Elastic Member Research Articles

Hybrid tools for improved removal and surface finish of metals and non-metals

Increasing productivity and surface quality in manufacturing is inevitable for the efficient use of resources. Precision smooth surfaces are generally achieved through sequential milling, grinding, fine-grinding, and polishing. This research aims to increase productivity through a shorter process chain. Hybrid tooling technology is presented where an elastic fine grinding tool is integrated with a conventional milling cutter or a grinding tool, in order to produce smooth surfaces on metal and non-metals. A hybrid milling cutter with an elastic tool could produce a low-waviness surface as compared to that of a milled-only surface. Surface roughness could be reduced by almost 50% using the hybrid milling tool on a steel workpiece. A monocrystalline silicon surface was machined with a hybrid grinding tool. Surface roughness of Ra ~ 100 nm could be obtained for hybrid tool in comparison to Ra ~ 200 nm with grinding only tool. The surface machined with a hybrid tool showed ductile mode cutting streaks, whereas, the ground surface was observed to be completely in brittle mode. Additionally, the hybrid tools also showed reduced machining vibrations due to the damping effect induced by the elastic tool member.

Emergent elasticity relations for networks of bars with sticky magnetic ends

Magneto-elastic materials have unique mechanical properties arising from the coupling between the magnetic and elastic components, which can be used in many engineering applications, such as waveguide systems, impact mitigation, and soft robotics. Traditional designs of magneto-elastic materials embed magnets or magnetic particles in a monolithic body. Under extreme conditions, the elastic matrices are prone to permanent damage and loss of functionality. An alternative framework was previously proposed by the authors in which 2D magneto-elastic networks were created through vibration-driven self-assembly from a dilute system of elastic bars with sticky magnetic ends. While these networks were demonstrated to fail gracefully under extreme loading and re-assemble under random excitation, how their emergent elasticity depends on magnet and elastic member characteristics remains to be fully understood. In this paper, to calculate the 2D bulk modulus of a given magneto-elastic network, particle dynamics simulations are first performed. An analytical framework is then developed to predict the bulk modulus of derived networks with varying design parameters, such as bar length and magnetic strength, based on the Cauchy–Born approximation. Through dimensional analysis, we demonstrate that 2D bulk modulus is linearly proportional to a composite variable that combines magnet strength, elastic member length, and wall thickness of the magnet holder, as evidenced by the collapse of 120 systems onto a single line. The numerical and analytical investigation of the bulk modulus of this architected magneto-elastic material demonstrates the broad tunability of its emergent elasticity, thereby enabling a myriad of promising applications of these systems.

Investigation of high-energy impact system using a physical model

The aim of the experimental research is to validate the theoretical findings obtained from a mathematical model of a two-mass impact system. The research object is a physical model of a two-mass impact system, designed to prevent the transfer of the reactive component to the tool carrier. The model includes a housing, inertial mass, elastic member and impact part. In the operating position, a compressed elastic member is placed between the inertial mass and the impact part, held together by dogs. The height at which the impact part detaches from the inertial mass is determined by the position of the clamp, which separates the moving impact part and inertial mass during free fall. The study involved the fundamental principles of similarity theory, planning theory and data processing. The height at which the impact part detaches from the inertial mass and the impact part is taken as an independent factor, while the energy of a single impact serves as the response function, determined by the diameter of the cone impression delivered by the impact part onto a wooden base. Based on the analysis of physical laws, similarity criteria for the impact mechanism were established, along with dependent and independent indicators, and transfer equations from real parameters to model parameters were derived. The research findings indicate that the total area of air holes should be at least half of the cross-sectional area of the housing for a physical model. The relationship between the diameter of the cone impression on the wooden base and the impact energy was determined. The adequacy of the mathematical model describing the processes in the impact device was confirmed, with a maximum discrepancy of 18% between the results of mathematical and physical modelling of the operating process for the impact mechanism characterised by an increased energy of a single impact. Therefore, the research results validate the results obtained from the mathematical model of the impact mechanism. Further studies should focus on refining the physical model to record the rebound height of the inertial mass as a function of the parameters of the impact mechanism.

A Rubber Protective Barrier for Oral Protection Against Accidental Swallowing

Background: During dental treatment, it is often necessary to isolate the teeth from the oral environment with a rubber barrier so that saliva does not flow into the doctor's operating area, and to prevent the tongue from being scratched by dental instruments during treatment, and to prevent the inhalation or swallowing of foreign bodies due to human error. Objective: To provide an oral anti-swallowing rubber protection barrier for medical procedures without the need for wetting the tooth surface. Method: The oral anti-swallowing rubber protective barrier includes a pharyngeal barrier body, a tongue sleeve body, a bracket, a first elastic fixing member and a second elastic fixing member. With this new oral anti-swallowing rubber protective barrier, on the one hand, the support frame is used to support the pharyngeal barrier body to form a protective barrier for the pharyngeal passage to prevent inhalation or swallowing of foreign bodies; on the other hand, the tongue sleeve body is used to cover the tongue to prevent dental instruments from accidentally injuring the tongue. The use of the telescopic and spring-loaded connecting bar ensures that the curved bar is held against the palate while the height is adjusted according to the size of the patient's opening, extending the range of application; the use of the elastic fixing member stuck to the posterior area of the molar not only holds the rubber protective barrier in place but also assists in holding the mouth open. Results: The use of the rubber barrier in oral treatment is clinically effective and can significantly improve patient comfort and reduce treatment complications. Conclusion: An oral anti-swallowing rubber shield is provided to solve the problem of inadvertent swallowing of foreign objects such as instruments during medical operations without wetting the tooth surface.

Thermodynamic Aspects of Viscoelastic Materials’ Linear and Nonlinear Behavior

Materials that exhibit neither purely elastic nor purely viscous behavior, are dealt by viscoelasticity theory. Therein, each material is represented by a viscoelastic model. In this paper a viscoelastic exploration is dealt, focused to the quantification of energy acting during the load – response processes of viscoelastic material. In line with thermodynamic principles, nonnegativity of dissipated energy is supposed within the process, whereby the only reason of energy dissipation is the dashpot, i.e. the viscous member of viscoelastic matter present in the model. The assumption of potential energy storing by and only by the elastic member is taken into account at the same time. Each time we refer a model, the material matching with the model is meant. This work is a continuation, the enhancement of previous research of authors where particular investigations in this field were focused.

Power performance enhancement of vortex-induced vibration wind turbines using a semi-active control approach

ABSTRACT Bladeless wind turbines based on vortex-induced vibration usually consist of a cylindrical body mounted on a flexible support. An inherent feature of this kind of turbines is that the power generation is considerable only in a narrow wind speed band, when the frequency of shedding vortices is close to the structural natural frequency. The present study proposes a novel semi-active approach for tuning the turbine response to widen the effective power generation region. Based on numerical modeling of aeroelasticity interaction phenomenon, a parametric analysis is done and the effective parameters on the turbine performance are highlighted. The proposed tuning technique then works to maintain the effective parameters at the optimum value from the power generation point of view. To realize this, a supporting mechanism is suggested that can change the elastic member length and consequently structural natural frequency. However, to avoid phenomenon attenuation due to power extraction process, a second level of tuning the structure damping ratio is added. Results of numeric simulations showed that, compared to previous work, the proposed approach has considerably broadened the effective wind speed range. The conversion efficiency is greater than or equal 15% over a wind speed range of 3.3–6 m/s.

Structural properties of superior design solutions of steel buildings associated with BRBs

A design algorithm is proposed for rational seismic design solutions of steel buildings associated with buckling restrained braces (BRB). The strengths and locations of BRBs in addition to the section sizes of structural members are considered as discrete design variables. The steel volume including BRBs is minimized as an objective function under various practical design constraints. A seven-story office building is examined for application in two different types of structural systems, i.e. one mainly consisting of lateral frames and the other with limited utilization of lateral frames typically in perimeter separately from gravity frames. The derived solutions, defined as superior design solutions (SDSs), satisfy serviceability and limit-state constraints, taking into consideration the seismic energy dissipation effect of BRBs using the calculation of resistance and limit-state method. Their rationale is validated with response history analysis. Furthermore, the influences in SDSs by the seismic demand levels and elastic member constraint are investigated. The structural characteristics of SDSs associated with BRBs are objectively evaluated using the proposed design algorithm.

New pile foundation structures for swelling clay soils

The information on the basics of designing pile foundations on swelling clay soils is presented and analyzed. New designs of conical piles and those with a variable cross-section, in which the soil mass swelling is accompanied by the effect of pile pinching, have been developed. Moreover, new pile foundation structures with protective shells involving a calcium elastic rolling member and some rubbing elements like low-friction plastic and metal braces are proposed.

Flutter instability in an internal flow energy harvester

Abstract

Structural optimization of ultra-thin leaf spring for weakening elastic hysteresis effect and enhancing fatigue life

Small-size ultra-thin leaf spring as the key elastic sensitive member is widely used in the precision electro-mechanical products. However, owing to the unavoidable elastic hysteresis effect of leaf spring, it always suffers from a significant graceful degradation of designed deflection and subsequently fatigue fracture under the condition of cyclic loading. In order to weaken the elastic hysteresis effect, structural optimization according to sequential quadratic programming method for reducing stress concentration of leaf spring was first carried out by simulations, and then the identification of elastic hysteresis effect for optimal leaf spring was carried out by experiments. Compared with the original design, the maximum deflection deviation for single cycle is decreased from 0.026 mm to 0.002 mm. For the sake of predicting the fatigue life of optimal structure of leaf spring being on the service, a loading block with multistage variable stress amplitudes was experimentally recorded and fitted by normal probability density function, and then a statistical probability method by mathematical analysis was proposed. Compared with the original design, the predicted fatigue life of leaf spring is 736000 loading blocks, which is ten times than that before structural optimization. A structural optimization for reducing stress concentration can significantly weaken the elastic hysteresis effect and enhance the fatigue life, which is benefit for the elastic stability of leaf spring during engineering application.

Visco-elastic response of combined footings on earth beds with geocell-geomembrane inclusions

Visco-elastic response of combined footings lying on earth beds with geocell-geomembrane inclusions has been studied using a simple lumped parameter model. The earth bed has been simulated with the help of series of Burgers model, i.e., Maxwell and Kelvin models coupled in series, connected by an elastic member. Overlying the soft visco-elastic bed, there exists a geocell layer with soil infill idealized by a beam having finite flexural rigidity. On top of this, granular mat has been laid and idealized as Pasternak shear layer underlying the combined footing considered as a beam. The footing has been subjected to equi-spaced columnar loads. The weight of granular mat has been considered on top of reinforcing beam. A lumped-parameter model has been used for idealizing the physical problem. Thereafter the governing differential equations have been developed and solved numerically with the help of suitable boundary conditions. Validation of the proposed model has been done before taking up the detailed study to exhibit the influence of various model parameters on the response of footing-soil system. Magnitude of columnar loads, location of geocell layer, relative elastic and viscous coefficients of Burgers model, and tension in elastic membrane have been found to have significant impact on deflection and bending moment in both footing and the geocell. All the analyses and results have been presented in terms of non-dimensional parameters. Many parameters combining together forms a number (non-dimensional) and the same number can be used in designing a typical case of combined footings using the charts developed.

Astronomical survey camera shutter locking mechanism design, analysis, and testing

During the launch phase of a survey camera, its shutter will experience a harsh dynamic environment. We propose an elastic compression scheme to prevent the shutter blade from hitting the surrounding structure. The elastic member has a maximum stress at each stage of locking. In order to make this stress as small as possible, we optimize the thickness of the elastic member from 1070 to 666 MPa, which meets the safety factor requirement. We perform finite element simulations and experiments on the locking mechanism, and the results show that the motor torque curves obtained from theoretical calculations, simulation analysis, and tests coincide well. The maximum locking torque of the locking mechanism obtained by theoretical calculations, simulation analysis, and experiments also coincide well, and all three of them are within the design target of about 25 N m, which meets the requirements of shutter locking torque greater than 20 N m. Our proposed elastic compression scheme effectively solves the problem of blade fixation during the shutter launch phase.

Гармонический анализ упругого колосниково-карточного элемента динамически активной просеивающей поверхности вибрационного грохота

Поверхностные вибрирующие сита должны обеспечивать довольно сложное движение просеивания частиц сыпучего материала. Для обеспечения необходимых условий для работы просеивающих поверхностей предлагается использовать новую конструкцию динамической упругой поверхностно-активной просеивающей решетки самоочищающейся решетки - карты. Композитные упругие элементы решетки-карты без предварительной деформации, установленные в коробке вибрационного грохота. Консольные горизонтальные полки решетки элементов карты под воздействием виброустойчивых данных совершают сложные вибрационно-пространственные движения. Поскольку пласт URCC апертуры «активен» консольными горизонтальными полками, возникает необходимость в изучении их траекторий движения с учетом конструктивных параметров сита и вибрационной камеры вынужденных колебаний. Цель исследования: метод определения собственных частот и форм мод упругого (резинового) элемента, образующего тканевый ситовый вибратор, который достигнет наибольшей амплитуды колебаний при работе вибрационного грохота. Задача исследования: разработать модель решетчатого элемента карточного сита URCC для гармонического анализа методом конечных элементов. Поскольку элемент решетки имеет сложную форму, предлагается решение с использованием метода конечных элементов. Рассматривается решение задачи гармонического анализа движения составного элемента колосниково-карточного сита вибрационного грохота с помощью метода конечных элементов грохота. Для существующего элемента определено, что при диапазоне варьирования модуля упругости собственная частота горизонтальных колебаний изменилась в пределах 17…34 Гц, а вертикальных – 37…72 Гц.

Multi-Objective Design Optimization of a Shape Memory Alloy Flexural Actuator

This paper presents a computational model and design optimization strategy for shape memory alloy (SMA) flexural actuators. These actuators consist of curved SMA wires embedded within elastic structures; one potential application is positioning microcatheters inside blood vessels during clinical treatments. Each SMA wire is shape-set to an initial curvature and inserted along the neutral axis of a straight elastic member (cast polydimethylsiloxane, PDMS). The elastic structure preloads the SMA, reducing the equilibrium curvature of the composite actuator. Temperature-induced phase transformations in the SMA are achieved via Joule heating, enabling strain recovery and increased bending (increased curvature) in the actuator. Actuator behavior is modeled using the homogenized energy framework, and the effects of two critical design parameters (initial SMA curvature and flexural rigidity of the elastic sleeve) on activation curvature are investigated. Finally, a multi-objective genetic algorithm is utilized to optimize actuator performance and generate a Pareto frontier, which is subsequently experimentally validated.

Numerical analysis and cable activation in hybrid bending-active structures with multiple cables

Recent applications of bending-active structural principles have facilitated the development of unique, material and energy efficient, free-form lightweight systems. The systems are realized through the application of an interdisciplinary design, computational fabrication, exclusive assembly techniques and construction. These aspects are directly linked to the form-finding process through the bending-active members’ activation. A number of design and construction parameters necessary for the morphological objectives succession, as well as the consideration of the deformation behavior of the systems, have raised the challenge of associating generative configuration parameters with their respective post-formed load-deformation behavior. Along these lines, the present paper examines the design of a planar hybrid bending-active system that consists of a single elastic member interconnected with cable elements at equal length intervals of 1 m. The three-stage development of the system consists of its assembly in planar arrangement (i) and erection (ii) following an initial uniform cables’ length reduction, in connection with the appropriate kinematic constraints of the ground supports. In a consecutive post-tensioning stage (iii), the supports are fixed and the cables’ length is further reduced to provide higher system prestress conditions and a differentiated span to height ratio. In a preliminary stage, the system load-deformation behavior under uniformly distributed vertical load is investigated at the end of its erection (ii&Q) and post-tensioning stage (iii&Q). The analysis examines seven system configurations with increasing number of cable segments, from two to eight. For the eight cable segments system, fourteen alternative post-tensioned configurations, emerging from individual, or group, cable activation, are investigated in their load-deformation behavior. The analysis provides insights into the configurability of the hybrid systems and their load-deformation behavior. In conclusion, the paper discusses design aspects that contribute towards structurally efficient configurations of the hybrid system series.

Derivation and analysis of methods for calculation of axially loaded steel compression members based on different building codes

The article presents the physical significance of the study of axially loaded steel compression members and the origin of accepted analytical models, which are the basis for the methods of their calculation in current building codes of CIS and European countries. An approximate solution of the problem of eccentrically loaded elastic compression member is given and analytical relationships for determining the buckling coefficient as a result of solving an analytical problem and as a result of applying building codes are obtained. Based on the results from solving the structural analysis problem, a solution for axially loaded compression member buckling coefficient, which is the ratio of such stress value from axial compression to the yield stress of steel at which the outermost fibers of the cross section yield, is given. When obtaining the solution of the buckling coefficient for axial compression, it is justified that the clarity of obtaining a solution is achieved by introducing the number Pi in place of the numerical values. It is indicated that the reason for shifting relative eccentricity from the ideal value of 0.2 is the impossibility of buckling at small slenderness ratios. It is justified that the calculation methods described in Eurocode and the building code of Russia (SNiP), despite the difference in the definition of nominal slenderness ratio, have common physical significance and their difference is only in approaches to the definition of random eccentricity. The building code approaches to calculating relative eccentricity included in buckling coefficient are stated and analyzed and their physical significance is described. The significance of relative eccentricity which is included in European and Russian codes is unfolded and the relationship between relative eccentricity and imperfections in the shape and type of cross-section is indicated. The significance of the imperfection factor in accordance with EN 1993-1-1: 2005 which depends on initial imperfections, the shape of the cross-section and the technology of member manufacture is explained and the application of approximating linear function, which reflects the technological factor of precision of manufacturing and inevitably arising imperfections, is justified. The significance of the coefficients of imperfection α and β, which are included in the Russian building code for steel structures, is unfolded.

Shear and bending performance of new type enhanced lattice truss structures

In this work, the new type enhanced lattice (defined as hourglass) truss structures with the improved resistance of their core members and attached face sheets have been fabricated by an innovative interlocking method. The shear and bending properties of the produced sandwich structures characterized by three different relative densities have been investigated using various analytical methods and the obtained results were in good agreement with the experimental data. The truss failure under shear loading was dominated by the inelastic buckling of the truss members, while the four possible analytical models describing the bending properties and failure mechanism of the hourglass truss beams included elastic face sheet buckling, face sheet yielding, elastic core member buckling, and core member yielding were studied. The bending specimens, which were designed by constructing failure mechanism maps, were used to examine the yielding behavior of the truss core members as well as the elastic buckling and yielding of the face sheet members. The obtained results revealed that the specific shear strengths and bending failure loads of the studied hourglass truss structures were superior to those of pyramidal truss structures, and that the former could be considered promising candidates for manufacturing lightweight structures with high specific strength.

Three-dimensional finite element analysis for soil slopes stabilisation using piles

ABSTRACTThis paper presents the analytical methods of slope-stabilising piles using the three-dimensional (3-D) finite element (FE) analysis with the strength reduction method (SRM). This 3-D FE model is employed to overcome the limitations observed in two-dimensional (2-D) FE analysis. The solutions obtained from 3-D FE analyses are verified to be less conservative in this paper. The 3-D analysis is considered to be of particular importance to pile-slope problems. The soil that flows between piles cannot be taken account properly in the 2-D FE analysis. The method adopted in this paper can avoid the assumption of soil movement and the pressure distribution along the piles subjected to soil movement. The numerical analysis employs the Mohr–Coulomb failure criterion with the strength reduction technique for soil and an elastic member for piles. The spacing effect of the pile is considered in the 3-D model, the S/D (S: centre to centre, D: diameter of pile) ratio, equal to 4.0, is found to be equivalent to the single pile stabilisation. The middle portion of the slope is identified as the optimal location to place the piles. The proper length of the pile, which can be used to stabilise the slope, is also examined using 3-D FE analyses. It is concluded that L/H greater or equal 0.70 is recommended (L: pile length, H: slope height). The numerical analyses are conducted based on a coupled analysis, which simultaneously considers both the slope stability and the pile response. The failure mechanisms of the pile-slope system subjected to the pile locations, pile head conditions and pile length are each discussed. The contact pressure, shear force and moment along the piles are presented to illustrate the pile stabilising mechanism herein.

Geometrical optimization of strain gauge force transducer using GRA method

This paper presents the geometrical optimization of strain gauge ‘Double Ended Shear Beam’ (DESB) force transducer. Multi objective optimization of elastic member of transducer is carried out by maximum stress sustaining capacity of strain gauge by minimizing volume. Optimal design utilize the Finite Element Method (FEM) software. Combined Taguchi and Grey Relational Analysis (GRA) is used for optimization. Taguchi method has been applied to construct an orthogonal array based on selected parameters. Next, multi-objective optimization is performed. As Taguchi method is unable to perform multi-objective optimization combined approach of Taguchi and Grey Relational Analysis (GRA) is carried out. This combined approach gives optimum parametric combination based on highest Grey Relation Coefficient (GRC). Analysis of Variance (ANOVA) is statistical technique is used to investigate contribution of each process parameters on the performance characteristic.

ASEISMATIC PERFORMANCE OF HYBRID STEEL COLUMN CONSISTS OF HIGH STRENGTH STEEL FLANGE AND CONVENTIONAL STEEL WEB

Recently in Japan, the pulse type earthquakes that cause large displacement responses have been more noticeable. Some of them are predicted to become much larger than the magnitude level used in the current design, so it is promoted to set new seismic wave levels for design and to study about new design methods. To reduce damage of buildings against huge earthquakes, it has been considered to increase the elastic limit deformation using high strength steels in columns and girders. In this study, on the contrary, we propose the frames using conventional girders and hybrid H-section columns that consist of flange manufactured from high strength steel and web made with conventional strength steel. In order to apply the hybrid H-section columns to a building, the following items should be clarified; (1) method of evaluating full-plastic strength, (2) understanding the behavior of the hybrid H-section alone, (3) understanding the behavior of the hybrid H-section column in a frame. To investigate these items, we fabricated several specimens and conducted stub column tests, bending and shear tests, and cruciform tests. The experimental findings are complemented by a finite element simulation study. In Chapter 2, at first, we derive a full-plastic moment of hybrid H-section column under combined stress, including axial force, shear force and bending moment. Secondly we assumed the application limit of the formula. The following chapter describes that the stub-column tests and bending and shear tests were conducted to comprehend the elasto-plastic behavior caused by local buckling. Chapter 5 and 6 describes that we conducted the beam-to-column subassemblages test to verify the effects on high strength steel flange caused by axial force and plastic deformation of beam-column connection. By the series of experiments and analyses, we obtained the following results; (1) Full-plastic moment of hybrid H-section column and the application limit are shown in chapter 2. (2) Within the limit of application, platicizing of conventional strength steel web has little effects on high strength steel flange, therefore the hybrid H-section column can be regarded as elastic member until it reaches full-plastic strength. Further, if the width-thickness ratio satisfies the FA rank, the axial-yield of the web in an early stage has little effects on flange local buckling strength and plastic deformation capacity. (3) The extension of axial tensile strain, which is one of the factors of the stress degradation, can be reduced by column axial force. “Break by tensile strain” of the hybrid H-section column can be avoided unless the column axial force is neutralized by the fluctuating axial force in the case of earthquakes. (4) The relationship between column-to-beam strength ratio and the deformability of a cruciform frame is revealed by finite-element analyses in chapter 6. We proposed the design method of the hybrid H-section column that consists of flange made with high strength steels and web made with conventional strength steels. We expect the hybrid H-section column to be utilized as reasonable aseismatic column member for reducing the damage against huge earthquakes.