Influence Of Geometrical Parameters Research Articles

A novel polar mechanical metamaterial with dual deformation characteristics

Polarity refers to the phenomenon of an object exhibiting opposite intrinsic properties in opposing directions, which plays a fundamental role in various fields including mechanical diodes, mechanical logic gates, and shock protection. This paper proposes a new mechanical metamaterial with polar and dual deformation characteristics based on a fishbone-like structure to enable a given surface structure to be hard while its opposite side is soft, while also enabling the task of adapting to different load levels on the soft side. The mechanical metamaterial displays double-stress platforms and exhibits a significant difference in mechanical response when loaded on opposite sides. Through numerical simulations, the polarity characteristic spectrum of the mechanical metamaterial is identified. The stress platform with a soft boundary predicted using Euler's instability theory was verified through both numerical simulation and experimentation. The dimensionless parameters for load differences are defined to evaluate the polar characteristics of polar mechanical metamaterials, and design guidelines are provided for achieving significant polar characteristics of polar mechanical metamaterials by discussing the influence of geometrical parameters. The proposed polar mechanical metamaterial introduces a novel design concept applicable to signal transmission, isolation, and energy absorption for different load levels.

Shear capacity of corrugated steel plates with a random corrosion damage

Corrugated steel plates have been utilized widely in engineering structures, such as underground utility tunnels, web of steel beams, underground pipelines, and shear walls. The influence of corrosion on the buckling capacity of corrugated steel plates differs from that of flat steel plates. A numerical model of corrugated steel plates with random corrosion is initially established and validated using theoretical results. The influence of pitting corrosion on the shear capacity of corrugated steel plates is investigated through stochastic numerical analysis. The influences of geometric parameters, including pitting size, plate thickness, and corroded thickness, on the shear capacity of randomly corroded steel plates are also investigated. In addition, the changing trend of shear capacity along with mass loss ratio is derived.

Study on the Influence of Geometric Parameters and Shape Optimization of Single Tenon Joint in Assembled Subway Station

The various components of fully prefabricated metro stations are mainly connected using grouted tenon and mortise joints. Therefore, studying the mechanical properties of the joint locations is of significant importance for the overall safety and stability of the station. This paper focuses on the single tenon-long joint as the research object and applies an orthogonal experiment plan to investigate the relationship between the lower bottom length, upper bottom length, and height of the joint and its flexural load carrying capacity. After comparing various loading methods, uniformly distributed loads are chosen as the method for applying axial forces and bending moments. The objective is to determine the dimensions of the tongue and groove that exhibit optimal mechanical properties based on the law of opening displacement and maximum deflection variation with bending moment. The influence of geometrical parameters on the flexural strength of tenon joints is analyzed by means of range analysis in order to find the combination of geometrical parameters with the best mechanical properties. The degree of influence of each geometrical parameter was also ranked. Using these insights, the authors proposed a modified cross-shaped tenon based on the optimal combination of geometrical parameters, which was verified by comparing the M–θ curves of the optimal combination and the optimum working condition. The main conclusions are as follows: (1) the ranking of the geometric parameters of the joint in terms of their influence on the flexural capacity is as follows: height has a greater impact than the bottom length, and the bottom length has a greater impact than the top length. Among these parameters, the influence factor of the height is significantly greater than the other two. (2) The optimum geometry for the tenon and mortise joint is 385 mm for the lower bottom length, 230 mm for the upper bottom length, and 200 mm for the height; the joint’s ratio of height to total width should be 25%, the ratio of lower bottom length to total width should be 48%, and the ratio of upper bottom length to total width should be 29%. (3) The load carrying capacity of the cross-shaped tenon is significantly higher than that of the optimal combination and optimum working condition, providing a significant improvement. This research’s results will serve as a valuable reference for designing assembly nodes in prefabricated assembly metro stations.

Machine learning approach to predict heat transfer and fluid flow characteristics of integrated pin fin-metal foam heat sink

Integrated pin fin-metal foam (PF-MF) heat sink offers enhanced thermal performance owing to the higher surface area and flow mixing. By realizing the strong influence of geometrical parameters of PFs, morphological properties of MF, and coolant hydrodynamics on the thermal-hydraulic performance of the PF-MF heat sink, this article presents a machine learning (ML) surrogated multiparameter and multi-objective optimization framework to determine optimal PF-MF heat sink layouts within the laminar flow regime to enhance the thermal performance of the heat sink with a minimal pumping power penalty. Four supervised regression ML models, namely random forest, extreme gradient boosting, support vector regressor, and artificial neural networks (ANN), were considered while searching for the best surrogate. Four geometrical parameters of PFs, such as PFs diameter (D), height (h), longitudinal pitch, transverse pitch, two morphological properties of MF, i.e., pore density porosity and coolant flow condition, i.e., Reynolds number have been considered as design parameters. The heat transfer and fluid flow performance of the heat sink are evaluated using nondimensional Nusselt number and friction factor A high-fidelity 3-D computational fluid dynamics/heat transfer (CFD/HT) model has been developed to evaluate the thermal-hydraulic performance of all PF-MF heat sink layouts. Furthermore, utilizing the numerical data, ML models have been trained and fine-tuned to accurately predict the overall performance of the PF-MF heat sink. Upon testing the prediction and interpolation capability of all considered ML models, ANN outperforms other models, hence, ANN model has been coupled with genetic algorithm (GA) optimizer to identify three different optimized PF-MF heat sink layouts at three different Finally, the result shows that the ANN surrogated GA-optimized PF-MF heat sink layout can improve the overall thermal-hydraulic performance by approximately 19–35% compared to the best PF-MF heat sink layout among the used input feature space for ML model.

Effect of geometric parameters of electrodes on skin heating for the design of non-ablative radiofrequency device.

Non-ablative radiofrequency (RF) has been widely used in clinical and at-home cosmetics devices. RF electrode geometry can influence the heat distribution in the tissue. This study analyzes the influence of geometric parameters of the electrode on the heat distribution in the layered tissue. The finite element simulation of the electrothermal coupling field was performed to obtain the three-dimensional (3D) temperature distribution of the four-layer tissue. The electrode geometric parameters including the inter-electrode spacing (5-12mm), width (1-3mm), length (3-10mm), shapes (bar, dot and circle), and the coupling gel's electrical conductivity (0.2-1.5 S/m) were simulated. The maximum temperature at 2mm depth (T-2mm ) and the temperature difference (Tdiff ) between the maximum skin surface temperature and T-2mm were obtained to evaluate the effectiveness and safety. The effect of geometric parameters on the effectiveness and safety was mixed. The maximum T-2mm occurred with the 5mm inter-electrode spacing, 3mm width, 10mm length, the circle-shaped electrode, and the 1.5 S/m coupling gel's electrical conductivity. The ratio of inter-electrode spacing to width at around four can achieve rapid temperature rise and skin surface temperature protection. The electrode shape influenced the area of temperature rise in the tissue's cross-section. The coupling gel's electrical conductivity should be close to that of the skin to avoid energy accumulation on the skin surface. The electrode's geometric parameters affect the effectiveness and safety of the RF product. This study has provided the simulation procedure for the electrode design.

Investigation on the influence of geometric parameters on two-phase ejector performance with R290

In this paper, the effect of geometric parameters on a two-phase ejector performance was experimentally studied, and the R290 was used as the working fluid. The four geometric parameters of the ejector were discussed in detail, including the diameter of the nozzle throat (Dt), the nozzle exit position (NXP), the diameter of the mixing section (Dm) and the length of the mixing section (Lm). The experimental results indicated that the pressure lift ratio (rp) of the ejector was sensitive to Dt and NXP. Within the increase of Dt and NXP discussed in this paper, the rp of the ejector varied from 1.13 to 1.33 and 1.32 to 1.07, respectively. In addition, a maximum rp of the ejector could be obtained when Dm was 3 mm to 4 mm under different nozzle throat diameter. When the Dt was 0.7 mm, the entrainment ratio of the ejector varied from 0.402 to 1.406 as the Dm varied from 2 mm to 6 mm. The Lm of the ejector diffuser had little effect on the ejector performance. Moreover, the empirical correlations for the efficiencies of R290 two-phase ejector components were summarized based on the experimental result and ejector model.

Geometry-informed dynamic mode decomposition in Kresling origami dynamics

Origami structures often serve as the building block of mechanical systems due to their rich static and dynamic behaviors. Experimental observation and theoretical modeling of origami dynamics have been reported extensively, whereas the data-driven modeling of origami dynamics is still challenging due to the intrinsic nonlinearity of the system. In this study, we show how the dynamic mode decomposition (DMD) method can be enhanced by integrating geometry information of the origami structure to model Kresling origami dynamics in an efficient and accurate manner. In particular, an improved version of DMD with control, that we term geometry-informed dynamic mode decomposition (giDMD), is developed and evaluated on the origami chain and dual Kresling origami structure to reveal the efficacy and interpretability. We show that giDMD can accurately predict the dynamics of an origami chain across frequencies, where the topological boundary state can be identified by the characteristics of giDMD. Moreover, the periodic intrawell motion can be accurately predicted in the dual origami structure. The type of dynamics in the dual origami structure can also be identified. The model learned by the giDMD also reveals the influential geometrical parameters in the origami dynamics, indicating the interpretability of this method. The accurate prediction of chaotic dynamics remains a challenge for the method. Nevertheless, we expect that the proposed giDMD approach will be helpful towards the prediction and identification of dynamics in complex origami structures, while paving the way to the application to a wider variety of lightweight and deployable structures.

Многовариантное моделирование параметров конструкции упругих клемм современных рельсовых скреплений с анализом их напряженно-деформированного состояния

Purpose: To determine the influence of geometric parameters on the most common elastic rod clip used in modern intermediate rail fastenings — the B-shaped clip (such as reinforced concrete rail (RCR) clip and anchor rail fastening (ARF)) — on changes in its stress-strain state. To propose a further direction of improving the design of elastic rod clips of rail fasteners to increase the reliability of the structure. Methods: The article presents the results of multivariate modeling of the geometric parameters of the clips (RCR — 20 pcs., ARF — 13 pcs.) with the analysis of their stress-strain state, using the methods of software and computer systems SolidWorks and Ansys Workbench. Results: Analysis of the design of modern fasteners has shown that the intervals for varying the geometric parameters of the clips (rod diameter, vertical radius, horizontal radius) have small limits and significant limitations associated with the requirements for ensuring the strength, elasticity and operability of the entire fastening. The necessity of considering options with vertical radii less than 60 mm has been revealed, which entails the need for a radical change in the shape of the clips themselves. Practical significance: As a result of the analysis of the calculations of multivariant models, the degrees of influence of the intervals of variation of the geometric parameters of rod clips (rod diameter, vertical radius, horizontal radius) on the stress-strain state have been determined. It is established that in order to further increase the elasticity of the clips, it is necessary to develop a new type of rail fastening with a fundamentally different shape (different from the modern B-shaped) elastic clip that does not have modern design limitations in geometric parameters.

Transforming Alcoholic Vinasse: Improving Biodegradability and Reducing Toxicity through Hydrodynamic Cavitation – A Review

This review examined the viability of hydrodynamic cavitation as a pretreatment method to improve biodegradability and reduce toxicity in alcoholic vinasse. The growing interest in environmental impacts and the demand for sustainable solutions in the alcohol production industry have driven the search for efficient methods to treat vinasse, a complex and polluting by-product. The basic principles of hydrodynamic cavitation and its application in contaminant removal are explored in detail. Through a critical review of existing research, the efficiency of removal of organic load and recalcitrant contaminants, the influence of geometric parameters, the operational parameters of the process, and the challenges of applying hydrodynamic cavitation as pretreatment of alcoholic vinasse are analyzed. Despite its limitations, its potential as a solution to address pollution problems in alcohol production stands out. Ultimately, this review aims not only to collect and analyze the available information but also to encourage future research in this direction. Therefore, this review article is presented as an essential resource that guides future researchers and practitioners towards more sustainable and effective solutions, significantly contributing to environmental improvements in the industry.

An energy dissipation metamaterial based on Coulomb friction and vibration

Compared with traditional energy dissipation structures, negative stiffness metamaterials can repeatedly dissipate energy without incurring irreversible plastic deformation. The existing negative stiffness structures are generally multistable, and their energy dissipation mechanism is either through internal component vibration or friction. In this paper, a self-recoverable negative stiffness structure was proposed which can dissipate energy through both vibration and Coulomb friction. The structure consists of an external I-shaped structure and a buckle-like structure composed of a plug and cantilever beams inside. The proposed structure achieves monostable characteristics by utilizing the concept of self-contact. To investigate the mechanical properties, quasi-static loading-unloading experiments were performed and verified using finite element simulation. The energy dissipated in the proposed structure by vibration and friction was quantified theoretically. The influence of geometric parameters on energy dissipation was studied using simulation and analytical methods. This type of metamaterial has the potential to be employed in the production of multi-functional metamaterial structures such as deformable robots or reusable bumpers.

Low-frequency broadband absorber with coherent coupling based on perforated panel and space-coiling channels

Efficient broadband absorption of low-frequency sound via ultra-thin structure remains challenging due to the narrow-band property generated by the dispersive nature of resonance. In this study, we investigate the absorption mechanism of a component composed of a perforated panel and space-coiling channels through the coupling effect, acoustic impedance matching, and complex frequency analysis. In addition, the influence of geometrical parameters, resonance frequency intervals, and number of components in the coupled system on the band is investigated. Accordingly, the strategy for developing absorbers is to design individual components in the under-damped state by adjusting the geometrical parameters, then put together multiple components with different channel lengths in parallel. On the basis of this strategy, a low-frequency and broadband absorber is theoretically proposed and experimentally demonstrated, which can achieve broadband absorption from 250 Hz to 450 Hz. The design strategy has potential applications in low-frequency noise control engineering, such as plants, automotive and aerospace industries.

All-optical switching based on coherent control of metasurface

In this paper, we propose a novel method to design ultrafast all-optical switchings based on the coherent perfect absorption principle of metasurface. Using the coherent interaction between two beams of coherent light and the metasurface, the absorption can be modulated between 0.3% and 98. 3%. Since no nonlinear dielectric is used, the ultrafast all-optical switching function can be achieved at arbitrary low intensity conditions. We further studied the mechanism of resonant absorption on metasurface, and analyzed the influence of geometric parameters on resonant absorption. Through time-domain simulation analysis, when the incident laser pulse duration is 40 fs, the switching response time is 82 fs, which provides a switching contrast ratio of more than 108.

Numerical investigation of entropy generation of turbulent flow in twisted tri-lobed tubes

Twisted tri-lobed tubes have garnered attention due to their exceptional heat transfer efficiency and straightforward fabrication. Existing literature lacks comprehensive assessments of the overall heat transfer performance of twisted tri-lobed tubes from the perspective of energy loss and irreversibility. This research aims to investigate entropy generation during turbulent water flow within twisted tri-lobed tubes, examining the influence of geometric parameters on local and average entropy production. Findings indicate that larger small circle radius (r) and straight lengths (l), coupled with smaller transition circle radius (R) and twist pitch lengths (p), result in diminished local and average heat transfer entropy production while enhancing local and average frictional entropy production, with heat transfer entropy generation dominating the overall entropy production. Additionally, with increasing Reynolds numbers, all twisted tubes demonstrate an increasing trend in average frictional entropy production, except for some cases (Case 1-Case 4) that exhibit an initial rise followed by a decline in average heat transfer entropy generation. Among the examined Reynolds range, Case 4 displays lower overall irreversibility compared to a plain tube. Following the second law of thermodynamics, Case 4 is preferred. The findings and methodology contribute to enhancing the thermodynamic evaluation of convective heat transfer in twisted tri-lobed tubes.

Bearing failure analysis in the design of bolted connections with austenitic stainless steel

AbstractThe use of stainless steel in structures has been improved; nevertheless, the application of this material is not considered trivial by most designers, as there as still limited design codes providing specific rules. Current codes provide conservative approaches in certain cases, which do not corroborate with the objective of reducing the initial cost of projects incorporating stainless steel. In order to contribute to an adequate comprehension about the structural behavior of austenitic steel in bolted connections, a study was conducted regarding the influence of geometric parameters on the connections with a bolt under two shear planes, encompassing the evaluation of the phenomenon recognized as curling. Concerning to conclusions, it was observed that the geometric parameters e1, e2, d0, affects the curling effects, which has the potential to compromise the structural behavior of a thin‐plate connection if this deformation is greater than the thickness of the plate. Furthermore, the results provided by the equations employed in the design codes was assessed in this study, revealing an adequate prediction of the SCI in terms of the failure mode. However, both the manual and current codes exhibited conservative load for the investigated connections.

Compact Coplanar Waveguide Antenna Using Arm Patch for Software Defined Radio

This article proposes a compact coplanar waveguide (CPW) antenna with a semicircular patch and patch arm above the feed line. The method used in this antenna research is experimental, with antenna parameter optimization, fabrication, and measurement steps. The antenna was 40 mm × 46 mm × 0.8 mm and was printed on an FR4 substrate. Antenna optimization was carried out with CST Studio Suite to obtain optimal results. Based on return loss measurement results, the proposed antenna has an operational frequency of 2 GHz–7 GHz. The antenna arm has a significant effect on the operational frequency of the antenna, as proven by a parameter study of the antenna arm. Parametric studies were carried out on the antenna by investigating the influence of geometric parameters on the frequency characteristics. Optimization results were printed then measured by a Vector Network Analyzer (VNA) and a spectrum analyzer. The fabricated CPW antenna has a wider operating frequency than the simulation. An omnidirectional radiation pattern was observed at 2 GHz–4 GHz. The antenna has been used as a transmitter and receiver at 2.4 GHz, 3 GHz, and 4 GHz. The antenna is able to receive the signal emitted from the signal generator.

Numerical Simulation and Structural Optimization of Swirl Flow Micro-Nano Bubble Generator

The development of the bubble generator that can efficiently generate micro-nano bubbles has always been recognized as a challenge. Swirling flow is considered to be an efficient method to enhance hydrodynamic cavitation. The vortex supply chamber and the variable-diameter accelerated vortex cavitation reaction chamber were combined to obtain a stable high-speed tangential liquid flow and improve the cavitation effect inside the generator in this study. The central air intake column was innovatively installed above the cavitation reaction chamber, which prolonged the shear fracture time of bubbles under high shear force and improved the gas–liquid contact and mixing efficiency. The influence of geometric parameters on the internal and external flow fields of the generator was analyzed through the numerical simulation. The optimized central air intake column was located 10 mm above the inlet of the cavitation reaction chamber. The optimized variable diameter contraction angle was 16°, and the optimized generator outlet diameter was 15 mm. Through the bubble performance test, it was verified that the micro-nano bubbles with the minimum size and average size of 0.31 μm and 3.42 μm could be generated by the manufactured generator. The enforcement of the research provided theoretical guidance and data support for the development of efficient micro-nano bubble generators.

Radial Gradient Seismic Metamaterials with Ultra-Low Frequency and Ultra-Wide Band Gap

In this paper, a radial gradient seismic metamaterial (RGSM) is proposed. The structural unit cell is composed of an external square soil embedded with a triangular-cross-sectioned steel ring, which is filled at different angles of multiple steel rings to form a supercell. The dispersion curve and attenuation spectrum of the unit cell are calculated by the finite element method, and the opening mechanism of the band gap is explained by analyzing the modes at the band gap boundary. The influence of geometric parameters and material parameters on the band gap is further studied, and the optimized supercell radial gradient seismic metamaterial (OS-RGSM) structure is designed through structure and parameter optimization. The ultra-low broadband excellent band gap in the range of 2.35–20 Hz for seismic Lamb waves is realized, and its three-dimensional frequency response and displacement field diagram are calculated. In addition, the attenuation characteristics of the optimized supercell seismic metamaterial on the seismic surface wave are calculated and analyzed. It is found that the attenuation can reach more than 50% in the ultra-low frequency range of 3.5–9 Hz. The seismic wave barrier is verified by the vibration transmission characteristics of RGSM under finite period and dynamic time history analysis. The results show that RGSM can effectively shield from seismic Lamb waves in the ultra-wideband with the starting frequency of 2.35 Hz and can also effectively attenuate the seismic surface wave in semi-infinite space.

FEATURES OF THE FLOW STRUCTURE IN A RECTANGULAR TRENCH

The study of features of the flow structure in rectangular trenches in a wide range of Reynolds numbers was carried out by means of direct numerical simulation of the flow in the channel and on а plate. Both isothermal and non-isothermal formulations of the problem were considered. Water and air were used as the investigated fluids. The flow structure inside and around the trench in the rectangular channel in the range of Reynolds numbers based on the trench length Re<=9000 was studied in a three-dimensional setting. In the Reynolds numbers range Re>=10000, unsteady flow around a plate with a trench was considered in two-dimensional formulation of the problem. Depending on the Reynolds number, the flow structure in the trench, the influence of geometric parameters on the vortices scales in the trench, their localization and intensity were analyzed. The scale of inhomogeneity of the trench flow in the transverse direction was obtained. The features of non-stationary behavior and interaction of vortex formations with each other and with the external flow at higher Reynolds numbers are considered, development of instability of the vortex structure in the trench and its influence on characteristics of the external flow are shown: from regular oscillations at certain frequency to gradual chaosization of the flow around the trench as the Reynolds number increases, when fractional and multiple frequencies appear. A comparison was made with the vortex structure obtained by other researchers for similar geometric parameters of the trench. The contributions of frictional drag and shape drag to the overall hydraulic drag of the trench, as well as the streamlined surface downstream the trench, are considered. Intensity of heat exchange processes inside the trench, localization of the maximum values of heat fluxes, dependence of heat transfer on the oncoming flow speed were evaluated.

The Influence of Geometrical Parameters on Temperature Deformation of Spherical Honeycomb Sandwich Structure

As a reflector of the high-precision measurement system, the reflecting surface RMS has a significant impact on the accuracy of the entire system. Currently, studies on honeycomb sandwich structures mainly focus on optimization with lightweight as the goal and stiffness and strength as constraints. And studies on temperature deformation are limited. Consulting the honeycomb sandwich equivalent theory, this paper has studied the influence of geometric parameters of honeycomb sandwich structure on the reflecting RMS in different temperature fields. In global temperature fields, the reflecting surface RMS is linked to curvature radius R, temperature changes, and the length a closely. The height mainly causes the translation of the reflecting surface in the Z direction. In temperature gradient fields, the reflecting surface RMS is linked to the height h, temperature gradient, and length a closely. And the curvature radius R has little effect.

Controlling size and shape of pores during metal solidification for manufacturing of functionally graded metal foams

Manufacturing of metal foams by solidification processing involves numerous challenges related to achieving localized control of porosity with a limited material selection. The objective of this work is to control the size and shape of pores during metal solidification in a casting process by harnessing the thermal decomposition of discrete polymer features upon their interaction with molten metal. The influence of geometrical parameters and physical properties of these features on the evolution of pores generated from their interaction with molten metal was studied in detail. We firstly used an analytical model to evaluate the thermal response of such features in a model molten metal medium to determine the process window within which pores can be generated and captured in place during metal solidification. Systematic experiments were conducted to demonstrate the influence of the feature geometry on the evolution of the size and shape of captured pores. We further demonstrate that the relative separation of these features can exert a strong influence on the interaction of adjacently generated pores during metal solidification. This work essentially exhibits the potential of exploiting a lattice of discrete features that can enable the spatial control of pore capture during a metal solidification process.