Numerical and Experimental Study of Clearance Nonlinearities Based on Nonlinear Response Reconstruction

Author(s):  
Jie Liu ◽  
Bing Li ◽  
Huihui Miao ◽  
Anqi He ◽  
Shangkun Zhu

With the growing structural complexity and growing demands on structural reliability, nonlinear parameters identification is an efficient approach to provide better understanding of dynamic behaviors of the nonlinear system and contribute significantly to improve system performance. However, the dynamic response at nonlinear location, which cannot always be measured by the sensor, is the basis for most of these identification algorithms, and the clearance nonlinearity, which always exists to degrade the dynamic performance of mechanical structures, is rarely identified in previous studies. In this paper, based on the thought of output feedback which the nonlinear force is viewed as the internal feedback force of the nonlinear system acting on the underlying linear model, a frequency-domain nonlinear response reconstruction method is proposed to reconstruct the dynamic response at the nonlinear location from the arbitrary location where the sensor can be installed. For the clearance nonlinear system, the force graph method which is based on the reconstructed displacement response and nonlinear force is presented to identify the clearance value. The feasibility of the reconstruction method and identification method is verified by simulation data from a cantilever beam model with clearance nonlinearity. A clearance test-bed, which is a continuum structure with adjustable clearance nonlinearity, is designed to verify the effectiveness of proposed methods. The experimental results show that the reconstruction method can precisely reconstruct the displacement response at the clearance location from measured responses at reference locations, and based on the reconstructed response, the force graph method can also precisely identify the clearance parameter.

Author(s):  
Chaodong Zhang ◽  
Jian’an Li ◽  
Youlin Xu

Previous studies show that Kalman filter (KF)-based dynamic response reconstruction of a structure has distinct advantages in the aspects of combining the system model with limited measurement information and dealing with system model errors and measurement Gaussian noises. However, because the recursive KF aims to achieve a least-squares estimate of state vector by minimizing a quadratic criterion, observation outliers could dramatically deteriorate the estimator’s performance and considerably reduce the response reconstruction accuracy. This study addresses the KF-based online response reconstruction of a structure in the presence of observation outliers. The outlier-robust Kalman filter (OKF), in which the outlier is discerned and reweighted iteratively to achieve the generalized maximum likelihood (ML) estimate, is used instead of KF for online dynamic response reconstruction. The influences of process noise and outlier duration to response reconstruction are investigated in the numerical study of a simple 5-story frame structure. The experimental work on a simply-supported overhanging steel beam is conducted to testify the effectiveness of the proposed method. The results demonstrate that compared with the KF-based response reconstruction, the proposed OKF-based method is capable of dealing with the observation outliers and producing more accurate response construction in presence of observation outliers.


Author(s):  
S. Khajehpour ◽  
R. G. Sauve´ ◽  
N. Badie

A method has been developed to incorporate the local three-dimensional shell behavior of two concentric tubes in the two-dimensional beam modeling of the problem. The two dimensional modeling of fuel channels in CANDU pressurized heavy water nuclear reactors is used in lieu of a more accurate three dimensional finite element approach in order to reduce the on-line simulation time which greatly affects the SLAR (Spacer Location And Repositioning) maintenance operation cost during outage. However, effort must be made to include the three-dimensional shell behavior of these channels into the two-dimensional modeling. In recent studies a nonlinear force-dependent model for contact stiffness between the calandria tube and pressure tube has been developed. However, local deformation of calandria the tube at spacer locations due to in-reactor creep leads to settling of the spacer into the calandria tube that consequently reduces the gap between the two tubes. In this work, the effect of local deformation (elastic and creep) of calandria tubes on modeling of contact at spacer locations is assessed using a three dimensional finite element code. The result is incorporated into a two-dimensional beam model of the problem as a reduction in size of the spacers that separate the two tubes. It is shown that the proposed method increases the accuracy of prediction of contact time and the spacer. In general, the method described in this paper suggests a way to incorporate local shell deformation into beam models of slender shell structure.


2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Dinh Kien Nguyen ◽  
An Ninh Thi Vu ◽  
Ngoc Anh Thi Le ◽  
Vu Nam Pham

A bidirectional functionally graded Sandwich (BFGSW) beam model made from three distinct materials is proposed and its dynamic behavior due to nonuniform motion of a moving point load is investigated for the first time. The beam consists of three layers, a homogeneous core, and two functionally graded face sheets with material properties varying in both the thickness and longitudinal directions by power gradation laws. Based on the first-order shear deformation beam theory, a finite beam element is derived and employed in computing dynamic response of the beam. The element which used the shear correction factor is simple with the stiffness and mass matrices evaluated analytically. The numerical result reveals that the material distribution plays an important role in the dynamic response of the beam, and the beam can be designed to meet the desired dynamic magnification factor by appropriately choosing the material grading indexes. A parametric study is carried out to highlight the effects of the material distribution, the beam layer thickness and aspect ratios, and the moving load speed on the dynamic characteristics. The influence of acceleration and deceleration of the moving load on the dynamic behavior of the beam is also examined and highlighted.


1993 ◽  
Vol 20 (2) ◽  
pp. 287-298 ◽  
Author(s):  
J. L. Humar ◽  
A. M. Kashif

In spite of a number of analytical and experimental investigations on the dynamic response of bridges to moving vehicle loads, the controlling parameters that govern the response have not been clearly identified. This has, in turn, inhibited the development of rational design procedures. Based on an analytical investigation of the response of a simplified beam model traversed by a moving mass, the present study identifies the governing parameters. The results clearly show why attempts to correlate the response to a single parameter, either the span length or the fundamental frequency, are unsuccessful. Simple design procedures are developed based on relationships between the speed ratio, the weight ratio, and the dynamic amplification factors; and a set of design curves are provided. Key words: dynamic response of bridges, vehicle–bridge interaction, moving force model, moving sprung mass model, dynamic amplification factor.


Author(s):  
H Ramezannejad Azarboni ◽  
SA Edalatpanah

In the studies of the dynamic response of carbon nanotubes, the stability, predictable, and unpredictable chaotic vibrations are fundamental characteristics. In this paper, we investigate the chaotic and periodic vibrations of a single-walled carbon nanotube resting on the viscoelastic foundation, based on the nonlocal Euler–Bernoulli beam model. It is assumed that the single-walled carbon nanotube is subjected to an external harmonic excitation. The axial thermomagnetic field and the surface effect on the governing equation of single-walled carbon nanotube are taken into account. We also solve the nonlinear governing equation by using the Galerkin decomposition method along with the fourth-order Rung–Kutta numerical integration scheme. Furthermore, we analyze the effects of amplitude and frequency of excitation on the formation of chaotic and periodic regions using bifurcation diagrams and largest Lyapunov exponents. Moreover, we present the phase portrait, Poincare maps, and time history to observe the periodic and chaotic responses of the system. The results show that the nonlinear dynamic response of single-walled carbon nanotube is much more sensitive to both amplitude and frequency of excitation.


2011 ◽  
Vol 105-107 ◽  
pp. 491-494
Author(s):  
Tie Jun Liu ◽  
Yong Zhang ◽  
Gang Li ◽  
Feng Hui Wang

In design of solar powered aircraft wing panel, vibration properties of wing panel should be considered, especially for the peak value of dynamic response. In this research, a viscoelastic damping layer is built for vibration isolation, wing panel finite element models of stiffened and no-stiffened structures base on fiber-reinforced laminates with damping layer in the middle are built. Natural frequency and displacement response are analyzed with different thickness of damping layer and structures. Result shows natural frequencies decrease as thickness increased, and that of laminates are lower than stiffened structure. The maximum displacement response value decreased when thickness increased and that of laminates is higher than structured with stiffer. The presented work is helpful for type selection and designing of solar powered aircraft wing panel.


Author(s):  
Ping Yang ◽  
Ying Peng

The dynamic response of one-way stiffened plates with clamped edges subjected to uniformly distributed blast-induced shock loading is theoretically investigated using a singly symmetric beam model. The beam model is based on the rigid-perfectly plastic assumption. The bending moment-axial force capacity interaction relation or yield curve for singly symmetric cross-section is derived and explicitly presented. The deflection condition that a plastic string response must satisfy is determined by the linearized interaction curve and associated plastic flow rule. Moreover, the possible motion mechanisms of the beam are discussed under different load intensity. Finally the dynamic response of a one-way stiffened plate is calculated theoretically and numerically. Good agreements are obtained between the presented theoretical results and those from numerical calculations of the FEM software ANSYS and ABAQUS/Explicit. It is concluded that the basic assumptions and approximations for simplifying calculations are reasonable and the beam model in theoretical analysis is adoptable. The example also shows that an arbitrary blast load can be replaced equivalently by a rectangular type pulse.


2013 ◽  
Vol 333-335 ◽  
pp. 2151-2155
Author(s):  
Xue Feng Han ◽  
Yan Dong Wang ◽  
Tao Wang ◽  
Tong Chao Ding ◽  
Hong Guang Jia

In order to study the dynamic response of the cylindrical shell structure which is similar to the missile cabin under the combined effects of axial compressive load and radial aerodynamic load, the equilibrium equation of dynamic response of cylindrical shell is derived based on the Hamiltons principle. The displacement response of cylindrical shell is calculated through employing the numerical method. The calculation results show that the axial displacement response and the radial displacement response of cylindrical shell are much greater than the circumferential displacement response; the radial displacement will be maximum when the excitation frequencies are 285Hz, 594Hz, 1039Hz, 1062Hz, 1093Hz, 1962Hz and 1987Hz; the axial displacement will be maximum when the corresponding excitation frequencies are 81Hz and 294Hz; the peak values of displacement response in non-load plane are not all obtained at the resonance frequency and a certain effect is generated due to the modal coupling.


2013 ◽  
Vol 36 (2) ◽  
pp. 422-455 ◽  
Author(s):  
Louis Thibault ◽  
Peter Avitabile ◽  
Jason Foley ◽  
Janet Wolfson

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