Results Of Numerical Analysis Research Articles

Equation for the simplified calculation of the horizontal shear stress in composite beams of rectangular cross-section with considerable width

The theory of elasticity allows describing the law of variation of shear stresses Τzy and Tzx for a beam of rectangular cross-section, however, the expressions are extensive and complex. For beams with a width/depth ratio equal to 0.25, it is allowed to calculate approximately the maximum shear stress Tzy, with the Collignon-Zhuravski equation. Depending on the width/depth ratio of the beam, it will depend on the percentage of error made. Unfortunately, for the shear stress Tzx there is no approximate formula available to determine the value of the shear stress. Using a simplified procedure, a differential beam element was analyzed in the elastic field for different width/depth ratios and a very simple expression was obtained. The results of the approximate formula were compared with the values obtained from the application of the exact formula and the results of a linear numerical analysis using the finite element method. For cross-sections of homogeneous beams and composite beams of considerable width, it is essential to determine the horizontal shear stresses Tzx in particular in the case of vertical planks, arranged side by side, connected solidly by horizontally arranged mechanical connectors, since the shear stresses Tzx developed across the width of the cross-section may considerably exceed the vertical shear stresses Tzy and furthermore govern the pattern, spacing and cross-section of the mechanical connectors. The validity of the approximate expression for calculating the maximum value of the shear stress Tzx was limited to beams with a width/depth ratio between 0.25 and 10.0.

Strength capacity of RC beams without shear reinforcement: Numerical analysis and comparisons with code provisions

The investigation of the behavior of reinforced concrete (RC) elements without shear reinforcement is a current focal point, driven by the incomplete consolidation of predictive formulas for shear strength in RC elements. Currently, the literature provides, indeed, a limited number of experimental and numerical studies on this subject. This paper seeks to advance the comprehension of the behavior and collapse mechanisms of RC beams not provided of shear reinforcement, as commonly employed in RC slabs of bridges. The paper commences with a critical review of several predictive formulas for the shear strength of RC elements lacking transverse reinforcement, as stipulated by various international codes. The objective is to identify the principal parameters involved in the formulations and discuss their roles also by means of sensitivity analysis. Following this, the results of nonlinear numerical analyses, based on a three-dimensional finite element (FE) model, are presented. The FE model was initially calibrated using experimental results from a benchmark beam lacking shear reinforcement, retrieved from the literature, which exhibited a brittle shear failure. Subsequently, several specimens were prepared for the numerical investigation, assuming multiple combinations of geometrical and mechanical parameters. For specimens experiencing shear failure, the strength was compared with that provided by code formulas, as well as using the strut-and-tie approach for the cases characterized by a reduced shear span-to-depth ratio. In general, these analytical tools significantly underestimated the numerical strength, underscoring the necessity for further insights based on experimental tests. The numerical outcomes have been, indeed, prodromal to design an experimental campaign.

Design and experimental study of a stepped magnetorheological damper with power generation

Traditional vehicle suspension magnetorheological dampers have problems with low output damping force and require additional energy input to operate, to improve the performance of the vehicle suspension magnetorheological damper, in this paper, we propose and investigate a stepped magnetorheological damper structure with power generation, and conducts structural design and magnetic circuit analysis. The effects of different currents, damping gaps, coil slot positions, and coil turns on the damping performance of the stepped magnetorheological damper with power generation are numerically studied. The magnetic circuit sensitivity analysis of the power generation structure and the magnetorheological damper structure is also performed. Experiments have verified the effects of different input excitations on damping and energy-feeding performance, and the results of numerical analysis have been verified. The results show that when the excitation coil is wound for 257 turns, the magnetic circuit requirements are met. And the influence of different amplitudes, frequencies, and currents on the output damping force was studied through experiments. The results showed that the damping force would increase with the increase of single parameter values. When the amplitude was 7 mm, the frequency was 1 Hz, and the current was 2 A, the output damping force could reach 4500 N, meeting the requirements for use.

Numerical and experimental verification of column web in transverse compression

This paper focuses on the problem of steel members of open double symmetrical cross-sections in transverse compression. First, the problem is introduced with examples of its application in steel structures of buildings and followed by the overview of selected substantial literature resources and current design codes provisions. The essential part of the paper is a presentation of results of experimental tests and advanced numerical analysis of members subjected to selected cases of transverse compression. Where possible, the results are compared with resistances obtained using provisions in currently valid design codes for steel structures. The influence of selected parameters on the resistance in transverse compression is quantified within the evaluation with specific attention paid to plate buckling of the web. Based on data obtained from the experimental and numerical investigations, the most notable findings are summarized.

Numerical and Experimental Modal Analysis of a Gyroid Inconel 718 Structure for Stiffness Specification in the Design of Load-Bearing Components.

The study aims to investigate the modal properties of a 60 × 70 × 80 mm gyroid structure made of Inconel 718 with 67.5% porosity. The geometry model for sample production was created using the software PTC Creo, whereas the geometry model for numerical analysis was created using the Python application ScaffoldStructures. FE analysis was performed using ANSYS 2024 R1 software. Free boundary conditions were used in experimental modal analysis to ensure feasibility. The analysis identified the first four natural frequencies ranging from 10 to 16 kHz. The results revealed that the first natural frequency corresponds to the first torsional frequency about the Z axis, the second to the first flexural mode in the XZ plane, the third to the first bending mode in the YZ plane, and the fourth to the first torsional mode about the X axis. Small differences between the results of numerical and experimental modal analysis can be attributed to geometric errors in the manufactured sample, careless removal from the platform, and due to reduction in the complexity of the numerical FE model. Employing modal analysis of a component, the stiffness of a lightweight component can be revealed. In the case of the sample with the cellular structure of gyroid type, relatively high stiffness regarding the material savings was identified, which can be advantageously used in many applications.

Long-term accuracy of numerical approximations of SPDEs with the stochastic Navier–Stokes equations as a paradigm

Abstract This work introduces a general framework for establishing the long time accuracy for approximations of Markovian dynamical systems on separable Banach spaces. Our results illuminate the role that a certain uniformity in Wasserstein contraction rates for the approximating dynamics bears on long time accuracy estimates. In particular, our approach yields weak consistency bounds on ${\mathbb{R}}^{+}$ while providing a means to sidestepping a commonly occurring situation where certain higher order moment bounds are unavailable for the approximating dynamics. Additionally, to facilitate the analytical core of our approach, we develop a refinement of certain ‘weak Harris theorems’. This extension expands the scope of applicability of such Wasserstein contraction estimates to a variety of interesting stochastic partial differential equation examples involving weaker dissipation or stronger nonlinearity than would be covered by the existing literature. As a guiding and paradigmatic example, we apply our formalism to the stochastic 2D Navier–Stokes equations and to a semi-implicit in time and spectral Galerkin in space numerical approximation of this system. In the case of a numerical approximation, we establish quantitative estimates on the approximation of invariant measures as well as prove weak consistency on ${\mathbb{R}}^{+}$. To develop these numerical analysis results, we provide a refinement of $L^{2}_{x}$ accuracy bounds in comparison to the existing literature, which are results of independent interest.

Determining the Size of Representative Volume Elements for a Two-Dimensional Random Aggregate Numerical Model of Asphalt Mortar without Damage.

The size of the representative volume element (RVE) for the two-dimensional (2D) random aggregate numerical model of asphalt mortar in a non-destructive state, which directly affects the time required to simulate the linear viscoelastic behavior from asphalt mastic to asphalt mortar. However, in the existing literature, limited research has been conducted on the size determination of the numerical model RVE for asphalt mortar. To provide a recommended size for the typical 2D random aggregate numerical model RVE of asphalt mortar in a nondestructive state, this paper first applies the virtual specimen manufacturing method of asphalt concrete 2D random aggregate to asphalt mortar. Then, it generates numerical model RVEs of asphalt mortar with different maximum particle sizes, after which geometric and numerical analyses are conducted on these models. Finally, based on the geometric and numerical analysis results, the recommended minimum sizes of RVE for the 2D asphalt mortar numerical model are provided.

Sudden weather disasters as triggers for ethnic protest in autocracies?

Under what conditions do disastrous storms and floods provoke anti-government protests in autocracies? While grievances, as they often occur after disastrous weather events, are necessary preconditions for protests, they are by no means sufficient. This is particularly true in undemocratic states, where protesters typically fear repressive sanctions. Therefore, this essay hypothesizes that disastrous storms and floods primarily result in anti-government mobilization in autocracies when they occur in the homelands of marginalized ethnic groups. In such scenarios, the immediate hardships caused by the disaster come on top of underlying more structural grievances. Moreover, groups with shared ethnic identities are more likely to mobilize for collective action. This argument is tested using quantitative cross-national protest-event data from the Mass Mobilization in Autocracies Database (MMAD). The results of numerous regression analyses on a sample pre-processed with Coarsened Exact Matching to address potential concerns of endogeneity yield robust support for the outlined hypothesis.

Design, optimization, and performance analysis of a subsonic high-through flow turbine

This paper presents the design method and numerical analysis results of a two-stage high-through flow (HTF) high-pressure turbine. Compared to conventional design principles, the HTF turbine proposed in this study is a kind of high flow coefficient turbine. This design scheme enables the turbine to effectively increase the output power and thrust while maintaining the same windward area. At the design speed, the pressure ratio of the HTF turbine is 3.8, with an adiabatic efficiency of 91.46%. The flow coefficients of the first and second stage are 0.76 and 0.86, respectively, and the loading coefficients are 2.55 and 1.47. Detailed design parameters, flow characteristics, and aerodynamic performance are presented in this paper. Based on the preliminary design result, the second stage turbine was optimized for a wide range of operating conditions. The computational fluid dynamics simulation results show that compared with the traditional turbine, the loading form of the HTF turbine changes from aft-loaded to front-loaded. In addition, there is a certain increase in tip leakage of the turbine. This study achieves high efficiency, while increasing the turbine flow rate, and provides a corresponding reference for the design method of improving turbine flow capacity.

압축기 형상 변화에 대한 유동해석 방법 연구

In this study, numerical analyses were conducted using ANSYS CFX code to predict the performance of a turbo compressor, and the results are compared with the experimental data. A compressor is a machine that plays an important role in various industrial fields. It supplies high-pressure gas by compressing the volume of gas received from outside. In this study, a numerical-analytical approach is presented to solve problems arising in the design and operation of turbo compressors. To simulate the complex flow phenomenon in the compressor, a frame-change model was applied to the rotator. Subsequently, a methodology considering compressible fluids and turbulence model was employed to accurately predict the flow around the impeller. Additionally, numerical analysis was performed using commercial CFD code, ANSYS CFX. This software exhibits excellent convergence and analysis accuracy when rotating and stationary areas are mixed, effectively predicting the compressor performance. The numerical analysis results using the CFX code were consistentwiththeexperimentaldata,indicatingthatCFXisasuitabletoolforpredictingtheperformanceofturbocompres sors.Itisalsoexpectedtobeusefulinthedesignandoperationofcompressorsinthefuture.

Numerical and experimental investigation of the gyroid heat exchanger

This paper presents a study of a novel type of heat exchanger (HE) whose core is built based on a Triply Periodic Minimal Surface structure. The core of this exchanger is built as a periodic structure based on a gyroid-type lattice and is manufactured by laser powder-bed fusion technology. This solution is distinguished not only by an exceptionally favorable ratio of the heat exchange surface area to the volume occupied but also by a unique geometry that additionally turbulates the flow and intensifies the heat exchange process. This article contains the results of numerical analyses of the entire exchanger under different operating conditions and the results of analyses of small fragments of the core filled with cells of different sizes. Numerical analyzes of the lattice-type exchanger are performed on the basis of the experimentally validated numerical model. The objective of the study is to determine the performance of the gyroid HE under different operational conditions and select the best elementary cell size per exchanger core for the assumed operating conditions. The printed HE was compared with a plate HE that was 30% larger, although the lattice one managed to achieve 10.5% higher values in on average Number of Transfer Units (NTU) and on average 5% higher temperature effectiveness (TE) in the studied range of flow parameters.

Computer Simulation of Charge Transfer In a DNA Molecule within a Simple Model of an Open Quantum System

The quantum-statistical model proposed earlier by Skourtis and Nitzan to describe a charge (hole) propagation in a fragment of artificial DNA molecule has been generalized and further investigated. A numerical simulation of a charge transport was carried out taking into account two different dissipative processes, including the capture of the charged carrier by the environment and the decoherence of its quantum wave properties due to the influence of stochastic fields of the environment. The interaction of the carrier with the environment is regulated by a small set of phenomenological parameters whose values vary in the process of simulation. Within this model, the propagation of a hole carrier in DNA is described by solving the quantum Franke-Kossakovski–Lindblad–Glauber–Sudarshan equation (hereinafter referred to as the Lindblad equation) for the carrier density matrix using the Lindblad MPO Solver program. Results of numerical analysis of the model are in a good agreement with experimental observations and demonstrate two different types of the charged carrier motion, presumably tunneling and incoherent hopping. The model is put in more general context and non-unitary dynamics of the hole carrier is treated within the framework of a theory of continuous quantum measurements by the environment in an open quantum system. The main concepts of the theory of decoherence and superselection for open quantum systems and the prospects for their application for further study of various mechanisms of motion of a charged carrier in DNA are briefly discussed.

Experimental Research and Application of Small-Strain Soil Hardening Model Parameters in a Major Project in Hangzhou

According to current research, the small-strain soil hardening model (HSS model) is being used more and more widely because it can consider the small-strain characteristics of soil, making the corresponding numerical analysis results more accurate. At present, research into the test value of HSS model parameters of soil mass is mainly concentrated in Shanghai. Given the limits of the test conditions, there has been notably insufficient research into the value of small-strain parameters. Considering the regional differences of soil parameters, this paper, based on an actual project, conducts the HSS model parameter test value study on the main soil layers in the west of Hangzhou, focusing on the value study of small-strain parameters. The corresponding results are used for numerical analysis. The research shows that, compared with the Mohr–Coulomb model, the numerical analysis results using the HSS model are obviously closer to the measured data, and the prediction of the lateral deformation and its change law of the diaphragm wall is obviously more accurate. At the same time, when other HSS model parameters are unchanged, the numerical results using in situ small-strain parameters are closer to the measured results than using indoor small-strain parameters, and the corresponding deformation prediction accuracy is higher. The research results provide valuable references for determining HSS model parameters and engineering applications in the western area of Hangzhou.

Pollution concentration monitoring using a new Birnbaum–Saunders control chart

AbstractAir pollution monitoring is an important issue in environmental science. The Birnbaum–Saunders (BS) distribution, originally applied to describe product failure time distribution to fatigue failures and general random wear failures, is also well to describe the pollutant concentration data due to accumulations of various pollutants in the air over time. Sulfur dioxide (SO2) is a critical factor in air pollution. Hence, it is important to monitor its concentration variation for air pollution prevention. Due to the complexity of its distribution form, there is no reliable and easy‐to‐use control chart for monitoring pollutant concentrations based on the BS distribution. We found that the SO2 concentration data follows the BS distribution. In this study, we propose a new median control chart based on the exact sampling distribution of the monitoring statistic to detect shifts in the median of BS distribution. Thus, given the false alarm rate, the control limits for such control charts can be obtained precisely satisfying a preset in‐control average run length using Monte Carlo simulations. The out‐of‐control average run lengths are calculated by simulation to evaluate the detection performance of the proposed chart when the median shifts occur. We further compare the detection performance of the proposed chart and those of the existing control charts based on asymptotic sampling distributions. In order to improve the detection ability of the proposed chart for small median shifts, an exponentially weighted moving average (EWMA) control chart is constructed. The results of numerical analyses demonstrated that the proposed EWMA chart performs much better than all existing control charts for monitoring the median of BS distribution. Finally, the proposed control charts are applied to monitor the median of SO2 concentrations for air pollution control, showing that both charts can effectively detect a shift in the median of SO2 concentrations. The proposed EWMA control chart even detects out a small shift in the median of SO2 concentrations. The results provide a continuous monitoring solution for air pollution prevention.

Analysis of the impact of key strata failure on overlying strata and surface transport patterns

After mining the coal seam under the slope terrain in the southwestern mining area, it is difficult to predict the damage characteristics of the overlying strata and the surface movement and deformation law. To solve this problem, this paper comprehensively analyses the key strata by applying the theory, similarity simulation and the GDEM simulation software, and explores the influence of the change of the key strata’s height and thickness on the damage characteristics of the overlying strata and the surface movement and deformation. By analysing the key strata in the “inclined step” structure, the minimum support force for the key strata not to slip is obtained, and the minimum support force required for the key strata at different levels is deduced. The results of similar tests and numerical simulation analyses show that the vertical displacement of the overburden and surface will be smaller as the key layer is further away from the coal seam. AT the same time, the damage to the overlying strata and the surface is smaller when the key strata fails, and the location of the first subsidence of the slope surface due to mining is usually located in the area close to the bottom of the slope. In the stable structure from the key strata to the ground surface, once the key strata is unstable and broken, the damage and vertical displacement of the ground surface will increase dramatically, thus causing a series of geological disasters such as ground subsidence. Therefore, before the key strata are broken, grouting reinforcement measures are carried out for the rock fissures below the key strata to enhance the tensile strength of the key strata, which can effectively reduce the surface subsidence and deformation.

An investigation on bending fatigue in a corrosive environment of dual-phase 1000 sheet steel RSW joints and damage model via experiment and numeric analysis

Fatigue, corrosion, and fatigue damage models are best addressed to improve and understand the service performance of materials, particularly automotive steel. This study is an attempt to experimentally and finite element investigates plain bending fatigue performance and damage model of DP 1000 sheet steel resistance spot welding (RSW) joints in 3% NaCl aqueous corrosive treatment. RSW applications were carried out using different weld currents. The joint samples were then subjected to optical image analysis, tensile shear, and fatigue tests (3% NaCl-aqueous and normal atmosphere). A proper damage model of RSW junctions was developed and corrected by numeric analysis. Besides, RSW nugget formation, tensile shear, and plain bending fatigue tests were also applied. Consequence, fatigue behavior, tensile load carrying capacity, and effective fracture behavior of resistance spot welded joint specimens were evaluated. Results showed that a corrosive environment negatively affected fatigue performance. With the developed model, it was observed that the fatigue life of the samples decreased by 30–35% in the fatigue tests performed in the corrosive environment. Experimental and numerical analysis results of plain bending were compatible.

Tensile Forces Behavior on Longitudinal Reinforcement and CFRP Strips on Circular Hollow Reinforced Concrete Columns

Abstract Currently, there is not much research on strengthening structural elements with hollows. This manuscript presents the test results from twelve circular reinforced concrete column specimens strengthened with CFRP strips. This study focuses on the strain behavior of longitudinal reinforcement and CFRP strips due to high shear force intensity. Hollows in the cross-section are used to see the effect of voids on the column strain distribution. Nine specimens have a hollow cross-section with hollow diameters of 1.5", 2.5", and 3.5" for each of the three specimens. Meanwhile, the other three specimens have a solid crosssection. All specimens do not use stirrups to determine the contribution of concrete and CFRP strips to resist shear. Strain gauges are placed in certain positions to read the strain on the longitudinal reinforcement and CFRP strips. The test results are in the form of tensile forces and are then analyzed to obtain the movement pattern of tensile forces in the longitudinal reinforcement and CFRP strips. Numerical analysis using a fiber element model is used to obtain the strain in each reinforcement layer. The numerical analysis results were then compared with the test results and showed close results. Then, an equation for calculating the tensile force in CFRP strips is proposed. The proposed equation approximates the test results with an accuracy level of 90%.

Mechanism study on the influences of buffer osmotic pressure on microfluidic chip-based cell electrofusion.

Cell electrofusion is a key process in many research fields, such as genetics, immunology, and cross-breeding. The electrofusion efficiency is highly dependent on the buffer osmotic pressure properties. However, the mechanism by which the buffer osmotic pressure affects cell electrofusion has not been theoretically or numerically understood. In order to explore the mechanism, the microfluidic structure with paired arc micro-cavities was first evaluated based on the numerical analysis of the transmembrane potential and the electroporation induced on biological cells when the electrofusion was performed on this structure. Then, the numerical model was used to analyze the effect of three buffer osmotic pressures on the on-chip electrofusion in terms of membrane tension and cell size. Compared to hypertonic and isotonic buffers, hypotonic buffer not only increased the reversible electroporation area in the cell-cell contact zone by 1.7 times by inducing a higher membrane tension, but also significantly reduced the applied voltage required for cell electroporation by increasing the cell size. Finally, the microfluidic chip with arc micro-cavitieswas fabricated and tested for electrofusion of SP2/0 cells. The results showed that no cell fusion occurred in the hypertonic buffer. The fusion efficiency in the isotonic buffer was about 7%. In the hypotonic buffer, the fusion efficiency was about 60%, which was significantly higher compared to hypertonic and isotonic buffers. The experimental results were in good agreement with the numerical analysis results.

Flexible and Multifunctional Composites with Highly Strain Sensing and Impact Resistance Properties.

The development of smart protective clothing will help detect injuries from contact sports, traffic collisions, and other accidents. The combination of ecoflex, spacer fabric, and graphene-based aerogel provides a multifunctional composite. It shows a strain sensitivity of 17.71 at the strain range of 40~55%, a pressure sensitivity of 0.125 kPa-1 at the pressure range of 0~15 kPa, and a temperature sensitivity of -0.648 °C-1. After 50 impact tests, its protection coefficient only dropped from 60% to 55%. Additionally, it shows thermal insulation properties. The compression and impact process results of finite element numerical simulation analysis are in good agreement with the experimental results. The ecoflex/aerogel/spacer fabric sensor exhibits a simple structure, large pressure strain, high sensitivity, flexibility, and ease of fabrication, making it a candidate for smart protective clothing resistant to impact loads.

Metro-induced vibration attenuation using rubberized concrete slab track

This paper addresses two important worldwide environmental concerns: disposal of waste tyres and attenuation of trains induced vibration. To this end, use of the waste materials in construction of railway concrete slabs for reduction of train induced vibration is investigated in this research. For this purpose, rubber tyre particles with different dosages were used in the concrete mixtures of test specimens. Extensive laboratory tests were conducted on the rubberized concrete specimens to measure their compressive strength, density and damping of the specimens. The effect of rubberized slab track on attenuation of vibration propagated from slab track was investigated by numerical modeling using results of laboratory tests as the input data. The laboratory results obtained indicate that adding rubber particles to the railway slab causes up to 96% increase in damping ratio (for concrete with 10% rubber). Results of numerical analysis elucidates that the rubberized slab track causes up to 21% reduction of the train induced vibration. By compromising between compressive strength and damping of vibration, it is shown that the optimum amount of crumb rubber in the concrete of railway slabs is 2.5% by which the best performance of the railway slabs is obtained.