A new algorithm for detecting impact point in anisotropic plates by the acoustic emission technique

The wave speed in an anisotropic plate is dependent on the direction of propagation and therefore the conventional triangulation technique does not work for the prediction of the impact point. A method based on the optimization technique was proposed by Kundu et al. to detect the point of impact in an anisotropic plate. They defined an objective function that uses the time of flight information of the ultrasonic signals to the passive transducers attached to the plate and the wave propagation direction (θ) from the impact point to the receiving sensors. This function is very sensitive to the arrival times. A small variation in any one arrival time results in a significant change in the impact point prediction. This shortcoming is overcome here by modifying the objective function and following a new algorithm. Both old and new objective functions (denoted as functions 1 and 2) are used in the new algorithm. This algorithm uses different sets of transducers and identifies the common predictions from different sets. The proposed algorithm is less sensitive to the arrival time variation and thus is capable of predicting the impact point correctly even when the measured arrival time has some error. The objective function 2 is simpler, so the computer code run time is reduced and it is less likely to converge to the local minima when using the simplex or other optimization techniques. The theoretical predictions are compared with experimental results.