Acoustic emission location of defects by analytical and tabular methods during static loading the composite caisson of the aircraft wing

The article presents the results of acoustic emission testing of an aircraft wing box made of composite material ACM 102 130 C UD. The load was changed in steps with a step of 10 % of its maximum value. Before loading, the control zones consisting of four piezoelectric transducers of acoustic emission were calibrated. In order to reduce the influence of anisotropy and design features of the wing box on the errors in defect location, a new technique consisting of analytical and tabular methods was developed. In the analytical method, the coordinates of defects were calculated using three sensors of the piezoantenna, and the location error included random and systematic components. Inaccurate determination of the difference in the times of signal arrival at the sensors of the piezoantenna was the main source of the random component of the error. The complexity of the design influenced the appearance of the systematic error. At the same time, the features of the test object hampered the rectilinear propagation of the sound wave. When using the tabular method, the caisson structure was divided into a number of zones and the matrix of correspondence between the difference in signal arrival times and the coordinates of the selected cells was calculated. It was shown that the number of signals localized using the tabular method was bigger than that using the analytical method. Practical application of the developed location method showed that the average value of the reduced error decreased two fold when calculating the X coordinate and six fold when calculating the Y coordinate. This made it possible to reduce the location errors associated with the location of the calibration points on the structure. If the signal location error exceeded the permissible value determined by the cell size, they were excluded from further consideration as not localized.