Abstract
This paper presents a detailed study on the impact source identification of a plate structure using time-reversal (T-R) method. Prior to impact monitoring, the plate is calibrated (or characterized) by transfer functions at discrete locations on the plate surface. Both impact location and impact loading time-history are identified using T-R technique and associated signal processing algorithms. Numerical verification for finite-size isotropic plates under low velocity impacts is performed to demonstrate the versatility of T-R method for impact source identification. The tradeoff between accuracy of the impact location detection and calibration spacing is studied in detail. In particular, the effect of plate thickness on calibration spacing has been examined. A number of parameters selected for determining the impact location, approximated transfer functions and steps taken for reconstructing the impact loading time-history are also examined. Two types of noise with various intensities contaminated in strain response and/or transfer functions are investigated for demonstrating the stability and reliability of the T-R method. The results show that T-R method is robust against noise in impact location detection and force reconstruction in circumventing the inherent ill-conditioned inverse problem. Only transfer functions are needed to be calibrated and four sensors are requested in T-R method for impact identification.
Highlights
The safety and reliability of aerospace structures are always alerted by various external impact sources, including tool drops, runway debris, hails, birds and unknown events
The spacing of the calibration location of transfer functions for plates with various thicknesses, the selection of characteristic parameters in location detection, transfer function approximation, the effect of noise in impact location detection and force reconstruction by approximated transfer functions are to be investigated in detail as follows
The transfer function (Green’s) represents the relationship between the calibrated impact force acting at the location, ξ, in the plate and the strain response observed at a sensor location are calibrated in frequency domain by
Summary
The safety and reliability of aerospace structures are always alerted by various external impact sources, including tool drops, runway debris, hails, birds and unknown events. Impact monitoring techniques have been developed to detect the impact location and reconstruct the impact loading time-history on structures while in service using a permanently mounted array of sensors. The identification of impact source based on sensor data and some characteristics of the structure is an inverse problem. In impact source identification problems, the uniqueness and the stability of the solution are generally violated because of incomplete information collected by a practically limited number of sensors, the existence of measurement error and noise, and etc. Transfer functions can be calibrated directly by experiments [19,20] for all structures, but the argument between the accuracy and the time consumption should be considered Based on these functions in time or frequency domain, a deconvolution technique is commonly used to solve this inverse problem. The spacing of the calibration location of transfer functions for plates with various thicknesses, the selection of characteristic parameters in location detection, transfer function approximation, the effect of noise in impact location detection and force reconstruction by approximated transfer functions are to be investigated in detail as follows
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