A Hierarchical Impact Force Reconstruction Method for Aerospace Composites

Abstract

This research work presents a hierarchical method able to reconstruct the time history of the impact force on a composite wing stringer-skin panel by using the structural responses measured by a set of surface bonded ultrasonic transducers. Time reversal method was used to identify the impact location by the knowledge of structural responses recorded from a set of excitation points arbitrarily chosen on the plane of the structure. Radial basis function interpolation approach was then used to calculate the transfer function at the impact point and reconstruct the impact force history. Experimental results showed the high level of accuracy of the proposed impact force reconstruction method for a number of low-velocity impact sources and energies.

Acoustic emission localization in composites using the signal power method and embedded transducers

“…The used RBF interpolation method is explained in detail in [14,15]. In some recent works the authors demonstrated that hierarchical radial basis functions (RBFs) provide high accuracy in the data reconstruction when information related to a point on the structure is not available [11,12]. In the proposed paper, the unknown data are the power values related to the M points on the sample surface, whose known spatial coordinates are the inputs of the RBF interpolation method, in addition to the known N power values to be interpolated and related to the sensor locations.…”

“…𝑃 𝑁 are the power values at 𝑁 transducer locations. As performed in other research works [11,12] the thin plate spline (TPS), whose kernel is 𝜙(•) = (•) 2 𝑙𝑛(•), was used as radial basis function for its peculiar characteristics [16].…”

“…Once estimated the signal power values, the location of the impact event was estimated by a center-of-gravity method [11,12], involving the power values and the relative spatial coordinates [13]:…”

“…Another approach able to identify the location of an impact event is the time reversal method, where impact localization is achieved by measuring the structural response on a set of calibration points on the specimen and cross-correlating these recorded signals with the signal coming from an actual impact event [8][9][10]. The "impact cell" is estimated as the one with the maximum correlation coefficient, averaged among its corner points, and then the actual impact location is evaluated by a center-of-gravity method [11,12]. This paper proposed a new impact localization algorithm based on the estimation of the signal power of measured elastic waves.…”