Elastic Configuration Research Articles

Elastic Polarization Configuration Coupled with Activity Rattling Space Boosts Energy Harvesting Performance of Lead‐Free Piezoceramic

AbstractPiezoelectric energy harvesting technology is drawing substantial attention as an eco‐friendly method to promote energy transformation, which is at the forefront of current scientific research. However, the difficulties involved in obtaining a stable output voltage (Vout) and a controllable output current density (Iout) represent bottlenecks in the development of piezoelectric energy harvesters (PEHs) for practical applications. Here, a novel strategy that couples elastic polarization configuration with activity rattling space in lead‐free potassium sodium niobate‐based piezoceramics is proposed to break through this barrier. The cantilever beam‐type PEHs assembled using the rationally designed piezoceramic system show a stable Vout (≈22 V) and a controllable Iout over the range from 6.09 to 20.16 µA cm−2, which is sufficient to drive multiple types of wireless sensors that have the same rated voltage but different rated current requirements. These fantastic power generation performances are associated with a stable piezoelectric voltage coefficient (g33), an increasing piezoelectric charge coefficient (d33), and a weakened electrostrictive coefficient (Q33) that stem from polarization configuration optimization in combination with introduction of the activity rattling space design. This work provides a good approach to modulation of the overall performance of piezoelectric materials to meet the demands of advanced PEH applications.

The influence of torsion on acceleration demands in low-rise RC buildings

AbstractThis paper presents a study of acceleration demands in low-rise reinforced concrete (RC) buildings with torsion, evaluated by quantifying peak floor accelerations (PFAs) and floor response (acceleration) spectra (FRS). The study was performed with the aim to provide simple empirical formulas to quantify the amplification effects due to torsion, which can occur in most of the existing and new RC buildings. With this goal in mind, a set of eight archetype buildings was selected, characterized by an increasing floor eccentricity obtained by moving the centre of rigidity (CR) away from the centre of mass (CM). Numerical models of the proposed set of archetype RC buildings were considered in both linear elastic and nonlinear configurations. For the latter, the properties of models were widely varied, by systematically modifying parameters of plastic hinges, in order to obtain a sample of 1000 models. Non-structural components (NSCs) were considered linear elastic in all cases. To investigate acceleration demands, a set of forty Eurocode 8 spectrum-compatible ground motion records were used as input. For linear elastic building models, it was observed that the change of demands depends on the position of the NSC (in-plan and in-height), and on the distance between CR and CM. On the other hand, for nonlinear models, additional parameters must be considered, such as the building ductility (μ) and yielding force (Vy). New regression models were proposed for quantifying the observed differences in PFAs and FRS when torsion occurs. The efficiency of the proposed models was assessed by testing the new formulas on an existing case study building, as well as on the well-known SPEAR building.

Experimental measurements of two elastic taut-slack mooring configurations for the multi-float M4 WEC

Moorings are a vital and often problematic component of any floating offshore renewable energy system, whether for wind or wave energy conversion, and here we consider the multi-float WEC system M4 in a 122 configuration. Previous experimental work has shown elastic cables to reduce extreme snap loads by a factor of about 6 when considering single cables between the bow float and a mooring buoy, and between the mooring buoy and the bed [1]. Here we compare results for two alternative configurations designed to reduce the mooring footprint as well as extreme snap loads. The first system, shown in Figure 1 (a), consists of a large surface buoy connected to the seabed with three equi-spaced elastic cables in pre-tension, with a single elastic cable to the bow float. The second system, shown in Figure 1 (b) has a smaller submerged buoy, again connected to the seabed with three equi-spaced elastic cables in pre-tension, however, this is connected to a smaller surface buoy which is subsequently connected to the bow float. Both systems are taut-slack. In this paper we present experimental measurements taken at the COAST laboratory at the University of Plymouth. Both configurations are tested in irregular (JONSWAP) wave conditions up to limiting steepness, with run times of 35 mins at 1:40 scale or about 3.5 hours full scale. Peak, mean and rms bed loads for both configurations are presented along with rms and peak relative angular pitch response with drive train disengaged (free hinge between mid and stern floats).
 References[1] P. Stansby et al., “Experimental study of mooring forces on the multi-float WEC M4 in large waves with buoy and elastic cables,” Ocean Eng., vol. 266, no. P4, p. 113049, 2022.

Application of modified partial capacity design on six-story L-shaped reinforced concrete buildings with variations on elastic columns configurations

Modified Partial Capacity Design (M-PCD) is an alternative design method for seismic-resistant structures. M-PCD adopts the partial side sway mechanism for its failure mechanism where beams and some columns are allowed to develop plastic hinges. This method uses two models for design. The first model simulates a small earthquake occurrence and is used to design beams and plastic columns. The second model simulates a larger earthquake occurrence and damages on the structure. The elastic columns are designed based on the superposition of internal forces from the first and second models, provided that the effects from gravity loads are considered only once. This study focuses on the application of M-PCD on six-story L-shaped reinforced concrete buildings with variations on elastic columns configurations. Nonlinear time history analyses are used to determine the buildings’ performance on two earthquake levels (EDRS and MCER) and two earthquake directions (0° and 45° rotated earthquake). The results show that the partial side sway mechanism is observed in most of the analyzed structures and drifts are within set boundaries.

Triple longitudinal fracture of inhomogeneous beam under four-point bending an analytical study by using a non-linear elastic material model

The present paper is devoted to fracture analysis of an inhomogeneous non-linear elastic beam configuration with three parallel longitudinal cracks. The material is continuously inhomogeneous along the beam height. The beam is subjected to four-point bending. The longitudinal fracture behavior is studied by applying the J-integral approach. Solutions to the J-integral are obtained for the three cracks. For this purpose, the curvature and the coordinates of neutral axes of the crack arms are determined by using the equations for equilibrium of the elementary forces in the cross-sections of different portions of the beam. The solutions to the J-integral are valid for arbitrary locations of the cracks along the beam height. Thus, the solutions are very useful for evaluating of the effects of locations of cracks on the fracture. The longitudinal fracture behavior is studied also in terms of the strain energy release rate in order to verify the solutions to the J-integral. Solutions to the strain energy release rate are derived for the three cracks by considering the complementary strain energy in the beam. The solutions to the J-integral are applied to evaluate the effects of locations of the cracks, the material inhomogeneity, the sizes of the beam cross-section, and the coordinates of the applications points of the external forces on the longitudinal fracture behavior of the beam.

THE PROBLEM OF ASSESSING THE BAKING QUALITY OF WHEAT WITH GENETICALLY DIFFERENT ALLELES OF STORAGE PROTEINS

The article is devoted to the study of the wheat samples of the 3rd classwith the same quality indicators according to DSTU 3768, but had different baking properties. In particular, the “strength” of flour (W) significantly differed. The quantitative and qualitative state of the gluten-protein complex is significant factor for obtaining grain and flour of high baking quality. But only the quality indicators of red winter wheat according to DSTU 3768 - protein content, amount and quality of gluten cannot objectively characterize the baking quality of a specific batch of grain. For the main indications of the Ukrainian standard for wheat, all batches of wheat are practically identical. Foreign buyers do not use our Ukrainian standards, they give precedence to international methods and one of the most integral of them is the “strength” (W). The method demonstrates the main characteristics of the physical properties of wheat dough, which maybe especially important during bread making: elasticity (P), extensibility (L) and alveogram configuration coefficient (P/L). It has been established that the reason is the difference in the genetically determined alleles of the storage proteins of the studied samples. In the last years "filler" and "weak" varieties of wheat of domestic and foreign selection have appeared in Ukraine. In the conditions of replacing traditionally grown varieties of "strong" wheat in Ukraine with new high-yielding varieties of domestic and foreign breeding, it is not enough to determine the parameters recorded in DSTU 3768 to determine the baking quality, it is necessary to introduce new, more objective research methods. It is concluded that for an objective assessment of the baking properties of wheat, international standards ISO 27971, ISO 21415, ISO 5529 should be used.

Cloud Workload and Data Center Analytical Modeling and Optimization Using Deep Machine Learning

Predicting workload demands can help to achieve elastic scaling by optimizing data center configuration, such that increasing/decreasing data center resources provides an accurate and efficient configuration. Predicting workload and optimizing data center resource configuration are two challenging tasks. In this work, we investigate workload and data center modeling to help in predicting workload and data center operation that is used as an experimental environment to evaluate optimized elastic scaling for real data center traces. Three methods of machine learning are used and compared with an analytical approach to model the workload and data center actions. Our approach is to use an analytical model as a predictor to evaluate and test the optimization solution set and find the best configuration and scaling actions before applying it to the real data center. The results show that machine learning with an analytical approach can help to find the best prediction values of workload demands and evaluate the scaling and resource capacity required to be provisioned. Machine learning is used to find the optimal configuration and to solve the elasticity scaling boundary values. Machine learning helps in optimization by reducing elastic scaling violation and configuration time and by categorizing resource configuration with respect to scaling capacity values. The results show that the configuration cost and time are minimized by the best provisioning actions.

Growth mechanics of the viscoelastic membranes

Living membranes can grow as a response to their environment, and they are also known as viscoelastic materials. However, the growth phenomenon and the viscoelastic behavior of these membranes have been studied separately up to now. The main goal of this paper is to develop a general formulation that can account for growth and viscoelastic behaviors in membranes, simultaneously. Therefore, we propose a formulation for growing quasi-linear viscoelastic membranes. The growth model begins with a multiplicative decomposition of the gradient deformation tensor into elastic and growth tensor, where the growth of the membrane is considered as a single scalar-valued parameter. Furthermore, the quasi-linear viscoelasticity theory is utilized in the elastic configuration as additive decomposition of the second Piola–Kirchhoff stress tensor. To solve the evolution equations for both growth and quasi-linear viscoelastic relations, two implicit second order accuracy integration methods are employed. Moreover, strain-driven and stress-driven growth phenomena are accounted for based on a Total Lagrangian (TL) finite element formulation. The developed formulations can capture growth phenomena and viscoelastic properties of the membranes, individually, and it also enables to model co-existence of growth and viscoelasticity. Eventually, to evaluate the applicability of the developed formulation, several examples are investigated and compared to those available in the literature.

Opportunistic admission and resource allocation for slicing enhanced IoT networks

Network slicing is envisioned as one of the key techniques to meet the extremely diversified service requirements of the Internet of Things (IoT) as it provides an enhanced user experience and elastic resource configuration. In the context of slicing enhanced IoT networks, both the Service Provider (SP) and Infrastructure Provider (InP) face challenges of ensuring efficient slice construction and high profit in dynamic environments. These challenges arise from randomly generated and departed slice requests from end-users, uncertain resource availability, and multi-dimensional resource allocation. Admission and resource allocation for distinct demands of slice requests are the key issues in addressing these challenges and should be handled effectively in dynamic environments. To this end, we propose an Opportunistic Admission and Resource allocation (OAR) policy to deal with the issues of random slicing requests, uncertain resource availability, and heterogeneous multi-resources. The key idea of OAR is to allow the SP to decide whether to accept slice requests immediately or defer them according to the load and price of resources. To cope with the random slice requests and uncertain resource availability, we formulated this issue as a Markov Decision Process (MDP) to obtain the optimal admission policy, with the aim of maximizing the system reward. Furthermore, the buyer-seller game theory approach was adopted to realize the optimal resource allocation, while motivating each SP and InP to maximize their rewards. Our numerical results show that the proposed OAR policy can make reasonable decisions effectively and steadily, and outperforms the baseline schemes in terms of the system reward.

Selection of size dependency theory effects on the wave's dispersions of magneto-electro-thermo-elastic nano-beam resting on visco-elastic foundation

Current research develops a comprehensive wave propagation analysis of a magneto-electro-thermo-elastic (METE) nano-beam (NB) resting on the visco-elastic medium. To model the size dependency effects, modified couple stress (MCS) and Eringen's nonlocal (ENL) theories are employed to analyze and describe the wave propagation behaviors for those nano-beams. These theories were the most used in the literature due to the inclusion of one additional size-dependent length scale parameter. Those theories are compared side by side in this investigation and their impacts/differences on the wave propagation of specific materials are explored. Sinusoidal shear deformation beam model with Hamilton's principle is adopted to develop the governing equations of motion. Then, an analytical solution is executed to extract numerical results for transverse wave propagation in both elastic and METE configurations of the nano-beam. The effects of size-dependent length scale of both theories, thickness of NB, Winkler-Pasternak coefficients, thermal gradient, and magnetic potential and external electric voltage are illustrated and discussed in details. It is concluded that wave frequency decreases with increment of nonlocal parameter for ENL model. On the other hand, a stiffening effect takes place for the wave frequency when the MCS model is considered. Hence, the results indicate that there is a significant difference between ENL and MCS theories in the estimation of the behavior of wave propagation in small-scale structures. One of the main results of this investigation indicates that the MCS theory has similar nonlocal effects as the Eringen's theory for specific conditions.

Nonlinear Dynamics of a Star-Shaped Structure and Variable Configuration of Elastic Elements for Energy Harvesting Applications.

The subject of the model research contained in this paper is a new design solution of the energy harvesting system with a star-shaped structure of elastic elements and variable configuration. Numerical experiments focused mainly on the assessment of the configuration of elastic elements in the context of energy harvesting efficiency. The results of computer simulations were limited to zero initial conditions as it is the natural position of the static equilibrium. The article compares the energy efficiency for the selected range of the dimensionless excitation frequency. For this purpose, four cases of elastic element configurations were compared. The results are visualized based on the diagram of RMS voltage induced on piezoelectric electrodes, bifurcation diagrams, Lyapunov exponents, and Poincaré maps, showing the impact of individual solutions on the efficiency of energy harvesting. The results of the simulations show that the harvester’s efficiency ranges from 4 V to 20 V depending on the configuration and the frequency range of the excitation, but the design allows for a smooth adjustment to the given conditions.

Beyond muscles: role of intramuscular connective tissue elasticity and passive stiffness in octopus arm muscle function.

The octopus arm is a 'one of a kind' muscular hydrostat, as demonstrated by its high maneuverability and complexity of motions. It is composed of a complex array of muscles and intramuscular connective tissue, allowing force and shape production. In this study, we investigated the organization of the intramuscular elastic fibers in two main muscles composing the arm bulk: the longitudinal (L) and the transverse (T) muscles. We assessed their contribution to the muscles' passive elasticity and stiffness and inferred their possible roles in limb deformation. First, we performed confocal imaging of whole-arm samples and provided evidence of a muscle-specific organization of elastic fibers (more chaotic and less coiled in T than in L). We next showed that in an arm at rest, L muscles are maintained under 20% compression and T muscles under 30% stretching. Hence, tensional stresses are inherently present in the arm and affect the strain of elastic fibers. Because connective tissue in muscles is used to transmit stress and store elastic energy, we investigated the contribution of elastic fibers to passive forces using step-stretch and sinusoidal length-change protocols. We observed a higher viscoelasticity of L and a higher stiffness of T muscles, in line with their elastic fiber configurations. This suggests that L might be involved in energy storage and damping, whereas T is involved in posture maintenance and resistance to deformation. The elastic fiber configuration thus supports the specific role of muscles during movement and may contribute to the mechanics, energetics and control of arm motion.

Wind piezoelectric energy harvesting enhanced by elastic-interfered wake-induced vibration

Inspired by wake induced vibration (WIV) of tandem arranged cylinders, a piezoelectric wind energy harvester with up and down stream interferences is proposed for highway wind resource exploitation. The WIV energy harvester is composed of a piezoelectric cantilever beam and an interference-affected bluff body that attached to the beam tip. The static and elastic interference configurations are investigated to enhance the aerodynamic force of the harvester. The upstream obstacle produces vortices impinging on the energy harvester and interfering with its shedding vortex. The downstream obstacle generates gap push between the harvester and itself. To capture these physical causes, fluctuating lift and drag forces dependent on the motion of the harvester are employed to model the unsteady aerodynamic force. An aeroelastic and electromechanical coupled governing equation is established using the electromechanical extended Hamilton’s principle. Computational fluid dynamics is performed to analyze the flow pattern, wake structure and lift coefficient of the WIV wind energy harvester. Wind-tunnel experiments investigate the effect of the upstream-wise and the downstream-wise spacings on harvesting power. The analytical model well predicts the wind-tunnel experimental results that the upstream-wise spacing is more important than the downstream-wise spacing. Maximum average powers of 0.169 W, 0.076 W and 0.038 W are harvested by the elastic configuration at the respective wind speeds of 10 m/s, 7.6 m/s and 6 m/s. The theoretical derivations explain that the harvested power by the wake-induced vibration is proportional to the third power of the wind speed. Therefore, the proposed wake-induced vibration in tandem configuration greatly improves the performance of galloping energy harvesting.

Osteosynthesis of diaphyseal tibia fracture with locking compression plates: A numerical investigation using Taguchi and ANOVA.

Performance of the locking compression plate (LCP) is a multifactorial function. The control parameters of plating, such as geometries, material properties, and physical constraints of the LCP components, affect basic functions associated with the bone fixation, including the extent of stress shielding and subsequent bone remodeling, strength and stability of the bone-LCP construct, and performance of secondary bone healing. The main objectives of this research were as follows: (1) to find the appropriate values of control parameters of an LCP construct to achieve the optimized performance throughout bone healing; and (2) to unravel relationships between LCP parameters and the LCP's performance. Different values for the plate/screw modulus of elasticity (E), plate width (W), plate thickness (T), screw diameter (D), bone-plate offset (O), and screw configuration (C), as six control parameters, were considered at five different levels. Taguchi method was adopted to create trial combinations of control parameters and determining the best set of parameters, which can optimize the overall performance of the LCP. All design cases were analyzed using the finite element method. The optimal set of control parameters consisting of 150 GPa, 12 mm, 4 mm, 5.5 mm, 2 mm, and 123,678 were determined for E, W, T, D, O, and C, respectively. Furthermore, ANOVA was used to rank the most influential parameters on each function of the LCP fixation. In the overall performance of the LCP fixation, E, D, T, C, W, and O showed a contribution percentage of 46%, 22%, 10%, 11%, 8%, and 3%, respectively.

금속 적층 제조된 격자 구조물의 1/4 압축시험 변형 거동 분석

With the development of Additive Manufacturing process, lattice structures have recently been fabricated with fine quality. Lattice structures have unique performances which encompass various elastic responses. In this study, shear characteristics of the lattice structures (BCC and OTC) fabricated by SLM process, under optimized manufacturing conditions, were analyzed by 1/4 compression tests. As a result, several fracture modes and elastic configurations were found by comparing the compression test results of various lattice structures. In addition, the lattice structures possessed certain shear elasticity and normal elasticity among different types of lattices at elastic region when shearing. As the 1/4 compression test was simulating the lattice structure on concentrate load or shearing load, the test represented shock introspection characteristics of the lattice inner structure.

Numerical Study of Airfoil Tonal Noise Reduction using Segmented Elastic Panel Configuration

In this paper, a novel passive method for airfoil tonal noise reduction is proposed using a configuration of two segmented elastic panels mounted on the airfoil. Numerical investigation using perturbation evolution method is carried out at a low Reynolds number based on airfoil chord of 5x10 and an angle of attack of 5. The passive method of employing a single panel has shown promising tonal noise reduction capabilities where the resonating panel located just ahead of the sharp growth of boundary layer instability within the airfoil separation bubble provided the strongest reduction of instabilities and noise reduction up to 3 dB has been achieved. The idea is extended in the present study by employing a two-panel configuration based on the localized flow characteristics over the airfoil surface. Five different panel configurations are designed and their effectiveness in terms of tonal noise reduction is evaluated and compared with baseline configuration. The azimuth and spectral analyses indicate the different extent of noise reduction for each configuration and even noise amplification in one of them. A significant noise reduction up to 8 dB is observed for the optimum configuration indicating the effectiveness of this novel method for devices operating at low Reynolds number.

A comparative performance-based seismic assessment of strongback steel braced frames

A recently introduced structural steel braced frame known as the strongback system (SBS) is a hybrid of a conventional bracing system and an essentially elastic vertical truss. This elastic backbone is designed to distribute seismic demands uniformly over the height of the building and consequently prevent damage concentration. Recent studies on developing design procedures for SBSs revealed that prescriptive code-based methods are inadequate to estimate their seismic demands, and they cannot ensure to fulfill the performance objectives properly. Here, to properly evaluate the seismic behavior of a wide variety of the practical configurations of SBS, a comprehensive parametric study is carried out on elastic backbone configuration, rigidity, and height. To this end, a series of different SBS archetypes are designed using a direct performance-based method, and the fulfillment of the performance targets is probabilistically assessed. Their over-strength factors, ductility ratios, and collapse fragility curves are compared together and with the performance of structures using conventional system and design method. Results indicate that the archetypes with the brace intersection point of two-third of the length of the beam, namely X-2/3 configuration, have shown the largest ductility ratio and lowest collapse probability, while the archetypes with chevron configuration have shown the smallest ductility ratio and highest collapse probability. Further, by increasing the rigidity of the vertical backbone, ductility ratio and the median spectral acceleration at collapse level are improved, and SBS archetypes tended to have uniform story drift distribution patterns. Applying the direct performance-based method in six-story structures reduces the story drift ratios of SBS up to 30%.

Longitudinal Fracture Analysis of Inhomogeneous Beams with a Continuously Varying Height

Longitudinal fracture behavior of nonlinear elastic inhomogeneous beam configurations with a continuously varying height along its length is analyzed. The general solution of the strain energy release rate problem is obtained by considering the energy balance. Beam configurations with the longitudinal crack located arbitrarily along the height are analyzed. The beams exhibit smooth material inhomogeneity in the height direction. The solution derived is valid within the arbitrary law of continuous beam height variations. Longitudinal fracture in a simply supported nonlinear elastic inhomogeneous beam with a height that varies in a parabolic law is investigated by applying the general solution of the strain energy release rate problem. The J-integral approach is used to verify this solution. The effect of various geometrical and material parameters on the longitudinal fracture of the simply supported beam configuration is evaluated and discussed in detail.

Passive airfoil tonal noise reduction by localized flow-induced vibration of an elastic panel

In this paper a novel passive control method is explored for airfoil tonal noise reduction using localized flow-induced vibration of a short elastic panel flush mounted on suction surface of a NACA 0012 airfoil at low Reynolds number. The key idea is to provide local absorption of energy of natural instabilities evolving in the laminar boundary layer by self-sustained flow-induced vibration of a properly designed panel. The panel ultimately acts to weaken the aeroacoustic feedback loop responsible for airfoil tonal noise radiation. Perturbation evolution method with acoustic broadband excitation is utilized to assess the tonal noise reduction potential with various combinations of elastic panel design parameters and optimal resonating and non-resonating elastic panel configurations are determined. Subsequently, direct aeroacoustic simulation of airfoil flow with optimal panel configurations are carried out to uncover the mechanism of tonal noise reduction using localized flow-induced vibration in a quantitative manner. Extensive analysis of numerical results reveals that a resonating panel located just ahead of the sharp growth of boundary layer instability within the airfoil separation bubble provides the strongest reduction of flow instabilities and an overall tonal noise reduction up to 3 dB. Such significant noise reduction is achieved without any sacrifice in the original aerodynamic characteristics of the airfoil. The outcomes of the study evidently suggest that the proposed passive control method with a localized flow-induced panel vibration is effective in suppressing the fundamental mechanism responsible for tonal noise generation of airfoil flow, making it a promising approach for modifying the acoustics of existing aerodynamic or wing profile operating at low Reynolds numbers.

An effective numerical strategy for retrieving all characteristic parameters of an elastic scatterer from its FFP measurements

A new computational strategy is proposed for determining all elastic scatterer characteristics including the shape, the material properties (Lamé coefficients and density), and the location from the knowledge of far-field pattern (FFP) measurements. The proposed numerical approach is a multi-stage procedure in which a carefully designed regularized iterative method plays a central role. The adopted approach is critical for recognizing that the different nature and scales of the sought-after parameters as well as the frequency regime have different effects on the scattering observability. Identification results for two-dimensional elastic configurations highlight the performance of the designed solution methodology.