#### Vol. 3, No. 3, 2008

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Estimation of parameters of a three-layered sandwich beam

### Nilson Barbieri, Renato Barbieri, Luiz Carlos Winikes and Luis Fernando Oresten

Vol. 3 (2008), No. 3, 527–544
##### Abstract

In this work the physical parameters of a sandwich beam made with the association of hot rolled steel, polyurethane rigid foam, and high impact polystyrene, used for the assembly of household refrigerators and food freezers, are estimated using measured and numeric frequency response functions. The mathematical models are obtained using the finite element method and the Timoshenko beam theory. The physical parameters are estimated using the amplitude correlation coefficient and genetic algorithm methods. Initially, the experimental procedure to determine the material’s mechanical properties, Young and shear moduli, and the density of the components of the sandwich beam is described. The elastic properties were obtained through tension and torsion tests. The shear modulus ${G}_{c}$ of the polyurethane rigid foam core was determined using a rectangular specimen and the Young’s moduli of the steel and high impact polystyrene were determined using a conventional tension test. To estimate the dynamical values of the parameters in the frequency range from 10 to 400 Hz, separated dynamic sweeping tests were conducted using cantilevered beams of polyurethane rigid foam and high impact polystyrene. The experimental data from a three layered sandwich beam were obtained using an impact hammer and four accelerometers, displaced along the cantilevered beam sample. The parameters estimated are the Shear modulus and the loss factor of the polyurethane rigid foam, and the Young’s modulus and the loss factor of the high impact polystyrene.

##### Keywords
sandwich beam, genetic algorithm, amplitude correlation coefficient, parameter updating
##### Milestones
Revised: 4 September 2007
Accepted: 18 September 2007
Published: 1 May 2008