A matrix framework is developed for single and multispan micro-cantilevers Timoshenko beam models of use in atomic force microscopy (AFM). They are considered subject to general forcing loads and boundary conditions for modeling tipsample interaction. Surface effects are considered in the frequency analysis of supported and cantilever microbeams. Extensive use is made of a distributed matrix fundamental response that allows to determine forced responses through convolution and to absorb non-homogeneous boundary conditions. Transients are identified from intial values of permanent responses. Eigenanalysis for determining frequencies and matrix mode shapes is done with the use of a fundamental matrix response that characterizes solutions of a damped second-order matrix differential equation. It is observed that surface effects are influential for the natural frequency at the nanoscale. Simulations are performed for a bi-segmented free-free beam and with a micro-cantilever beam actuated by a piezoelectric layer laminated in one side.

Abstract. We discuss the mth-order linear differential equation with matrix coefficients in terms of a particular matrix solution that enjoys properties similar to the exponential of first-order equations. A new formula for the exponential matrix is established with dynamical solutions related to the generalized Lucas polynomials.1. Introduction. The study of higher-order linear differential equations with square matrix coefficients is usually left aside for being equivalent to a first-order equation having the companion matrix as its coefficient. The handling of this matrix is not an amenable task for obtaining results proper of higher-order equations which are shadowed or simply unknown. The companion matrix, although sparse, does not preserve any common property that the involved matrix coefficients might share.In this paper, we shall present a direct study of higher-order equations in terms of a particular square matrix solution, which is characterized by zero initial "displacement" values and a unit initial "impulse" value, and that we shall refer to in the sequel as the dynamical solution. It will be shown that this solution enjoys intrinsic properties not necessarily shared by the complementary basis solutions, and that in a certain way the dynamical solution should do for higher-order equations what the

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We consider the obtention of modes and frequencies of segmented Euler-Bernoulli beams with internal damping and external viscous damping at the discontinuities of the sections. This is done by following a Newtonian approach in terms of a fundamental response of stationary beams subject to both types of damping. The use of a basis generated by the fundamental solution of a differential equation of fourth-order allows to formulate the eigenvalue problem and to write the modes shapes in a compact manner. For this, we consider a block matrix that carries the boundary conditions and intermediate conditions at the beams and values of the fundamental matrix at the ends and intermediate points of the beam. For each segment, the elements of the basis have the same shape since they are chosen as a convenient translation of the elements of the basis for the first segment. Our method avoids the use of the first-order state formulation also to rely on the Euler basis of a differential equation of fourth-order and it allows to envision how conditions will influence a chosen basis.

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Microbeam models with surface and piezoelectric effects are considered for atomic force microscopy (AFM). These models include rotatory inertia and shear deformation as proposed by Timoshenko and they are subject to forcing loads. Eigenanalysis of the free dynamic matrix model is performed with the use of a fundamental matrix response to determine the modal frequency equation and matrix mode shapes. The fundamental response governs the behaviour of a non-classical damped second-order matrix differential equation. It was observed that surface effects are influential for the natural frequency at the nanoscale. When the beam length increases from nanometers to microns, the surface effects disappear and the results converge into natural frequencies of classical Timoshenko model. Simulations with the piezoelectric model were performed to observe the effects of forcing pulses located at different positions of the microbeam.Keywords-Dynamic of nanomaterials, Atomic force microscopy, surface and piezoelectric effects, Timoshenko beam model.

In this work we consider segmented Euler-Bernoulli beams that can have an internal damping of the type Kelvin-Voight and external viscous damping at the discontinuities of the sections. In the literature, the study of this kind of beams has been sufficiently studied with proportional damping only, however the effects of non-proportional damping has been little studied in terms of modal analysis. The obtaining of the modes of segmented beams can be accomplished with a the state space methodology or with the classical Euler construction of responses. Here, we follow a newtonian approach with the use of the impulse response of beams subject both types of damping. The use of the dynamical basis, generated by the fundamental solution of a differential equation of fourth order, allows to formulate the eigenvalue problem and the shapes of the modes in a compact manner. For this, we formulate in a block manner the boundary conditions and intermediate conditions at the beam and values of the fundamental matrix at the ends of the beam and in the points intermediate. We have chosen a basis generated by a fundamental response and it derivatives. The elements of this basis has the same shape with a convenient translation for each segment. This choice reduce computations with the number of constants to be determined to find only the ones that correspond to the first segment. The eigenanalysis will allow to study forced responses of multi-span Euler-Bernoulli beams under classical and non-classical boundary conditions as well as multi-walled carbon nanotubes (MWNT) that are modelled as an assemblage of Euler-Bernoulli beams connected throughout their length by springs subject to van der Waals interaction between any two adjacent nanotubes.