Comment on "Response of Nonlinear Flat Panel to Periodic and Randomly Varying Loadings"
L1 presents an interesting analysis of the dynamic response of a flat plate when the nonlinear effects of the membrane forces are significant. Unfortunately, the author has neglected to reference several previous publications presenting results pertinent to this problem, some of which are listed here. Also, the author's treatment of the random-excitation case deserves some comment. The equivalent linearization technique used seems to be of questionable value in this case, since an exact solution for the mean-square response (as well as other statistical measures) of the randomly excited cubic system is available.' It is true that the exact solution is limited to the case of white-noise excitation; however, the limitations of the equivalent linearization method imply much the same restriction. That is, the "true" linear frequency and the equivalent linear frequency cannot be far separated, and the spectrum of the excitation normally may be considered constant over this restricted frequency range. In any case, it is not clear from the article why the author feels that the results of this approximate technique are valid for the case of nonwhite excitation. The statements concerning the "effective transfer function" also may be questioned. Not all people who are working on the problem of nonlinear panel response would agree that physical occurrence of the upper branch of the nonlinear response curve is as unusual as the author implies. Certainly, if the response of a panel does lie on the upper branch, the effect of damping may not be considered unimportant.