Influence Of Geometrical Parameters Research Articles

Development of a test specimen carrier for the Taylor anvil test using 3D additive printing technology

Dynamic material testing is increasingly crucial for establishing a comprehensive description of material models. One of the primary testing methods is the Taylor Anvil Test (TAT). In this test, strain rates of up to 105 s−1 can be achieved at impact speeds of 250 m/s. Proper evaluation of a specific material specimen in this test relies on delivering the test specimen to the impact point both centrally and perpendicularly, as well as at the moment of reaching the maximum impact speed. This Article addresses the development of a new carrier for round test specimens manufactured using additive 3D printing technology from a polyactide polymer adapted for the TAT device with a calibre of 17 mm. The Article closely examines the influence of geometric parameters of the carrier itself, optimized using the Ansys Fluid Flow software, with a focus on internal ballistics, particularly to achieve perpendicular impact and maximum impact speed without causing the destruction of the carrier. A new type of test carrier was designed and subsequently tested for round test specimens made of the aluminium alloy Al 2024-T3, evaluating both the impact speeds of the carrier under identical initiation pressure parameters in the filling chamber and the impact speed parameters of the specimen, respectively, the strain rate of the test specimen.

Plastic and punching shear strengths of concrete-filled steel tubular gapped K-joints without noding eccentricity under brace axial loading

This paper presents a comprehensive investigation, numerically and theoretically, into the structural behaviour and design aspects of concrete-filled steel tubular (CFST) gapped K-joints under brace axial loading. Finite element (FE) models were developed and validated against test results from existing experimental programmes. Based on the validated FE models, influences of geometric parameters and steel material properties on the load-deformation curve, plastic strength, ultimate strength and punching shear stress distribution of CFST K-joints were systematically assessed. In general, the chord diameter-to-thickness ratio 2γ, brace-to-chord diameter ratio β and steel material strength are crucial to the structural behaviour of CFST K-joints, whilst the brace-to-chord thickness ratio τ was found to have minimal influence. A shear stress distribution model was proposed as well to predict the shear stress distribution at ultimate load. To accurately account for the radial support of inner concrete, the classical ring model was modified accordingly. Based on the proposed shear stress distribution model and modified ring model, analysis-orientated and design-orientated equations were formulated to estimate both the plastic and ultimate strengths of CFST K-joints. The calculated plastic and ultimate strengths were compared against the experimental and numerical results, and the comparison demonstrates the ability of the proposed design methods to accurately and reliably determine the plastic and ultimate strengths of CFST K joints.

Study on the Influence of Geometric Parameters on Vibration Characteristics of Hydraulic Oscillator Used in Oil Drilling

Abstract Hydraulic oscillator is an important drilling equipment extensively used in petroleum extraction and drilling work. It generates vibration along the axis direction to drive the drilling tool to drill and the drilling effect largely depends on the axial impulsive loading and frequency of the hydraulic oscillator. However, few present studies have been conducted on the influence of variations in key geometric parameters on axial impulsive loading and frequency of hydraulic oscillators, and systematic analysis is still lacking. Optimization calculations were carried out on throat inner diameter, throat length, nozzle spacing, and nozzle angle of the hydraulic oscillator. The analysis results show that: The overall impact of throat length and nozzle angle changes on axial load is small, while throat inner diameter has the greatest impact on the axial load. The axial load is 375.78 N when throat inner diameter is 10 mm, which is 8 times larger than that when throat inner diameter is 20 mm. Moreover, the throat inner diameter is smaller, both the axial load and amplitude are greater. Nozzle spacing has a significant influence on the axial load within a narrow spacing range. As nozzle spacing increases, the axial load increases overall while the amplitude shows a decreasing trend. Particularly, when nozzle spacing exceeds a certain value, the axial load does not vary significantly.

Tensile behavior of square-twist origami inspired mechanical metamaterials with soft joints and chirality applications

The performance and behavior of origami-inspired mechanical metamaterials are closely related to their structural design and the joints sub equivalent to the crease, in addition to material selection. Current research on square-twist origami focused on the unidirectional formation between its stable states. However, the complete process of squeezing-folding and stretching-unfolding as well as the mechanical behavior under tensile loading have not been thoroughly studied. In this study, square-twist origami mechanical metamaterials (STOMMs) with soft joints are proposed and investigated. The complete process of typical STOMMs from a flat state to folded stable state by extrusion folding and then returning to a flat state by stretch unfolding is explored using the finite element method. The strain energy and deformation characteristics of STOMMs are revealed at eight special stages during the folding, stable state, and unfolding processes. Additionally, the influence of geometric parameters on strain energy, deformation, and tensile behavior is also investigated. Finally, inspired by origami chirality, combinatorial mechanical metamaterials with self-locking/non-self-locking behavior are proposed and validated for their tensile and self-locking behavior. The studies could provide new content for origami-inspired soft joint mechanical metamaterials in terms of self-locking and load-bearing.

Design of hyperbolic quasi-zero stiffness metastructures coupled with nonlinear stiffness for low-frequency vibration isolation

Quasi-zero stiffness (QZS) metastructures with simple structures exhibit a high low-frequency vibration isolation performance, but the bearing capacity and working regions are limited due to the linear positive stiffness elements. In this study, a novel hyperbolic QZS metastructure coupled with nonlinear stiffness is designed by combining a pair of cosine-shaped beams and arc-shaped beams for low-frequency vibration isolation. Finite element models (FEM) and experimental analysis are utilized to examine the static characteristics of the metastructure, revealing a wide QZS region and significant load-bearing capacity. The metastructure can achieve effective vibration isolation properties through reasonably designing the unit cells. The influence of geometrical parameters on the QZS region is investigated to optimize and realize desirable QZS features. The dynamic equation and response of the vibration isolation system are determined using the harmonic balance method. Moreover, the corresponding displacement transmissibility is confirmed by numerical simulation. The results of the dynamic sweep frequency experiment further verify the validity of the theoretical analysis model. The hyperbolic QZS metastructure system possesses good vibration isolation performance due to the introduction and compensation of a nonlinear positive stiffness arc beam element. The proposed hyperbolic QZS metastructure provides a significant route for the stiffness compensation of metastructures.

Numerical investigation on performance optimization of steam ejector considering full geometric parameters and working conditions

As an energy-saving device for energy transduction, a steam ejector has been crucial in energy saving and emission reduction, energy consumption reduction, and energy reuse. An optimization method of full geometric parameters and a preferred method of working conditions were considered to rise the entrainment ratio of a steam ejector and improve its entrainment capacity. The related models of the ejector were established and numerically simulated. The influence of geometric parameters on the entrainment capacity of the ejector researched by adopting the control variable method and the 11-factor 5-level orthogonal test. The effect of working conditions on the entrainment ratio for the optimized ejector discussed, and the preferred method of working conditions of the ejector proposed. The results show that the entrainment ratio of the optimized ejector by the control variable method rises by 30.8 % to that of the original ejector, and the entrainment ratio of the new ejector by orthogonal test rises by 78 %. The constant cross-section diameter is a critical parameter affecting the entrainment capacity of the ejector. Contrasted with the original ejector, the maximum entrainment ratio under preferred working conditions rises by 242%–471 % via using the preferred method of working conditions. Considering the optimization of full geometric parameters and working conditions, the influence of the optimized process on the entrainment capacity of ejectors is evident, which provides an effective way and reference for the optimization research and development of other types of ejectors.

Low frequency bandgap and high stiffness of innovative auxetic metamaterial with negative thermal expansion

Achieving multifunctional integration is crucial in mechanical metamaterials to meet the requirements of structures and equipment serving in complex environments across various engineering fields. In this study, we propose two novel bi-material and tri-material metamaterials based on the original edge-shared quadrangle (EQ/EQO) metamaterial, which exhibit negative thermal expansion (NTE), negative Poisson's ratio (NPR), and bandgap characteristics. The effective thermoelastic properties, including coefficient of thermal expansion (CTE), Poisson's ratio (PR), and Young's modulus, are compared and analyzed through theoretical formulation based on Timoshenko beam theory and numerical simulation using continuum elements with Abaqus. Additionally, finite element analysis is employed to calculate the energy band structures of these metamaterials based on Bloch's theorem, while the transmission characteristic curve verifies the validity of the obtained band structure. We systematically discuss the bandgap characteristics, coupling relationship between bandgaps and thermoelastic properties, as well as the influence of geometrical parameters on both bandgaps and thermoelastic properties. Our results demonstrate that the effective thermoelastic properties of these metamaterials are primarily determined by their frame structure's geometrical parameters, particularly the incline angle. Furthermore, for bi-material metamaterials, their specific stiffness closely relates to their bandgaps; however, for tri-material metamaterials, only the central local resonant unit determines their bandgap behavior. Notably, planar and 3D tri-material metamaterials can concurrently achieve a low-frequency bandgap along with high stiffness as well as NTE/NPR behavior. This work presents a new design strategy for optimizing multifunctional metamaterials' bandgaps while incorporating NTE behavior.

A synergistic approach to optimizing the performance of a concentrating solar segmented variable area leg thermoelectric generator using numerical methods and neural networks

This study presents an optimized design for segmented variable area leg thermoelectric modules using finite element methods and Bayesian regularized neural networks. We explored the impact of geometry and thermal parameters on module performance using ANSYS software, identifying optimal parameters for power output and efficiency. Key findings revealed the higher influence of geometric parameters and confirmed the advantages of segmented thermoelectric generators for high-temperature applications like concentrated solar systems. With this optimization, power output and efficiency of the module increased by 875% and 165%, respectively, under 25 Suns. To refine the optimization process, a Bayesian regularized neural network was utilized, proving effective in predicting module performance with a low mean squared error and high coefficient of determination. This research provides important insights into high-performance thermoelectric modules for sustainable energy applications, demonstrating the significant role of advanced computational methods in energy solutions.

Reusable energy-absorbers design harnessing snapping-through buckling of tailored multistable architected materials

Abstract Multistable metamaterials are artificially engineered materials that possess microarchitectures capable of maintaining multiple stable configurations. However, the realization of mechanical metamaterials with numerous programmable stable configurations using Double-Curved Beam (DCB) elements remains an ongoing challenge. In this study, we exploit the snapping-through buckling phenomenon exhibited by architected DCB structures to devise a mechanical metamaterial with a unique deformation mode, encompassing Multi-stability, Multi-path, Multi-platform, and Multi-step characteristics, hence referred to as a 4M mechanical metamaterial. By employing DCB as fundamental building block elements, architected metamaterials with two-dimensional (2D) series or parallel lattices are successfully constructed, as well as three-dimensional (3D) tubular geometries, denoted as DCB-n-m-C and DCB-n-m-M metamaterials, respectively. These metamaterials exhibit reversible energy absorption characteristics and the stiffness can be transformed from positive to negative under both small and large elastic deformations. Functional gradient design and tailored deformation capability are given by adjusting the wall thickness of each layer of double-curved beams, thereby demonstrating the multi-path deformation features inherent in 4M metamaterials. DCB-n-m-M metamaterials has multiple energy platforms in the process of snapping-through, which reflects the multi-platform characteristics of 4M metamaterial. Consequently, novel properties such as multistability, programmability, and reusable energy absorption characteristics are achieved. To comprehensively understand the mechanical response of the metamaterials, a thorough investigation into the influence of geometric parameters is conducted, including the number of polygonal edges, the number of the layers, and the aspect ratio Q. This investigation involves a combination of theoretical analyses, numerical simulations, and experimental verifications. The introduced design strategy paves a way for the innovative design of multistable, multi-step, tailored, and reversible deformation metamaterials.

Viscoelastic modelling and analysis of two-dimensional woven CNT-based multiscale fibre reinforced composite material system

Carbon nanotube (CNT) has fostered research as a promising nanomaterial for a variety of applications due to its exceptional mechanical, optical, and electrical characteristics. The present article proposes a novel and comprehensive micromechanical framework to assess the viscoelastic properties of a multiscale CNT-reinforced two-dimensional (2D) woven hybrid composite. It also focuses on demonstrating the utilisation of the proposed micromechanics in the dynamic analysis of shell structure. First, the detailed constructional attributes of the proposed trans-scale composite material system are described in detail. Then, according to the nature of the constructional feature, mathematical modelling of each constituent phase or building block’s material properties is established to evaluate the homogenised viscoelastic properties of the proposed composite material system. To highlight the novelty of this study, the viscoelastic characteristics of the modified matrix are developed using the micromechanics method of Mori–Tanaka (MT) in combination with the weak viscoelastic interphase (WI) theory. In the entire micromechanical framework, the CNTs are considered to be randomly oriented. The strength of the material (SOM) approach is used to establish mathematical frameworks for the viscoelastic characteristics of yarns, whereas the unit cell method (UCM) is used to determine the viscoelastic properties of the representative unit cell (RUC). Different numerical results have been obtained by varying the CNT composition, interface conditions, agglomeration, carbon fibre volume percentage, excitation frequency, and temperature. The influences of geometrical parameters like yarn thickness, width, and the gap length to yarn width ratio on the viscoelasticity of such composite material systems are also explored. The current study also addresses the issue of resultant anisotropic viscoelastic properties due to the use of dissimilar yarn thickness. The results of this micromechanical analysis provide valuable insights into the viscoelastic properties of the proposed composite material system and suggest its potential applications in vibration damping. To demonstrate the application of developed novel micromechanics in vibration analysis, as one of the main contributions, comprehensive numerical experiments are conducted on a shell panel. The results show a significant reduction in vibration amplitudes compared to traditional composite materials in the frequency response and transient response analyses. To focus on the aspect of micromechanical behaviour on dynamic response and for the purpose of brevity, only linear strain displacement relationships are considered for dynamic analysis. These insights could inform future research and development in the field of composite materials.

Numerical modeling and analysis of fluid-filled truncated conical shells with ring stiffeners

This study uses a hybrid finite element method to predict dynamic behavior of truncated conical shells with ring stiffeners under fluid loading. The proposed approach combines classical shell theory and the finite element method, making use of displacement functions derived from exact solutions of Sanders’ shell equilibrium equations for conical shells. The analysis of the shell-fluid interface involves leveraging the velocity potential, Bernoulli’s equation, and impermeability conditions to determine an explicit expression for fluid pressure. To the best of our knowledge, this paper is the first to compare the methods applied to ring-stiffened shells against other numerical and experimental findings. Our results on conical shells in various conditions, with and without ring stiffeners, are largely consistent with previous findings. This study also explores the influence of geometric parameters, stiffener quantity, cone angle, and applied boundary conditions on the natural frequency of fluid-loaded ring-stiffened conical shells. The paper concludes with a discussion of several useful implications for further research.

High-flexibility three-dimensional serial folded hinges

A new three-dimensional flexible hinge capable of large, linear-domain displacements is proposed for extended spatial workspace mechanisms. The hinge structure is compact and modular consisting of a large number of circular- and straight-axis segments connected in series and disposed in two parallel planes in a folded manner. The analytical, linear-model compliance matrix, which is necessary in direct/inverse kinematics and controls analysis, is derived based on simplified hinge geometry and small-deformation theory. The compliance model is accurate, as demonstrated by finite element simulation and experimental testing of a prototype. The compliance model is also utilized to determine the hinge piston-motion stiffness and the static response of several hinges connected in series. Another analytical compliance model is formulated to predict the hinge maximum loads and displacements in terms of allowable stresses. The mathematical models are further utilized to comprehensively investigate the influence of geometric parameters on the hinge performance.

A flexible, reusable and adjustable high-performance energy absorption system inspired by interlocking suture structures

Energy absorption systems play a very important role in impact protection under complex load conditions. However, traditional protective structures cannot adjust the mechanical properties on demand to accommodate variable load characteristics once manufactured. Therefore, inspired by the superior compression resistance of the diabolical ironclad beetle, a modular energy absorption system is developed by combining the efficient mechanical properties of thin-walled tubes and the robust connectivity of interlocking suture structures, which can be easily assembled from only bio-inspired tubes without external constraints. FEM simulations were performed to systematically investigate the static and dynamic mechanical properties of the developed system, and its crushing performance was demonstrated experimentally. Additionally, the influence of geometric parameters on the mechanical properties of the system has been investigated, and the insensitivity of secondary geometrical parameters and assembly defects has been verified, which shows that the system has a certain safety margin to avoid catastrophic accidents caused by fabrication defects. Moreover, the system exhibits excellent reusability under multi-impact load environments and its energy absorption capacity does not degrade after the primary impact. Furthermore, the system exhibits good designability thanks to the discrete modular structures, its mechanical properties can be tuned by stiffness design without affecting the energy absorption capacity, and its specific energy absorption can be effectively improved by lightweight design. This study provides a novel design strategy for the protection system applied in multiple complex environments.

Failure and Damage of Reciprocating Lip Seals for Pneumatic Cylinders in Dry Conditions

Lip seals are components subjected to high mechanical stress and they are responsible for many out-of-service in pneumatic cylinders. The aim of this work is the development of an experimental methodology to evaluate lifetime duration and analyse failures and damages of rod lip seals for pneumatic cylinders. A dedicated test bench was designed and manufactured which reproduces actual working conditions of the seals i.e., compressed air action (seal pressurisation) and relative linear reciprocating motion. Three types of seals made of two elastomers (NBR and polyurethane) were tested; dry condition was considered to speed up the tests. The influence of geometric parameters like seal seat dimension and seal axis misalignment with respect to the rod axis, was analysed by multiple experimental tests. Results in terms of seal life duration and failure modes are presented which allow comparison of seals performance and provide a helpful tool to end-users in a proper selection of seals geometry, material and key working parameters.

ANALYSIS OF SIMULATION DATA OF A SUPERSONIC FLOW IN A SHORT NOZZLE WITH A NOZZLE

In this paper, we analyzed the influence of the geometric parameters of a shortened nozzle when operating under various conditions - at sea level (at Р=1 bar) and upper atmosphere (Р= 0.1 bar). The influence of geometrical parameters of the nozzle, pressure at the inlet, and the environment on the impulse characteristics of the flow are considered. It is shown that the momentum factor decreases with decreasing inlet pressure, but with increasing flight altitude, i.e. a decrease in the pressure of the external environment, the momentum coefficient decreases to a certain value, and then increases again. This character of the dependence is explained by the wave structure of the flow in a shortened nozzle. The study of simulation data can be used to create new types of nozzles for rocket and space technology.

Rigid-Elastic Combined Metamaterial Beam With Tunable Band Gaps for Broadband Vibration Suppression

Abstract Extensive research efforts have been dedicated to exploring the application of metamaterial beams for vibration suppression. However, most existing designs primarily focused on utilizing the translational motion of local resonators to create band gaps. To address this limitation of employing solo motion to induce a relatively narrow band gap, this study proposes a novel design: a rigid-elastic combined metamaterial beam utilizing both translational and rotational motions of local resonators. Theoretical framework development involves extending the transfer matrix method to incorporate rigid bodies, with analytical results validated through finite element simulations and experimental data. Compared to conventional metamaterial beams, the proposed design exhibits an additional wide band gap in the low-frequency region that can be utilized for broadband vibration suppression. A parametric study elucidates the influences of geometric parameters on band gap formation, followed by an exploration of the tunability of the proposed meta-beam through a graded scheme and optimization strategy. In particular, a multiple-objective optimization approach is employed to enlarge the vibration suppression region and enhance vibration suppression ability. The optimized meta-beam demonstrates a remarkable 45% wider dominant suppression region and a 14% lower average transmittance compared to a uniform model.

The Influence of Geometric Parameters for Training an Artificial Neural Network to Predict the Band Structure of 1-D Fishbone Photonic Crystal

With the rising demand for the transmission of large amounts of information over long distances, the development of integrated light circuits is the key to improving this technology, and silicon photonics have been developed with low absorption in the near-infrared range and with sophisticated fabrication techniques. To build devices that work in different functionalities, photonic crystals are one of the most used structures due to their ability to manipulate light. The investigation of photonic crystals requires the calculation of photonic band structures and is usually time-consuming work. To reduce the time spent on calculations, a trained ANN is introduced in this study to directly predict the band structures using only a minimal amount of pre-calculated band structure data. A well-used 1-D fishbone-like photonic crystal in the form of a nanobeam is used as the training target, and the influence of adjusting the geometric parameters is discussed, especially the lattice constant and the thickness of the nanobeam. To train the ANN with very few band structures, each of the mode points in the band structure is considered as a single datapoint to increase the amount of training data. The datasets are composed of various raw band structure data. The optimized ANN is introduced at the end of this manuscript.

Nacre-inspired auxetic interlocking brick-and-mortar composites

We design auxetic 3D interlocking brick-and-mortar composites inspired by nacre - a natural strong and resilient high-performance material. The influences of geometrical parameters and base material properties on their effective elastic properties are systematically investigated by finite element simulations and computational homogenization. The numerical results indicate that the composites exhibit tunable negative Poisson’s ratios by properly tailoring the underlying microstructures. It is revealed that the auxetic behavior therein is attributed to the relative sliding between adjacent bricks with waviness, i.e., the sliding mechanism. These materials, with their auxetic properties and high fracture toughness, are well-suited for a wide range of engineering applications, such as serving as robust auxetic materials.

Influence of dowel group configuration on the stability of reinforced slopes

Introduction. Slope reinforcement with dowels is the most economical and environmentally friendly method of their stabilization. However, the lack of theoretically substantiated schemes for optimal placement of dowels in groups, confirmed by tests in various conditions, leads to inefficient, often excessive use of the material in the arrangement of engineering protection.Aim. To determine the most effective arrangement of dowels in groups with regard to the overall stability of the reinformed soil mass. To assess quantitatively the stability depending on the spacing and shape of dowels in the group.Materials and methods. A review of international and Russian literature on the problem of assessing the influence of geometric parameters of dowel and anchor groups was carried out. According to the results of the review, primary calculations with the use of numerical simulation in the PLAXIS 3D software package was carried out.Results. The available publications mainly analyze configurations of screw anchor groups, paying insufficient attention the use of dowels of cylindrical cross-section. This fact substantiates further research in this field. The conducted numerical simulation allowed the slope stability provided by five dowel group configurations to be compared. The calculation results show that the slope stability depends on the configuration and the number of dowels in the group. The difference between the stability factors for the polygonal and triangular three-row configuration was 0.072 %, with the polygonal configuration requiring three dowels less. Selection of optimal dowel placement contributes to increased landslide control efficiency and reduced costs.Conclusions. The relevance and importance of studying the effect of dowel group configuration on slope stability, emphasizing the need for more in-depth and comprehensive research in this area.

Multi-band tunable electromagnetically induced transparencies based on active metasurface with polarization-independent property

The analogue of an electromagnetically induced transparency (EIT) spectrum is achieved using a metasurface that consists of an array of cross and L-shaped resonators. The mechanism of the EIT-like phenomenon are analyzed, and the influence of geometrical parameters on the effect is discussed. We achieve a multi-band EIT-like through structure configuration. In particular, polarization-independent EIT is realized. A potential application in sensing is suggested and the sensitivity of 65 GHz RIU−1 is obtained. We also investigate the impact of analyte and substrate on the transmission spectrum. We find that when the analyte thickness is higher than 40 μm, the EIT spectral shift is less affected by the analyte thickness. The thickness insensitive characteristics are beneficial for reducing errors caused by analyte dose, thereby improving the accuracy of sensing. By introducing a phase change material, vanadium dioxide, we obtain active control of the EIT effect. Our results provide valuable insights into the development of multi-band tunable compact devices based on metasurfaces.