Results Of Numerical Analysis Research Articles

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.

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%.

The Flexural Behavior of Reinforced Ultra-High Performance Engineering Cementitious Composite (UHP-ECC) Beams Fabricated with Polyethylene Fiber (Numerical and Analytical Study)

Ultra-high performance engineered cementitious composite (UHP-ECC), which is a new and ductile version of concrete, has attracted researchers recently due to its exceptional mechanical properties: its very high compressive strength (from 100 to 200 MPa) and very high tensile strain capacity (not less than 3% and up to 8%). However, the available experimental literature is small due to its very high cost. To overcome the high cost of the experiments of UHP-ECC, the finite element modeling package ANSYS was used to create a new modeling technique using the Menetrey–Willam constitutive model, recently added to ANSYS. This technique was validated using previous experimental results for UHP-ECC beams and found to be accurate and effective. The previous FE model was used to conduct a parametric study and the variables—the compressive strength of the concrete, the percentage of the volume content of polyethylene fibers, the tensile reinforcement ratio, and the span-to-depth ratio—were found to be effective upon the flexure behavior of the reinforced UHP-ECC beams. As the analysis and design of UHP-ECC beams fabricated with polyethylene fiber are not available yet through design codes, an analytical model including some equations was deduced to calculate the flexure capacity of such beams. The results of the parametric study were used to investigate the validity and accuracy of the analytical model. The proposed equations demonstrated a good estimation compared with the numerical analysis results.

Performance Investigation of a Novel Staggered Round Table Channel for Proton Exchange Membrane Fuel Cells

Based on the internal mass transfer of a proton exchange membrane fuel cell (PEMFC), a novel staggered round table channel is proposed, namely, round table stoppers are arranged on both sides of the channel and in the direction of gas flow. The study systematically investigates the effects of various structural parameters on the PEMFC performance, including the arrangement of round tables on both sides of the channel, radius, degree of sparseness, and number. It is found that the staggered arrangement can improve the cell performance more significantly, and the current density can be increased by 5.0% compared with the direct channel. With the proper increase of the radius and number of round tables, the round table stopper forces the reactant to diffuse downward and improves the uniformity of reactant distribution. Compared with other sparsity, the equidistant arrangement of stoppers in the channel is conductive to accelerating the convective mass transfer and drainage characteristics of the cell. As shown by numerical analysis results, the performance and dewatering efficiency of PEMFC are the best when the round tables on both sides are staggered, the radius is 0.65 mm, the number is 10, and the round table in the channel is arranged equidistantly.

Introduction to the Investigation of reproduction of the real geometry of UBM panels

The article concisely describes UBM technology (Ultimate Building Machine), that can be used as a solution for buildings and roof structures. The structure of this technology is made of double corrugated thin-walled steel profiles manufactured on the construction site by a self-contained UBM manufacturing factory on wheels. These panels serve as both the building envelope and the structural system. The specificity of the construction poses many design problems, especially the determination of the strength parameters and stiffness of the double-corrugated panels from which the structure is made. The article presents the results of spatial scanning tests of double-corrugated steel sheets, which were carried out using commonly available 3D scanning devices: Leica 3D Disto and MagiScan app. Additionally, results of numerical analyses performed on scanned samples and a comparison of these results with preliminary laboratory tests have been presented in the article. The purpose of scanning was to obtain an accurate and real geometry of the UBM panels, to implement it into a numerical software, and then to perform numerical analyses. Commonly available 3D scanning devices were used because using advanced 3D scanners is not popular nowadays for economic reasons, and hand-built geometric models pose a lot of problems and are not accurate enough. Promising results were obtained, which form the basis for further research.

Mechanical properties of aramid and UHMWPE thermoplastic composites: numerical and experimental trials

The out-of-plane behaviour of 8 different composites exposed to very high deformation rates and non-standard conditions was investigated in our previous studies. The mechanical properties of these composites have been evaluated through tests conducted at deformation rates comparable to those experienced during explosions. Based on the relevant test results, this study conducted a numerical analysis of 3 best-performing Aramid UD GS3000, Artec Aramid/Woven Aramid CT736, and H62 UD-UHMWPE-reinforced composites. In this regard, LS-DYNA's MAT54 model was compared with other failure mechanics-based models and preferred because it requires less experimental data and can simulate damage progression in dynamic failures. Since the samples used in the study were non-standard, quasi-static tensile and shear tests were performed based on the loads to which the composites would be exposed to create an accurate numerical analysis. Both tensile and shear strength values of the Artec Aramid/Woven Aramid CT736 composite are higher than those of the Aramid UD GS3000 and H62 UD-UHMWPE composites. When the numerical analysis results were compared with the tensile test data, compliance rates of 99.84% for Aramid UD GS3000 reinforced composite, 99.34% for Artec Aramid/Woven Aramid CT736 reinforced composite, and 96.42% for H62 UD-UHMWPE reinforced composite were determined. The analysis showed that the shear stress-strain curves provided 100% agreement at the maximum stress value.

Calibration of Heat Source Models in Numerical Simulations of Welding Processes

This article presents issues related to the methodology of the correct definition of the heat source model in the numerical analyses of welding processes. The problem of determining the input data for the stage of a heat source model definition, obtaining input data from experiments, and their proper interpretation and use in defining the numerical model was discussed. Particular attention is paid to the specificity of the problem of defining the heat source model, the way of interpreting the results of the analyses and the way of comparing them with the results of real experiments. The basic problems related to the mapping of the complex geometry of the molten metal pool and the ways to solve them were indicated. The solutions and guidelines presented in the article allow to improve the accuracy and quality of the obtained results of numerical analyses, as well as to shorten the time of preparation of computational models by reducing the number of computational iterations related to the search for the maximum consistency of the compared values and temperature cycles.

Compact THz Polarization Splitter with Large Bandwidth Based on Cascade Hexagonal Porous Two-Core PCF

ABSTRACT A novel cyclic olefin copolymer (COC)-based terahertz (THz) polarization beam splitter (PBS) employing photonic crystal fiber (PCF) with cascade hexagonal porous two-core structure is proposed. The porous two-core is achieved by replacing the original two large air holes with three layers of small air holes. The mode coupling characteristics between the even and odd modes in the x- and y-polarization directions for the proposed THz PBS are explored using the time-domain finite difference (FDTD) method. The influence of PBS structural parameters on its coupling length is investigated. Numerical analysis results indicate that the bandwidths of 227.8 GHz (ranging from 1.8970 to 2.1248 THz) and 147 GHz (ranging from 1.928 to 2.075 THz) are acquired for the x- and y-polarization fundamental modes, respectively. The highest extinction ratios (ERs) are 114.5 dB and 72.3 dB, and the minimum insertion losses (ILs) are 0.0142 dB and 0.0369 dB for the x- and y-polarization fundamental modes, respectively. Moreover, the length of the proposed PBS is merely 11.655 mm. The proposed PBS will find potential applications in polarization-diverse THz systems, including broadband line-of-sight communication, real-time security checks, and high-resolution imaging.

Proposing New Standard and ANFIS Calculation Approaches for Precast Concrete Connections with Steel Tube Elements: Lessons from Experimental Studies

The importance of establishing a proper method for calculating newly studied structural elements and primarily translating the results of experimental and numerical analyses into practical standards poses a significant challenge for structural researchers. In this study, which focuses on the importance of previously studied connections for the precast industry as a case study, two approaches are proposed for calculating the capacity of elements connected by rectangular steel tubes. The first approach involves a step-by-step calculation for analyzing the forces and capacities of different steel tube or concrete section parts under bending and shear, aiming to establish a standard calculation approach. Despite its complexity, the standard calculation approach has proven its accuracy by successfully solving examples with features similar to those of the experimental tests describing the process. The second approach relies on a look-up table generated from experimental data, developing an Adaptive Neuro-Fuzzy Inference System (ANFIS) for interpreting the data. ANFIS not only facilitates the evaluation of the capacity of non-experimentally tested elements but also resembles the calculation process. Evaluating ANFIS’s performance concerning the original results underscores its remarkable capacity to analyze experimental data. With a maximum calculation error of only 13% when compared to the experimental tests, ANFIS demonstrates considerable accuracy and user-friendliness. Following the initial internal force evaluations, the proposed standard calculation method requires eight specific control inputs, and comparing these inputs with experimental tests further confirms the effectiveness and safety of this approach for connection design.

A large-scale supplier evaluation approach for circular economy in the presence of circular criteria interactions and weight consistency

Circular economy (CE) is an economic model in which we achieve sustainable development through resource recovery, reuse, and remanufacturing. Large-scale supplier evaluation is crucial for ensuring the sustainability of the CE supply chain and efficient utilization of resources. Especially, criterion interaction and consistency of criterion weights are two key factors of large suppliers’ evaluation in CE. However, current research often overlooks these key factors, this study proposes a large-scale supplier evaluation approach in CE to address these issues. The novel aspects of the proposed approach come with considering the interaction between circular and non-circular criteria, as well as eliminating the impact of large-scale complex information on the consistency of criterion weights. Firstly, large-scale hesitant evaluation information is fused by evidence reasoning, and interaction rules between circular and non-circular criteria are established. Then, the interaction weights of the criteria are obtained based on the interaction of circular criteria, and the comprehensive criteria weights are determined by an improved best-worst method. Next, the decision makers’ weights are generated by the utility value of the circular criterion. Finally, the results of numerical example and analysis show that 86% of the supplier ranking results are stable, and the consistency of the proposed approach is 0.9757, indicating that the proposed approach exhibits high validity and reliability. It emphasizes the significance of the supplier’s circular ability in CE and reduces the interference of large-scale complex information on the consistency of evaluation results.

Analysis and monitoring of the behavior of a rock fill dam ten years after construction: a case study of the Iran-Madani Dam

AbstractIn this study we compared dam monitoring results with those of numerical analysis to propose a plan for the first reservoir impounding of the Iran-Madani Rock fill dam, ten years after the completion of its construction. The stability of the dam body has been assessed using numerical analysis and data obtained from sensors installed in the dam. The correctness and accuracy of the geotechnical parameters of the dam body materials were confirmed by comparing the results of numerical analysis and monitoring through back analysis. The linear correlation coefficients between the experimental data and the numerical results for settlement, pore water pressure, and total stress are 84%, 67%, and 99%, respectively. In addition, the agreement between the design assumptions with both the numerical analysis results and instrumentation data was examined. The arching ratio values obtained from instrumentation and numerical analysis in the core of the dam are 0.47 and 0.35, respectively, indicating the safety of the dam. Finally, a numerical sensitivity analysis was conducted to present a special impounding program for the dam, with a focus on controlling simultaneous changes in pore water pressure and effective stress in the clay core, ten years after the completion of the dam body construction.

АНАЛІЗ РОЗПОДІЛУ КОНТАКТНИХ НАПРУЖЕНЬ У ДВОЗРІЗНОМУ БОЛТОВОМУ З'ЄДНАННІ КОМПОЗИТНИХ ТА МЕТАЛЕВИХ ЕЛЕМЕНТІВ

Bolted joining technique is the dominant joining method for CFRP load-carrying structures in aircraft. However, the weak point of such structures are the areas located in the vicinity of the fastener holes, which are the areas of increased stress concentration. In addition, drilling the holes results in structural discontinuities due to cutting material fibers. Among all failure modes of composite bolted joint, bearing failure is one of the most common type of damage. This failure is caused by the local compressive stresses acting normal to the contact surface, that leads to delamination of material due to insufficient strength of matrix. Therefore, it is extremely important to optimize the design of composite bolted joints in order to enhance the entire composite structure. To increase the load-carrying capacity of the composite joint structural parts and protect the hole walls from damage, a method for installing titanium bushing with glue into the holes of composite plate is proposed. The paper presents the results of numerical analysis of the impact of stacking sequence on the distribution of contact stresses in a double-shear bolted joint of composite plate to steel cover plates. Using the finite element method and ANSYS Workbench 2019 R3 software, a three-dimensional finite element model of a double-shear bolted joint was created, which enables to analyze the impact of the stacking sequence on the distribution of contact stresses at the bolts to titanium bushings interface in the case of uniaxial tension of the middle composite plate at the level of tensile stresses in the gross section of 100 MPa. The obtained result explains the fundamental difference in the behavior of composite and metal materials: due to the change in the orientation and sequence stacking, the stiffness of the composite element of the joint changes, which affects the ovalization of the holes and the level of local deformations of the bushings, which in turn leads to a change in the maximum contact stresses and their concentration. By optimizing stacking sequence, it was possible to reduce the level of maximum contact stresses by 1.1 times. At the same time, the degree of unevenness of the distribution of contact stresses decreased by 1.21 times. The optimal stacking sequence was one in which 37.5% of the fibers oriented at an angle of 0°, 50% of the fibers oriented at angles of ±45°, and 12.5% of the fibers oriented at an angle of 90°

Investigation of Tandem Queuing Systems Using Machine Learning Methods

This paper considers tandem queuing systems with limited buffer sizes in each phase. The system handles an incoming correlated MAP flow and the service time obeys a PH-distribution. Models of such systems and methods for their investigation are briefly reviewed from the historical perspective. According to the review, the problem statement presented below, the methods proposed for solving this problem, and the corresponding results are novel. An accurate algorithm for calculating the performance characteristics of low-dimensional tandem queuing systems is described, including an estimate of the algorithm’s complexity. An approach using both machine learning and simulation modeling is suggested for the investigation of high-dimensional tandem queuing systems. Numerical analysis results are provided to show the effectiveness of machine learning methods for estimating the performance of tandem queuing systems.

Mechanical Characteristics of Deep Excavation Support Structure with Asymmetric Load on Ground Surface

The purpose of this paper is to capture the mechanical response of the support structure of deep excavation subject asymmetric load. A two-dimensional (2D) numerical analysis model was established by taking a pipe gallery deep excavation subject to asymmetric load as an example. The numerical analysis results were in good agreement with the measured data, thus verified the validity of the numerical model. On this basis, the stress and displacement of support structure caused by the change in foundation asymmetric load were studied. According to the numerical results, horizontal displacement of the diaphragm wall (DW) was dominant, and the maximum horizontal displacement of the DW was 7.54 mm when the deep excavation was completed. With the increase in asymmetric load, the left wall displacement continued to increase, while the displacement of the right DW continued to decrease, and the maximum horizontal wall displacement occurred near the excavation face. The DW was the main bending component, and the maximum wall bending moment when the deep excavation was completed was 173.5 kN·m. The maximum wall bending moment increased with the increase in asymmetric load, and the maximum wall bending moment on the left of the deep excavation was greater than that on the right. The inner support sustained the main component of axial force, with the axial force peaking at 1051.8 kN when the deep excavation was completed. The axial force of the inner support increased with increasing the asymmetric load, and the axial force of the second inner support was obviously greater than that of the first inner support. This research has a positive effect on the design and optimization of deep excavation support structure subject to asymmetric load on ground surface.

Study on Multi-Parameter Variation of Smoke Flow in Inclined Roadway Fire

ABSTRACT Based on the fluid similarity theory, a “Mine inclined roadway fire simulation experimental system” with similarity ratio of 1:20 is established. The temperature, velocity, density and dynamic pressure of fire smoke under different inlet wind speed (0.5 m/s, 1.0 m/s, 1.5 m/s) were tested and analyzed, and the distribution of temperature, velocity, density and dynamic pressure of inclined roadway during fire was simulated and analyzed by Ansys numerical simulation software. The research shows that: The higher the inlet wind speed, the faster the heat diffusion and the temperature field tends to be flat and long, the wind speed changes in advance and the change is drastic, the gas density decreases, the dynamic pressure first decreases and then increases and then tends to stabilize, but the change trend of temperature, wind speed, gas density and pressure in the overall combustion process remains unchanged. The numerical analysis results are in good agreement with the experimental results. By studying the change law of smoke temperature, velocity, density and dynamic pressure of coal mine inclined roadway fire, the theory of coal mine roadway fire is further perfected, and the level of coal mine fire prevention and rescue is improved.

Machine learning-based residual drift prediction of concrete-filled steel tube columns under earthquake loads

This study introduces a machine learning (ML) model for predicting the residual (permanent) drift in concrete-filled steel tube (CFT) structures exposed to excessive loads. The relationship between the residual drift and design parameters of the CFT column was established through the adaptation of six distinct ML models. The accuracy of the proposed model was evaluated by comparing its predictions with the results derived from existing numerical models and code provisions. The proposed ML model surpasses existing residual drift prediction models by at least 4% in terms of R-squared value. To evaluate the effectiveness of the model, a nonlinear dynamic analysis of a three-story, three-bay CFT moment-resisting frame subjected to 44 ground motions was conducted using a numerical model. Additionally, two modified frame models were considered to investigate the influence of frame configuration on the performance of the ML model. Subsequently, the residual inter-story drift ratio derived from the seismic analysis using the numerical model was compared with the results obtained from the ML predictive model and code provisions. The proposed ML model exhibited greater accuracy in predicting the residual inter-story drift ratio than the code provisions when applied to the results of numerical analyses performed for weak-column strong-beam frames. The ML model showed a positive R-squared value, whereas the code provisions yielded a lower R-squared value. In turn, the ML model applied to the strong-column weak-beam moment-resisting frames tended to overestimate the residual inter-story drift ratio, with a ratio of the predicted value to the value obtained from the analysis equal to 3.5.

Manufacturing Technology, Experimental and Numerical Analysis of Static Bending of Three-Layer Composite Plate with Honeycomb Structure

The use of thin-walled constructions with honeycomb structure manufactured using additive technologies has several advantages compared to the constructions manufactured using traditional technologies. First of all, this is explained by the fact that additive technologies greatly simplify the production of honeycomb structures. A technology for manufacturing a three-layer composite plate with a honeycomb structure obtained using additive technologies is proposed in the paper. PLA plastic was chosen as the material for the honeycomb structure production. Printing was carried out using a "Delta" printer with parallel kinematic chains using FDM technologies. The printing temperature was 215 °C, table temperature – 60 °C. A fundamentally new scheme of an experimental plant for studying the bending of a three-layer plate is proposed. The aim of the research is to conduct tests of samples of a three-layer honeycomb panel for static bending when one edge of the sample is rigidly pinched. For the tests, a certified TiraTest 2300 universal testing machine (UTM), which allows to perform tensile and compression tests at a given traverse speed and measure the load with a relative error of 1%, was used. The UTM allows to load the sample and measure the load and displacement of the traverse. A sixteen-channel strain gauge station is used to measure the surface deformations of the housings. Transverse displacements of a three-layer plate were obtained as experimental data. The bending of the three-layer plate is modeled in the commercial package ANSYS. The results of experimental and numerical analysis coincide well.

Effect of Blade Material of Steam Turbine Rotor on Aeroelastic Characteristics

Elements of powerful steam turbines are subjected to significant unsteady loads, in particular the rotor blades of the last stages. These loads, in some cases, can 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 conditions for the occurrence of self-excited oscillations are influenced by both the geometric characteristics and the alloy from which the blade is made. To determine the effect of the blade material on the aeroelastic behaviour, a numerical analysis of the aeroelastic characteristics of the last stage blades made of steel and titanium alloy was performed. For the analysis, the method of simultaneous modeling of unsteady gas flow through the blade cascades and elastic vibrations of the blades (coupled problem) was used, which allows obtaining the amplitude-frequency spectrum of the interaction of unsteady loads and blade vibrations. The paper presents the results of numerical analysis for harmonic oscillations with a given amplitude and a given inter-blade phase angle, as well as for the regime of coupled vibration of blades under the action of unsteady aerodynamic forces. The dependences of the aerodamping coefficient on the inter-blade phase angle and the distribution of the coefficient along the blade are presented. The results of modeling the coupled vibration of the blades for the first six natural forms are presented in the form of a time-evolving displacement of the blade peripheral section, as well as forces and moments acting on the peripheral section. The corresponding amplitude-frequency spectra of displacements and loads in the peripheral section are also presented. The analysis of the results showed an insignificant difference in the characteristics of the proposed blade materials. For the first natural form of blade oscillations, the possibility of self-excited oscillations was found, and for the second form, there are conditions for the appearance of stable self-oscillations.

Investigating Dual Inlet Cyclone Separator Performance: Effects of Vortex Finder Diameter, Shape, and Particle Diameter on Separation Efficiency and Pressure Drop

The diameter and shape of the vortex finder of cyclone separator plays a significant role in separation efficiency and pressure drop. Currently, there have been many studies conducted on the shape and ratio of vortex finder of cyclone separator. This paper aims to compare numerical results of Raynold stress turbulence model RSM with K-ε RNG numerical analysis results and analyse the effect of further variation of the vortex finder diameter and shape of dual inlet cyclone separators. Five variation of vortex finder diameters namely 291mm, 310mm, 330mm, 348mm, and 366mm, four types of vortex finder shapes namely normal (cylindrical), spiral, divergent and spiral-divergent have been studied with different particle diameter and constant inlet velocity. The result obtained from this study suggests that increasing the vortex finder diameter have negative effect on separation efficiency. It also shows that increasing the vortex finder diameter consistently decrease the pressure drop. From the result, it is been found that the 291mm vortex finder has higher separation efficiency than the rest. Analysis with different vortex shapes, the spiral-divergent shape proved to be best in terms of separation efficiency.