Investigation of Feasibility of Ultrasonic Non-Destructive Testing in Dry Contact Conditions through Numerical Analysis

Ultrasonic non-destructive testing (NDT) consists of three stages involving the following: an ultrasonic transducer, an impedance matching medium, and a test object. Generally, water, oil, or grease is used as a matching medium and increases the energy transmission rate between the transducer and test object. However, during non-destructive testing of large structures, the media can cause inconvenience before and after testing, and conventional three-phase tests cannot be performed on test subjects such as batteries that cannot use matching media. In this case, ultrasonic NDT consisting of two stages (transducer. inspector) can be considered, but research on such NDT is scarce. In this study, finite element analysis was performed considering the contact condition between the probe and specimen without a matching medium as a dynamic contact condition involving the relative speed between the two contact objects; the resulting waveforms were analyzed. In addition, based on the linear elasticity theory, the energy transmittance between the ultrasonic transducer and specimen was analytically defined. This index can also be used as an indicator to evaluate the level of two-phase NDT technology and confirm the possibility of commercialization in the future. Furthermore, we propose a technique that can increase the ratio of energy transferred from the excitation transducer to the test object through simple modification of the experimental configuration.