A modal superposition method for vibration responses of atomic force microscope cantilevers using the Timoshenko beam model

2011 ◽  
Author(s):  
Thin-Lin Horng
Keyword(s):  
Atomic Force Microscope ◽  
Timoshenko Beam ◽  
Superposition Method ◽  
Beam Model ◽  
Timoshenko Beam Model ◽  
Modal Superposition ◽  
Atomic Force ◽  
Modal Superposition Method ◽  
Vibration Responses

Dynamic analysis of AFM by applying Timoshenko beam theory in tapping mode and considering the impact of interaction forces in a liquid environment

2014 ◽  
Vol 92 (6) ◽  
pp. 472-483 ◽  
Author(s):  
M. Damircheli ◽  
M.H. Korayem
Keyword(s):  
Dynamic Response ◽  
Atomic Force Microscope ◽  
Timoshenko Beam ◽  
Ambient Air ◽  
Beam Model ◽  
Timoshenko Beam Model ◽  
Interaction Forces ◽  
Liquid Environment ◽  
Atomic Force ◽  
Simulation Results

In an atomic force microscope (AFM), the cantilever vibrates by excitation at a frequency near the fundamental frequency, and the changes in vibration parameters, which result from the nonlinear forces of interaction between sample and cantilever tip, can be used as a tool to reveal the properties of the sample. To properly describe the images acquired by the AFM and to approximate the properties of the investigated sample, it is essential to use analytical and numerical models that can accurately simulate the dynamics of the cantilever and sample. For short beams, the Timoshenko model seems to be very accurate. Considering the fact that short beams (cantilevers) have many applications including the imaging of biological samples in liquid environments, the use of this theory seems to be necessary. In this paper, by employing the Timoshenko beam model, the effect of rotational inertia and shear deformation has been taken into consideration. The interaction forces between sample and cantilever in liquid, ambient air, and vacuum environments are quite different in terms of magnitude and formulation, and they play a significant role in the system’s dynamic response. These forces include hydrodynamic forces, electrostatic double layer force, etc. Using an accurate model for the interaction forces will improve the simulation results significantly. In this paper, the frequency response of the atomic force microscope has been investigated by applying the Timoshenko beam model and considering the forces of interaction between sample and tip in the air and liquid environments. The results indicate that the resonant frequency changes and cantilever vibration amplitude diminishes in a liquid environment compared to the air environment. The simulation results have good agreement with the experimental ones. The frequency responses for the attractive and repulsive regions in the two environments are compared and it is demonstrated that the dynamic response is highly dependent on the hydrodynamic and interaction forces in the liquid medium.

Structural Shape Reconstruction of FBG Flexible Plate Using Modal Superposition Method

2017 ◽  
Author(s):  
Li Li ◽  
Ben S. Zhong ◽  
Zi Y. Geng ◽  
Wei Sun
Keyword(s):  
Mode Shape ◽  
Shape Reconstruction ◽  
Displacement Sensor ◽  
Superposition Method ◽  
Flexible Plate ◽  
Structural Shape ◽  
Modal Superposition ◽  
Displacement Mode ◽  
Modal Superposition Method ◽  
Strain Data

Structural shape reconstruction is a critical issue for real-time structural health monitoring in the fields of engineering application. This paper shows how to implement structural shape reconstruction using a small number of strain data measured by fiber Bragg grating (FBG) sensors. First, the basic theory of structural shape reconstruction is introduced using modal superposition method. A transformation is derived from the measured discrete strain data to global displacement field through modal coordinate, which is the same for strain mode shape superposition and displacement mode shape superposition. Then, optimization of the sensor layout is investigated to achieve the effective reconstruction effect. Finally, structural shape reconstruction algorithm using modal superposition method is applied in experiments. The experiment results show that the reconstructed displacements match well with those measured by a laser displacement sensor and the proposed approach is a promising method for structural shape reconstruction.

Investigating vibrations of viscoelastic fluid-conveying carbon nanotubes resting on viscoelastic foundation using a nonlocal fractional Timoshenko beam model

2020 ◽  
pp. 239779142093170
Author(s):  
M Faraji Oskouie ◽  
R Ansari ◽  
H Rouhi
Keyword(s):  
Carbon Nanotubes ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Timoshenko Beam ◽  
Time Domain ◽  
Beam Model ◽  
Viscoelastic Foundation ◽  
Timoshenko Beam Model ◽  
Governing Equations ◽  
The Time Domain

On the basis of fractional viscoelasticity, the size-dependent free-vibration response of viscoelastic carbon nanotubes conveying fluid and resting on viscoelastic foundation is studied in this article. To this end, a nonlocal Timoshenko beam model is developed in the context of fractional calculus. Hamilton’s principle is applied in order to obtain the fractional governing equations including nanoscale effects. The Kelvin–Voigt viscoelastic model is also used for the constitutive equations. The free-vibration problem is solved using two methods. In the first method, which is limited to the simply supported boundary conditions, the Galerkin technique is employed for discretizing the spatial variables and reducing the governing equations to a set of ordinary differential equations on the time domain. Then, the Duffing-type time-dependent equations including fractional derivatives are solved via fractional integrator transfer functions. In the second method, which can be utilized for carbon nanotubes with different types of boundary conditions, the generalized differential quadrature technique is used for discretizing the governing equations on spatial grids, whereas the finite difference technique is used on the time domain. In the results, the influences of nonlocality, geometrical parameters, fractional derivative orders, viscoelastic foundation, and fluid flow velocity on the time responses of carbon nanotubes are analyzed.

An Error Compensation Method for Structural Responses and Sensitivities

2011 ◽  
Vol 421 ◽  
pp. 743-749
Author(s):  
Xiao Ming Wu ◽  
Chun Liu
Keyword(s):  
Error Compensation ◽  
Truncation Error ◽  
Compensation Method ◽  
Superposition Method ◽  
Truncation Errors ◽  
Modal Superposition ◽  
Modal Superposition Method ◽  
Structural Responses ◽  
Epsilon Algorithm ◽  
Modal Method

Abstract. The computation of the responses and their design sensitivities play an essential role in structural analysis and optimization. Significant works have been done in this area. Modal method is one of the classical methods. In this study, a new error compensation method is constructed, in which the modal superposition method is hybrid with Epsilon algorithm for responses and their sensitivities analysis of undamped system. In this study the truncation error of modal superposition is expressed by the first L orders eigenvalues and its eigenvectors explicitly. The epsilon algorithm is used to accelerate the convergence of the truncation errors. Numerical examples show that the present method is validity and effectiveness.

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