Boundary condition identification using condensation and inversion - Application to operating piping network

This paper deals with the experimental analysis of piping systems under operating conditions in the held of vibration and acoustic analysis. A new approach to identify the boundary conditions of a part of a curvilinear structure is presented. The basic concept consists of solving an inverse problem where the measured response of the system tested is combined with an incomplete analytical model in order to identify the boundary dynamical state in the frequency domain. As in finite element methods, the tested network is described using elements and nodes. An original technique using a transfer matrix of continuous elements provides a small-size analytical model. In addition, condensation procedure is used to eliminate all degrees of freedom (d.o.f.) having a modelled boundary condition and to reduce the size of the solved inverse problem. Since identification of boundary conditions is performed, the analysis of dynamic response of the tested network may be performed without further matrix computation. The validity and the feasibility of the approach are shown using actual test results. Examples concerning real applications are also presented. (C) 2000 Academic Press.