Results Of Numerical Analysis Research Articles

NUMERICAL MODELING OF DYNAMIC DEFORMATION OF A THREE-LAYER RIBBED CYLINDRICAL SHELL UNDER AXISYMMETRIC IMPULSE LOADS

The non-stationary vibrations of three-layer composite cylindrical shell under axisymmetric impulse loads have been researched. The mathematical model and method for calculating the dynamic deformation of the shell system under consideration is based on the geometrically nonlinear theory of Timoshenko’s type shells and ribs. The results of numerical analysis of the problem are presented.

Behavior of CFRP strengthened concrete-filled steel tubes with spherical-cap gap under axial compression

Carbon fiber-reinforced polymer (CFRP) strengthening can be considered as an effect approach to compensate the unfavorable influence caused by the spherical-cap gap on concrete-filled steel tube (CFST) structures. In the present study, the influence of CFRP wrapped on the mechanical behavior of CFST with spherical-cap gap (CFST-G) is examined. Sixteen CFST stub columns are experimentally tested under axial compression loads, considering the gap ratio and the number of CFRP layers (nCFRP) as the main parameters for analysis. The test results show that the bearing capacity decreases with increasing gap ratio, and the wrapped CFRP effectively improves the axial bearing capacity of CFST-G. Notably, the strengthening effect increases as nCFRP increases. Meanwhile, finite element (FE) models are established and verified against the test results. The proposed FE model is then used to conduct behavior analysis, and the working mechanism of CFST-G with CFRP strengthened is revealed. Parametric studies are also carried out by the FE model. The results show that, under the same gap ratio, the strength index decreases with increasing steel strength, steel ratio, and nCFRP, whereas it increases as the concrete strength increases. Based on the test and numerical analysis results, a simplified formula to calculate the bearing capacity of CFRP-strengthened CFST-G is proposed, providing a basis and reference for practical engineering and design codes.

Numerical Investigation and Machine Learning-Based Prediction of the Effect of Using Ring Turbulators on Heat Transfer Characteristics in a Counterflow Heat Exchanger

Background:: Pipe-type heat exchangers are commonly used in industrial applications to facilitate heat transfer between two fluids at different temperatures without mixing them. Method:: In this study, turbulators were employed in a counterflow concentric pipetype heat exchanger. Water at a flow rate of 50 l/h and a temperature of 298.14 K, and air at a temperature of 350 K were directed through the inner pipe. The different stages of circular turbulators placed inside the inner pipe were numerically investigated using the feasible κ-ε turbulence model. Heat transfer characteristics were examined for a turbulator-free heat exchanger and for turbulator-heat exchanger models with helical turbulators of 25, 50, 75, and 100 mm pitch at Reynolds numbers ranging from 4000 to 26000. The governing equations for three-dimensional and turbulent flow conditions in a steady state were solved using a computational fluid dynamics program based on the finite volume method. Temperature distributions and velocity contours in the heat exchanger were generated using the data obtained from numerical analysis. Additionally, predictions were made using artificial neural networks. Results:: The results revealed that the highest enhancement in heat transfer, amounting to 233.08% compared to the empty tube case, was achieved with the 25 mm pitch turbulator. Conclusion:: The predictions made using artificial neural networks were in good agreement with the numerical analysis results. The designed turbulators for the heat exchanger model promoted turbulent flow, increased the heat transfer area, and led to an improvement in heat transfer.

Communication performance optimization of coal mine goaf LoRa AD hoc network sensor system based on tree topology

Real-time accurate monitoring of goaf gas, temperature, and other parameters is of key significance for the prevention and control of spontaneous coal combustion in the goaf. In this paper, a tree network and communication protocol for LoRa technology are proposed to solve the problems of small communication coverage and short endurance of the traditional goaf wireless monitoring system. In this paper, a geometric topology structure is designed for wireless sensor nodes to find relay nodes through the path loss model, and an energy-saving optimization algorithm routing scheme is designed. In addition, LoRa AD hoc network experiment platform and upper computer system are developed and designed. Through numerical analysis and experimental results in coal mines, it is proved that the proposed method significantly reduces the energy consumption of the whole network. The coverage radius is increased by 300% compared with the traditional star wireless sensor system, which makes the endurance time and communication quality have higher reliability.

Active Optimization Method for Power Loss Distribution in T-Type Three-Level Converter Under Half-Wave Symmetry SHEPWM

For high-power converters, it is an important task to optimize the power loss in switching devices. The total power loss affects the efficiency and cooling design of converters, and the uneven power loss distribution causes the switching devices with the highest power loss to age prematurely and shorten the lifespan. Although some low switching frequency modulation strategies can decrease the total power loss, they are not able to balance the power loss distribution. On the contrary, some approaches can balance the power loss distribution by the software and hardware redundancy states of converters only under a high switching frequency. It results in an inability to reduce the total power loss. Therefore, this article proposes an active optimization method for T-type three-level converters to deal with the uneven power loss distribution under a relatively low switching frequency. By analyzing the inner connection between the power loss distribution and 3-order component, the constraint equations of half-wave symmetry selective harmonic elimination pulse width modulation (SHEPWM) are actively redesigned. Thus, both optimization objectives of the power loss can be achieved simultaneously under the proposed SHEPWM. Some numerical analysis and experimental results are given to demonstrate the correctness and feasibility of the proposed method.

Investigation of the Geomechanical Situation in the Rock Mass in the Zone of Influence of Cleaning Operations in the Conditions of the Khromtau Mine Field

Goal. The forecast of the stress-strain state (VAT) in the rock mass in the zone of influence of cleaning operations when using the self-destruction development system and the calculation of the bearing capacity of the supports of the mine workings used at the Khromtau mine. Methodology. The complex of geological and engineering data on the properties of the host rocks is analyzed. Numerical modeling of the stress-strain state of the rock mass and calculation of the bearing capacity of the types of supports used at the mine in the RS2 program, which works on the basis of the Finite Element Method in a two-dimensional formulation, which allowed us to take into account a significant number of factors affecting the state of the array. The HoekBrown model was used as a model of array behavior, the distinctive advantage of which is its nonlinearity. Results. The values of the main stresses and the load on the support are obtained. According to the results of numerical analysis of the stress-strain state of the rock mass at a depth of 900 m (horizon – 480 m), the dominant stresses are close to hydrostatic σ1 = σ3 = σz = 24.8 MPa. A predictive assessment of the stability reserve of mine workings before and after the cleaning work has been carried out, according to the results of which it should be assumed that the stability reserve of the workings passed in the cleaning area is below the minimum allowable, therefore, collapses and an increase in the load on the support are possible. The reference pressure on the support of the workings at a depth of 900 m (-480 m) is calculated. Calculation of the parameters of the support for workings laid at a horizon of 480 m was carried out.. Scientific novelty. The nature and features of the regularities of the formation of the stress-strain state within the boundaries of the influence of various variants of cleaning operations of block 20-28 on the horizon of 480 m are established and a quantitative assessment of the values of loads on the support of the pumping orts of the workings of the horizon is given. Practical significance. The results of the research can be applied to the creation of a geomechanical model of the deposit and the design of stable parameters of the support of mine workings

Study of Wear Resistance of a Radial Bearing Covered by a Polymer Coating with an Axial Groove on a Nonstandard Base Surface

This paper is devoted to study of increasing the wear resistance of a radial plain bearing. The operation of a bearing is considered in the hydrodynamic mode by means of application of an antifriction polymer composite coating with an axial groove and the micropolar properties on a nonstandard bearing surface adapted to the friction conditions of a bearing bush. The effect of pressure and temperature in the turbulent friction mode on the rheological properties of the lubricant is taken into account. Based on the equation for the micropolar fluid flow in a “thin layer” as well as on the dependence of the micropolar lubricant on the pressure and temperature and on the continuity equation, a self-similar solution has been found taking into account the axial groove on the surface of a bearing bush and without taking into account the axial groove. As a result, the velocity and pressure fields in the axial groove and on the surface of a polymer antifriction composite coating have been determined as has the load capacity and friction force, which make it possible to increase the load capacity, reduce the friction coefficient (increase wear resistance), and also increase the duration of the hydrodynamic mode. The results of numerical analysis of theoretical models and experimental evaluation of the suggested design are presented to verify and confirm the efficiency of the models obtained.

Comparison of ACI-318 and TS-500 codes for nonlinear seismic analysis of RC structures using force-based fiber element approach

The material properties such as compressive strength, tensile strength, and modulus of elasticity have been significant phenomena in the nonlinear seismic analysis of RC structures. In several national codes, different equations for the material properties of concrete based on compressive strength are suggested. The effectiveness of these equations in the analysis of RC structures should be investigated to determine the seismic response of the structure. In this study, the effectiveness of ACI-318 and TS 500 design codes is investigated in the numerical modeling of RC structures. For this purpose, the seismic responses of two RC structures experimented in the laboratory are used. The first structure is a two-dimensional three-bay and four-story RC bare frame structure that was tested in European Laboratory for Structural Assessment. The second structure is an RC tall bridge pier that was tested at Pacific Earthquake Engineering Research Center. The numerical solutions are obtained by using the Force-based Fiber Element Approach. The experimental and numerical analysis results are compared in terms of top displacements and damage zones. The concrete material properties which provide the best approximation to the experimental results are investigated for both design codes. It is concluded that the material properties of RC structures determined according to the ACI-318 code can be used for the Force-based Fiber Element Approach with regard to displacement response and damage regions.

Simultaneous Boundary and Interior Parameterization of Planar Domains Via Deep Learning

In isogeometric analysis (IGA), domain parameterization plays a crucial role as it significantly impacts the results of subsequent numerical analyses. Previous literature has often treated domain parameterization as two separate processes: boundary correspondence and interior parameterization. However, this division tends to decrease the quality of the final parameterization. To address this issue, this article proposes a learning-based method that simultaneously parameterizes the boundary and interior of a simply connected planar computational domain using a deep neural network. In our approach, we train a neural network to represent the inverse parameterization, which maps the computational domain to the parametric domain, based on the given boundary curve of the planar computational domain. The key component of our neural network is a Multilayer Perceptron (MLP), which takes the coordinates of a point in the computational domain as input and outputs the corresponding parametric values. The loss function of our method comprises three terms. First, it considers the area distortion and angular distortion of the parameterization, which are determined by the Jacobian matrix of the parameterization. Second, it incorporates the boundary difference, quantified by the Hausdorff distance between the boundary of the parametric domain and the image of the inverse mapping of the computational boundary. By optimizing this loss function, we achieve a robust parameterization. Once the network is trained, we employ a tensor-product B-spline function to fit the mapping from the parametric domain to the computational domain. To evaluate the effectiveness of our method, we conduct experiments on the MPEG-7 dataset. The experimental results demonstrate that our approach yields parameterization results with lower distortion and higher bijectivity ratio compared to state-of-the-art approaches.

Evaluation of Pile Driving Effects on Slope Stability in Clay

Pile driving can trigger slope failure, specifically in sensitive soil deposits or marginally stable slopes. Cases of slope failure during pile installation have been reported in countries such as Norway, Sweden and Canada where soft sensitive clay deposits are prevalent. Although a few approaches have been suggested to assess the factor of safety of a slope during pile driving, there is currently no standard method recognized by the geotechnical society to account for the reduction of safety factor of a slope as an effect of pile installation. Some approaches suggest using the excess pore pressure generated during pile driving to account for the reduction in soil strength (by reducing effective stresses), neglecting the change in total stresses. This paper discusses the accuracy of stability analysis methods currently in use for this problem by looking at stress changes in the soil during pile driving as well as using numerical analysis results. Importantly, the paper identifies the shortcomings regarding these approaches, thus allowing geo-engineers to understand the limitations of their analysis and the uncertainties in the models.

Study on the vibration characteristics of worm helical gear drive

The application of worm helical gear in smart car, smart home and other fields can significantly reduce the weight of products. Accordingly, the requirements for vibration and noise are also increased. In this paper, the lumped mass method is used to establish the dynamic model of point contact bending-twisting shaft meshing coupling worm helical gear drive. In this model, the contact ellipse is transformed into an equivalent rectangle, and the nonlinear factors such as time-varying meshing stiffness, tooth meshing error and meshing damping are considered. The vibration characteristics of worm helical gear drive in three directions and at meshing point are obtained for the first time. Machining accuracy, tooth surface modification and assembly errors are transformed into the error in the dynamic model respectively, and their effects on the vibration characteristics are analyzed. The closed vibration and noise performance test bench of worm helical gear drive is built, and the influence of three kind of errors on the vibration characteristics of worm helical gear drive are tested to verify the correctness of the dynamic model and its numerical analysis results. Both the theoretical analysis and the experimental results show that machining accuracy, tooth surface modification and the assembly error have a great influence on the vibration characteristics.

Finite element modeling and design equations of partially steel-reinforced concrete beam-to-steel tube column joint

Steel reinforced concrete beams are increasingly used as novel transfer structures in high-rise buildings. In this paper, numerical and theoretical studies were carried out on a novel joint of steel-reinforced concrete beam and steel tube column, in which the beam was reinforced by a short steel beam with partial length. Based on the previous experimental studies, finite element modeling was performed to consider the evolution of the concrete damage and to investigate the effects of the main design parameters on the seismic performance of the new joint. It was found that the length of the steel shape, the thickness of the concrete cover, and the concrete compressive strength have significant effects on the initial stiffness and peak capacity of the new joint, while changing those parameters may not change the failure mode of the joint. A theoretical analysis was performed to establish an analytical model for the shear capacity of the new connection that takes into account the contributions of the steel web, stirrups, and concrete. The model was verified against the database of experimental and numerical analysis results. Design equations and recommendations for checking the flexural and shear strength of the embedded steel shape, the composite beam and the RC part of the beam were also provided.

Prediction of Dynamic Behavior of Large-Scale Ground Using 1 g Shaking Table Test and Numerical Analysis.

Earthquake disasters can threaten human life and cause property damage. The dynamic analysis of the ground performance of the seismic field is essential. In this study, numerical analysis is used to predict the dynamic behavior and response analysis of large-scale models under different seismic waves. Firstly, the accuracy of numerical analysis is verified by a 1 g shaking table test under the same size. Then, according to the similarity law, numerical analysis is used to obtain the dynamic behavior of the model at different scales. The results show that the 1 g shaking table test results are in good agreement with the numerical analysis results and that the numerical analysis can predict the dynamic behavior of the scale model. The 1 g shaking table test provides a valuable method for evaluating the numerical analysis, which captures the complex behavior and resolves uncertainties, ultimately leading to more robust and reliable analyses.

A two-phase multi-criteria decision-making with interval-valued Pythagorean normal fuzzy information and its application for module hospital site selection in combating COVID-19

During the fight against COVID-19, module hospital saved tens of thousands of lives and families. Therefore, how to effectively select the site of module hospital is a critical issue. The site selection of module hospital is a multi-criteria decision-making (MCDM) problem. Recently, interval-valued Pythagorean normal fuzzy (IPNF) number has become an effective and powerful tool for handling ambiguity in decision-making. However, the weights of experts in existing IPNF decision-making are often directly given, lacking objectivity and persuasiveness. Moreover, the current research on aggregation operators in IPNFN only involves simple weighted average and geometry, while ignoring the interaction among fuzzy information. Motivated by these issues, this paper aims to develop a two-phase IPNF MCDM approach and apply it to the site selection of module hospital. Firstly, IPNF Einstein weighted averaging (IPNFEWA) operator, IPNF Einstein order weighted averaging (IPNFEOWA) operator, IPNF Einstein weighted geometric (IPNFEWG) operator, and IPNF Einstein order weighted geometric (IPNFEOWG) operator are proposed. Moreover, numerical and theoretical proofs of the proposed operators are carried out. Secondly, an algorithm for determining experts’ weights is developed using the proposed IPNF social network in the first phase, and the decision-making process is conducted in the second phase. Finally, a numerical example on the site selection of module hospital is provided to demonstrate the feasibility of the proposed method. The numerical results of comparisons and sensitivity analysis are further analyzed to confirm the advantages of the proposed method.

Numerical and experimental studies of the effects of WEC motion on a combined wind-wave energy platform

The development of eco-friendly carbon-free marine energy is actively underway to alleviate the impact of global climate change due to excessive emission of carbon dioxide. To reduce the variability of energy production according to marine environment conditions and maximize energy production, the need for research on a suitable ocean energy platform is increasing. Therefore, various studies on motion control of ocean energy platforms are being conducted.
 In this study, the motion response of a combined wind-wave energy platform equipped with multiple wave energy converters (WEC) capable of controlling the motion of a floating offshore wind turbine (FOWT) was numerically analysed and verified through a wave tank experiment. The combined energy platform with multiple WECs attached to the FOWT not only produces stable energy by controlling the motion response of the FOWT with the movement of the WEC, but also produces wave energy by the relative motion of the WEC.
 The FOWT is a spar platform with taut moorings, and WEC is a moving cylinder hinged to the FOWT. The motion reduction effect of the FOWT by the movement of the WEC was investigated. Numerical analysis used the ANSYS AQWA program, which is a potential flow-based hydrodynamic program. To consider the restraining force of the FOWT due to the motion of the WEC, the multi-body dynamics theory was applied. The accuracy of the numerical model was improved by applying mooring dynamics, weakly nonlinear Froude-Krylov force, and nonlinear hydrostatic force. The experimental model was fabricated on a scale of 1/100 of the numerical model and was performed in a two-dimensional mini wave tank. To prevent the sidewall effect of the tank, the experiment was conducted only for the incident waves with various periods under the head sea conditions.
 The numerical analysis results were in good agreement with the experimental results. In particular, the pitch of FOWT decreased significantly near the pitch resonance period because of the motion of WEC. The change in motion characteristics of the combined energy platform according to the movement of the WEC under various wave conditions was analysed.

Determination of the optimal connected and automated vehicles platoon size based on the merging success rate

ABSTRACT The platoon size is a critical parameter in connected and automated vehicle (CAV) platoon configuration. However, the optimal platoon size configuration for the mixed human-driven vehicles (HVs) and CAVs traffic has not been well-studied, especially in merging areas. This paper aims to determine the optimal platoon size in the merge area through numerical analysis. Specifically, the existing merge probability calculation model is improved considering the impact of mainline random platoon size on on-ramp vehicles. In the improved model, the CAV platoon is treated as a vehicle with different lengths, and the headway between the platoon and single vehicle and the headway between the platoons are related to the maximum platoon size and CAV penetration rate. Three key parameters, namely the CAV penetration rate, acceleration lane length, and mainline traffic volume, were combined at various values. Based on this input, the relationship between the success rate and the platoon size was analyzed. The numerical analysis results indicate that: (1) when the CAV penetration rate is 10% ~30%, the merge success rate increases and stabilizes as the platoon size increases, and the optimal platoon size is 4 ~ 6. (2) When the CAV penetration rate is 40% ~70%, the trend of merge success rate varies with increasing platoon size under different mainline traffic volumes and acceleration lane lengths. Under the situation with lower traffic and longer acceleration length, the merge success rate tends to decline easier with larger platoon sizes, with 3 ~ 8 being the optimal platoon size. (3) When the CAV penetration rate is 80% ~90%, as the platoon size increases, the merging success rate tends to increase to the highest point and decrease. The optimal platoon size is 3 ~ 5. Finally, the validity of the theoretical model is confirmed through simulation experiments, and its limitations are discussed.

The behavior of slab on pile structure with a variation of support end interconnection under earthquake load according to the SNI 2833:2016

This paper discusses the behaviour of the slab-on-pile (SOP) structure with variations support end interconnection under earthquake loads. Analysis of the SOP structure using macro modelling of numerical analysis. The SOP structure model is developed with three variations of the model with different support conditions, namely Model 1 with the end of the structure attached to the pile head and spun pile, Model 2 with the end of the structure attached to roller support, and Model 3 with the end of the structure not being supported, or the same as the cantilever system. Earthquake load is assigned using two methods according to SNI 2833:2016, namely the Single-mode Spectra Method and the Response Spectrum Method. Based on the analysis results, the vibration period of the SOP structure calculated by the single mode spectra method is 0.60 seconds for the first mode and 0.34 seconds for the second mode. Based on the numerical analysis results, the vibration period of Model 3 is greater than that of other models. The maximum internal forces and the most significant displacement occur in Model 3, while the most considerable base reaction occurs in Model 1. The magnitude of the base shear force occurs because Model 1 uses more piles, thus increasing the stiffness of the structure. This results in an increase in seismic forces but reduces displacement of the structure. Furthermore, for the analysis and design of SOP structures, Model 3 is the most reliable because this model produces the maximum load effect and the most significant displacement of the structure.

Seismic characterisation of aluminium fusible links in single‐storey steel buildings

AbstractThis work is part of the European RFCS “FISHWALL” project entitled “Fire and Seismic performances of hybrid fire walls in case of single‐storey industrial and commercial steel buildings”. The aim of the project is to design a hybrid firewall solution using sandwich panels for single‐storey buildings connected with the unprotected steel structure by means of fusible links, made of aluminium bolts. In this respect, the paper shows the results of preliminary numerical analyses performed on existing case studies of single‐storey steel buildings located in low and moderate seismicity zones and they were used: i) to estimate the seismic forces acting on the fusible links and ii) to subsequently design the specimens to be tested in the laboratory. In this respect, several finite elements models were developed in order to consider the widest range of configurations of the firewall with respect to the direction of the portal frame composing the steel buildings, i.e. firewall parallel and orthogonal to the portal frames. Based on the estimated forces, the design of the six different specimens was performed and it is thoroughly shown in the paper.

Study of Wear Resistance of a Radial Bearing Covered by a Polymer Coating with an Axial Groove on a Nonstandard Base Surface

This paper is devoted to study of increasing the wear resistance of a radial plain bearing. The operation of a bearing is considered in the hydrodynamic mode by means of application of an antifriction polymer composite coating with an axial groove and the micropolar properties on a nonstandard bearing surface adapted to the friction conditions of a bearing bush. The effect of pressure and temperature in the turbulent friction mode on the rheological properties of the lubricant is taken into account. Based on the equation for the micropolar fluid flow in a “thin layer” as well as on the dependence of the micropolar lubricant on the pressure and temperature and on the continuity equation, a self-similar solution has been found taking into account the axial groove on the surface of a bearing bush and without taking into account the axial groove. As a result, the velocity and pressure fields in the axial groove and on the surface of a polymer antifriction composite coating have been determined as has the load capacity and friction force, which make it possible to increase the load capacity, reduce the friction coefficient (increase wear resistance), and also increase the duration of the hydrodynamic mode. The results of numerical analysis of theoretical models and experimental evaluation of the suggested design are presented to verify and confirm the efficiency of the models obtained.

Test and numerical study of 7021-T6 high strength aluminum alloy anchor channel embedded in reinforced concrete structure

Test and numerical study of 7021-T6 high strength aluminum alloy anchor channel embedded in reinforced concrete structure were carried out in this study. The vertical tensile test, transverse shear test and longitudinal shear test were conducted. The mechanical performances including the vertical tensile property, transverse shear property and longitudinal shear property of the specimens were analyzed. The 207 numerical models of 7021-T6 high strength aluminum alloy anchor channel embedded in reinforced concrete structures were analyzed, including the numerical models of 180 specimens under vertical tensile loading and 27 specimens under longitudinal shearing loading. According to the numerical analysis results, it was suggested that the channel thickness and notch thickness of the 7021-T6 high strength aluminum alloy anchor channel embedded in reinforced concrete structure should not be less than 5 mm. In addition, the comprehensive coefficient K and calculated formula of the ultimate bearing capacity of the 7021-T6 high strength aluminum alloy anchor channel embedded in reinforced concrete structure in the tensile state were proposed. Finally, the mechanical model was established to calculated and analyzed the transverse shear capacity of 7021-T6 high strength aluminum alloy anchor channel embedded in reinforced concrete structure.