Rod Structures Research Articles

Elastic spin angular momentum of zero-order flexural mode in thin rod system

The exploration of elastic wave behaviors in solid materials has revealed their intricate topological properties in recent years, particularly highlighting the significance of a previously underappreciated characteristic known as elastic spin angular momentum. This aspect plays a crucial role in the dynamics of elastic waves. Our research has focused on elucidating the theoretical aspects of elastic spin angular momentum, especially concerning the zero-order flexural mode in thin rod systems. Through meticulous theoretical analysis, we have deduced the nature of this angular momentum and successfully calculated the distribution of spin within these systems. The implications of our findings are substantial, as they contribute to an enhanced physical comprehension of the topological attributes associated with the flexural mode in thin rod structures, thereby offering new avenues for understanding material behaviors and their potential technological applications.

Application of Sol-Gel Method for Synthesis of Nanostructured Piezoelectric Materials in Lead Zirconate-Titanate System (A Review). Part 2. Synthesis of Film and Rod Structures

Application of Sol-Gel Method for Synthesis of Nanostructured Piezoelectric Materials in Lead Zirconate-Titanate System (A Review). Part 2. Synthesis of Film and Rod Structures

Phase-field modeling of peritectic coupled growth in the TRIS–NPG model system

Microstructures forming during the directional solidification of the hypo-peritectic TRIS–NPG model alloy were studied by phase-field simulations. Steady state growth forms could be obtained under conditions similar to those in recent space experiments. In two dimensions, the wavelength range of stable lamellar structures has been determined as function of the temperature gradient and the melt composition. Front temperatures extracted from simulations were compared to the predictions of the modified Jackson–Hunt theory. In three dimensions, structures and phenomena known from eutectic systems were reproduced. Transitions between lamellar and rod structures were induced by slowly changing the melt composition. The regularizing effect of tilting the temperature gradient, transforming a random labyrinth pattern to an ordered one, has also been demonstrated. These simulations show the universality of the basic governing mechanism — that is, the competition of solute diffusion with capillary effects — in the pattern formation of these multi-phase systems.

Achieving high geometric fidelity in vat photopolymerization additive manufacturing through liquid surface support

The top-down vat photopolymerization (VPP) printing process, known for its extensive material adaptability and elimination of the release step between the printed object and the separation film, is widely used in 3D printing of advanced functional materials. However, for slurries that cannot achieve rapid self-leveling, edge morphology distortion in printed objects reduces geometric precision. This study investigated the issue of edge morphology distortion in the top-down VPP printing process, and proposes a liquid surface support (LSS) printing method that can be applied to general VPP printers. The results show that the protective slurry fence printed simultaneously with the object can provide excellent liquid surface support for the uncured layer above the printed object, which shifts the edge morphology distortion issue from the target object to the fence. The gap distance between the fence and the target sample is identified as the primary factor affecting edge morphology fidelity, which is influenced by surface tension. Finally, we successfully validated the application of the LSS printing method in the printing of ceramic dental prostheses and slender rod structures. This novel method significantly enhances the geometric precision of printed samples and is expected to promote the advancement of VPP printing applications for advanced functional materials.

Optimization of Al-doped NiCo2O4 hybrid nanostructures and their electrochemical activation feature in supercapacitors

The performance of supercapacitors majorly depends on electrode materials, while optimizing the composition and microstructure of materials is the key for boosting electrochemical activity. Herein, Al-doping and electrochemical activation strategy are combined to boost the electrochemical activity of NiCo2O4. The influence of Al dopant dosage on the performance is discussed firstly. With an increasing Al3+ dosage, Al-doped samples show a morphology transition from nanoneedles to hybrid structures of nanowire/nanosheet. Optimized Al1.0-NiCo2O4 sample with hybrid nanostructures delivers the highest areal capacitance of 8.22 F cm−2 at 1 mA cm−2, much higher than that of pristine NiCo2O4 and other Al-doped samples. Serving as a working electrode, the activation of Al1.0-NiCo2O4 is conducted to induce the reconstruction of microstructure and composition. When activated for 200 cycles, expansive rod structures consisted of vertical nanosheets are generated, which presents a high areal capacitance of 9.93 F cm−2. Under the same operating conditions, the activation is also proceeded on the Al0.5-NiCo2O4 sample with only nanowires. The maximum capacitance reaches 6.49 F cm−2, much lower than that of activated Al1.0-NiCo2O4, due to the absence of nanosheets in Al0.5-NiCo2O4. The activation process is confirmed as the structure transition from nanoparticles to thin nanosheets, with the composition transition from initial Al-doped NiCo2O4 to NiCoAl-OH/OOH. When applied in an asymmetric supercapacitor, the NF/Al1.0-NiCo2O4 electrode presents a superior electrochemical performance and a charge/discharge activation feature.

Interactive inverse design of periodic non-uniform/inhomogeneous rod structures based on q-learning method

The existing researches on controlling the longitudinal waves through periodic rods with frequency bands mainly focus on the analysis of band structures together with their influences by various geometrical/material parameters and on the corresponding forward design via passive/active modulations. This paper originally proposes the interactive inverse design method by virtue of the Q-Learning algorithm for catering required objectives with introducing the cross-sectional nonuniformity and material inhomogeneity to the constituent components in periodic rods. Firstly, theoretically analyzing the frequency bands of periodic non-uniform/inhomogeneous rods with linear variations to the cross-sectional area and to the Young’s modulus and material density, is presented using transfer matrix method (TMM). After verifying the analysis method by comparing it with the finite element method (FEM) for obtaining band structures in three kinds of exemplified periodic rods with non-uniform/inhomogeneous components, the effects of non-uniformity and inhomogeneity of components on the frequency bands are discussed. These effects provide qualitative judgment criteria to the results of inverse design. Secondly, the inverse design method by the Q-learning algorithm for periodic non-uniform/inhomogeneous rods is proposed as the optimization objective is the maximum of the first bandgap width. The optimization results of the periodic rods with only non-uniformity, with only inhomogeneity or with both non-uniformity and inhomogeneity are provided to validate the accuracy and efficiency of the proposed Q-Learning algorithm that has the advantages of obtaining the optimal result from any initial states and giving the evolutionary path along the gradient to the objective. It should be pointed out that our proposed inverse design method can actually be extended for other optimization objectives and to other kinds of periodic structures for controlling diversified elastic waves.

Stiffness of reinforced concrete structures under bending considering shear and axial forces (part 2)

The paper presents a physical and computational model for determining the parameters of limit states of reinforced concrete structures under complex stressed state - bending with axial and shear forces. Based on the adopted scheme of cross-section discretization and A.R. Rzhanitsyn's theorem of duality between force and deformation parameters, the forward and backward transfer for determining the coefficients of the stiffness matrix of reinforced concrete rod structures with inclined and normal cracks have been constructed. Stiffness of structures in the zone of inclined cracks is determined using the model of composite strips which separate the zone with inclined cracks. The hypothesis about the character of deformation distribution in a complex-stressed reinforced concrete element with inclined cracks is accepted.For this model the conditional shear modulus is obtained, which allows to determine the average relative linear and angular strains of concrete and reinforcement at the point adjacent to the shear joint between inclined cracks. Based on this model and using the experimentally obtained value of the relative shear in the inclined crack, the dowel forces in the reinforcing bar intersected by the inclined crack were determined. The application of the obtained analytical relationships in the practice of designing reinforced concrete structures allows not only to clarify significantly the definition of displacements and width of opening of inclined and normal cracks, but also to maximize the convergence of the design and physical model based on experimental data.

A study of analyzing longitudinal dynamic behavior of a double-rod system with longitudinal nonlinear supports

In engineering, shafting systems are typically subjected to longitudinal vibration excitations, which may result in unwanted vibration. To study the control of longitudinal vibration in shafting systems, they can be simplified to rod structures. Currently, engineers have attempted to apply the nonlinear principle to design nonlinear supports to control the vibration of flexible structures. However, the flexible structures referenced in the literature are usually composed of a single component, which limits the application of nonlinear supports to more complex structures. To explore the potential application of nonlinear supports in marine engineering, this work introduces a longitudinal vibration prediction model for a double-rod system equipped with longitudinal nonlinear supports. The generalized Hamilton principle is used to derive the governing equations for the double-rod system with longitudinal nonlinear supports. The longitudinal vibration responses of the double-rod system are numerically solved using the Galerkin truncation method. The numerical results confirm that a 1-term truncation number guarantees the stability of the longitudinal vibration prediction model. Under certain conditions, the longitudinal vibration responses are significantly affected by longitudinal nonlinear supports. It is recommended to install longitudinal nonlinear supports on both Rod 1 and Rod 2 simultaneously to suppress vibration in the first two main resonance orders. With reasonable excitations, the vibration state and magnitudes of the double-rod system can be effectively controlled by adjusting the longitudinal nonlinear supports. Complex longitudinal vibration responses are more readily induced by altering the parameters of the longitudinal nonlinear support installed on Rod 1. Choosing appropriate parameters for the nonlinear supports on Rod 1 and Rod 2 positively contributes to the reduction of vibration in the double-rod system.

The effect of thickener structure degradation on tribological properties: Study on the decay mechanism of polyurea grease under mechanical-thermal aging conditions

The aging of lubricants is a primary factor contributing to rolling bearing failures. The rolling stability test simulated the aging behavior of grease under shear and high-temperature circumstances. An investigation was conducted on how mechanical-thermal aging impacts the chemical and physical structures of polyurea grease, as well as how changes in thickener microstructure affect rheological and tribological properties. The results show that under shear and high temperature, structural changes in urea lead to a transformation of the thickener morphologies from the growth of entangled ribbon fiber to a large-diameter rod structure, with a significant decrease in the degree of entanglement. When a certain proportion of fibrous and rod structures coexist, the grease has good oil separation capacity, the structural stabilities of grease become weak, and the deformation resistance decreases. During this phase, the polyurea grease has the best tribological performance.

PIK3R1 fusion drives chemoresistance in ovarian cancer by activating ERK1/2 and inducing rod and ring-like structures

Gene fusions are common in high-grade serous ovarian cancer (HGSC). Such genetic lesions may promote tumorigenesis, but the pathogenic mechanisms are currently poorly understood. Here, we investigated the role of a PIK3R1-CCDC178 fusion identified from a patient with advanced HGSC. We show that the fusion induces HGSC cell migration by regulating ERK1/2 and increases resistance to platinum treatment. Platinum resistance was associated with rod and ring-like cellular structure formation. These structures contained, in addition to the fusion protein, CIN85, a key regulator of PI3K-AKT-mTOR signaling. Our data suggest that the fusion-driven structure formation induces a previously unrecognized cell survival and resistance mechanism, which depends on ERK1/2-activation.

Considerations for Space Grid Structures: Comprehensive Review of Key Design Aspects and Developing Trends

The investigation aimed to identify key directions for advancing space grid structures. It involved a comprehensive survey of existing structural solutions, nodal connections, and design features specific to spatial rod structures. The analysis included theoretical, numerical, and experimental studies on the stress-strain state, factors influencing it, geometric optimization, and design principles. The focus was on space grid structures, particularly structural plates and their prevalent nodal connections. The investigation revealed that scientific and technological progress, such as improvements in material properties, calculation methods, and software simulations, significantly contributed to the advancement of structural designs by enhancing accuracy and reducing complexity. Geometric dimensions of modular elements and the height-to-span ratio were identified as key parameters affecting structural efficiency. The study also examined global experiences in nodal connection development and provided a general classification of such connections. By identifying advantages and disadvantages of existing space grid structures, potential pathways for further improvement were illuminated. The findings underscored the importance of developing innovative nodal connections as a primary avenue for enhancing space grid structures.

Novel approach towards optically active and hexagonal plate morphology of Zinc doped Perylene Tetra Carboxylic Di Anhydride composite for high photovoltaic and flexible supercapacitor performances

This paper reports novel features like photo-voltaic and energy storage capacity as dual performance in Zinc-Perylene Tetra-Carboxylic Di-Anhydride (Zn-PTCDA) composite have synthesized via hydrothermal method. This follows escape-by-crafty mechanism chemical reaction that produces the orthorhombic crystal structure. The Morphology transformation from stacked pyramids of PTCDA into hexagonal plates and rod structures of Zn-PTCDA. The optical study suggest that Zn-PTCDA composite provide compelling evidence for the Dye sensitized solar cell (DSSC) with Power Conversion Efficiency (PCE) is lower 0.2 % due to charge carrier recombination and promote to utilize this as transport layer of any solar cell. The electrochemical performance of pure Zn-PTCDA exhibits capacitance retention of 44.2 % while Zn-PTCDA-Graphene Oxide (Zn-PTCDA-GO) has capacitance retention 84.5 % over 5000 Galvanostatic-Charging and Discharging (GCD) cycles. The best specific capacitance 561 F/g at 2 A/g along with discharge through light emitting diode (LED) illumination for 2–3 min and also excellent energy density 31.5 Whr/kg and power density 4.5 kW/kg values. The incorporation of Zinc into PTCDA dye demonstrates Metal Organic Frameworks can provide improvements in the performances of both supercapacitors and dye-sensitized solar cells. The integration of both can instant storage of converted energy is needed solution to solve energy demand in future.

Layout and cross-sectional size optimization of truss structures with mixed design variables based on gradient method

The object of the study was truss-type rod structures, which were investigated for the purpose of finding the optimal design solution in a mixed (continuous and discrete) space of variables. The parameters of the geometric scheme of the truss, as well as the dimensions of the cross-sections of its elements, were considered as design variables. The stated optimization problem is represented as a nonlinear programming task, in which the objective function and nonlinear constraints of the mathematical model are continuously differentiable functions of the design variables. The system of constraints includes strength and stability inequalities, formulated for the design cross-sections of the rod elements of the structure, which is subject to the effect of the design load combinations of the ultimate limit states. As a part of the system of constraints, the displacement constraints formulated for the specified structural nodes, which is subject to the action of design load combinations of the serviceability limit states, are considered. To solve the stated optimization problem, a method of the objective function gradient on the surface of active constraints was used, with the simultaneous elimination of residuals in the violated restrictions. For design variables, the variation of which must be performed according to a given set of possible discrete values, a discretization procedure for the optimal solution obtained in the continuous space of design variables is proposed. A comparison of the proposed optimization methodology with alternative metaheuristic methods and algorithms reported in the literature was performed. On the considered problem of parametric optimization of a 47-span tower structure, a design solution with a weight of 835,403 kg was obtained, which is 1.53...4.6 % better than the optimal solutions obtained by other authors

Boundary value problems of the dynamics of thermoelastic rods and their solutions

We consider spatially one-dimensional boundary value problems of uncoupled thermoelasticity, which can be used to study various rod structures under thermal heating conditions. As is known, rod structures are connecting and transmission links of various parts of the machines and mechanisms. Here we propose a unified technique for solving various boundary value problems typical for practical applications. The problems of determining the thermally stressed state of a thermoelastic rod under various boundary conditions at its ends and acting power and heat sources along the entire length of the rod are considered. Based on the method of generalized functions, generalized solutions of non-stationary and stationary direct and semi-inverse boundary value problems under the action of power and heat sources of various types, including stationary sources of periodic oscillations, are constructed. Acting sources can also be specified by singular generalized functions, under various boundary conditions at the ends of the rod. Shock elastic waves that arise in such structures under the action of shock loads are considered. Regular integral representations of generalized solutions are obtained, which provide an analytical solution to the posed boundary value problems. The peculiarity of the constructed solutions makes them convenient for studying network thermoelastic systems that can be modeled by thermoelastic graphs.

Modeling cable-pulley deployment systems of transformable rod structures

The aim of this article is to develop a simplified method for modeling cable-pulley deployment systems of rod structures based on the calculation of cable tensions and nodal driving forces with account for friction and other features of the system. Methods of theoretical mechanics, multibody dynamics, numerical integration of differential equations, and computer modeling were used during the research. The task of developing a simplified approach to modeling cable-pulley deployment systems for rod structures is considered. It is proposed to determine nodal driving forces by calculating cable tensions with account for friction and other features of the cable-pulley system, cables, and pulleys. To develop a model of cable-pulley deployment system, a rod system was chosen as the research object, which represents two sections of the transformable support truss of a reflector. Each section consists of diagonal and horizontal rods with tubular cross-sections. The sections are interconnected by hinge units. The structure is deployed using an upper and a lower cable, which pass through pulleys and are tensioned by an electric motor. The deploying forces are implemented by transferring the cable tension forces to the structure due to static friction and pressure between the cables and the pulleys. For further implementation of the model in an open-source software package, some simplifications were made due to the complexity of the design. A simplified method was developed for nodal driving force calculation in simulating rod structure deployment with the help of cables. The tensions, elongations, slacks, and neutral length of the cables and the forces transmitted from the cables to the pulleys were calculated as a function of time. Using them, the deployment of a rod structure was simulated for a constant cable speed. The results make it possible to control the rod system deployment time and rate depending on the characteristics and tension forces of the cables. The proposed approach is implemented using open-source software, and it provides modeling flexibility and reduces the model development and run time.

Modeling single-phase transverse flows in a PWR rod bundle at low Reynolds number

In normal functioning conditions, the primary component of the flow within the rod bundle of a PWR core is in the axial direction, along the rods. However, in accidental situations, such as the refilling or reflooding phase during a Loss of Coolant Accident, or a Steam Line Break accident, transverse flows may significantly affect thermal-hydraulic properties in the core. Such effects have received little attention in system codes such as CATHARE, particularly in anisotropic rod structures at low Reynolds numbers. Here, we develop macroscopic pressure drop models for flows spanning from the creeping regime to unsteady vortex shedding. The averaged model is a generalized Darcy–Forchheimer equation with an apparent permeability including a rotation matrix and a non-linear dimensionless coefficient. The constitutive relations for the intrinsic permeability matrix are derived from polynomial regressions based on results obtained from microscale numerical simulations at different flow directions and Reynolds numbers. We finally test our approach in a case where transverse flow is imposed through a differential of inlet velocities and validate by comparing results from CATHARE with those obtained from a finite element toolbox.

Mechanical design and energy absorption performances of novel plate-rod hybrid lattice structures

Hybrid lattice structures, integrating diverse structural components from fundamental lattice topologies, have attracted significant attention for their exceptional mechanical properties encompassing elastic modulus, yield stress, and energy absorption. To amalgamate the lightweight characteristics of rod structures with the robust mechanical properties of plate structures, a novel plate-rod hybrid lattice (PRHL) with controllable geometrical parameters and higher energy absorption was proposed and fabricated via the Selective Laser Sintering technique. In the PRHL design, the hybrid rod structure, interlinked with the center of each surface of the semi-open Octet plate lattice (SOPL), mutually provides support and deformation constraints. To identify the mechanical properties of PRHL, quasi-static uniaxial compression tests of PRHL samples sintered by Polylactic Acid powder were carried out. In comparison to SOPL, the newly proposed PRHL demonstrates an approximate 13.4% improvement in initial crush stress and an 18.5% increase in specific energy absorption capacity. Furthermore, numerical simulations incorporating the effect of printing orientation were performed to analyze the deformation mechanism of the PRHL structures. The present study also underscores the capacity to fine-tune the mechanical properties of PRHLs by regulating the plate thickness, rod diameter and excavated hole diameter.

Computing dispersion relations with modal analysis methods

Dispersion diagrams depicting dispersion relations are usually computed from a periodic structure single unit cell using either analytical methods, such as the plane wave expansion (PWE) method, or numerical methods, such as the wave finite element (WFE) method, by applying Bloch-Floquet periodic boundary conditions. However, the latter is still not available in most commercial FE codes. In this work, we propose a method to compute the dispersion diagram using standard modal analysis tools available in FE commercial codes currently used for structural analysis. We show that if a metastructure consisting of a few cells is "periodized" by "wrapping around" the degrees of freedom at its ends, its natural frequencies will be points on the dispersion curve pass bands. The wavenumbers corresponding to these natural frequencies can be obtained from the corresponding vibration modes using Prony's method. These natural frequencies are real for Hermitian structures and complex for non-Hermitian structures. Besides providing a useful tool for wave dispersion analysis using standard FE codes, the proposed method provides interesting insights into the dynamics of periodic structures. The proposed method is applied to simple passive and active periodic rod structures.

Multi-Order Mode Excitation and Separation of Ultrasonic Guided Waves in Rod Structures Using 2D-FFT.

The ultrasonic guided wave technique is extensively used for nondestructive structural testing, and one of the key steps is to extract a single mode with certain purity from multi-order mixed modes. In this paper, the propagation of ultrasonic guided waves in the cylindrical rod is simulated first; the appropriate broadband excitation signal is selected to excite the multi-order modes in a specific frequency range; and the time-space signal containing multi-order modes is converted to the frequency-wavenumber domain signal by two-dimensional Fourier transform. In the frequency-wavenumber domain, the frequency-wavenumber ridge is extracted from the multi-mode frequency-wavenumber domain based on the dynamic programming method, and then the time-domain signal corresponding to a single mode can be reconstructed. By comparing the excited multi-order mode and the separated single mode with the theoretical results, it is observed that the two results are consistent. Thus, the employed mode-excitation method can accurately excite the multi-order modes in rod structures. Furthermore, the proposed method enables the separation of a single-mode wave with high purity, providing a foundation for future utilization of isolated modes.

Photoluminescence Properties of Polythiophene/Tin Oxide (PTh/SnO2) Polymer Nanocomposites

In the present work, we have synthesized, polythiophene/tin oxide (PTh/SnO2) polymer nanocomposites through an in-situ chemical polymerization of thiophene monomers using anhydrous FeCl3 as an oxidant. The structural, thermal and optical characterization of PTh/SnO2 nanocomposites were investigated using X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analyzer and fluorescence emission spectroscopy. XRD spectra show the formation of pure polythiophene and incorporation of SnO2 nanofiller into the polythiophene matrix. FESEM images depict the formation of irregular rod and chain like structures with incorporation of SnO2 are noticed. TGA results reveal that the thermal stability of polymer nanocomposites is higher than that of pure polythiophene due to the strong interaction between nanofiller and polymer matrix. Fluorescence emission spectra show the emission intensity of polymer nanocomposites decreases as the concentration of SnO2 nanofiller increases due to the variation of rate of electron-hole recombination and conjugation length of polymer chain. Our results of fluorescence emission analyses suggest the PTh/SnO2 polymer nanocomposites could be a potential material for photonic devices.