Detection of Nonlinearities in Plates Via Higher-Order-Spectra: Numerical and Experimental Studies

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
M. Pasquali ◽  
W. Lacarbonara ◽  
P. Marzocca
Keyword(s):  
Mechanical Response ◽  
Gaussian White Noise ◽  
Experimental Studies ◽  
Laminated Composite ◽  
Composite Plates ◽  
Higher Order ◽  
Laminated Plates ◽  
Experimental Investigations ◽  
Structural Nonlinearities ◽  
Lumped Masses

Higher-order spectral (HOS) analysis tools are employed to extract the nonlinear dynamic response features of elastic and laminated plates by using both physics-based mechanical plate models and experimental data. Bispectral and trispectral densities are computed to highlight the presence and relative importance of quadratic and cubic nonlinearities. The former are associated with the presence of asymmetry either in the excitation or in the mechanical response of predeflected plates while the latter are due to midplane stretching effects. Besides the detection of these structural nonlinearities in perfect (baseline) fully clamped plates, the changes of such nonlinearities induced by the presence of small inertial imperfections (i.e., lumped masses) are identified and exploited to localize the imperfections. The numerical and experimental investigations are carried out both on isotropic and laminated composite plates subject to Gaussian white noise excitation. The effectiveness of the HOS-based procedure for detection of the nonlinearities is fully demonstrated for both types of plates.

Determination of Vibration Source Locations in Laminated Composite Plates Using Lamb Wave Analysis

2010 ◽  
Vol 123-125 ◽  
pp. 899-902
Author(s):  
Chao Du ◽  
Qing Qing Ni ◽  
Toshiaki Natsuki
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Laminated Composite ◽  
Composite Plates ◽  
Wave Dispersion ◽  
Laminated Plates ◽  
Vibration Source ◽  
Arrival Times ◽  
Wave Velocities

Signals propagate on plate-like structures as ultrasonic guided waves, and analysis of Lamb waves has been widely used for on-line monitoring. In this study, the wave velocities of symmetric and anti-symmetric modes in various directions of propagation were investigated. Since the wave velocities of these two modes are different, it is possible to compute the difference in their arrival times when these waves propagated the distance from the vibration source to sensor. This paper presents an evaluation formulation of wave velocity and describes a generalized algorithm for locating a vibration source on a thin, laminated plate. With the different velocities of two modes based on Lamb wave dispersion, the method uses two sensors to locate the source on a semi-infinite interval of a plate. The experimental procedure supporting this method employs pencil lead breaks to simulate vibration sources on quasi-isotropic and unidirectional laminated plates. The transient signals generated in this way are transformed using a wavelet transform. The vibration source locations are then detected by utilizing the distinct wave velocities and arrival times of the symmetric and anti-symmetric wave modes. The method is an effective technique for identifying impact locations on plate-like structures.

Stress analysis of smart composite plate structures

2020 ◽  
pp. 095440622097544
Author(s):  
Aniket Chanda ◽  
Utkarsh Chandel ◽  
Rosalin Sahoo ◽  
Neeraj Grover
Keyword(s):  
Shear Deformation ◽  
Transverse Shear ◽  
Laminated Composite ◽  
Composite Plates ◽  
Higher Order ◽  
Hyperbolic Function ◽  
Solution Technique ◽  
Shear Stresses ◽  
Laminated Composite Plates ◽  
Equilibrium Equations

In the present study, the electro-mechanical responses of smart laminated composite plates with piezoelectric materials are derived using a two-dimensional (2 D) displacement-based non-polynomial higher-order shear deformation theory. The kinematics of the mathematical model incorporates the deformation of laminates which account for the effects of transverse shear deformation and a non-linear variation of the in-plane displacements using inverse sine hyperbolic function of the thickness coordinate. The equilibrium equations are obtained using the minimization of energy principle known as the principle of minimum potential energy (PMPE) which is also based on a variational approach and the solutions are obtained using Navier’s solution technique for diaphragm supported smart laminated composite plates. The responses obtained in the form of deflection and stresses are compared with three dimensional (3 D) solutions and also with different polynomial and non-polynomial based higher-order theories in the literature. The transverse shear stresses are obtained using 3 D equilibrium equations of elasticity to enhance the accuracy of the present results. Various examples are numerically solved to establish the efficiency of the present model.

Thermomechanical Buckling of Laminated Composite Plates Using Mixed, Higher-Order Analytical Formulation

2002 ◽  
Vol 69 (6) ◽  
pp. 790-799 ◽  
Author(s):  
J. B. Dafedar ◽  
Y. M. Desai
Keyword(s):  
Strain Tensor ◽  
Single Layer ◽  
Laminated Composite ◽  
Composite Plates ◽  
Higher Order ◽  
Laminated Composite Plates ◽  
Individual Layer ◽  
Energy Principle ◽  
Transverse Stresses ◽  
Benchmark Solutions

A novel, analytical mixed theory based on the potential energy principle has been presented in this paper to investigate buckling response of laminated composite plates subjected to mechanical and hygrothermal loads. Two sets of higher-order mixed models have been proposed on the basis of an individual layer as well as equivalent single layer theories by selectively incorporating nonlinear components of Green’s strain tensor. Displacements, as well as transverse stress continuities, have been enforced in the formulation of models by incorporating displacements and transverse stresses as the degrees-of-freedom. The modal transverse stresses have been obtained as eigenvectors and thus their separate calculations have been advantageously avoided. Solutions from the models have been shown to be in excellent agreement with the available three-dimensional elasticity solutions. Few benchmark solutions have also been presented for the bi-axial compression-tension loading.

A cell-based smoothed finite element formulation for viscoelastic laminated composite plates considering hygrothermal effects

2020 ◽  
pp. 002199832098005
Author(s):  
Sy-Ngoc Nguyen ◽  
Tam T Truong ◽  
Maenghyo Cho ◽  
Nguyen-Thoi Trung
Keyword(s):  
Finite Element ◽  
Shear Deformation Theory ◽  
Laminated Composite ◽  
Composite Plates ◽  
Integral Form ◽  
Complex Stress ◽  
Laminated Plates ◽  
Element Formulation ◽  
Composite Laminated Plates ◽  
Smoothed Finite Element Method

In the present study, the viscoelastic analysis is investigated for composite laminated plates using a smoothed finite element method called cell/element based smoothed discrete shear gap method. Moreover, the hygrothermal effects is considered on the viscoelastic responses of composite laminated plates. The first-order shear deformation theory is employed due to its simplicity and accuracy. With the help of the convolution theorem in Laplace transformation, the complex stress-strain relationship in integral form is simplified to linear in transformed domain. Therefore, all computing procedures are performed in the transformed domain and then, using inverse techniques (Fast Fourier Transform) to converted back to the real-time domain. The study provides an effective computational tool to analyze the viscoelastic response of laminated composite taking into account the influence of the time and hygrothermal effects.

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