A quadratic layer element for analyzing stress waves in FGMs and its application in material characterization

A novel method is presented for investigating elastic waves in functionally graded material (FGM) plates excited by plane pressure waves. The FGM plat e is first divided into quadratic layer elements (QLEs). A general solution for the equation of motion governing the QLE has been derived. The general solution is then used together with the boundary and continuity conditions to obtain the displacement and stress in the frequency domain for an arbit rary FGM plate. The response of the plate to an incident pressure wave is o btained using the Fourier transform techniques. Results obtained by the pre sent method are compared with an existing method using homogeneous layer el ements. Numerical examples are presented to investigate stress waves in FGM plates. The relationship between the surface displacement response and the material property of quadratic FGM plates has been analytically obtained f or the material characterization. A computational inverse technique is also presented for characterizing material property of an arbitrary FGM plate f rom the surface displacement response data, using present QLE method as for ward solver and genetic algorithm as the inverse operator. This technique i s utilized to reconstruct the material property of an actual SiC-C FGM. (C) 2000 Academic Press.