Deflection Of Structure Research Articles

Comparative study on two-constant-amplitude input shapers to maneuver flexible satellite in small structural deflection

The satellite attitude maneuver using thrusters is studied in this paper. The satellite consists of a rigid main body and two symmetrical solar panels that are so large that their flexibility cannot be neglected. The finite element method is used to discretize the elastic motion of the solar panels. The solar panels are modeled as a set of rectangular plate elements and only out-of-plane displacement is taken into account. The satellite is controlled by a thruster in its main body, while there are no other control inputs on the solar panels. For the attitude maneuver, the roll, pitch and yaw torques generated by the on-off thruster are used and here can produce two different constant amplitudes. Then two types of fuel-efficient input shaping are formulated and applied to perform satellite attitude correction. The first type of input LHHL is preceded by the use of a small amplitude torque followed by a large amplitude one, while the sequence of torque applied to the second type of input HLLH is the opposite of the first input. The two types of inputs are applied separately to the same satellite. They managed to dampen the residual vibrations after reaching the desired attitude, but in achieving this condition the solar panels experienced considerable deflection during the transient response. Due to this, the effectiveness of the shaped inputs for maneuvering the satellites at small structural deflections of the solar panels during their transient responses is compared. The simulation results show that the use of the LHHL input shaper can minimize the structural deflection that occurs in the transient response during the satellite attitude maneuvering process.

Practical deflection analysis of tubular telecommunication towers subjected to a temperature gradient

The subject of the paper are tubular telecommunication towers, commonly used by mobile telephony operators to build relay stations placed at relatively short distances from each other. The advantage of this type of facilities is their simple structure and small surface area they occupy. It has been observed that during operation, as a result of solar radiation, the towers experience excessive deflection, resulting in disturbances in the operation of transmitting and receiving systems mounted on the towers. The issue of a reliable and relatively precise assessment of the phenomenon of uneven heating of the body surface due to sunlight is not a trivial issue. From a practical view-point, the greatest difficulty is to estimate the temperature to which the surface of a structure exposed to sunlight heats up. Even the attempts at numerical modeling of the phenomenon do not accurately reflect its essence. The paper presents a proposal of a simplified analytical computational model that allows for a practical and uncomplicated estimation of the thermal loads to which such structures are subjected as a result of insolation. The considerations were supplemented with examples from engineering practice, showing the differences in deflection of structures protected by zinc and paint coatings.

STRUCTURAL EVALUATION ON PEDESTRIAN BRIDGE CONSTRUCTED OF TRUSS STRUCTURE AND CASTELLATED BEAM

A pedestrian bridge is a structure linking a pedestrian or bike path over or around a major roadway, railway, or waterway. The truss bridge (TRB) and the bridge with a castellated beam (CBB) are the common models of the pedestrian bridge. Past studies have revealed the structural behavior of TRB and CBB, but the performances of both bridges have not yet been comparatively confirmed. This study examined the TRB and CBB structural performances to obtain the better bridge model due to applied loading. The research was started by establishing the bridge models and employing the load combinations. The analysis resulted in the internal forces and they were used to design the bridges. The design is referred to as the SNI-1729-2020. This research revealed that the TRB exhibited structural performances, i.e., deflection and internal force, better than those of the CBB. Nevertheless, due to the many steel members, the TRB presented a heavier bridge than the CBB.

Immune Escape Mechanisms of SARS-CoV-2 Delta and Omicron Variants against Two Monoclonal Antibodies That Received Emergency Use Authorization.

Multiple-site mutated SARS-CoV-2 Delta and Omicron variants may trigger immune escape against existing monoclonal antibodies. Here, molecular dynamics simulations combined with the interaction entropy method reveal the escape mechanism of Delta/Omicron variants to Bamlanivimab/Etesevimab. The result shows the significantly reduced binding affinity of the Omicron variant for both antibodies, due to the introduction of positively charged residues that greatly weaken their electrostatic interactions. Meanwhile, significant structural deflection induces fewer atomic contacts and an unstable binding mode. As for the Delta variant, the reduced binding affinity for Bamlanivimab is owing to the alienation of the receptor-binding domain to the main part of this antibody, and the binding mode of the Delta variant to Etesevimab is similar to that of the wild type, suggesting that Etesevimab could still be effective against the Delta variant. We hope this work will provide timely theoretical insights into developing antibodies to prevalent and possible future variants of SARS-CoV-2.

Analytical and numerical analysis of slamming induced vibrations on composite plates

Analytical solutions to study the elastic dynamic responses of a flat composite plate are developed based on the orthotropic thin plate theory and modal analysis. The spatial uniform slamming pressure is simplified to two types of time-dependent impact loads, i.e. an exponentially decaying impulse and a triangle impulses, which are characterized by the peak value and loading duration. To investigate the influence of the peak pressure and the loading duration on the plate structural behaviour, the dynamic responses of a simply supported flat plate under various impulses are calculated. Results show that the peak pressure affects only the amplitude of the response, while the loading periods affect both the phase and amplitude. Two numerical methods, i.e. a finite element dynamic analysis and a fully coupled hydroelastic analysis are applied to validate the analytical model and to investigate the hydroelastic effects. Comparisons of the analytical solution and hydroelastic analysis show that the slamming pressures on the flat composite plate fit the proposed triangle load model. With proper values on the peak pressure and loading period, the analytical model could provide good predictions on the structural deflections.

The application of basin modeling of oil and gas systems based on the capillary-gravity concept

ANNOTATION Oil and gas reservoirs exhibiting low reservoir properties often have significant deviations in structure of hydrocarbon reservoirs they contain, based on anticlinal theory of oil and gas accumulation. First, these deviations are related to sharp fluctuations found in water-oil and water-gas interfaces and failure to subordinate the shape of deposits to structural factor. When dealing with such objects, geologists often have to assign unreasonable structural deflections, various impermeable seals of tectonic or sedimentary origin whose presence is not always confirmed by seismic and drilling data. The reason for such difficulties is that anticlinal theory does not consider capillary forces counteracting hydrocarbon migration to be key to reservoir formation. Any oil and gas reservoir is a multiphase pore system with countless contacts, both between different fluids and in host pore space. As per molecular physics laws, the major role in oil and gas water distribution in such systems is controlled primarily by capillary properties of the environment such as capillary pressure at water-oil interface, interfacial tension magnitude, pore channel radius and wetting behavior of solid phase. Due to capillary forces, sharp fluctuations at water-oil interfaces and significant shifts of oil and gas reservoirs relative to vaults of anticlinal structures are observed

The X-structure/mechanism approach to beneficial nonlinear design in engineering

Nonlinearity can take an important and critical role in engineering systems, and thus cannot be simply ignored in structural design, dynamic response analysis, and parameter selection. A key issue is how to analyze and design potential nonlinearities introduced to or inherent in a system under study. This is a must-do task in many practical applications involving vibration control, energy harvesting, sensor systems, robotic technology, etc. This paper presents an up-to-date review on a cutting-edge method for nonlinearity manipulation and employment developed in recent several years, named as the X-structure/mechanism approach. The method is inspired from animal leg/limb skeletons, and can provide passive low-cost high-efficiency adjustable and beneficial nonlinear stiffness (high static & ultra-low dynamic), nonlinear damping (dependent on resonant frequency and/or relative vibration displacement), and nonlinear inertia (low static & high dynamic) individually or simultaneously. The X-structure/mechanism is a generic and basic structure/mechanism, representing a class of structures/mechanisms which can achieve beneficial geometric nonlinearity during structural deflection or mechanism motion, can be flexibly realized through commonly-used mechanical components, and have many different forms (with a basic unit taking a shape like X/K/Z/S/V, quadrilateral, diamond, polygon, etc.). Importantly, all variant structures/mechanisms may share similar geometric nonlinearities and thus exhibit similar nonlinear stiffness/damping properties in vibration. Moreover, they are generally flexible in design and easy to implement. This paper systematically reviews the research background, motivation, essential bio-inspired ideas, advantages of this novel method, the beneficial nonlinear properties in stiffness, damping, and inertia, and the potential applications, and ends with some remarks and conclusions.

Study on the Actuating Performance of an Embedded Macro Fiber Composite Considering the Shear Lag Effect.

Macro fiber composite (MFC), which are new ultrathin piezoelectric smart materials, are mostly applied in the fields of shell structure deformation and vibration control. Among others, the application of embedded MFCs in sandwich structures has received wide attention. Currently, its actuating force formula is primarily acquired based on the Bernoulli–Euler Model, which does not consider the shear lag effect and actuating force of MFC ends. To study the actuating performance of an MFC in a sandwich structure, according to its action characteristics, the MFC is divided into upper and lower actuating units without any interaction between to two under the condition of plane strain, and the shear lag effect is considered between the units and the top and bottom of the sandwich structure. The actuating force of the MFC ends is obtained by considering its influence on the bending deformation of the sandwich structure, which deduces the actuating force formula of the embedded MFC. In contrast to ANSYS piezoelectric simulation, the distribution of the MFC interior normal stress is similar to the result from ANSYS piezoelectric simulation, and there is a very small deviation between the MFC end and central normal stress and the result from ANSYS piezoelectric simulation. Taking the end deflection of the sandwich structure with an embedded MFC as an example, the actuating force simulation of the MFC considering the shear lag effect is compared with the ANSYS piezoelectric simulation and actuating force simulation based on the Bernoulli–Euler model. The result indicates that the actuating force simulation of the MFC considering the shear lag effect is closer to the ANSYS piezoelectric simulation, which proves the rationality and necessity of considering the shear lag effect and end actuating force of the MFC.

Pixel level vacuum packaging for single layer microbolometer detectors with on pixel lens

Abstract This paper presents a new approach for fabrication of single layer microbolometer detectors featuring pixel level vacuum packaging together with a lens on the pixel. The proposed lens structure can be used to increase the fill factor of the detector so that the pixel size can be decreased without decreasing the minimum feature size in the detector which is a problem in single layer microbolometers. The designs of the lens and the fabrication process of pixel level vacuum packaged microbolometer detector together with this lens are given in the framework of this study. The optical and mechanical simulations of the structure are performed. The radius of curvature of the lens is optimized to be 25 μm and it is shown that the condensing efficiency is 100% for 3 μm lens-detector distance. The deflection in the lens structure is found approximately as 0.8 nm in 1 atm environment pressure, showing that the proposed structure is durable. The proposed structure increases the fill factor to twice of the original value without decreasing the minimum feature size in the fabrication processes, resulting in the same amount of improvement in the performance of the detector. This approach can also be used to increase the yield and decrease the fabrication cost of single layer and also standard microbolometers with small pixel sizes, as it integrates the vacuum packaging in the fabrication steps.

Active Vibration Control of Piezoelectric Sandwich Plates.

This paper deals with the active vibration control of piezoelectric sandwich plate. The structure consists of a substrate plate layer sandwiched between two layers of piezoelectric sensor and actuator. Based on laminate theory and constitutive equation of piezoelectric material, the vibration active control dynamic equation of the sandwich structure is established by using hypothetical mode method and Hamilton principle. The Rayleigh-Ritz method is used to solve it. The form of hypothetical solution is used for approximate solution, which is simple and accurate. The method of this paper is verified by several examples. The parametric studies of the sandwich plate structures are carried out. The results show that applying different boundary conditions and piezoelectric patch positions to the structures have a great influence on the natural frequency. When the driving voltage increases, the deflection of the plate structures increase approximately linearly. The active vibration control studies are investigated as well. The results show that within a certain range, the larger the value of the speed feedback coefficient, the better the active control effect. The positions of the piezoelectric patches affect the effectiveness and cost of active control. When the piezoelectric plate is located at the fixed end, the effect and cost of active control are better than that at the midpoint and free end of the plate.

Modal analysis and damage localization in plate-type structures via TDD and PE methods based on the data of an integrated highspeed camera system

With the fast development of full-field vibration measurements by combining digital image correlation (DIC) technique with the integrated highspeed camera system, the structural characteristic deflection shapes (CDS’s) can be readily captured, which are sensitive for damage localization. Naturally, the mode shapes are preferred due to their higher signal to noise ratio. However, traditional modal analysis methods are inefficient in processing the large volumes of data that acquired by high-speed camera system for mode shape-based damage localization. Moreover, how to extract the damage features and enhance the damage localization results without the baseline-data of the intact state is another challenging issue. To address these problems, a novel damage localization method is proposed by enhancing the mode shape estimation and optimizing the damage feature extraction. Firstly, the dominant singular vector at each interested resonant frequency is individually evaluated as the mode shapes in the proposed time domain decomposition (TDD) method. Moreover, based on the extracted mode shapes, a pseudo-excitation (PE) method is proposed to reveal the damage locations without baseline-data by examining the perturbation of local dynamic equilibrium. To circumvent the effects of measurement noise on PE method, an adaptive denoising technique is proposed based on Gaussian smoothing. Furthermore, the local contiguity and spatial sparsity of the damage-caused features are harnessed by a hierarchical clustering to optimize the damage localization performance via tuning the scale parameter of Gaussian smoothing. Finally, numerical and experimental studies of crack damaged plates are conducted to validate the feasibility and effectiveness of the proposed mode shape estimation and damage localization methods. During the experiment, the full-field vibration measurements are acquired by using an integrated binocular highspeed camera system. In addition, a comparison study based on benchmark data is carried out to demonstrate the performance and reliability of the proposed damage localization method.

Investigation of the friction reduction and anisotropy of seta structure with large deflection cantilever beam model

Most insects can regulate friction with their seta structure when moving or crawling. To investigate the complicated friction behavior brought by the large deflection of seta structure, the nonlinear cantilever beam model with reactive support and friction force was established. The friction experiments of the seta structure were also conducted to verify the analytical results. The effect of loading conditions on the friction behavior of seta structure was discussed. It demonstrates that the friction force reacts nonlinearly with the applied normal displacement and exhibits obvious friction-reduction. The seta structure exhibits frictional anisotropy when sliding forward or backward which becomes more pronounced for small applied displacement and initial angle. Those findings provide valuable insights into the insects’ tribology mechanisms.

A Taguchi based iterative wing structural design for a low speed, hybrid UAV

An iterative structural design process for the conventional, composite wing of a low speed, hybrid Unmanned Aerial Vehicle (UAV) is presented in this paper. The relevant design goals are light weight, strength and stiffness derived from the customer specifications, conceptual design and STANAG-4671 airworthiness standards. To achieve the design goals, a modified Taguchi model was applied in conducting iterative Finite Element Analysis of the loads and stresses on the wing model, using ABAQUS CAE. In this analysis, the pitch of the rib and thicknesses of the spar and skin were applied as control factors in three levels, leading to an L9 orthogonal array. Mass, maximum deflection and Tsai-Hill failure index of the wing structure were measured as responses. The result shows that varying the skin thickness had the most impact on the wing mass, failure index and maximum deflection. The design goal of wing mass- less than 2.5kg, deflection of 10% and Tsai-Hill failure index value- less than 1 were achieved after 9 iterations.

Analysis and Design of R.C.C T-Beam Bridge Superstructure by using Different Codes & Load Combination for Performance Assessment

This study summarized comparative design and analysis of RCC T-Beam Bridge superstructure for Different Codes i.e., Indian Road Congress (IRC) codes and American Association of State Highway Transportation Officials (AASHTO) Specification Load Combinations for varying span length. The several codes are used to design the bridges. IRC 21-2000 used for designing bridges by working stress method (WSM), also IRC: 112-2011 introduced by Indian Road Congress for RCC and Pre- Stressed bridges by limit state method (LSM). Both the codes have different guidelines and procedure for design of bridges. This study based on IRC 112-2011 (LSM) and IRC: 6- 2017 is used for load considerations. In which this analysis depends on the analytical modelling by Finite Element Method (FEM) for in STAAD-Pro software and comparing the structural parameter Bending moment, Shear Force, Deflection and Area of Reinforcement for different girder span length 16M, 20M, 24M as per the IRC and AASHTO code. Class A & Class 70R consider from IRC 6-2017 and HS93 is the vehicular loading consider from AASHTO. Form the analysis understanding suitability design technique and the behavior of two-lane carriage way width of T- Beam bridge superstructure under different loading condition and by using different code and comparing the result, conclusions will be made that up to what extents similarities between both standards. Keywords: IRC: 21-2000, IRC: 112-2011, AASHTO (LRFD), STAAD-Pro.

Vibration attenuation of beam structure with intermediate support under harmonic excitation

The optimal position design of viscoelastic supports is studied for vibration attenuation of a beam under a harmonic excitation. By attaching the supports properly to the structure, the dynamic deflection of the steady-state response can be significantly suppressed. In this work, the derivative analysis of the dynamic deflection is first investigated with respect to the attachment location of a viscoelastic support. A closed-form formulation for the dynamic response sensitivity is gained readily by use of the discrete methodology. Then, a heuristic optimization algorithm is applied on the design sensitivity analysis to achieve the optimal solution of the supporting points to minimize the maximal steady-state displacement vibration of a beam structure. Finally, two typical examples are presented to demonstrate the validity and accuracy of the design sensitivity formulation developed. Numerical results show that the structural vibration deflections can be substantially reduced with optimization of the intermediate support positions.

Modeling of iced rotor dynamics via CFD/CSD coupling

Purpose The purpose of this paper is to advance the multiphysics analysis of helicopter rotors under icing conditions by coupling the iced rotor’s aerodynamics, analyzed by CFD, with the rotor’s structural characteristics, analyzed by CSD. Design/methodology/approach The current work introduces supercomputer-based computational approaches capable of assessing the impact of ice accretion on the aerodynamics, blade dynamics, vibrations and loading of a rotorcraft. The rigid and elastic motions of the blades are accounted for through a loose coupling of the flow solver to a multibody dynamics solver. The coupling framework allows for comprehensive aeroelastic simulations of iced rotors in hover and in forward flight. Findings The flow and structural modules were validated on a full helicopter configuration in forward flight using the ROBIN experimental model. The tip structural deflections were in very close agreement with the experimental measurements. Research limitations/implications The results of the CFD analyses are limited by the available experimental results they can be compared to. In dry air CFD, three-dimensional (3D) experiments occur first and CFD is then compared to them; in icing, the opposite is true: 3D experiments (if they are ever done, as they are very expensive) chase CFD and sometimes never occur. Practical implications This paper presents an outline of how CFD and computational stress dynamics (CSD) analyses can be linked and provides a toolbox for deeper investigation of the complex flows over helicopters operating under difficult in-flight icing conditions. Social implications More and more helicopters are designed to be able to operate in hostile environments such as rescuing and saving lives over the oceans or mountains, conditions under which icing encounters cannot be avoided. Originality/value A loosely coupled CFD/CSD framework that accounts for the rotor blades structural response to aerodynamic loading and ice accretion in hover and forward flight has been presented. This versatile and cost-effective framework provides a more accurate estimation of the helicopter rotor performance and its degradation due to icing encounters during the early design stages than traditional CFD tools.

Water entry dynamic analysis of lightweight sandwich plates with lattice core: A semi-analytical approach and comparative study

This is the third part of water entry hydro-elastic analysis of clamped sandwich plates with lattice core (CSPLC). In the first and second parts analysis, the engineering prediction model is built to estimate the dynamic responses of CSPLC. To discuss the responses of CSPLC in more detail, the objective of the present work is to investigate the hydro-elastic responses of rectangular, clamped sandwich plates with lattice core (CSPLC) subjected to water entry via combined a novel semi-analytical approach and multi-physical numerical simulation. In the theoretical approach, the hydro-elastic characteristics are quantified by coupling a hydrodynamic water entry model with a first shear displacement model of elasticity for CSPLC. The fluid-structure interaction (FSI) effects of water entry are taken into account by dividing the total impact pressure into the rigid water entry pressure and the interacting pressure. To capture the precise responses of CSPLC, both the global displacement field and the local displacement field are considered in the analytical model. The dynamic governing equations are derived from the energy variation principle and solved by employing the modal approach. Furthermore, the 3D FSI finite element simulation is carried out to get the detailed hydro-elastic characteristics of CSPLC. This engineering semi-analytical model is found to yield accurate results for dynamic responses and offers significant savings in computational cost compared to the FSI simulations. As a comparative study, for a same geometrical stiffened panel, the FSI impact pressure and structural deflection are also given respectively.

Effect of MWCNTs on microstructure and properties of WC-9Co gradient cemented carbides

WC-9Co-xMWCNTs (Multiwalled carbon nanotubes) gradient cemented carbides with cubic carbides free layer (CCFL) were prepared by powder metallurgy method. The effect of different MWCNTs content on the microstructure and mechanical properties of WC-9Co gradient cemented carbides have been studied. The microstructure and phase composition of WC-9Co-xMWCNTs composites were characterized by means of optical microscope, scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, the hardness, fracture toughness, bending strength and friction coefficients were tested by Vickers indenter, universal testing machine and tribometer. The results showed that the MWCNTs could promote the growth of CCFL. The minimum grain size of WC was obtained in the WC-9Co-0.08 wt% MWCNTs composites and the sample possessed the highest hardness and bending strength, the lowest friction coefficient and the best wear resistance at the same time. The fracture toughness and relative density increased steadily together with the addition of MWCNTs. Besides, the mechanism of MWCNTs enhancing the alloys include bridge connection, crack deflection, pull-out and strengthening effect of the network structure.

Experimental investigation into the response of GFRP S-shaped foldcore sandwich panels to impulsive loading

S-shaped foldcore sandwich structures have potential applications as protection structures under impact loading. In this paper, the S-shaped glass fiber composite foldcore sandwich structure was fabricated by hot pressing method and its impact resistance against the aluminum foam projectiles was studied using a one-stage gas gun.The three-dimensional digital image correlation system was used to measure the dynamic deformation of the sandwich panels. During the experiments, the dynamic response of the structure was studied when the projectile impacted the node and base locations of the sandwich structure, where the node location refers to the top platform of the core and the base location refers to the middle position between the nodes. In addition, the influence of the face sheet thickness and core thickness on the impact resistance of the sandwich structure was also investigated. The results show that the sandwich structure is dominated by tensile fracture of the face sheet, crush fracture or extrusion fracture of the core, and debonding failure between the face sheet and the core. The impact resistance of the node location is better than that of the base location for the same configuration. Moreover, the maximum deflection of the rear sheet increases linearly with the increase of the impact loading when impacting the base location. And increasing the face sheet thickness or core thickness can better reduce the structure deflection and improve the impact resistance of the structure.

Aeroelastic Analysis of a Single Element Composite Wing in Ground Effect Using Fluid–Structure Interaction

Abstract This work focuses on an advanced coupling of computational fluid dynamics (CFD) and structural finite element analysis (FEA) on the aeroelastic behavior of a single element inverted composite wing with the novelty of including the ground effect. The front wing of the formula one (F1) car can become flexible under the fluid loading due to elastic characteristics of composite materials, resulting in changing the flow field and eventually altering overall aerodynamics. The purpose of this study is to setup an accurate fluid–structure interaction (FSI) modeling framework and to assess the influence of elastic behavior of the wing in ground effect on the aerodynamic and structural performance. Different turbulence models are studied to capture better the changes of the flow field and variation of ride heights are considered to investigate the influence of ground effect on aerodynamic phenomena. A steady-state two-way coupling method is exploited to run the FSI numerical simulations using ansys, which enables simultaneous calculation by coupling CFD with FEA. The effect of various composite structures on the wing performance is extensively studied concerning structure configuration, ply orientation, and core materials. The numerical results generally represent good agreement with the experimental data, however, discrepancy, especially in the aerodynamic force, is presented. This may be a consequence of a less effective angle of attack due to the wing deflection and deterioration of vortex-induced effect. For the structural analysis, the woven structure gives rise to more stable structural deflection than the unidirectional structure despite the associated weight penalty.