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1
Zheng, Zumei, Shasha Zhou, Jun Chen, Naoto Mitsume e Shunhua Chen. "A Multi-Resolution MPS/FEM Coupling Method for Three-Dimensional Fluid–Structure Interaction Analysis". Journal of Marine Science and Engineering 11, n. 8 (25 luglio 2023): 1483. http://dx.doi.org/10.3390/jmse11081483.
Abstract (sommario):
This work aims to propose an efficient MPS/FEM coupling method for the simulation of fluid–structure interaction (FSI), where the MPS and FEM are respectively employed to account for fluid flows and structural deformation. The main idea of our method is to develop a multi-scale multi-resolution MPS method for efficient fluid simulations in the context of MPS/FEM coupling. In the developed multi-scale MPS method, the fluid domain is discretized into particles of different resolutions before calculation, where particles close to the interest domain will be discretized into high resolution, while the rest are discretized into low resolution. A large particle interacting with small particles is divided into several small particles virtually, and weight functions are redefined to maintain the simulation stability. A bucket-sort-based algorithm is developed for the fast search of multi-resolution neighboring particles. The capacity of a newly proposed ghost cell boundary model is further enhanced, so as to accurately treat wall boundary problems with particles of different resolutions. On this basis, the multi-resolution MPS method is coupled with the FEM for FSI simulations. Finally, several numerical examples are conducted to demonstrate the accuracy and efficiency of the development method.
2
Song, Eun Jeong, Jung Soo Lee, Hyungpil Moon, Hyouk Ryeol Choi e Ja Choon Koo. "A Multi-Curvature, Variable Stiffness Soft Gripper for Enhanced Grasping Operations". Actuators 10, n. 12 (29 novembre 2021): 316. http://dx.doi.org/10.3390/act10120316.
Abstract (sommario):
For soft grippers to be applied in atypical industrial environments, they must conform to an object’s exterior shape and momentarily change their stiffness. However, many of the existing grippers have limitations with respect to these functions: they grasp an object with only a single curvature and a fixed stiffness. Consequently, those constraints limit the stability of grasping and the applications. This paper introduces a new multicurvature, variable-stiffness soft gripper. Inspired by the human phalanx and combining the phalanx structure and particle jamming, this work guarantees the required grasping functions. Unlike the existing soft pneumatic grippers with one curvature and one stiffness, this work tries to divide the pressurized actuating region into three parts to generate multiple curvatures for a gripper finger, enabling the gripper to increase its degrees of freedom. Furthermore, to prevent stiffness loss at an unpressurized segment, this work combines divided actuation and the variable-stiffness capability, which guarantee successful grasping actions. In summary, this gripper generates multiple grasping curvatures with the proper stiffness, enhancing its dexterity. This work introduces the new soft gripper’s design, analytical modeling, and fabrication method and verifies the analytic model by comparing it with FEM simulations and experimental results.
3
Wei, Wei, Songjian Yu e Baozuo Li. "Research on Magnetic Characteristics and Fuzzy PID Control of Electromagnetic Suspension". Actuators 12, n. 5 (17 maggio 2023): 203. http://dx.doi.org/10.3390/act12050203.
Abstract (sommario):
This paper proposes an electromagnetic suspension with an electromagnetic actuator, which can improve the riding comfort and stability of the vehicle without changing the safety of traditional MacPherson suspension. First, the electromagnetic suspension structure is introduced, and the principle of the proposed actuator is described in detail. Second, a magnetic flux density model of a single PM ring (permanent magnetic ring) and a magnet assembly are built, and a theoretical analysis of the magnetic flux density is carried out for comparison. Then, the magnetic flux distribution of the magnetic field is simulated and analyzed using the finite element method (FEM), and is compared with theoretical and other experimental data. Finally, a vehicle dynamics model with 7 DOF is built, and vehicle simulations based on the fuzzy PID algorithm are carried out on a C-grade road surface and a deceleration strip. The theoretical results and simulation analyses of the FEM indicate that compared with the MacPherson suspension, the root mean square values of the acceleration of centroid acceleration for the electromagnetic suspension are increased by 59.08% and 33.34%, respectively, on a C-grade road surface and a deceleration strip, and other physical quantities have also been improved. The structure and characteristics of the proposed electromagnetic suspension that improve the riding comfort of the suspension and enhance the stability of the MacPherson suspension are feasible.
4
Kien, Dang Van, Do Ngoc Anh e Do Ngoc Thai. "Numerical Simulation of the Stability of Rock Mass around Large Underground Cavern". Civil Engineering Journal 8, n. 1 (1 gennaio 2022): 81–91. http://dx.doi.org/10.28991/cej-2022-08-01-06.
Abstract (sommario):
Geotechnical problems are complicated to the extent and cannot be expected in other areas since non-uniformities of existing discontinuous, pores in materials and various properties of the components. At present, it is extremely difficult to develop a program for tunnel analysis that considers all complicated factors. However, tunnel analysis has made remarkable growth for the past several years due to the development of numerical analysis method and computer development, given the situation that it was difficult to solve formula of elasticity, viscoelasticity, and plasticity for the dynamic feature of the ground when the constituent laws, yielding conditions of ground materials, geometrical shape and boundary conditions of the structure were simulated in the past. The stability of rock mass around an underground large cavern is the key to the construction of large-scale underground projects. In this paper, the stability analysis was carried out based on those parameters by using 2D FEM RS2 program. The calculated stress and displacements of surrounding rock and rock support by FEM analysis were compared with those allowable values. The pattern of deformation, stress state, and the distribution of plastic areas are analyzed. Finally, the whole stability of surrounding rock mass of underground caverns was evaluated by Rock Science - RS2 software. The calculated axial forces were far below design capacity of rock bolts. The strong rock mass strength and high horizontal to vertical stress ratio enhanced safe working conditions throughout the excavation period. Thus wide span caverns and the system of caverns could be stability excavated sedimentary rock during the underground cavern and the system of caverns excavation by blasting method. The new method provides a reliable way to analyze the stability of the caverns and the system of caverns and also will help to design or optimize the subsequent support. Doi: 10.28991/CEJ-2022-08-01-06 Full Text: PDF
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Xiao, Enzhao, Shengquan Li, Ali Matin Nazar, Ronghua Zhu e Yihe Wang. "Antarctic Snow Failure Mechanics: Analysis, Simulations, and Applications". Materials 17, n. 7 (25 marzo 2024): 1490. http://dx.doi.org/10.3390/ma17071490.
Abstract (sommario):
Snow failure is the process by which the stability of snow or snow-covered slopes is destroyed, resulting in the collapse or release of snow. Heavy snowfall, low temperatures, and volatile weather typically cause consequences in Antarctica, which can occur at different scales, from small, localized collapses to massive avalanches, and result in significant risk to human activities and infrastructures. Understanding snow damage is critical to assessing potential hazards associated with snow-covered terrain and implementing effective risk mitigation strategies. This review discusses the theoretical models and numerical simulation methods commonly used in Antarctic snow failure research. We focus on the various theoretical models proposed in the literature, including the fiber bundle model (FBM), discrete element model (DEM), cellular automata (CA) model, and continuous cavity-expansion penetration (CCEP) model. In addition, we overview some methods to acquire the three-dimensional solid models and the related advantages and disadvantages. Then, we discuss some critical numerical techniques used to simulate the snow failure process, such as the finite element method (FEM) and three-dimensional (3D) material point method (MPM), highlighting their features in capturing the complex behavior of snow failure. Eventually, different case studies and the experimental validation of these models and simulation methods in the context of Antarctic snow failure are presented, as well as the application of snow failure research to facility construction. This review provides a comprehensive analysis of snow properties, essential numerical simulation methods, and related applications to enhance our understanding of Antarctic snow failure, which offer valuable resources for designing and managing potential infrastructure in Antarctica.
6
Chen, Peng, Xiaorong Cai, Na Min, Yunfan Liu, Zhengxiong Wang, Mingjiang Jin e Xuejun Jin. "Enhanced Fatigue Resistance of Nanocrystalline Ni50.8Ti49.2 Wires by Mechanical Training". Metals 13, n. 2 (10 febbraio 2023): 361. http://dx.doi.org/10.3390/met13020361.
Abstract (sommario):
In this paper, the fatigue resistance of superelastic NiTi shape memory alloy (SMA) wires was improved by combining mechanical training and nanocrystallization. Fatigue tests were performed after mechanical training with a peak stress of 600 MPa for 60 cycles of nanocrystalline (NC) NiTi wires, and the associated microscopic mechanism was investigated by using transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD). The results showed that stress-controlled training effectively improved the functional stability (the accumulated residual strain decreased by 83.8% in the first 5000 cycles) of NC NiTi SMA wires, as well as increased the average structural fatigue life by 187.4% (from 4538 cycles to 13,040 cycles). TEM observations and TKD results revealed that training-induced dislocations resulted in lattice rotation and preferential grain orientation. The finite element method (FEM) simulation results indicated that the training-induced preferential grain orientation tended to decrease the local stress concentration and strain energy density. Combined with fractography analysis, the uniform deformation caused by mechanical training changed the crack growth mode from multi-regional propagation to single-regional propagation, improving the structural fatigue life.
7
Gil, Javier, Clara Sandino, Miguel Cerrolaza, Román Pérez, Mariano Herrero-Climent, Blanca Rios-Carrasco, Jose Vicente Rios-Santos e Aritza Brizuela. "Influence of Bone-Level Dental Implants Placement and of Cortical Thickness on Osseointegration: In Silico and In Vivo Analyses". Journal of Clinical Medicine 11, n. 4 (16 febbraio 2022): 1027. http://dx.doi.org/10.3390/jcm11041027.
Abstract (sommario):
The purpose of this research is to study the biomechanical response of dental implants in bone-level type locations, 0.5 mm above and below the bone level. In addition, the influence of the thickness of the cortical bone on osseointegration is determined due to the mechanical loads transfer from the dental implant to the cortical and trabecular bone. The thicknesses studied were 1.5 mm and 2.5 mm. Numerical simulations were performed using a finite element method (FEM)-based model. In order to verify the FEM model, the in silico results were compared with the results obtained from a histological analysis performed in an in vivo study with 30 New Zealand rabbits. FEM was performed using a computerized 3D model of bone-level dental implants inserted in the lower jawbone with an applied axial load of 100 N. The analysis was performed using different distances from the bone level and different thicknesses of cortical bone. The interface area of bone growth was evaluated by analyzing the bone–implant contact (BIC), region of interest (ROI) and total bone area (BAT) parameters obtained through an in vivo histological process and analyzed by scanning electron microscopy (SEM). Bone-level implants were inserted in the rabbit tibiae, with two implants placed per tibia. These parameters were evaluated after three or six weeks of implantation. FEM studies showed that placements 0.5 mm below the bone level presented lower values of stress distribution compared to the other studied placements. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that this position presented the highest BIC value after three or six weeks of implantation. In this placement, vertical bone growth could be observed up the bone level. The smallest thickness of the study showed a better transfer of mechanical loads, which leads to a better osseointegration. In silico and in vivo results both concluded that the implants placed 0.5 mm below the cortical bone and with lower thicknesses presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.
8
Ren, Qinghua, Junhong Chen, Xin Liu, Songsong Zhang e Yuandong Gu. "Design and 3D FEM Analysis of a Flexible Piezoelectric Micromechanical Ultrasonic Transducer Based on Sc-Doped AlN Film". Sensors 22, n. 21 (22 ottobre 2022): 8100. http://dx.doi.org/10.3390/s22218100.
Abstract (sommario):
In this paper, a flexible piezoelectric micromachined ultrasonic transducer (PMUT) based on Scandium (Sc)-doped Aluminum Nitride (AlN) film was designed and modeled by the three-dimensional finite element method (3D-FEM). The resonant frequency of 218.1 kHz was reported. It was noticeable that a high effective electromechanical coupling coefficient (k2eff) of 1.45% was obtained when a combination of a flexible PI and a thin Si layer was used as the PMUT supporting structure layer. Compared with a pure Si supporting layer counterpart, the coupling coefficient had been improved by 110.68%. Additionally, the increase of Sc doping concentration in AlN film further enhanced the device electromechanical coupling coefficient and resulted in an improvement for transmitting/receiving sensitivity of the proposed flexible PMUT. When the doping concentration of Sc reached 30%, the emission sensitivity was as large as 1.721 μm/V, which was 2.86 times greater than that of conventional AlN film-based PMUT. The receiving sensitivity was found to be 2.11 V/KPa, which was as high as 1.23 times the performance of an undoped device. Furthermore, the bending simulation result showed that the proposed flexible PMUT device can maintain a good mechanical stability when the bending radius is greater than 1.5 mm. The simulation of sound field characteristics demonstrated that the flexible PMUT based on AlScN could receive stable sound pressure signals under the bending radius of 1.5 cm.
9
Sanchaniya, Jaymin Vrajlal, Inga Lasenko, Vishnu Vijayan, Hilary Smogor, Valters Gobins, Alaa Kobeissi e Dmitri Goljandin. "A Novel Method to Enhance the Mechanical Properties of Polyacrylonitrile Nanofiber Mats: An Experimental and Numerical Investigation". Polymers 16, n. 7 (4 aprile 2024): 992. http://dx.doi.org/10.3390/polym16070992.
Abstract (sommario):
This study addresses the challenge of enhancing the transverse mechanical properties of oriented polyacrylonitrile (PAN) nanofibers, which are known for their excellent longitudinal tensile strength, without significantly compromising their inherent porosity, which is essential for effective filtration. This study explores the effects of doping PAN nanofiber composites with varying concentrations of polyvinyl alcohol (PVA) (0.5%, 1%, and 2%), introduced into the PAN matrix via a dip-coating method. This approach ensured a random distribution of PVA within the nanofiber mat, aiming to leverage the synergistic interactions between PAN fibers and PVA to improve the composite’s overall performance. This synergy is primarily manifested in the structural and functional augmentation of the PAN nanofiber mats through localized PVA agglomerations, thin films between fibers, and coatings on the fibers themselves. Comprehensive evaluation techniques were employed, including scanning electron microscopy (SEM) for morphological insights; transverse and longitudinal mechanical testing; a thermogravimetric analysis (TGA) for thermal stability; and differential scanning calorimetry (DSC) for thermal behavior analyses. Additionally, a finite element method (FEM) analysis was conducted on a numerical simulation of the composite. Using our novel method, the results demonstrated that a minimal concentration of the PVA solution effectively preserved the porosity of the PAN matrix while significantly enhancing its mechanical strength. Moreover, the numerical simulations showed strong agreement with the experimental results, validating the effectiveness of PVA doping in enhancing the mechanical properties of PAN nanofiber mats without sacrificing their functional porosity.
10
Hatipoglu, Kenan, Mohammed Olama e Yaosuo Xue. "Model-Free Dynamic Voltage Control of Distributed Energy Resource (DER)-Based Microgrids". Energies 13, n. 15 (27 luglio 2020): 3838. http://dx.doi.org/10.3390/en13153838.
Abstract (sommario):
In this paper, we present a new control technique for sustaining dynamic voltage stability by effective reactive power control and coordination of distributed energy resources (DERs) in microgrids. The proposed control technique is based on model-free control (MFC), which has shown successful operation and improved performance in different domains and applications. This paper presents its first use in the voltage stability of a microgrid setting employing multiple synchronous generator (SG)-based and power electronic (PE)-based DERs. MFC is a computationally efficient, data-driven control technique that does not require modelling of the different components and disturbances in the power system. It is utilized as an online controller to achieve the dynamic voltage stability of a microgrid system under different disturbances and fault conditions. A 21-bus microgrid system fed by multiple DERs is considered as a case study and the overall dynamic voltage stability is investigated using time-domain dynamic simulations. Numerical results show that the proposed MFC provides improvements on the dynamic load bus voltage profiles and requires less computational time as compared to the traditional enhanced microgrid voltage stabilizer (EMGVS) scheme. Due to its simplicity and low computational requirement, MFC can be easily implemented in resource-constrained computing devices such as smart inverters.
11
Li, Shanjun, Zehua Yang, Qiang Wan, Jianfeng Hou, Yangyi Xiao, Xin Zhang, Rui Gao e Liang Meng. "Increase in Wear Resistance of Traction Wheel via Chromizing: A Study Combining Experiments and Simulations". Coatings 12, n. 9 (2 settembre 2022): 1275. http://dx.doi.org/10.3390/coatings12091275.
Abstract (sommario):
The wear failure of traction wheels in orchard transport severely restricts the stability of orchard conveyors and impedes the mechanization of orchard work. In this study, the thermal-diffusion chromizing method was employed to increase the hardness of a traction wheel for the enhancement of wear resistance. The results show that a uniform and dense chrome coating with a thickness of 16 μm was formed on the surface. The coating was revealed to have a hardness of 1752.7 HV and benefited from the formation of Cr-C compounds. A friction test and a wear simulation test under both dry-friction and lubrication conditions were conducted to assess the enhanced wear resistance based on the friction coefficient and wear loss. The friction coefficient of QT400 and that of the chrome coating were 0.37 and 0.36, respectively, under dry conditions. Additionally, the friction coefficient of QT400 decreased to 0.12, while that of the chrome coating remained at 0.35, under lubrication conditions. In the wear simulation test, the wear loss of the chromed traction wheel was about 1/28 of that of the QT400 traction wheel under dry-friction conditions. In addition, the wear loss of the chromed traction wheel was about 1/24 of that of the QT400 traction wheel under lubrication conditions. Moreover, the wear mechanism was analyzed with a microstructure study and finite element analysis (FEA). The synergetic effect between fatigue wear and abrasive wear was likely responsible for the wear failure of the traction wheel. The method proposed in this study may be a promising way to enhance the wear resistance of QT400 traction wheels through the application of a chrome coating without sacrificing the loading capacity, and this work contributes to the understanding of the wear failure mechanism of traction wheels.
12
Chetty, Nelson Dhanpal, Gulshan Sharma, Manoj Kumawat e Pitshou N. Bokoro. "Application of optimal control for wind integrated power system". Indonesian Journal of Electrical Engineering and Computer Science 32, n. 2 (1 novembre 2023): 654. http://dx.doi.org/10.11591/ijeecs.v32.i2.pp654-663.
Abstract (sommario):
<div align="center"><span>This paper presents the modeling and application of an optimal controller for frequency and tie-line power stability for a two-area interconnected hydro-thermal power plant having tandem compound non-reheat turbines integrated with wind power generation having doubly fed induction generator (DFIG) wind turbines in each area. The power system is interconnected using AC tie-lines. The designed optimal controller was implemented and the system dynamic responses for three power system model states were obtained considering a 1% load fluctuation in one of the areas. The optimal control strategy presented in this paper depends on formulating an error value and finding the feedback gains corresponding to each state of the system, which are easily attainable as outputs. The analysis was undertaken and verified by calculating the performance index value, the closed ring real and imaginary values, finding the feedback gains, and through graphical simulations of the three system models under investigation. The output of the optimal controller was enhanced when the DFIG-based wind turbines were installed in each area combined with a superconducting magnetic energy storage (SMES) unit and a thyristor control phase shifter (TCPS).</span></div>
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Vogt, Alexander, Holger Geßwein, Johann Chable, Aljoscha Baumann, Daniel Mutter, Daniel F. Urban, Christian Elsässer, Jérôme Lhoste e Joachim R. Binder. "K0.5FeF3 as a New Zero-Strain Cathode Material for Lithium-Ion Batteries". ECS Meeting Abstracts MA2023-02, n. 2 (22 dicembre 2023): 260. http://dx.doi.org/10.1149/ma2023-022260mtgabs.
Abstract (sommario):
The stability of the cathode is of crucial importance for the service life of lithium-ion batteries (LIB). In the cathode, the lattice parameter usually changes during (de-)insertion of lithium, which causes various signs of aging that have a negative effect on the capacity of the cell. This problem can be tackled using a specific type of materials called zero-strain (ZS) materials. These materials do not show any (de-)intercalation-induced structural changes and stresses. Such a zero-strain effect was already demonstrated with fluorine-containing materials [1] and even for the similar material K0.6FeF3 [2] for sodium-ion batteries (SIB). In this case, potassium ions are removed in the first cycle and the vacant lattice sites can be used for the incorporation of sodium ions, while keeping the structural integrity of the host material. Complementary to experiments, theoretical atomistic simulations are powerful to develop design criteria for further ZS-materials. Combining experiments and simulations in this work, the structural behavior of the material K0.5FeF3 was investigated when used as a cathode material in a LIB. The synthesis of K0.5FeF3 was achieved by a Rapid Microwave-Enhanced Solvothermal Process, which allowed to obtain the material in a TTB-type (Tetragonal Tungsten Bronze) phase with a high degree of purity. The material was then processed into electrodes, which were galvanostatically cycled against lithium metal. It was shown that the material is suitable for LIB as a cathode material. X-ray diffraction experiments showed that the lattice parameter changed by less than 1% after the incorporation of Li-Ions, in good agreement with the theoretical calculations conducted in parallel. Lattice Parameter Charged Discharged a[Å] 12.74±0.024 12.73±0.006 c[Å] 3.99±0.008 4.00±0.002 Volume [Å3] 647.57±2.67 647.75±0.76 This work was supported by the German Research Foundation (DFG) BI 1636/7-1 and EL 155/29-1. References [1] De Biasi, L., et al. Journal of Power Sources, 2017, 362. Jg., S. 192-201. [2] Han, Y., et al. Journal of Materials Chemistry A, 2016, 4. Jg., Nr. 19, S. 7382-7389. Figure 1: Diffractograms of an electrode with K0.5FeF3, which was measured before use and an electrode after the first successful discharge, down to a voltage of 1.8 V. Figure 1
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Wang, Qian, Jianmin Bian, Yihan Li, Chunpeng Zhang e Fei Ding. "Bimolecular Reactive Transport Experiments and Simulations in Porous Media". Water 12, n. 7 (7 luglio 2020): 1931. http://dx.doi.org/10.3390/w12071931.
Abstract (sommario):
For reactive transport process in porous media, limited mixing and non-Fickian behavior are difficult to understand and predict. To explore the effects of anomalous diffusion and limited mixing, the column-based experiments of bimolecular reactive migration were performed and simulated by the CTRW-FEM model (continuous time random walk-finite element method). Simulated parameters were calibrated and the correlation coefficients between modeled and observed BTCs (breakthrough curves) were greater than 0.9, indicating that CTRW-FEM can solve over-prediction and tailing problems effectively. Porous media with coarser particle size show enhanced mixing and the non-Fickian behavior is not affected by particle size. β (a parameter of CTRW-FEM) and Da (Damköhler number) of CTRW-FEM under different Pe (Péclet number) values showed logarithmic linear relationship. Model sensitivity analysis of the CTRW-FEM model show that the peak concentration is most sensitive to the average pore velocity and the arriving peak time of peak concentration is most sensitive to β. These findings provide a theoretical basis for handling mixing and non-Fickian behavior patterns under actual environmental conditions.
15
Šapalas, Vaidotas, Michail Samofalov e Viačeslavas Šaraškinas. "FEM STABILITY ANALYSIS OF TAPERED BEAM‐COLUMNS". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 11, n. 3 (30 settembre 2005): 211–16. http://dx.doi.org/10.3846/13923730.2005.9636352.
Abstract (sommario):
This paper deals with a theoretical and a numerical analysis of tapered beam‐columns subjected to a bending moment and an axial force. A standard FEM code COSMOS/M has been used for a numerical estimation of a critical load multiplier. It has been assumed that the critical force of an axially loaded tapered column could be calculated in an analogous way as for uniform member just with an additional correction factor αn. Similarly, a critical bending moment of the tapered column subjected to a pure bending could be determined by using a correction factor αm. A large number of simulations carried out within a wide range of the ratios of second moments of area allowed to determine the proper values of theses two factors. For practical engineers, solution of such kind of problems can be easier when an equivalent cross‐sectional height htr is used.
16
Lai, Xin, Li Sheng Liu, Qi Wen Liu, Dong Feng Cao, Zhen Wang e Peng Cheng Zhai. "Slope Stability Analysis by Peridynamic Theory". Applied Mechanics and Materials 744-746 (marzo 2015): 584–88. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.584.
Abstract (sommario):
Peridynamic simulations have been carried out to perform the slope stability analysis. A slope is first modelled with discretized particles in 2D. Then the non-ordinary state-based Peridynamic model is utilized. In order to obtain a more realistic behavior of the soil, Drucker-Prager constitutive model is used to describe the mechanic properties of soil. Results show great agreements with the FEM results, while provides the dynamic slide progress in the post-failure process.
17
Lakruwan, Mihira, Akiyoshi Kamura e Motoki Kazama. "Effect of 3D water table profile of horizontal drains on slope stability and idealization of 3D-FEM flow modeling to 2D-FEM flow modeling". E3S Web of Conferences 347 (2022): 03002. http://dx.doi.org/10.1051/e3sconf/202234703002.
Abstract (sommario):
Horizontal drains (HDs) are commonly used in the groundwater regime management of landslides. The groundwater table (GWT) profile of slopes with HDs have a complicated formation in three-dimensional (3D) space, requiring 3D analyses to obtain accurate results. However, owing to the complexity of 3D simulations, idealized two-dimensional (2D) cross sections are widely used in numerical simulations of such slopes. Unfortunately, stabilities are overestimated by 2D simulations because the 3D variation of the GWT is neglected. Finite element analysis is performed in this study to evaluate the effect of 3D variation of the GWT on the stability of slopes with HDs and to evaluate the effectiveness of 2D idealizations. The results demonstrate that idealized 2D analyses neglect the high pore water pressures between HDs, thereby overestimating the slope stability, especially with high rainfall intensities and large drain spacings. Alternatively, accurate results can be obtained in 2D analyses by manually estimating an average GWT profile using the Crenshaw and Santi method for steady-state conditions. Each method has its own limitations and, therefore, the selection of an appropriate method should be made based on the specific conditions and requirements of the problem.
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De Basabe, Jonás D., e Mrinal K. Sen. "Grid dispersion and stability criteria of some common finite-element methods for acoustic and elastic wave equations". GEOPHYSICS 72, n. 6 (novembre 2007): T81—T95. http://dx.doi.org/10.1190/1.2785046.
Abstract (sommario):
Purely numerical methods based on finite-element approximation of the acoustic or elastic wave equation are becoming increasingly popular for the generation of synthetic seismograms. We present formulas for the grid dispersion and stability criteria for some popular finite-element methods (FEM) for wave propagation, namely, classical and spectral FEM. We develop an approach based on a generalized eigenvalue formulation to analyze the dispersive behavior of these FEMs for acoustic or elastic wave propagation that overcomes difficulties caused by irregular node spacing within the element and the use of high-order polynomials, as is the case for spectral FEM. Analysis reveals that for spectral FEM of order four or greater, dispersion is less than 0.2% at four to five nodes per wavelength, and dispersion is not angle dependent. New results can be compared with grid-dispersion results of some classical finite-difference methods (FDM) used for acoustic or elastic wave propagation. Analysis reveals that FDM and classical FEM require a larger sampling ratio than a spectral FEM to obtain results with the same degree of accuracy. The staggered-grid FDM is an efficient scheme, but the dispersion is angle dependent with larger values along the grid axes. On the other hand, spectral FEM of order four or greater is isotropic with small dispersion, making it attractive for simulations with long propagation times.
19
NOCHETTO, RICARDO H., e JAE-HONG PYO. "THE GAUGE-UZAWA FINITE ELEMENT METHOD PART II: THE BOUSSINESQ EQUATIONS". Mathematical Models and Methods in Applied Sciences 16, n. 10 (ottobre 2006): 1599–626. http://dx.doi.org/10.1142/s0218202506001649.
Abstract (sommario):
The Gauge-Uzawa finite element method (GU-FEM)13 is a fully discrete projection type method to solve the evolution Navier–Stokes equations, which overcomes many shortcomings of projection methods and displays superior numerical performance. In this second part, we apply the GU-FEM to the evolution Boussinesq equations, which model the thermal driven motion of incompressible fluids. We show unconditional stability and error estimates for velocity, pressure and temperature, the three physical unknowns. We use a new variational approach13 and realistic regularity assumptions. We conclude with two physically relevant numerical simulations, the Benard convection problem and the thermal driven cavity flow.
20
Kalyani, V. Mohana, J. Preetha Roselyn, C. Nithya e D. Devaraj. "Enhanced Crowbar Protection for Fault Ride through Capability of Wind Generation Systems". International Journal of Power Electronics and Drive Systems (IJPEDS) 7, n. 4 (1 dicembre 2016): 1366. http://dx.doi.org/10.11591/ijpeds.v7.i4.pp1366-1376.
Abstract (sommario):
Due to increasing demand in power, the integration of renewable sources like wind generation into power system is gaining much importance nowadays. The heavy penetration of wind power into the power system leads to many integration issues mainly due to the intermittent nature of the wind and the desirability for variable speed operation of the generators. As the wind power generation depends on the wind speed, its integration into the grid has noticeable influence on the system stability and becomes an important issue especially when a fault occurs on the grid. The protective disconnection of a large amount of wind power during a fault will be an unacceptable consequence and threatens the power system stability. With the increasing use of wind turbines employing Doubly Fed Induction Generator (DFIG) technology, it becomes a necessity to investigate their behavior during grid faults and support them with fault ride through capability. This paper presents the modeling and simulation of a doubly fed induction generator according to grid code compatibility driven by a wind turbine connected to the grid. This paper analyses the voltage sag due to a three-phase fault in the wind connected grid. A control strategy including a crowbar circuit has been developed in MATLAB/SIMULINK to bypass the rotor over currents during grid fault to enhance the fault ride through capability and to maintain system stability. Simulation results show the effectiveness of the proposed control strategies in DFIG based grid connected wind turbine system.
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Litak, Grzegorz, Mirosław Kondratiuk, Piotr Wolszczak, Bartłomiej Ambrożkiewicz e Abhijeet M. Giri. "Energy Harvester Based on a Rotational Pendulum Supported with FEM". Applied Sciences 14, n. 8 (12 aprile 2024): 3265. http://dx.doi.org/10.3390/app14083265.
Abstract (sommario):
The proposed energy harvesting system is based on a rotational pendulum-like electromagnetic device. Pendulum energy harvesting systems can be used to generate power for wearable devices such as smart watches and fitness trackers, by harnessing the energy from the human body motion. These systems can also be used to power low-energy-consuming sensors and monitoring devices in industrial settings where consistent ambient vibrations are present, enabling continuous operation without any need for frequent battery replacements. The pendulum-based energy harvester presented in this work was equipped with additional adjustable permanent magnets placed inside the induction coils, governing the movement of the pendulum. This research pioneers a novel electromagnetic energy harvester design that offers customizable potential configurations. Such a design was realized using the 3D printing method for enhanced precision, and analyzed using the finite element method (FEM). The reduced dynamic model was derived for a real-size device and FEM-based simulations were carried out to estimate the distribution and interaction of the magnetic field. Dynamic simulations were performed for the selected magnet configurations of the system. Power output analyses are presented for systems with and without the additional magnets inside the coils. The primary outcome of this research demonstrates the importance of optimization of geometric configuration. Such an optimization was exercised here by strategically choosing the size and positioning of the magnets, which significantly enhanced energy harvesting performance by facilitating easier passage of the pendulum through magnetic barriers.
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Lv, Xueman, Shuo Wang, Zihe Xu, Xuanting Liu, Guoqin Liu, Feipeng Cao e Yunhai Ma. "Structural Mechanical Properties of 3D Printing Biomimetic Bone Replacement Materials". Biomimetics 8, n. 2 (19 aprile 2023): 166. http://dx.doi.org/10.3390/biomimetics8020166.
Abstract (sommario):
One of the primary challenges in developing bone substitutes is to create scaffolds with mechanical properties that closely mimic those of regenerated tissue. Scaffolds that mimic the structure of natural cancellous bone are believed to have better environmental adaptability. In this study, we used the porosity and thickness of pig cancellous bone as biomimetic design parameters, and porosity and structural shape as differential indicators, to design a biomimetic bone beam scaffold. The mechanical properties of the designed bone beam model were tested using the finite element method (FEM). PCL/β-TCP porous scaffolds were prepared using the FDM method, and their mechanical properties were tested. The FEM simulation results were compared and validated, and the effects of porosity and pore shape on the mechanical properties were analyzed. The results of this study indicate that the PCL/β-TCP scaffold, prepared using FDM 3D printing technology for cancellous bone tissue engineering, has excellent integrity and stability. Predicting the structural stability using FEM is effective. The triangle pore structure has the most stability in both simulations and tests, followed by the rectangle and honeycomb shapes, and the diamond structure has the worst stability. Therefore, adjusting the porosity and pore shape can change the mechanical properties of the composite scaffold to meet the mechanical requirements of customized tissue engineering.
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Kumar, Avishek, Deepshikha Ghosh e Mithun Radhakrishna. "Surface Patterning for Enhanced Protein Stability: Insights from Molecular Simulations". Journal of Physical Chemistry B 123, n. 40 (2 settembre 2019): 8363–69. http://dx.doi.org/10.1021/acs.jpcb.9b05663.
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Mohd Saim, Noraida, e Anuar Kasa. "Prediction Reinforced Slope Stability Using Pile Using Adaptive Neuro-Fuzzy Inference System (ANFIS) Model". Jurnal Kejuruteraan 36, n. 2 (30 marzo 2024): 591–99. http://dx.doi.org/10.17576/jkukm-2024-36(2)-19.
Abstract (sommario):
Predictive analysis using artificial intelligence (AI) has transformed the landscape of forecasting analysis in various research fields. The advancements in AI modelling algorithms have enhanced decision-making, trend identification, and process optimization. In geotechnical engineering, AI assists in predicting soil behaviour, structural stability, and slope stability. The AI model discussed in this paper is the Adaptive Neuro-Fuzzy Inference System (ANFIS). In this study, the ANFIS model predicts slope stability by examining the Factor of Safety (FOS) value. Slope stability analyses reinforced with continuous bored pile walls generated by the numerical computation of the finite element method (FEM) in two dimensions (2D) and three dimensions (3D) are compared with the predictions of the ANFIS model. The numerical FEM computations employ PLAXIS 2D and PLAXIS 3D software. Meanwhile, the ANFIS model is designed within the MATLAB software platform involving 112 data samples. With six input pile parameters and one output, the finding shows that the ANFIS model can learn complex non-linear data and accurately predict the output. This is supported by the R² values of 0.9771 and 0.9965 from comparing the forecasting output with the 2D and 3D FEM outputs, respectively. Meanwhile, the low RMSE values of 0.0187 and 0.0180 each confirm this.
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Hüser, Lucie, Tobias Pahl e Peter Lehmann. "Polarization dependency of the 3D transfer behavior in microsphere enhanced interferometry". EPJ Web of Conferences 266 (2022): 10006. http://dx.doi.org/10.1051/epjconf/202226610006.
Abstract (sommario):
Enhancing the lateral resolution limit in optical microscopy and interferometry is of great interest in recent research. In order to laterally resolve structures including feature dimensions below the resolution limit, microspheres applied in the optical near-field of the specimen are shown to locally improve the resolution of the imaging system. Experimental and simulated results following this approach obtained by a high NA Linnik interferometer are analyzed in this contribution. For further understanding of the transfer characteristics, measured interference data are compared with FEM (finite element method) based simulations with respect to the polarization dependency of the relevant image information.
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Giżejowski, M. A., R. B. Szczerba, M. D. Gajewski e Z. Stachura. "Beam-Column In-Plane Resistance Based on the Concept of Equivalent Geometric Imperfections". Archives of Civil Engineering 62, n. 4 (1 dicembre 2016): 35–72. http://dx.doi.org/10.1515/ace-2015-0108.
Abstract (sommario):
AbstractAssessment of the flexural buckling resistance of bisymmetrical I-section beam-columns using FEM is widely discussed in the paper with regard to their imperfect model. The concept of equivalent geometric imperfections is applied in compliance with the so-called Eurocode’s general method. Various imperfection profiles are considered. The global effect of imperfections on the real compression members behaviour is illustrated by the comparison of imperfect beam-columns resistance and the resistance of their perfect counterparts. Numerous FEM simulations with regard to the stability behaviour of laterally and torsionally restrained steel structural elements of hot-rolled wide flange HEB section subjected to both compression and bending about the major or minor principal axes were performed. Geometrically and materially nonlinear analyses, GMNA for perfect structural elements and GMNIA for imperfect ones, preceded by LBA for the initial curvature evaluation of imperfect member configuration prior to loading were carried out. Numerical modelling and simulations were conducted with use of ABAQUS/Standard program. FEM results are compared with those obtained using the Eurocode’s interaction criteria of Method 1 and 2. Concluding remarks with regard to a necessity of equivalent imperfection profiles inclusion in modelling of the in-plane resistance of compression members are presented.
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Bambach, M., Gerhard Hirt e J. Ames. "Quantitative Validation of FEM Simulations for Incremental Sheet Forming Using Optical Deformation Measurement". Advanced Materials Research 6-8 (maggio 2005): 509–16. http://dx.doi.org/10.4028/www.scientific.net/amr.6-8.509.
Abstract (sommario):
The present paper focuses on a new methodology to quantitatively evaluate finite element calculations on incremental sheet forming (ISF). ISF is a new manufacturing process for prototypes and small lot sizes. In ISF, a part is manufactured by the CNC-driven movement of a simple tool, giving rise to very challenging problems concerning the efficient modeling of the alternating contact conditions and the material's response to the cyclic deformation. The quantitative validation of the finite element analysis is achieved by an optical deformation measurement system which has been enhanced by a new calibration procedure, yielding a precisely defined local coordinate system for deformation measurements during forming. In combination with mapping algorithms for large point sets, this allows for a quantitative validation of process simulations and material input data.
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Maity, Kalipada, e Mayank Choubey. "Modeling and process simulation of vibration assisted workpiece in micro-EDM using FEM". World Journal of Engineering 13, n. 3 (13 giugno 2016): 242–50. http://dx.doi.org/10.1108/wje-06-2016-033.
Abstract (sommario):
Purpose Micro-electro discharge machining (EDM) plays an important role in the fabrication of micro holes in an electrically conductive high-strength material. The flushing of debris poses a great challenge in the micro-EDM operation. The vibration of workpiece plays a significant role in the flushing of debris of the workpiece. Design/methodology/approach This study aims that the finite element analysis is performed using ANSYS software to find out the maximum displacement of the workpiece at a different location at different frequencies. For the convergence of this analysis, the natural frequency obtained from ANSYS is validated with some available literature. Findings The continuous up and down vibration of the workpiece results in the formation of vapor bubbles in a low-pressure region that contributes to material removal due to the fracture of bubbles. The vibration-assisted workpiece in the micro-EDM process causes the pressure variation of dielectric between the electrode and workpiece that enhances material removal rate because of cavitation. Originality/value In workpiece vibration-assisted micro-EDM, the selection of correct vibration frequency and displacement is of greater importance because improper frequency selection can cause bending of the wire electrode, affecting machining stability and short circuiting.
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Han, Jike, Bo Yin, Michael Kaliske e Kenjiro Tarada. "Incorporation of gradient-enhanced microplane damage model into isogeometric analysis". Engineering Computations 38, n. 8 (4 giugno 2021): 3388–415. http://dx.doi.org/10.1108/ec-08-2020-0455.
Abstract (sommario):
Purpose This study aims to develop a new analysis approach devised by incorporating a gradient-enhanced microplane damage model (GeMpDM) into isogeometric analysis (IGA), which shows computational stability and capability in accurately predicting crack propagations in structures with complex geometries. Design/methodology/approach For the non-local microplane damage modeling, the maximum modified von-Mises equivalent strain among all microplanes is regularized as a representative quantity. This characterization implies that only one additional governing equation is considered, which improves computational efficiency dramatically. By combined use of GeMpDM and IGA, quasi-static and dynamic numerical analyses are conducted to demonstrate the capability in predicting crack paths of complex geometries in comparison to FEM and experimental results. Findings The implicit scheme with the adopted damage model shows favorable numerical stability and the numerical results exhibit appropriate convergence characteristics concerning the mesh size. The damage evolution is successfully controlled by a tension-compression damage factor. Thanks to the advanced geometric design capability of IGA, the details of crack patterns can be predicted reliably, which are somewhat difficult to be acquired by FEM. Additionally, the damage distribution obtained in the dynamic analysis is in close agreement with experimental results. Originality/value The paper originally incorporates GeMpDM into IGA. Especially, only one non-local variable is considered besides the displacement field, which improves the computational efficiency and favorable convergence characteristics within the IGA framework. Also, enjoying the geometric design ability of IGA, the proposed analysis method is capable of accurately predicting crack paths reflecting the complex geometries of target structures.
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Ortner, Michael, Neosha Navaei e Martin Lenzhofer. "Modeling Planar Fluxgate Structures". Proceedings 2, n. 13 (10 dicembre 2018): 830. http://dx.doi.org/10.3390/proceedings2130830.
Abstract (sommario):
Planar fluxgate structures have been the focus of multiple experimental studies. However, theoretical treatises are still limited to the classical models that describe 3D structures. In this paper we derive an effective fluxgate equation for planar systems, dealing with strong stray fields and direct coupling, and show the stability and applicability of the Vacquier implementation. To support the theoretical model, FEM simulations are performed that also provide means of layouting planar fluxgates by pure magnetostatic simulation.
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Ma, Kuichao, Ruojin Wang, Heng Nian, Xiaodong Wang e Wei Fan. "Nonlinear Model Predictive Control for Doubly Fed Induction Generator with Uncertainties". Applied Sciences 14, n. 5 (22 febbraio 2024): 1818. http://dx.doi.org/10.3390/app14051818.
Abstract (sommario):
Doubly fed induction generators (DFIG) find extensive application in variable-speed wind power plants, providing notable advantages such as cost-effectiveness, operational flexibility across varying speeds, and enhanced power quality. This research focuses on the control of DFIGs employed in variable-speed wind turbine configurations. A suitable mathematical model is chosen for representative systems following a comprehensive review of contemporary research. Subsequent analysis reveals the instability of the open-loop time response of the system. To address this instability, the initial approach involves the implementation of the conventional model predictive controller (MPC). However, the outcomes indicate that this controller falls short of delivering satisfactory performance despite the enhanced stability. In the subsequent phase, efforts are made to mitigate the impact of wind input variability by utilizing the Kalman filter, given its effectiveness in handling high variability. Following this, a novel methodology is introduced, which combines nonlinear MPC with the Lyapunov function. This method is based on the nonlinear model of the system. By using the Lyapunov function in the nonlinear MPC structure, the stability of the designed controller is guaranteed. To validate the proposed control approach, the results are compared with PID based controller in MATLAB/Simulink. The simulation results showed that the output variables of the modeled DFIG system achieve stability within a reasonable timeframe applying the input.
32
Mueller, Jan, Akira Kyotani e Hans-Georg Matuttis. "Grid-algorithm improvements for dense suspensions of discrete element particles in finite element fluid simulations". EPJ Web of Conferences 249 (2021): 09006. http://dx.doi.org/10.1051/epjconf/202124909006.
Abstract (sommario):
For homogeneous systems like classical fluid dynamics and structural mechanics, finite element method (FEM) grid generation has reached a mature state. On the other hand, for multi-physics-problems like fluids with a high density of immersed particles, many researchers may not even be aware of the types of instabilities which may be triggered by unsuitable meshes. We review common types of grid generation, point out previously unrecognised types of instabilities for particles in fluids as well as remedies to obtain particle-fluid simulations with higher stability and fewer redundant degrees of freedom.
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de Barros Cavalcante, João Paulo, Daniel Nelson Maciel e Marcelo Greco. "Impact Response of Flying Objects Modeled by Positional Finite Element Method". International Journal of Structural Stability and Dynamics 18, n. 06 (giugno 2018): 1850076. http://dx.doi.org/10.1142/s0219455418500761.
Abstract (sommario):
This paper analyzes the dynamic response of space and plane trusses with geometrical and material nonlinear behaviors using different time integration algorithms, considering an alternative Finite Element Method (FEM) formulation called positional FEM. Each algorithm is distinguished from each other by its specific form of position, velocity, acceleration and equilibrium equation concerning the stability, consistency, accuracy and efficiency of solution. Particularly, the impact problems against rigid walls are analyzed considering Null-Penetration Condition. This formulation is based on the minimum potential energy theorem written according to the nodal positions, instead of the structural displacements. It has the advantage of simplicity when compared with the classical counterparts, since it does not necessarily reply on the corotational axes. Moreover, the performance of each temporal integration algorithm is evaluated by numerical simulations.
34
Wang, Bingxiang, Youping Yi, Shiquan Huang e Hailin He. "Reduction of Residual Quenching Stresses in 2A14 Aluminum Alloy Tapered Cylinder Forgings via a Novel Cold Bulging Process". Metals 11, n. 5 (27 aprile 2021): 717. http://dx.doi.org/10.3390/met11050717.
Abstract (sommario):
This study combined finite element method (FEM) simulations and physical experiments to develop a novel cold bulging process, with the aim of studying and mitigating the quenching residual stresses in 2A14 tapered cylinder forgings. The samples underwent cold bulging at different ratios (0–4.0%) to evaluate the residual stress reduction performance (via the hole-drilling strain-gauge method) and the improvements in their mechanical properties. The FEM simulation and experimental results revealed that our proposed cold bulging process reduced the quenching residual stresses by up to 85–87%. The density and uniformity of the precipitated phases increased along with the extent of cold bulging, as confirmed by transmission electron microscope (TEM) observations. Furthermore, compared to the unprocessed samples, the tensile and yield strengths, and elongation of the samples with 3% cold bulging were significantly enhanced (65 MPa, 55 MPa, and 1.7%, respectively).
35
Xu, Chao, Jin Ling Lu e Jin Long Zhou. "A Control Strategy for Transient Stability Improvement of Doubly-Fed Wind Power Generation System". Advanced Materials Research 953-954 (giugno 2014): 337–41. http://dx.doi.org/10.4028/www.scientific.net/amr.953-954.337.
Abstract (sommario):
A novel inverter control strategy to enhance the transient stability of grid-connected wind farm based on doubly-fed induction generator (DFIG) is presented. Adding transient angle control strategy in the rotor side converter active control loop, this can dissipate the system unbalancing energy and restrain the system oscillations by the variation of wind turbine speed. Adding transient voltage control strategy in reactive control loop, this can provide fast reactive power compensation and support the restoration and reconstruction of the grid voltage when fault occurred. The control strategy which can improve the transient Angle stability and transient voltage stability at the same time is put forward. Finally, a testing system including a DFIG-based wind farm is realized using DigSILENT/Power Factory, the strategy validation and the contribution to power system stability enhancement are verified by simulation.
36
Baek, Seung Yub. "Determination for Tool Edge Geometry and Cutting Conditions by Using FEM Simulations and Experiments". Applied Mechanics and Materials 378 (agosto 2013): 449–54. http://dx.doi.org/10.4028/www.scientific.net/amm.378.449.
Abstract (sommario):
Hardened steel, Ni-based alloys and brittle materials are very difficult to machine using conventional cuttingmethods.A tool edge with a small nose radius can alleviate the regenerative chatter. In general, it is important for conventional cuttingto use the smallest possible tool nose radius. A sharp tool shape has an adverse effect on tool strength and the instability of machining process still occurs. A tool wear model with small nose radius proposed by past researchers is evaluated for predicting metal cutting tool wear when machining the copper. Tool temperature values are determined using finite element methods simulation. These temperatures are related to tool wear measured after metal cutting turning tests on a copper workpiece to determine tool edge geometry in low metal tool model.In this study, the effects of cutting conditions and tool edge geometry on process stability in turningare investigated through experiments and FEM simulations.
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Szweda, Jan, Zdenek Poruba, Roman Sikora e Jiří Podešva. "Computational Analysis of Mechanism Operability". Applied Mechanics and Materials 315 (aprile 2013): 879–83. http://dx.doi.org/10.4028/www.scientific.net/amm.315.879.
Abstract (sommario):
This article deals with a way of interpretation the results of numerical simulations solved for the mechanism of lifting platform. Subject of analysis is the atypical design solution of lifting mechanism with one degree of freedom, which members are connected by revolute joints and linear sliding guidance. The mechanism movement is provided by linear hydromotors. Computational simulations are carried out by FEM, where linear coupling equations are used for modeling of revolute joints and linear sliding guidance is modeled by structural contact of rail and slider. The way of modeling and parameters setting of structural contact significantly affects the stability of numerical solutions and the obtained results. The authors assume that the interpretation of the observed behavior and results of the numerical simulations allow to deduce the mechanism operability and gives a clue for setting the gap of real bounds.
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Chrášťanský, Lukáš, Jan Šanovec, Yatna Yuwana Martawirya e Michal Valeš. "APPLICABILITY VERIFICATION OF AUTOFORM SOFTWARE FOR FEM SIMULATION OF MECHANICAL FIXATION OF HEMMED JOINTS". Acta Polytechnica 59, n. 6 (31 dicembre 2019): 554–59. http://dx.doi.org/10.14311/ap.2019.59.0554.
Abstract (sommario):
This paper deals with the problematics of fixation of hemmed joints, especially with one specific mechanical method how to ensure a dimensional stability of a hemmed joint of car-body parts, such as doors, bonnet and trunk lid, during the production process in the automotive industry. It also evaluates simulations and verify the possibility of the use of the Autoform software for this problematics. In the paper, the possibility of using the law of similarity in the analysis of the compressibility of small parts by Autoform is described.
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Přinosil, Michal, e Petr Kabele. "Numerical Analysis of Masonry Enhanced by Fiber Reinforced Lime-Based Render". Key Engineering Materials 624 (settembre 2014): 246–53. http://dx.doi.org/10.4028/www.scientific.net/kem.624.246.
Abstract (sommario):
Out of plane load bearing capacity of a masonry structure enhanced by surface render made of high performance lime-based mortar is investigated by numerical simulations using the finite element method (FEM). The response of the wall is simulated firstly without render (as a reference) then with surface render consisting of conventional lime mortar with increased tensile strength (by addition of the metakaolin) without fibers and finally with the proposed lime-metakaolin mortar reinforced with PVA fibers. The thickness of the surface render is considered in two configurations (20 mm and 40 mm). Material parameters of masonry units (bricks), joints (mortar between bricks) and conventional plain render are chosen with regard to investigations of historic structures (reported in the literature), material characteristics of fiber reinforced render are evaluated based on experiments or numerical simulations of these experiments. Using these parameters and characteristics, the numerical simulations of masonry wall subjected to out of plane bending are performed. The results allow us to identify influence of the thickness and the material of render on load-bearing and deformation capacity, failure mode and amount and width of cracks. The results show that the conventional plain mortar improves load-bearing capacity and deformation capacity proportionately to the thickness of render, but the response remains brittle. Fiber reinforced mortar significantly increases the deformation capacity and load-bearing capacity and the amount of absorbed energy is significantly improved.
40
Kouider, Khaled, e Abdelkader Bekri. "Enhancing transient stability and dynamic response of wind-penetrated power systems through PSS and STATCOM cooperation". International Journal of Renewable Energy Development 12, n. 5 (18 luglio 2023): 816–31. http://dx.doi.org/10.14710/ijred.2023.53249.
Abstract (sommario):
The large-scale integration of doubly-fed induction generator (DFIG) based wind power plants poses stability challenges for power system operation. This study investigates the transient stability and dynamic performance of a modified 3-machine, 9-bus Western System Coordinating Council (WSCC) system. The investigation was conducted by connecting the DFIG wind farm to the sixth bus via a low-impedance transmission line and installing power system stabilizers (PSSs) on all automatic voltage regulators (AVRs). A three-phase fault simulation was carried out to test the system, with and without power system stabilizers and a static synchronous compensator (STATCOM) device. Time-domain simulations demonstrate improved transient response with PSS-STATCOM control. A 50% reduction in settling time and 70% decrease in power angle undershoots at the slack bus are achieved following disturbances, even at minimum wind penetration levels. Load flow analysis shows the coordinated controllers maintain voltages within 0.5% of nominal at 60% wind penetration, while voltages at load buses can deviate up to 15% without control. Eigenvalue analysis indicates the PSS-STATCOM boosts damping ratios of critical oscillatory modes from nearly 0% to over 30% under high wind injection. Together, the present findings provide significant evidence that PSS and STATCOM cooperation enhances dynamic voltage regulation, angle stability, and damping across operating ranges, thereby maintaining secure operation in systems with high renewable integration.
41
Kovalevsky, Lukasz, Vladimir I. Andreev e Stanislav Emelo. "Numerical simulations of local and global buckling of hyperelastic tubes with different cross-sections". Vestnik MGSU, n. 2 (febbraio 2019): 169–78. http://dx.doi.org/10.22227/1997-0935.2019.2.169-178.
Abstract (sommario):
Introduction. An approach to the application of finite element programs (FEM) ABAQUS/Standard and ABAQUS/Explicit with various equations of state of incompressible isotropic hyperelastic materials is presented when analyzing compressed and stretched shell elements of elastomers. Elastomers are commonly used in construction as well as in structural shell elements, in particular pipes of different cross sections. Materials and methods. Three FEM models for pipes with the same length and initial stiffness were created. Pipes with elliptical, square and triangular cross sections are considered. Three types of structural models of rubber-like material (elastomer) were used - with a polynomial elastic energy function in the form of the MV model and the standard models of Neo - Hooke and Mooney - Rivlin. In the FEM models of the analyzed pipes, not enter initial imperfections. Numerical modeling buckling of pipes was performed for two types of initial and boundary conditions - for quasistatic and dynamic problems. Results. It is shown that the type of buckling depends on the cross section of the pipe. Comparison of buckling solutions for simulated pipes with different structural models demonstrated a good correlation of the results. An approximate history of the deformation of an elliptical sample analyzed by ABAQUS/Standard, loaded by moving the boundary, is given. Conclusions. It has been established that the ABAQUS/Standard program allows the use of incompressible hyperelastic materials, the ABAQUS/Explicit program does not provide this possibility. This implies the need to set the parameters of the material associated with the spherical part of the stress tensor. The parameter should not be too small, otherwise it will lead to numerical errors. Solving problems on the stability of pipe models with different physical models give good correlations of results.
42
Jung, Sang Jin, Tanvir Alam Shifat e Jang-Wook Hur. "A Hybrid Fault Diagnosis Approach Using FEM Optimized Sensor Positioning and Machine Learning". Processes 10, n. 10 (22 settembre 2022): 1919. http://dx.doi.org/10.3390/pr10101919.
Abstract (sommario):
Sensor acquired signal has been a fundamental measure in rotary machinery condition monitoring (CM) to enhance system reliability and stability. Inappropriate sensor mounting can lead to loss of fault-related information and generate false alarms in industrial systems. To ensure reliable system operation, in this paper we investigate a system’s multiple degrees-of-freedom (DOF) using the finite element method (FEM) to find the optimum sensor mounting position. An appropriate sensor position is obtained by the highest degree of deformation in FEM modal analysis. The effectiveness of the proper sensor mounting position was compared with two other sensor mounting points, which were selected arbitrarily. To validate the effectiveness of this method we considered a gear-actuator test bench, where the sensors were mounted in the same place as the FEM simulation. Vibration data were acquired through these sensors for different health states of the system and failure patterns were recognized using an artificial neural network (ANN) model. An ANN model shows that the optimum sensor mounting point found in FEM has the highest accuracy, compared to other mounting points. A hybrid CM framework, combining the physics-based and data-driven approaches, provides robust fault detection and identification analysis of the gear-actuator system.
43
Rozylo, Patryk, Michal Rogala e Jakub Pasnik. "Buckling Analysis of Thin-Walled Composite Structures with Rectangular Cross-Sections under Compressive Load". Materials 16, n. 21 (24 ottobre 2023): 6835. http://dx.doi.org/10.3390/ma16216835.
Abstract (sommario):
The purpose of this research was the analysis of the stability of compressed thin-walled composite columns with closed rectangular cross-sections, subjected to axial load. The test specimens (made of carbon–epoxy composite) were characterized by different lay-ups of the composite material. Experimental tests were carried out using a universal testing machine and other interdisciplinary testing techniques, such as an optical strain measurement system. Simultaneously with the experimental studies, numerical simulations were carried out using the finite element method. In the case of FEA simulations, original numerical models were derived. In the case of both experimental research and FEM simulations, an in-depth investigation of buckling states was carried out. The measurable effect of the research was to determine both the influence of the cross-sectional shape and the lay-up of the composite layers on the stability of the structure. The novelty of the present paper is the use of interdisciplinary research techniques in order to determine the critical state of compressed thin-walled composite structures with closed sections. An additional novelty is the object of study itself—that is, thin-walled composite columns with closed sections.
44
Long, Kai. "FDM 3D printer temperature control system based on PID control". Applied and Computational Engineering 28, n. 1 (6 dicembre 2023): 72–79. http://dx.doi.org/10.54254/2755-2721/28/20230129.
Abstract (sommario):
With the continuous development of manufacturing technology today, the emerging technology of 3D printing is becoming more mature, and the surface accuracy and quality of printed products are receiving increasing attention from users. The stability and appropriateness of the nozzle temperature have a significant impact on the quality of the prints. This project focuses on the fused deposition modeling (FDM) 3D printer as the research subject, introduces the structure types of FDM 3D printers, and addresses the temperature control issue of FDM printers by using PID control for improvement. By applying SIMULINK to model and simulate the nozzle temperature control system, the simulation results of PID control are analyzed and compared. The results show that PID control shortens the stabilization time, improving the stability and control accuracy of the control system. PID control can enhance the temperature control accuracy of FDM printers, thus improving the precision and surface quality of the printed products.
45
Danilewicz, Andrzej, e Zbigniew Sikora. "Numerical Simulation of Crater Creating Process in Dynamic Replacement Method by Smooth Particle Hydrodynamics". Studia Geotechnica et Mechanica 36, n. 3 (28 febbraio 2015): 3–8. http://dx.doi.org/10.2478/sgem-2014-0022.
Abstract (sommario):
Abstract A theoretical base of SPH method, including the governing equations, discussion of importance of the smoothing function length, contact formulation, boundary treatment and finally utilization in hydrocode simulations are presented. An application of SPH to a real case of large penetrations (crater creating) into the soil caused by falling mass in Dynamic Replacement Method is discussed. An influence of particles spacing on method accuracy is presented. An example calculated by LS-DYNA software is discussed. Chronological development of Smooth Particle Hydrodynamics is presented. Theoretical basics of SPH method stability and consistency in SPH formulation, artificial viscosity and boundary treatment are discussed. Time integration techniques with stability conditions, SPH+FEM coupling, constitutive equation and equation of state (EOS) are presented as well.
46
Santos, Hugo, Pedro Pinho e Henrique Salgado. "Patch Antenna-in-Package for 5G Communications with Dual Polarization and High Isolation". Electronics 9, n. 8 (29 luglio 2020): 1223. http://dx.doi.org/10.3390/electronics9081223.
Abstract (sommario):
In this paper, we describe the design of a dual polarized packaged patch antenna for 5G communications with improved isolation and bandwidth for K-band. We introduce a differential feeding technique and a heuristic-based design of a matching network applied to a single layer patch antenna with parasitic elements. This approach resulted in broader bandwidth, reduced layer count, improved isolation and radiation pattern stability. The results were validated through finite element method (FEM) and method of moments (MoM) simulations. A peak gain of 5 dBi, isolation above 40 dB and a radiation efficiency of 60% were obtained.
47
Sayyad, Gholamreza, Amin Khodabakhshian e Rahmatollah Hooshmand. "A Systematic Approach and Genetic Algorithm Method to Power System Stabilizer Design for Wind Turbine Equipped with DFIG". Applied Mechanics and Materials 229-231 (novembre 2012): 1095–99. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.1095.
Abstract (sommario):
This paper develops a power system stabilizer (PSS) design for a wind turbine equipped with doubly fed induction generator (DFIG) which is based on vector control to improve the performance and dynamic stability of DFIG under fault conditions. The proposed PSS design is combined with genetic algorithm to obtain the higher-fitness answer as a strong optimization technique to the design of PSS parameters. A study network containing a wind farm equipped with DFIG was employed and all simulations will be carried out using MATLAB. It is shown that the employment of a proposed PSS can substantially enhance the contribution of a DFIG-based wind farm to network damping and dynamic stability.
48
Kong, Yan Mei, Rui Wen Liu, Bin Bin Jiao, Di Ke Lu, En Cheng Zhu, Qiang Sheng Fu e Da Peng Chen. "Performance-Enhanced Heat Converter Used in FPA Utilizing a SiOx/Al Corrugated Micro-Cantilever Actuator". Key Engineering Materials 645-646 (maggio 2015): 951–56. http://dx.doi.org/10.4028/www.scientific.net/kem.645-646.951.
Abstract (sommario):
This paper proposes a performance-enhanced SiOx/Al corrugated micro-cantilever structure, which transfers heat to mechanical deformation. Analytical simulations are carried out using the Finite Element Method (FEM), compared to the traditional straight bi-material structure (TSBMS) with same lengthL, the corrugated bi-material structures (CBMS) have higher temperature response sensitivitySTand lower stiffness factor K. Furthermore, two types of cantilever was fabricated, and the test result verifies the change of the stiffness factorK. Finally, the thermal mechanical uncooled infrared focal plane array (FPA) with CBMS was fabricated, and the test results show that the bending response of the CBMS is about 2 times greater than TSBMS with same length. The CBMS proposed in this paper could be used widely in MEMS apparatus field based on bimaterial microcantilever.
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Homlamai, Kan, e Montree Sawangphruk. "Enhancing the Performance and Stability of Li-Ion Batteries with Fluorinated Electrolytes: Insights from MD Simulation and Experimental Analysis". ECS Meeting Abstracts MA2023-02, n. 2 (22 dicembre 2023): 269. http://dx.doi.org/10.1149/ma2023-022269mtgabs.
Abstract (sommario):
The significance of using fluorinated electrolytes, particularly fluorinated ethylene carbonate (FEC) and difluoro ethylene carbonate (DFEC), in the electrolyte system of 1.2 M LiPF6 in dimethyl carbonate (DMC)/fluorinated solvent (FEC/DFEC), was explored using classical molecular dynamic (MD) simulation and density functional theory (DFT) calculation in this work. Various parameters, such as radial distribution function (RDF), integral over RDF, transference number, coordination number, and solvation energy, were analyzed. The study demonstrated that DFEC enhances the reduction in binding energy of the solvation sheath compared to FEC. Additionally, the electrochemical performance of a practical full-cell 18650 of LiNi0.88Co0.10Al0.02O4 (NCA) cathode and graphite anode batteries was examined, confirming that 1.2 M LiPF6 in DMC/FEC/DFEC (4:0.5:0.5 %v) demonstrated the highest capacity retention after 1,000 cycles, surpassing 1.2M LiPF6 in DMC/fluorinated (4:1 %v, FEC and DFEC, respectively) and the previous electrolyte 1.2 M LiPF6 in EC/EMC/DEC/FEC (1:1:1:1.3 %V). Spectroscopy techniques, including DEMS, NMR, and GC-MS, were utilized to investigate the electrolyte decomposition, revealing CO2 and H2 as the main gas products during decomposition. NMR results identified some species, such as HF, H2O, acetal, formaldehyde, and unknown products, while GC-MS confirmed that all the solvents in the electrolyte take part in the decomposition process. This study highlights the potential of fluorinated electrolytes in battery systems and provides insight into their decomposition mechanism, contributing to the development of more efficient and stable battery systems.
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Bosse, Stefan, Armin Lechleiter e Dirk Lehmhus. "Data Evaluation in Smart Sensor Networks Using Inverse Methods and Artificial Intelligence (AI): Towards Real-Time Capability and Enhanced Flexibility". Advances in Science and Technology 101 (ottobre 2016): 55–61. http://dx.doi.org/10.4028/www.scientific.net/ast.101.55.
Abstract (sommario):
Data evaluation is crucial for gaining information from sensor networks. Main challenges include processing speed and adaptivity to system change, both prerequisites for SHM-based weight reduction via relaxed safety factors. Our study looks at soft real time solutions providing feedback within defined but flexible, application-controlled intervals. These can rely on minimizing computation/communication latencies e.g. by parallel computation. Strategies towards this aim can be model-based, including inverse FEM, or model-free, including machine learning, which in practice bases training on a defined system state, too, hence also facing challenges at state changes. We thus introduce hybrid data evaluation combining multi-agent based systems (MAS) with inverse FEM, mainly relying on matrix operations that can be partially distributed: The MAS perform sensor data acquisition, aggregation, pre-computation, and finally application (the LM/SHM itself and higher information processing and visualization layers, i.e., WEB interfaces). System capabilities are evaluated against a virtual test case, demonstrating enhanced stability and reliability. Besides, we analyze system performance under conditions of in-service change and discuss system layouts suited to improve coverage of this issue.