Modal filters may be obtained by a weighted sum of the signals of an array of sensors distributed on the host structure. However, the effect of parametric uncertainties on the effectiveness of the modal filter has received little attention. This work presents some numerical and experimental results on the effect of uncertainties of sensor array spatial distribution and weighting coefficients on the modal filtering effectiveness. For that, a free rectangular plate with twelve bonded piezoelectric sensors is considered. The spatial distribution of the array of piezoelectric sensors was optimized in a previous work to improve the effectiveness and frequency range of a set of modal filters. An experimental implementation of the modal filters was performed through a voltage divider and summing amplifier circuits and used to validate the performance of the modal filters. From numerical and experimental analysis, it was noticed, however, that the effectiveness of the modal filters are quite sensitive to the array spatial distribution and weighting coefficients. First, the effect of uncertainties of the array spatial distribution on the output of the modal filters was analyzed numerically using a finite element model. In this case, the main challenge was the cost of function evaluation and, thus, focus was put on solutions for the parameters sampling and approximations using response surface methods. Then, the effect of uncertainties of the weighting coefficients was evaluated using stochastic modeling combined with the measurement of individual responses of piezoelectric sensors. Confidence intervals for the modal filters output were evaluated and compared to experimental results with satisfactory results.

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This paper shows theoretical models (analytical formulations) to predict the mechanical behavior of thick composite tubes and how some parameters can influence this behavior. Thus, firstly, it was developed the analytical formulations for a pressurized tube made of composite material with a single thick ply and only one lamination angle. For this case, the stress distribution and the displacement fields are investigated as function of different lamination angles and reinforcement volume fractions. The results obtained by the theoretical model are physic consistent and coherent with the literature information. After that, the previous formulations are extended in order to predict the mechanical behavior of a thick laminated tube. Both analytical formulations are implemented as a computational tool via Matlab code. The results obtained by the computational tool are compared to the finite element analyses, and the stress distribution is considered coherent. Moreover, the engineering computational tool is used to perform failure analysis, using different types of failure criteria, which identifies the damaged ply and the mode of failure.

ObstractPolymers exhibit significant strain rate dependence in their mechanical strength. The impact simulations accuracy is associated with the use of mechanical properties obtained at high strain rates. These properties are often not available to engineers introducing a risk on the product development step. This paper presents a method for adjusting the parameters of the Cowper-Symonds, used for a constitutive material model, through computational experiments carried out considering the simulation of the Izod impact test.The proposed adjustment method allows reducing the Izod impact strength error from 44% to 2.4%.

Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. GUIMARÃES, Osvaldo Sena II. Título. CDD-620 Sônia Márcia Soares de Moura -CRB 6/1896 O conteúdo deste livro está licenciado sob a Licença de Atribuição Creative Commons 4.0. Com ela é permitido compartilhar o livro, devendo ser dado o devido crédito, não podendo ser utilizado para fins comerciais e nem ser alterada.O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos seus respectivos autores.

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