Nondestructive Testing of Materials Using Thermal Imaging

摘要

Nondestructive testing is helpful in preventing unintended failures in manufactured components. The research presented here examines a thermal nondestructive testing method that makes use of laser heating. Potential defects are found by using a thermal camera to examine the temperature response on the nonheated side of the object being tested. A mathematical model for the temperature response is generated using a two-dimensional numerical conduction solution in cylindrical coordinates. The presence of defects is difficult to detect by simply examining thermal images, but if the temperature response calculated by the mathematical model is subtracted from the measured temperature field, any defects in the material become much more obvious. In examining what is, essentially, the residual temperature field, which should ideally consist of measurement noise, any aberrations in measured temperature from material defects are effectively magnified. The sensitivity with which defects can be detected is strongly affected by the degree to which the physical heating process is correctly described by the mathematical model. Synthetic experiments are used to show the impact of the accuracy with which the thermal parameters are known on the effectiveness of the analysis method. Physical experiments are also examined to show practical applications of the method.