An Inverse Technique Based On Transient Responses For Material Characterization Of A Functionally Graded Beam

With the gradually increasing applications of functionally graded materials, there is a need for an effective method to non-destructively measure the material property of functionally graded materials. Based on the difficulties in evaluating functionally graded materials by traditional techniques and the limitations of advanced non-destructive evaluation in engineering application, an inverse procedure built on the transient response analysis of functionally graded beam is presented for charactering the material property of functionally graded materials.Focusing on the functionally graded material (FGM), the wave propagation in FGM was analyzed. The inverse procedure for charactering the material property of functionally graded beam is based on the analysis of transient response and material property sensitivity of the functionally graded beam built by the finite element software.Based on the analysis of wave propagation behaviors in functionally graded beam, the inverse problem was established combined with genetic algorithm and an inverse procedure by using transient response analysis of functionally graded beam was developed for determining the material property. The dynamic displacement responses of functionally graded beam obtained by the finite element software were employed as the input data, and the volume fractions were output data.A surrogate-based method was provided, and the dynamic response model of functionally graded beam was substituted by response surface model as forward calculation technique of the inverse procedure. The design of experiment technique was employed to establish different surrogate models for comparing analysis, and the response surface model was proved to be accurate to substitute the wave propagating model of functionally graded beam.Finally, the inverse procedure presented in this thesis was validated by two applications for charactering material property of SiC-C and SS-SN functionally graded beams.The study shows that the research on wave propagation behaviors in FGM provides an effective method for charactering material property of FGM, and is able to be conducted by the commercial finite element software. The efficiency of the inverse procedure is improved by employing surrogate model technique. The inverse procedure combined with genetic algorithm is accurate to determine material property of functionally graded beam.