Bar Structure Research Articles

DETDO: An adaptive hybrid dandelion optimizer for engineering optimization

Dandelion Optimizer (DO) is a recently proposed swarm intelligence algorithm that coincides with the process of finding the best reproduction site for dandelion seeds. Compared with the classical Meta-heuristic algorithms, DO exhibits strong competitiveness, but it also has some drawbacks. In this paper, we proposed an adaptive hybrid dandelion optimizer called DETDO by combining three strategies of adaptive tent chaotic mapping, differential evolution (DE) strategy, and adaptive t-distribution perturbation to address the shortcomings of weak DO development, easy to fall into local optimum and slow convergence speed. Firstly, the adaptive tent chaos mapping is used in the initialization phase to obtain a uniformly distributed high-quality initial population, which helps the algorithm to enter the correct search region quickly. Secondly, the DE strategy is introduced to increase the diversity of dandelion populations to avoid algorithm stagnation, which improves the exploitation capability and the accuracy of the optimal solution. Finally, adaptive t-distribution perturbation around the elite solution successfully balances the exploration and exploitation phases while improving the convergence speed through a reasonable conversion from Cauchy to Gaussian distribution. The proposed DETDO is compared with classical or advanced optimization algorithms on CEC2017 and CEC2019 test sets, and the experimental results and statistical analysis demonstrate that the algorithm has better optimization accuracy and speed. In addition, DETDO has obtained the best results in solving six real-world engineering design problems. Finally, DETDO is applied to two bar topology optimization cases. Under a series of complex constraints, DETDO produces a lighter bar structure than the current scheme. It further illustrates the effectiveness and applicability of DETDO in practical problems. The above results mean that DETDO with strong competitiveness will become a preferred swarm intelligence algorithm to cope with optimization problems.

THE PROBLEM OF FORECASTING THE ROD STRUCTURES SURVIVABILITY

Purpose. Methods of metal structures calculation which would take into account sudden changes of the design scheme and its elements destruction as a result, are not perfect enough and are often fragmentary. The research of survivability of multi-element bar structures affected by negative factors will improve the efficiency of the such structures calculation with the prospect of further expanding the possibilities of forecasting the survivability of metal structures depending on its operation conditions. As a research object three-dimensional metal bar structures are considered, which are characterized by a high degree of production significance and responsibility during the operation. Methodology. The considered normative documents do not have a single approach regarding the identification of the problem and technique of generating possible solutions, but they combine all the listed standards. Approaches and methods for assessing the degree of a structure damage or serviceability are somewhat different: in some documents the area of damaged floor structures is limited; in others, the state of structures that have not gone out of work is assessed; as well as the economic forecast of a new building construction or restoring an old one. If we group the normative documents’ provisions of the different countries, we can single out two established approaches on "progressive destruction" protection. According to the first approach, it is necessary to use indirect protection measures, according to the second one, it is necessary to use the ability of key (bearing) elements to perceive damaging effects, the ability of structure to redistribute loads in case of some elements’ failures. Results. To increase the stability of building structures to progressive destruction, metal ones particularly, it is necessary to consider the possibility of local destruction already at the stage of building design. Its increase is facilitated by a decrease in the number of hinged joints, in some cases the use of integral structural elements, the use of building materials affected by plastic deformation, as well as the identification of building structure elements which under normal operating conditions do not perform bearing functions, but perform them in the case of the local destruction appearance. Scientific novelty. The analyses of the regulatory base and the researchers’ works in a number of countries including Ukraine regarding the progressive destruction is performed. The necessity to improve the concept of designing construction objects is justified. The basis of this concept should consist of both theoretical research and experimental confirmation of the accepted assumptions. Practical value. The necessity of forming a unified approach for determining the problem of survivability and durability of structures, redistribution of loads on undamaged structural elements is substantiated. Directions for the development of measures and design solutions regarding the prevention of the progressive destruction of multi-element bar structures are proposed.

Size and Topology Optimization of Truss Structures Using Quantum-Based HS Algorithm

With the development of various metaheuristic algorithms, research cases that perform weight optimization of truss structures are steadily progressing. In particular, due to the possibility of developing quantum computers, metaheuristic algorithms combined with quantum computation are being developed. In this paper, the QbHS (Quantum based Harmony Search) algorithm was proposed by combining quantum computation and the conventional HS (Harmony Search) algorithms, and the size and topology optimization of the truss structure was performed. The QbHS algorithm has the same repetitive computational structure as the conventional HS algorithm. However, the QbHS algorithm constructed QHM (Quantum Harmony Memory) using the probability of Q-bit and proposed to perform pitch adjusting using the basic state of Q-bit. To perform weight optimization of truss structures using the proposed QbHS algorithm, 20 bar, 24 bar, and 72-bar truss structures were adopted as examples and compared with the results of the QE (Quantum Evolutionary) algorithm. As a result, it was confirmed that the QbHS algorithm had excellent convergence performance by finding a lower weight than the QE algorithm. In addition, by expressing the weight optimization results of the truss structure with an image coordinate system, the topology of the truss structure could be confirmed only by the picture. The results of this study are expected to play an important role in future computer information systems by combining quantum computation and conventional HS algorithms.

Manufacturing-Cost-Driven Topology Optimization of Welded Frame Structures

Abstract This work presents a method for the topology optimization of welded frame structures to minimize the manufacturing cost. The structures considered here consist of assemblies of geometric primitives such as bars and plates that are common in welded frame construction. A geometry projection technique is used to map the primitives onto a continuous density field that is subsequently used to interpolate material properties. As in density-based topology optimization techniques, the ensuing ersatz material is used to perform the structural analysis on a fixed mesh, thereby circumventing the need for re-meshing upon design changes. The distinct advantage of the representation by geometric primitives is the ease of computation of the manufacturing cost in terms of the design parameters, while the geometry projection facilitates the analysis within a continuous design region. The proposed method is demonstrated via the manufacturing-cost-minimization subject to a displacement constraint of 2D bar, 3D bar, and plate structures.

The Parallax and 3D Kinematics of Water Masers in the Massive Star-forming Region G034.43+0.24

We report a measurement of the trigonometric parallax of 22 GHz water masers in the massive star-forming region G034.43+0.24 as part of the Bar and Spiral Structure Legacy Survey using the Very Long Baseline Array. The parallax is 0.330 ± 0.018 mas, corresponding to a distance of kpc. This locates G034.43+0.24 near the inner edge of the Sagittarius spiral arm and at one end of a linear distribution of massive young stars that cross nearly the full width of the arm. The measured three-dimensional motion of G034.43+0.24 indicates a near-circular Galactic orbit. The water masers display arc-like distributions, possibly bow shocks, associated with winds from one or more massive young stars.

Control of the Dynamic Parameters of a Flat Beam Structure by Selection of Fixing

This article proposes a method for the justified choice of the fixing method, the type of supports and their stiffness for flat beam structures of an axisymmetric cross section in order to ensure the specified values of the first frequency of natural bending vibrations and the first critical load, by taking into account the action of longitudinal forces and temperature changes. The technique is based on the well-known provisions of the theory of beam oscillations, the Euler’s theory of stability, and uses the coefficients of supports as a criterion for choosing a fixing method, which are pre-normalized to achieve comparable values. The selected fixing provides the specified value of the first natural oscillation frequency, the value of the first critical temperature, or simultaneously both conditions of working efficiency. According to the developed method, comparative calculations of a flat bar structure using the finite element method have been performed. They has shown good convergence of the results for all controlled parameters. The proposed approach can be used in the design of support fixing of flat beam structures for various purposes to ensure their dynamic behavior.

Generalized Forms of an Overconstrained Sliding Mechanism Consisting of Two Congruent Tetrahedra

The motions of a bar structure consisting of two congruent tetrahedra are investigated, whose edges in their basic position are the face diagonals of a rectangular parallelepiped. The constraint of the motion is the following: the originally intersecting edges have to remain coplanar. All finite motions of our bar structure are determined. This generalizes our earlier work, where we did the same for the case when the rectangular parallelepiped was a cube. At the end of the paper we point out three further possibilities to generalize the question about the cube, and give for them examples of finite motions.

Structure and strain state of aluminum bars at the initial phase of extrusion

The structure of insufficiently deformed areas at the non-steady phase of extrusion was studied. The tests at Kamensk Uralsky Metallurgical Works using a 120 MN press and 800 mm dia. container, in order to extrude a 355.6 mm dia. Bar was performed. The bar material is the Al–Mg–Si AD33 aluminum alloy (GOST 4784), similar to ASTM 6061. The percentage reduction was 80 %, and the reduction ratio was 5.06. After that, the macrostructure, microstructure, and average grain size along the radius, mechanical properties at room and elevated temperatures were investigated. It was found that the extruded bar macrostructure is fine-grained, homogeneous, and dense, with no nonmetallic or intermetallic inclusions. The cross-section contained several structures. The central part is weakly deformed preserving the dendritic cell structure inherited from the casting. At the circumference, a streaked structure is formed. Its components are crushed and uniformly distributed. We measured the strength at elevated temperatures and compared the results to the data available in the literature. The tested material strength almost doubled, thus indicating its incomplete softening. The ductility was also performed. The DEFORM-2D software, in order to simulate the low reduction of extrusion was used. The metal at the circumference is exposed to a greater strain from the extrusion beginning. A step-by-step analysis indicated that at the first step, the strain is localized near the die hole. In the second step, a rigid area is formed in the vicinity of the die/container liner interface. The circumference layer of metal with a 1.75–2.00 reduction of area is formed. At the bar center, this range is 0.75–1.00 (half of the circumference value). In the third step, the circumference layer with an elevated strain has a wedge-like shape. In the fourth step, the circumference layer (with elevated strain) has an equal thickness along the extrusion axis. This indicates the steady phase. The plastic strain at the bar front end is higher at the circumference than in the center. This confirms the structural analysis results. They show that the central part of the bar may retain its cast structure, while the circumference is deformed. If the bar central part is required to have some specific properties, the bar has to undergo another manufacturing operation to increase the accumulated strain. Re-extrusion processes the areas insufficiently deformed during the first extrusion.

Lightweight Optimization Design and Fatigue Lifetime Analysis for Anti-rolling Torsion Bar of Rail Vehicle

Based on the fatigue strength assessment method in the FKM standard, the lightweight design of a type of anti-rolling torsion bar is studied by using the finite element method. Firstly, the finite element model of the torsion bar structure is constructed by using the Creo software and the HyperMesh software, and then the finite element analysis is carried out by using the ABAQUS software. The numerical simulation results indicate that under the condition of ultimate load 29.2kN, the static strength, anti-rolling stiffness and fatigue strength of the torsion bar are all satisfy with the design requirements. Secondly, the orthogonal numerical test method is utilized to investigate the influence of geometric parameters on the anti-rolling stiffness and Factor of Strength (FOS) value of the torsion bar. Taking the structural geometric parameters as variables and the FOS value as the objective function, a second-order response surface model is established. The single objective and multi-factor optimization design for the torsion bar under the condition of stiffness constraint is conducted by using the Isight software and multi-island genetic algorithm. The results show that, comparing with the original structure, the weight of the optimized structure is reduced by 20.89%, and the static and dynamic strength, and anti-rolling stiffness of the optimized structure are match with the design requirements. Finally, the static and dynamic strength tests for the optimized torsion bar are individually operated at the ultimate load and under two-stage cyclic loading with amplitude 18.0kN and 29.2kN. the results show that the calculated stiffness coefficient is consistent with the test one, and the service lifetime of the torsion bar is satisfy with the design requirement.

Dynamic Response of Metaconcrete Beam Under Blast Load

A number of recent studies have demonstrated numerically and experimentally that metaconcrete made of engineered aggregates can mitigate the propagation of stress waves induced by impulsive load. The energy imparted into the metaconcrete structure from impulsive load can be absorbed by engineered aggregates because of the local vibration of heavy cores. The previous studies considered simple 1D metaconcrete bar structure to investigate its effectiveness on mitigating stress wave propagations. The performance of structural components made of metaconcrete under impulsive load has not been investigated yet. In this study, 3D meso-scale models of three typical beams, namely, normal concrete (NC) beam, normal metaconcrete (NMC) beam composed of normal engineered aggregates (NEA) and enhanced metaconcrete (EMC) beam composed of enhanced engineered aggregates (EEA) are generated to investigate the responses of beam structure subjected to impulsive loading. The engineered aggregates NEA and EEA are designed via the software COMSOL to have the bandgaps coincident with the primary frequencies of stress wave generated in NC beam by the considered impulsive loads. Dynamic responses of three beams subjected to near-field blast loads with different scaled distances are studied via the software LS-DYNA. It is found that the EMC beam experiences less compressive and spalling damage than NC and NMC beams subjected to near-field explosion with the scaled distance of 0.15[Formula: see text]m/kg[Formula: see text]. Under blast loading from larger scaled distance explosions, the EMC beam experiences less severe flexural and flexural-shear damage than NC and NMC beams. It can be concluded that the EMC beam demonstrates better blast-resistance performance than NC and NMC beams.

Computational and experimental study of longitudinal stability of the thin-walled flat bar structure

The paper studies longitudinal stability of the centrally compressed flexible flat bars using computational and experimental methods. Calculations were carried out according to the dynamic analysis methodology in the LS-DYNA software package. This methodology is based on three determining factors, i. e. volume, technological deviations and real-time mode. When constructing a hinged bar model, 3D finite elements, elastic-plastic material model, asymmetrical cuts of small volumes simulating geometric technological deviations were used. Critical forces determined by the methodology were compared with the Euler forces and with the experimental data. The experiment was carried out on bars with pointed ends, which were abutted against the angular technological equipment and provided with free rotation of the bar ends. As a result of the computational and experimental study of the flexible bars stability, it was established that in real bar designs there appeared initial shape imperfections noticeably affecting the critical forces magnitude, and the more flexible the bar was, the stronger this effect was. Quantitative relationship was also found between the experimentally measured critical forces and those calculated by the methodology and by the Euler formula. The issues of the origin of initial form imperfections in real bars were touched upon. Three possible directions for searching for a solution to the problem of bar stability using the methodology of dynamic analysis are shown depending on the method of introducing technological deviations into the structure calculation scheme. Diagrams of the hinged flat bars deformation during compression tests are provided.

Abutment-Bar Structure Connection Geometry: An Important Design Parameter for Implant-Supported Bar-Retained Overdentures With Cantilever Extension.

When extended distally due to higher loading in the posterior region, implant-supported bar-retained overdentures with cantilever bar extension exhibit greater bending moments on the implants closest to the cantilever bar and increased stresses in the overdenture components. In this study, a new abutment-bar structure connection was introduced to minimize undesired bending moments and reduce the resulting stresses by increasing the rotational mobility of the bar structure on the abutments. Copings of the bar structure were modified to have 2 spherical surfaces, sharing the same center, located at the centroid of the top surface of the coping screw head. The new connection design was applied to a 4 implant-supported mandibular overdenture to create a modified overdenture. Both the classical and modified models had bar structures with cantilever extensions in the first and second molar areas and were analyzed for deformation and stress distribution using finite element analysis, which was also conducted for both the overdenture models without cantilever bar extensions. Real-scale prototypes of both models with cantilever extensions were manufactured, assembled on implants embedded in polyurethane blocks, and subjected to fatigue testing. Both models' implants were subjected to pullout testing. The new connection design increased the rotational mobility of the bar structure, minimized the bending moment effects, and reduced the stress levels in the peri-implant bone and overdenture components, whether cantilevered or not. Our results verify the effects of rotational mobility of the bar structure on the abutments and validate the importance of the abutment-bar connection geometry as a design parameter.

Constrained Form-Finding of Tension–Compression Structures using Automatic Differentiation

This paper proposes a computational approach to form-find pin-jointed bar structures subjected to combinations of tension and compression forces. The generated equilibrium states can meet additional structural and geometrical constraints via gradient-based optimization. We achieve this by extending the combinatorial equilibrium modeling (CEM) framework in three important ways. First, we introduce a new topological object, the auxiliary trail, to expand the range of structures that can be form-found with the framework. Then, we leverage automatic differentiation (AD) to obtain an exact value of the gradient of the sequential and iterative calculations of the CEM form-finding algorithm, instead of a numerical approximation. Finally, we encapsulate our research developments into an open-source design tool written in Python that is usable across different CAD platforms and operating systems. After studying four different structures –a self-stressed tensegrity, a tree canopy, a curved bridge, and a spiral staircase– we demonstrate that our approach enables the solution of constrained form-finding problems on a diverse range of structures more efficiently than in previous work. • A computational form-finding method is extended to enhance the form generation of spatial structures in static equilibrium subjected to tension and compression forces. The output forms can satisfy combinations of force and geometric constraints via gradient-based optimization. • A new topological modeling object, the auxiliary trail, is presented which simplifies the representation of a structure as a valid input to the method herein extended. • Automatic differentiation (AD) is leveraged to obtain an exact value of the gradient of a sequential and iterative form-finding algorithm with marginal human intervention. The application of AD leads to significant computational performance gains, especially when solving large constrained form-finding problems. • A standalone, open-source design tool is developed which enables the formulation and the solution of constrained form-finding problems in plain and simple Python code. The design tool is readily usable on three different operating systems and on three distinct 3D modeling software environments.

Universal conductance fluctuations in a Bi1.5Sb0.5Te1.8Se1.2 topological insulator nano-scaled Hall bar structure

We present low-temperature magnetotransport measurements characterizing the promising quaternary Bi1.5Sb0.5Te1.8Se1.2 topological insulator material. The measurements performed on a nano-Hall bar grown by selective-area molecular beam epitaxy revealed pronounced universal conductance fluctuations. It is shown that these fluctuations originate from phase-coherent loops within the topologically protected surface states. Furthermore, the decay of the fluctuation amplitude with increasing temperatures suggests a quasi one-dimensional transport regime.

Geometry-Dependent Magnetoelectric and Exchange Bias Effects of the Nano L-T Mode Bar Structure Magnetoelectric Sensor.

The geometry-dependent magnetoelectric (ME) and exchange bias (EB) effects of the nano ME sensor were investigated. The sensor consisted of the Longitudinal-Transverse (L-T) mode bi-layer bar structure comprising the ferromagnetic (FM) and ferroelectric (FE) materials and the anti-ferromagnetic (AFM) material. The bi-layer ME coefficient was derived from constitutive equations and Newton's second law. The trade-off between peak ME coefficient and optimal thickness ratio was realized. At the frequency × structure length = 0.1 and 1200, minimum and maximum peak ME coefficients of the Terfenol-D/PZT bi-layer were around 1756 and 5617 mV/Oe·cm, respectively, with 0.43 and 0.19 optimal thickness ratios, respectively. Unfortunately, the bi-layer could not distinguish the opposite magnetic field directions due to their similar output voltages. PtMn and Cr2O3, the AFM, were introduced to produce the EB effect. The simulation results showed the exchange field starting at a minimum PtMn thickness of 6 nm. Nevertheless, Cr2O3 did not induce the exchange field due to its low anisotropy constant. The tri-layer ME sensor consisting of PZT (4.22 nm)/Terfenol-D (18 nm)/PtMn (6 nm) was demonstrated in sensing 2 Tbit/in2 magnetic bits. The average exchange field of 5100 Oe produced the output voltage difference of 12.96 mV, sufficient for most nanoscale magnetic sensing applications.

ЖЕСТКОСТЬ ЖЕЛЕЗОБЕТОННЫХ КОНСТРУКЦИЙ ПРИ ИЗГИБЕ С УЧЁТОМ ПОПЕРЕЧНОЙ И ПРОДОЛЬНОЙ СИЛ (ЧАСТЬ 1)

The paper provides a physical and computational model for determining the parameters of limit states of reinforced concrete structures under complex stress state such as bending with effect of axial and shear forces. The forward and backward transitions for determining the stiffness matrix coefficients of reinforced concrete bar structures with inclined and normal cracks have been constructed on the basis of the adopted cross-section discretization scheme and the duality theorem between force and deformation parameters by A.R. Rzhanitsyn. Determination of the stiffness of structures in the zone of inclined cracks was performed on the basis of the model of composite strips into which the zone with inclined cracks is divided. It is assumed a hypothesis about the character of deformation distribution in a complexly stressed reinforced concrete element with inclined cracks. For this model the effective shear modulus has been obtained. It 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. Using this model and the experimentally obtained value of the relative shear in the inclined crack, the dowel forces in the reinforcing bar crossed by the inclined crack were determined. The use of the obtained analytical dependences in the practice of designing reinforced concrete structures allows to clarify significantly the definition of displacements and width of opening of inclined and normal cracks, as well as to bring the calculation and physical model based on experimental data as close as possible.

Coupling Modal Analysis with the BEM for the Transient Response of Bar Structures Interacting with Three-Dimensional Soil Profiles

Coupling Modal Analysis with the BEM for the Transient Response of Bar Structures Interacting with Three-Dimensional Soil Profiles

Enhanced Fano resonance for high-sensitivity sensing based on bound states in the continuum

Although previously reported terahertz absorbers can achieve high-sensitivity refractive index sensing, the resonant peak is too broad, which leads to a low figure of merit (FOM). Transmissive sensors based on bound states in the continuum (BIC) can achieve high FOM, but they have some limitations in high sensitivity. Herein, we propose a periodic triple parallel metal bars structure to obtain high quality, a strong field, and multiple hot spots by the Friedrich–Wintgen BIC. Numerical results show the sensitivity and FOM can reach 1877 GHz/RIU and 665, respectively. Compared to the previously reported transmissive sensors based on BIC, the sensitivity has been greatly improved.

Parallel Twin Spindle Lathe with a Unique Turret Bar Structure Equipped with a High-Speed Gantry Loader Supports the Mass-Production Machining Field

Parallel Twin Spindle Lathe with a Unique Turret Bar Structure Equipped with a High-Speed Gantry Loader Supports the Mass-Production Machining Field

Orbit-superposition Dynamical Modeling of Barred Galaxies

Barred structures are important in understanding galaxy evolution, but they were not included explicitly in most dynamical models for nearby galaxies due to their complicated morphological and kinematic properties. We modify the triaxial orbit-superposition Schwarzschild implementation by van den Bosch et al. to include barred structures explicitly. The gravitational potential is a combination of a spherical dark matter halo and stellar mass; with the 3D stellar density distribution deprojected from the observed 2D image using a two-component deprojection method, including an axisymmetric disk and a triaxial barred bulge. We consider figure rotation of the galaxy with the bar pattern speed as a free parameter. We validate the method by applying it to a mock galaxy with integral field unit (IFU) data created from an N-body simulation with a boxy/peanut or X-shaped bar. Our model fits the observed 2D surface density and all kinematic features well. The bar pattern speed is recovered well with a relative uncertainty smaller than 10%. Based on the internal stellar orbit distribution of the model, we decompose the galaxy into an X-shaped bar, a boxy bulge, a vertically extended structure and a disk, and demonstrate that our model recovers these structures generally well, similar to the true structures in the N-body simulation. Our method provides a realistic way of modeling the bar structure explicitly for nearby barred galaxies with IFU observations.