Lamb, Matthew and Parker, Anthony James (2012) Improving Structural integrity assessment of nonlinear packaging materials. In: Proceedings: the 7th Australasian Congress on Applied Mechanics (ACAM 7). Engineers Australia, Barton, A.C.T., pp. 439-448.

Abstract

During the distribution phase, packaged consignments are exposed to a variety of environmental hazards (such as vibrations) which, if excessively severe, may cause damage to or even destroy the product. Structural deterioration can be tracked by monitoring variations in the packaging system's modal parameters, particularly its natural frequency (stiffness). Natural frequency estimates are often extracted using a least squares regression curve fit, applied to an estimate of the system's frequency response function (FRF). FRF estimates are generally obtained using the Fourier transform with a single input and single output (SISO). This approach is suitable for many applications; however, as the nonlinearity of the system under analysis increases, the ability of this technique to accurately monitor changes in the system will decrease. This paper discusses an approach which is designed to separate the linear component of the system's FRF using a reverse multiple input/single output (RMISO) algorithm. Such separation will allow traditional modal parameter extraction techniques to be used to monitor the condition of nonlinear systems. The paper presents the results of preliminary experiments in which expanded polystyrene samples were subjected to broad-band random base excitation with a free-moving load placed atop the cushion sample. Continuous acceleration measurements of the vibration table and the free moving load are used to compute the FRFs of the cushions and the differences between a conventional (SISO) approach and the RMISO based parameter extraction technique are discussed. 7th Australasian Congress on Applied Mechanics (ACAM 7), 9-12 December 2012, the University of Adelaide, North Terrace Campus

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