Browsing by Author "Sun, S. J."

Now showing 1 - 2 of 2

Free-vibration analysis and material constants identification of laminated composite sandwich plates
(2007-08-01)
Lee, C. R.
;
Kam, T. Y.
;
Sun, S. J.
;
機械工程學系
;
Department of Mechanical Engineering
Free vibration of symmetrically laminated composite sandwich plates with elastic edge restraints is studied via the Rayleigh-Ritz approach. The proposed Rayleigh-Ritz method is constructed on the basis of the layer-wise linear displacement theory. The accuracy of the method in predicting natural frequencies of composite sandwich plates with different boundary conditions is verified by the results reported in the literature or the experimental data obtained in this study. The proposed method is then applied to the material constant identification of free composite sandwich plates using the first six theoretical natural frequencies of the plates. In the identification process, trial material constants are used in the present method to predict the theoretical natural frequencies, a frequency discrepancy function is established to measure the sum of the squared differences between the experimental and theoretical natural frequencies, and a stochastic global minimization algorithm is used to search for the best estimates of the material constants by making the frequency discrepancy function a global minimum. Applications of the material constant identification technique are demonstrated by means of several examples.
System parameters evaluation of flexibly supported laminated composite sandwich plates
(2007-09-01)
Lee, C. R.
;
Sun, S. J.
;
Kam, T. Y.
;
機械工程學系
;
Department of Mechanical Engineering
A nondestructive evaluation technique established on the basis of a global minimization method is presented for the system parameters identification of flexibly supported rectangular laminated composite sandwich plates using measured natural frequencies of the sandwich plates. In this study, the first eight natural frequencies extracted from impulsive vibration testing data are used to identify the system parameters of the flexibly supported sandwich plates. In the identification process, the trial system parameters are used in the Rayleigh-Ritz method to predict the theoretical natural frequencies of the sandwich plate, a frequency discrepancy function is established to measure the sum of the squared differences between the experimental and theoretical predictions of the natural frequencies, and the global minimization method is used to search for the best estimates of the system parameters by making the frequency discrepancy function a global minimum. The accuracy and efficiency of the proposed technique in identifying the system parameters of several flexibly supported sandwich plates made of different face and core materials are studied via both theoretical and experimental approaches. The reasonably good results obtained in this study have demonstrated the applicability of the proposed technique.