Impact Location in an Isotropic Plate Without Training

Abstract

ABSTRACT IMPACT LOCATION IN AN ISOTROPIC PLATE WITHOUT TRAINING by Prasanna Rajbhandari The University of Wisconsin-Milwaukee, 2016 Under the Supervision of Professor Dr. Nathan Salowitz Unexpected impacts are major concerns in the aerospace industry that can cause difficulty to detect damage. Techniques have been developed to determine the impact location using piezoelectric sensors. Most existing systems require training data to develop a database of known structural responses and properties that can be referenced for location of impacts. This data collection is time consuming and if an impact and corresponding sensor data is outside the range of training data, the system may not be able to analyze it correctly. Some methods use specific sensor positions to reduce this phenomenon. Current systems typically utilize data from 3 or 4 sensors and are dependent on the knowledge of the speed of wave propagation in the material or reference data. This thesis develops a method of impact detection and location based on hyperbolic positioning suitable for isotropic homogenous plates that does not require training or knowledge of wave speed in the material. This derivation is not dependent on specific sensor layouts though sensor locations must be known and potential certain degenerate cases should be avoided. Equations were developed based on the time difference of arrival of strain waves at sensors with known location for impact location. This technique utilizes data from additional sensors to eliminate the need for training data or known propagation velocity. This technique translates Matlab code that was written based on these equations to automate the calculation and experimental validation that was performed using data from real specimens. Impact position error comparable to prior existing systems was verified.