technique in the future can be extended for application in experiments of electron-probe spectroscopy, which will make it possible to study changes in the state of the electron-phonon subsystem of superconductors up to phase transitions associated with melting of the crystal lattice.

Gyroid Lattice Heat Exchangers: Comparative Analysis on Thermo-Fluid Dynamic Performances

In recent years, additive manufacturing has reached the required reliability to effectively compete with standard production techniques of mechanical components. In particular, the geometrical freedom enabled by innovative manufacturing techniques has revolutionized the design trends for compact heat exchangers. Bioinspired structures, such as the gyroid lattice, have relevant mechanical and heat exchange properties for their light weight and increased heat exchange area, which also promotes the turbulent regime of the coolant. This work focuses its attention on the effect of the relevant design parameters of the gyroid lattice on heat exchange performances. A numerical comparative analysis is carried out from the thermal and fluid dynamic points of view to give design guidelines. The results of numerical analyses, performed on cylindrical samples, are compared to the experimental results on the pressure drop. Lattices samples were successfully printed with material extrusion, which is a low-cost and easy-to-use metal AM technology. For each lattice sample, counter pressure, heat exchange, and turbulence intensity ratio are calculated from the numerical point of view and discussed. At the end, the gyroid lattice is proven to be very effective at enhancing the heat exchange in cylindrical pipes. Guidelines are given about the choice of the best lattice, depending on the considered applications.

Implicit conformal design for gradient architected materials

This paper develops a conformal architected materials design method based on implicit modeling, which enables functional gradient modulation. This method utilizes the mapping relationship between conformal hexahedral element and the cubic bounding box of architected material to construct the signed distance field. To enhance strength and stiffness of the structure, this study integrates the relative density distribution obtained from topology optimization to regulate the density of conformal architected materials through density mapping. Compared to traditional methods, the proposed method not only reduces the damage of the boundary structure caused by cutting, achieving a mutual match between the architected materials and curved geometry, but also retains the ability to control the distribution of relative density. The numerical analysis and experimental results demonstrate that conformal gradient architected materials exhibit better structural strength and stiffness compared to array-generated gradient architected materials, which indicates that the proposed method has potential applications in lightweight design.

Assessment of the Numerical Behavior of Remolded and Undisturbed Clayey Soil

Abstract The simulation of soil behavior using finite element analysis depends mainly on the input parameters considered in analysis, moreover, in the case of clayey soil, most of the experimental studies for small models are performed on remolded samples because of difficulty of providing undisturbed soils. This leads to unreal results for numerical analysis as the validation process of numerical results is performed on remolded sample. It was conducted experimental work on remolded clay including load-settlement tests of model footing at three states on undrained cohesion (cu), and then performed unconfined compression tests at the same undrained cohesion. After that, performing numerical modeling of the model footing from the data of unconfined compression tests. It was observed that the value of the modulus of elasticity in clay from unconfined test considering the initial tangent is low for remolded state compared to the findings of the previous research. Moreover, great care must be taken in selecting the elasticity modulus in performing the numerical analysis of the clayey soil, however, for undisturbed clay it is greater than remolded, the difference in the value is up to two times for stiff clay in the case of large scale footing, while it was reaches about four times.

SUBSTANTIATION OF THE REGULARITIES OF THE SUBGRADE STRESS-STRAIN STATE AFTER THE IMPLEMENTATION OF THE EUROPEAN TRACK

Purpose. The implementation of the European track (1435 mm) on the existing subgrade, built on the territory of Ukraine, is a factor that leads to a change in the stress-strain state. The purpose of the article is to substantiate the regularities of the stress-strain state of the subgrade based on the results of numerical analysis of finite-element models. Methodology. For numerical analysis based on the finite element method, a 6 m high subgrade model for the combined track was developed. The developed model reproduces all the real geometric characteristics of the subgrade, the upper structure of the track, as well as the sleeper for the combined track. The developed model allows to vary the application of the train load with the setting of a couple of forces on the rails, which have the Ukrainian value of the track gauge (1520 mm), as well as the European one. The model also simulates the reinforcement of the subgrade for four options (without pile, with pile length of 2.0, 4.0 and 6.0 m). Findings. The results of the numerical analysis made it possible to obtain the values of horizontal and vertical stresses, as well as to obtain the regularities of the stress-strain state of the subgrade before the introduction of the European track. Qualitative analysis of the train position shows that the reduction of the track gauge and its asymmetric location on the sleeper increases vertical deformations. The biggest problem is precisely the asymmetric distribution of vertical displacements. It was found that the increase in the length of the vertical reinforcement element provides a reduction in displacements by 1.1 … 1.2 times. It was found that the patterns of changes in the displacements of the subgrade, when the length of the vertical reinforcement element is varied, are linear for the horizontal component and polynomial of the second degree for the vertical component. Originality. For the first time, based on the regularities of the stress-strain state of the subgrade, a picture of the stresses formation and the distribution of deformations before and after the implementation of the European track was obtained. Practical value. Based on the results of the numerical analysis, it was found that increasing the length of the vertical reinforcement element by 2.0 m provides a reduction in displacements by 10 … 20 %. This data makes it possible to create a methodology for the initial selection of the reinforcement element parameters.

Compressive Behaviour of Circular High-Strength Self-Compacting Concrete-Filled Steel Tubular (CFST) Stub Columns Under Chloride Corrosion: Numerical Simulation

This paper investigates the strength and behaviour of high-strength self-compacting concrete-filled steel tubular (HSSC-CFST) stub columns under axial compression. HSSC-CFST columns are high-performance structural members with wide applications in engineering structures. Nevertheless, relevant studies have commonly focused on the mechanical performance of HSSC-CFST in indoor environments. A finite element (FE) model was developed to predict the axial load capacity of HSSC-CFST stub columns subjected to chloride corrosion. According to this, several crucial geometric and material parameters were designed to investigate the influences on strength, initial stiffness, and ductile performance. Moreover, the analysis on failure mechanisms was investigated by N-ε curves and stress development in the whole loading process. The impacts of key parameters on the reduction factor of axial load capacity were also identified. The numerical analysis results indicate that the axial strength of HSSC-CFST stub columns under chloride corrosion was significantly heightened by increasing the strength of core self-compacting concrete, while contrary results were found with the increase in the steel ratio and yield strength of the steel tube. Lastly, design recommendations for the axially loaded HSSC-CFST were presented by modifying the design codes in CECS104-99. The proposed model is shown to be able to estimate the axial load-bearing capacity of HSSC-CFST stub columns more accurately.

Modeling of Stress-Strain State and Coseismic Effects of Epicentral Zone of Tangshan Earthquake (Southeastern China)

The paper presents the results of numerical modeling and analysis of stress-strain state of the epicentral zone of the strong earthquake in the north-east of China, which occurred on 27.07.1976 with Ms=7.8. Many present-day works continue to discuss the reasons for such a strong earthquake, which occurred in tectonic conditions ‒ far from interplate boundaries, inside the Tangshan tectonic block bounded by tectonic faults. However, published new geodynamic, seismological, geophysical and geodetic data provide confidence in the determining role of fault tectonics in this region. Based on the analysis of the results of modeling of the stress-strain state preceding the Tangshan earthquake with coseismic geophysical and geodetic data, we propose a model of earthquake rupture formation. The results of comparison of independent estimates of shear stresses with the results of modeling in the sources of strong earthquakes suggest that the areas of tectonic stress concentration are localized in the interfault rupture of the Tangshan fault, reaching maximum values at the termination of fault ruptures σi ≈ 50 MPa и τxy ≈ 20 MPa. The hypocenter of the main seismic event (taking into account the error of coordinate determination) is located in the region of stress intensity 35‒50 MPa and the ratio of main stresses σxx/σyy ≈ 8–10. It should be expected that these zones are the starting site of rupture, the extent of which depends on the amount of accumulated elastic potential energy of tectonic stresses in the adjacent region. For the Tangshan earthquake, this area corresponds to a high intensity of stresses exceeding 30 MPa in a band with a length more than 30 km and a width reaching 4.5 km.

Determining Thermophysical Parameters of Cryopreserved Articular Cartilage Using Evolutionary Algorithms and Experimental Data.

Cryopreservation is the process of freezing and storing biological cells and tissues with the purpose of preserving their essential physiological properties after re-warming. The process is applied primarily in medicine in the cryopreservation of cells and tissues, for example stem cells, or articular cartilage. The cryopreservation of articular cartilage has a crucial clinical application because that tissue can be used for reconstruction and repair of damaged joints. This article concerns the identification of the thermophysical parameters of cryopreserved articular cartilage. Initially, the direct problem was formulated in which heat and mass transfer were analyzed by applying the finite difference method. After that, at the stage of inverse problem investigations, an evolutionary algorithm coupled with the finite difference method was used. The identification of the thermophysical parameters was carried out on the basis of experimental data on the concentration of the cryoprotectant. In the last part, this article presents the results of numerical analysis for both the direct and inverse problems. Comparing the results for the direct problem, in which the thermophysical parameters are taken from the literature, with the experimental data, we obtained a relative error between 0.06% and 15.83%. After solving the inverse problem, modified values for the thermophysical parameters were proposed.

A new uniaxial material model for the simulation of lateral buckling of steel rebars

Lateral buckling of longitudinal rebars is a crucial phenomenon in the response of reinforced concrete structures since it often anticipates crushing of the core concrete and triggers failure of the member. Owing to this, lateral buckling has been simulated in some uniaxial steel models available in the literature. However, most of these models concentrate their novelties on the compression backbone curve of rebars characterised by low-to-medium slenderness ratios and inaccurately simulate the response of bars characterised by high slenderness ratio or the transition from the compression backbone curve to tension. Moreover, all these models neglect the effects of the concrete cover on the lateral buckling of the rebar. This paper presents a new uniaxial material model of reinforcing steel bars with the aim of achieving a more accurate evaluation of the response of rebars including the effects of lateral buckling. The proposed model is calibrated on the results of numerical analyses conducted on refined models of steel rebars characterised by low-to-high slenderness ratios. The proposed model incorporates the possibility to simulate the behaviour of bare and embedded rebars. The response is path-dependent and described by means of smooth curves so as to guarantee numerical stability in nonlinear finite element simulations. The accuracy of the model has been validated by comparison with the response of laboratory tests performed by other researchers on steel rebars. Finally, applications are shown on six reinforced concrete columns in order to highlight the effects of the simulation of buckling of the steel rebars on the global and local responses.

Finite element modeling of the influence of FRP techniques on the seismic behavior of an arch stone bridge of historical interest

In this paper, a masonry bridge is simulated in order to assess both its structural and seismic vulnerability. Therefore, the present study aimed to approximately analyze the real behavior of Mikron Bridge structure. The modeling was conducted by combining the finite element method (FEM) and discrete element method (DEM) using the ABAQUS® software. By comparing the results of numerical and experimental modal analyses, the accuracy of simulation was verified. To simulate the seismic behavior of the Mikron Bridge, the component of Erzincan earthquake occurred in 1992 was used. The results extracted from the seismic analysis show that some parts of the bridge structure are damaged but not destroyed.

Finite element modeling of the influence of FRP techniques on the seismic behavior of an arch stone bridge of historical interest

In this paper, a masonry bridge is simulated in order to assess both its structural and seismic vulnerability. Therefore, the present study aimed to approximately analyze the real behavior of Mikron Bridge structure. The modeling was conducted by combining the finite element method (FEM) and discrete element method (DEM) using the ABAQUS® software. By comparing the results of numerical and experimental modal analyses, the accuracy of simulation was verified. To simulate the seismic behavior of the Mikron Bridge, the component of Erzincan earthquake occurred in 1992 was used. The results extracted from the seismic analysis show that some parts of the bridge structure are damaged but not destroyed.

Performance Analysis and Operation Parameter Optimization of Shaker-Type Harvesting for Camellia Fruits

This study aims to address the challenges of achieving a high harvesting rate and low flower bud damage rate during the harvesting of camellia fruits. To this end, a dynamic model of the camellia osmantha tree and a self-developed shaker-type harvesting machine were used as research subjects. The first 24 natural frequencies and mode shapes of the camellia tree were solved using the finite element method, and the effects of vibration frequency, excitation position, and vibration duration on the harvesting rate and flower bud damage rate were quantitatively analyzed through an orthogonal experiment. The numerical analysis results indicate that the camellia tree exhibits good response characteristics at vibration frequencies of 10–15.5 Hz and 38.5 Hz. The three-factors orthogonal experiment figured out that the optimal operational parameters for shaker-type harvesting were determined to be a vibration duration of 30 s, a motor output frequency of 12.5 Hz, and a gripping position height of 50 to 60 cm above the ground. Meanwhile, under these operational parameters, the harvesting efficiency reached 96.97%, while the flower bud damage rate was only 6%.

Floor Heave Mechanism and Control Technique of Water‐Rich Soft‐Rock Roadway in Thick Coal Seam

ABSTRACTThe severe deformation of the surrounding rock of the coal floor in Shanghaimiao mining area is affecting the safe, efficient production of mine wells in this region. In this study, the heave mechanism and control of the roadway floor were investigated through laboratory experiments, field research, theoretical analysis, numerical simulation, and on‐site testing. The results showed that the main reason for the serious damage to the roadway floor was the low strength of the surrounding rock of the roadway floor, and floor damage was exacerbated by the low support strength, hydraulic effects, and mining impact. A mechanical model of the asymmetric floor heave was established, and it was found that the stability of the roadway floor was positively correlated with the floor rock type, the stress concentration coefficients on the two sides of the roadway, and the burial depth, whereas it was negatively correlated with the cohesive force and internal friction angle of the floor rock mass. Expressions for the upward resultant force R of the roadway floor and the stress concentration coefficients K and K′ on both sides of the roadway were derived. The results of a FLAC3D numerical simulation analysis showed that the stress peak in front of the working face was 36 MPa, with a stress concentration factor of 3.7. After the floor support was reinforced, the floor heave was remarkably reduced, with a maximum value of approximately 600 mm, and the floor deformation became somewhat asymmetric. Finally, a double‐seal floor‐reinforcing “inverted arch” control technique was proposed and tested on‐site. The new system could efficiently and stably support the surrounding rock of the roadway.