Showing papers on "Deflection (engineering) published in 2020"

Kinetostatic and Dynamic Modeling of Flexure-Based Compliant Mechanisms: A Survey

Abstract: Flexure-based compliant mechanisms are becoming increasingly promising in precision engineering, robotics, and other applications due to the excellent advantages of no friction, no backlash, no wear, and minimal requirement of assembly. Because compliant mechanisms have inherent coupling of kinematic-mechanical behaviors with large deflections and/or complex serial-parallel configurations, the kinetostatic and dynamic analyses are challenging in comparison to their rigid-body counterparts. To address these challenges, a variety of techniques have been reported in a growing stream of publications. This paper surveys and compares the conceptual ideas, key advances, and applicable scopes, and open problems of the state-of-the-art kinetostatic and dynamic modeling methods for compliant mechanisms in terms of small and large deflections. Future challenges are discussed and new opportunities for extended study are highlighted as well. The presented review provides a guide on how to select suitable modeling approaches for those engaged in the field of compliant mechanisms.

Frequency characteristics of FG-GPLRC viscoelastic thick annular plate with the aid of GDQM

Abstract: This is the first research on the free vibration analysis of functionally graded graphene platelets reinforced composite (FG-GPLRC) viscoelastic annular plate resting on the visco-Pasternak foundation and subjected to the nonlinear temperature gradient and mechanical loading within the framework of higher-order shear deformation theory (HSDT). Hamilton's principle is employed to establish governing equations within the framework of HSDT. In this paper, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Generalized differential quadrature method (GDQM) is applied to obtain a numerical solution. Numerical results are compared with those published in the literature to examine the accuracy and validity of the applied approach. A comprehensive parametric study is accomplished to reveal the influence of the stiffness of the substrate, patterns of temperature rise, axial load, damper and viscoelasticity coefficient, weight fraction and distribution patterns of GPLs and geometric dimensions of GPLs on the frequency response of the structure. The results revealed that applying sinusoidal temperature rise and locating more square-shaped GPLs in the vicinity of the top and bottom surfaces have important effect of the highest natural frequency and buckling load of the FG-GPLRC viscoelastic structure.

Optimizing ANN models with PSO for predicting short building seismic response

Abstract: The present study aimed to optimize the artificial neural network (ANN) with one of the well-established optimization algorithms called particle swarm optimization (PSO) for the problem of ground response approximation in short structures. Various studies showed that ANN-based solutions are a reliable method for complex engineering problems. Predicting the ground surface respond to seismic loading is one of the engineering problems that still has not received any ANN solution. Therefore, this paper aimed to assess the application of hybrid PSO-based ANN models to the calculation of horizontal deflection of columns in short building after being subjected to a significant seismic loading (e.g., The Chi-Chi earthquake used as one of the input databases). To prepare both of the training and testing datasets, for the ANN and PSO-ANN network models, a series of finite element (FE) modeling were performed. The used FEM simulation database consists of 8324 training datasets and 2081 testing datasets that is equal to 80% and 20% of the whole database, respectively. The input includes Chi-Chi earthquake dynamic time (s), friction angle (φ), dilation angle (ψ), unit weight (γ), soil elastic modulus (E), Poisson’s ratio (v), structure axial stiffness (EA), and bending stiffness (EI) where the output was taken horizontal deflection of the columns at their highest level (Ux). The result indicates higher reliability of the PSO-ANN model in estimating the ground response and horizontal deflection of structural columns in short structures after being subjected to earthquake loading.

Weak deflection angle of extended uncertainty principle black holes

Abstract: We discuss the effects of quantum fluctuations spewed by a black hole on its deflection angle. The Gauss-Bonnet theorem (GBT) is exploited with quantum corrections through the extended uncertainty principle (EUP), and the corresponding deflection angle is obtained. Moreover, we have attempted to broaden the scope of our work by subsuming the effects of plasma medium on the deflection angle. To demonstrate the degree of difference, the acquired results are compared with the prevailing findings.

ABAQUS modeling for post-tensioned reinforced concrete beams

Abstract: Finite element analysis (FEA) using ABAQUS software was performed to investigate the behavior of post-tensioned concrete beams. This study is an attempt to examine the concrete damage behavior using a concrete damaged plasticity (CDP) model in ABAQUS, as well as the effect of an external post-tensioning (EPT) steel rod system. Concrete is a well-used material in many architectural and civil structures, with behavior exhibiting different characteristics in compression and tension; it also shows an inelastic-nonlinear behavior. These properties of concrete make modeling or simulation of the material difficult. In reinforced concrete, there is particular difficulty with respect to the bond-slip relationship between concrete and steel. However, in this paper the finite element analysis for concrete beams through ABAQUS simulation has been carried out with some assumptions, including perfect bond of steel and concrete and the CDP model for concrete property. In comparing analysis and experimental results, the simulated tensile deformations are similar to actual crack patterns in tests and the analytical responses such as strength, deflection, and stress of external rods are in good agreement with the measured responses.

Investigating the behaviour of hybrid fibre-reinforced reactive powder concrete beams after exposure to elevated temperatures

Abstract: This study investigated the structural behaviour of reinforced reactive powder concrete (RPC) beams under service load and fire exposure. The beams were composed of hybrid fibres (50% polypropylene fibres and 50% steel fibres) at different volume fractions relative to nonfibrous-reinforced RPC beams. The bottom and both sides of the beams which were simply supported and loaded with two-point loads were exposed to a controlled fire for 120 min in accordance with ASTM E 119 standard time–temperature curve. The midspan deflection was recorded every 5 min. The experiment also included loading tests on fire-damaged beams after cooling. The nonfibrous-reinforced RPC beams failed during the fire test after 38 min because of the spalling of the reinforcement cover which directly exposed the reinforcing steel to elevated temperatures. By contrast, the beams with hybrid fibres could resist failure during the entire test period. The rate of increase in deflection during fire exposure declined with an increase in hybrid fibre content. Increases in fibre volume fraction from 0.25% to 0.75% and 1.25% decreased the midspan deflection of the reinforced RPC beams by 33% and 36%, respectively. Adding hybrid fibres could considerably improve the residual stiffness of fire-damaged beams.

Tunable Metasurface Inverse Design for 80% Switching Efficiencies and 144° Angular Deflection

Abstract: Tunable metasurfaces have demonstrated the potential for dramatically enhanced functionality for applications including sensing, ranging and imaging. Liquid crystals (LCs) have fast switching speed...

Numerical Study of Frequency and Deflection Responses of Natural Fiber (Luffa) Reinforced Polymer Composite and Experimental Validation

Abstract: The natural fiber (Luffa cylindrica fiber) reinforced epoxy composite has been fabricated and their structural responses (frequency and deflection) have been computed experimentally and numerically...

Experimental and numerical investigation of the mechanical behavior of full-scale wooden cross arm in the transmission towers in terms of load-deflection test

Abstract: This paper aims to carry out an experimental and numerical investigation of the mechanical behavior of full-scale wooden 123 KV 13 L Cross-arm that used in transmission towers. Two points bending test was conducted to obtain load-deflection data of both scenarios, normal condition scenario and broken wire condition scenario. Balau wood was used to fabricate the whole structure of the cross-arm which includes main, tie and bracing members. When it comes to the normal condition, standard load 7.98 K N, with 8 organized steps with angle Θ = 54.2° at YZ plan from Y-axis were applied. while Fr = 16 K N with 16 organized steps with angle Θ = 12.6° at the horizontal plan, α = 17.57° at vertical plane was applied for the broken wire condition. Deflection values due to these loads were determined by using 25 dial gauges that installed on both main members and tie members. Load-deflection investigation of both X–Y plots was considered for the main members while the Load-deflection investigation of Y plot was considered for tie members. Experiments of load-deflection data were validated by conducting a simulation process of normal conditions. The simulation process was designated to the first point (at R,L 734 mm) on the main members in both directions X and Y-axis during the normal condition. The numerical results of simulation have proven that the experiments were confident 93%.

Impact of static and dynamic loads of vehicles on pavement

Abstract: The present paper substantiates urgency of studies on early deterioration of pavement layers and on reasons entailing it. The aim was to investigate static and dynamic loads imposed on a road surface by vehicles in order to detect signs of early deterioration of pavement and understand its reasons. Certain tasks were set: to define diagnostic capacity for performing test works on road surface with the use of static and dynamic loading equipment; to carry out an elastic modulus analysis on the basis of static and dynamic loading tests performed; to assess strength properties of flexible pavement. The paper describes methods for determining strength properties of a road surface with the use of special static and dynamic loading equipment. The authors provide data on diagnostic capacity of tests of a pavement performed with the use of special testing equipment. The paper gives a list of potentials, advantages and fundamental features of the following units of equipment: apparatus for plate bearing tests, Dina-3M, UDN-NK, Dynatest apparatus. The main parameters of equipment for dynamic loading tests are provided. The results of both dynamic and static loading tests performed in Saint Petersburg and the Leningrad region are given. Deflection bowls and elastic modulus were determined. Coefficients of the dynamic elastic modulus being reduced to the static one were calculated. Strength properties of flexible pavement were assessed.

Experimental Investigation on Flexural Behavior of Reinforced Ultra High Performance Concrete Low-Profile T-Beams

Abstract: The flexural behavioral properties of ultra high performance concrete (UHPC) low-profile T-beams reinforced with a combination of steel fibers and steel reinforcing bars were investigated in this paper. Five large scale T-beams were tested and analyzed regarding their deflection, ductility, strain, curvature, load capacity and crack development. The experimental variables include the reinforcement ratio, the slenderness (length to diameter ratio) of the fiber reinforcements, and the fiber type. The experiments showed that all specimens exhibit flexural failure with the yielding of steel bars and excessive expansion of flexural crack, and the compression zone in the reinforced UHPC low-profile T-beam is not crushed because of the ultra high compressive strength and area of UHPC. In addition, it was concluded that using hooked-end fibers can effectively increase the specimen’s durability-based cracking load in comparison to straight fibers of same slenderness, whereas the reinforcement ratio and the slenderness of the fibers have little influence on this. Increasing the reinforcement ratio and using hooked-end instead of straight fibers increase the load capacity and bending stiffness of the specimen, as well as reduces the crack width at comparable applied load. A model was established to compute the ultimate capacity of UHPC low-profile T-beams and the prediction agrees well with the experimental results in the present and published investigations.

An experimental study of the feasibility of phase-based video magnification for damage detection and localisation in operational deflection shapes

Abstract: Optical measurements from high-speed, high-definition video recordings can be used to define the full-field dynamics of a structure. By comparing the dynamic responses resulting from both damaged and undamaged elements, Structural Health Monitoring (SHM) can be carried out, similarly as with mounted transducers. Unlike the physical sensors, which provide point-wise measurements and a limited number of output channels, high-quality video recording allows very spatially dense information. Moreover, video acquisition is a non-contact technique. This guarantees that any anomaly in the dynamic behaviour can be more easily correlated to damage and not to added mass or stiffness due to the installed sensors. However, in real-life scenarios, the vibrations due to environmental input are often so small that they are indistinguishable from measurement noise if conventional image-based techniques are applied. In order to improve the signal-to-noise ratio (SNR) in lowamplitude measurements, Phase-Based Motion Magnification (PBMM) has been recently proposed. This study intends to show that model-based SHM can be performed on modal data and time histories processed with PBMM, whereas unamplified vibrations would be too small for being successfully exploited. All the experiments were performed on a multidamaged box beam with different damage sizes and angles.

Nonlinear dynamic responses of layered skew sandwich composite structure and experimental validation

Abstract: The time-dependent deflection responses of the mechanically excited layered skew sandwich shell panels are computed numerically via a generic model developed mathematically using the higher-order shear deformation theory including the effects of the large displacement. The model includes the large displacements associated with the structural distortion under the small strain regime through Green–Lagrange nonlinear strain kinematics. The derived nonlinear system governing equation is converted to a set of algebraic form with the help of finite element steps. Subsequently, the time-dependent displacement values are computed numerically through the direct iterative technique including Newmark’s integration scheme. The dynamic deflections of the sandwich structural component under the influence of the externally excited mechanical loading are obtained through a generic computer code (developed in MATLAB) via the nonlinear higher-order finite element model. Before the implementation of the proposed model for the sandwich analysis, the solution stability and accuracy have been established by solving different kinds of numerical example from the published domain. Additionally, a few layered sandwich plates of different face sheet layers have been fabricated and the experimental dynamic data are recorded for the comparison purpose with the help of available modal test rig. Finally, the influences of the different structure-dependent design parameters on the nonlinear dynamic responses are investigated using the presently developed numerical model of skew sandwich shell panel, which also reveals that the present results give more accurate results.