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The determination of the state of a structure represents an important factor in the use of structural systems. This is known as structural health monitoring (SHM). Several methods, the most of them visuals, are employed. These require a direct access to the possible damaged zone an can be very time consuming and costly, a reason by which the researchers in this field are focused in others method, like modal analysis. The wavelet transform is also a very powerful toll in crack detection in early stages. This problem should be studied in a practical and theoretical way. In this paper a transverse closed crack is represented in an Euler-Bernoulli beam, as Bovsunovsky. Continuous and finite element models are used, and the wavelet transform is applied to the eigenmodes. [ABSTRACT FROM AUTHOR]

A finite element model of a real laminated spring under bending should include the phenomena of contact and friction between leaves, in order to obtain values of displacements, stresses, gap, etc. close to reality. Considering contact and friction leads to a non-linear problem, which must be solved using numerical methods (Newton-Raphson), resulting in a classic optimization problem with constraints. The success of solution depends strongly on boundary conditions and initial values. A strategy for determining penalty values in the case of a multi leaf bending problem is presented, allowing a good correspondence with real displacements. The non-linear behavior of the leaf spring suspension referred to spring rate is shown. The modal analysis also gave firsts natural frequencies in the usual span for trucks and semi-trailers. [ABSTRACT FROM AUTHOR]

In this paper is presented the design, construction and experimental validation of a dynamometric device of natural variable frequency where the influence of the natural frequency values in the magnitude of the mean value of cutting forces measured in a lathed process were determined. The dynamometer with three values of natural frequency, in ranges of 2000, 6000 and 8000 Hz was designed by means of the finite elements method. A dynamometer device was constructed for the verifications of the natural frecuencies obtained by finite element method. The experimentally results validation confirmed the developed models [ABSTRACT FROM AUTHOR]