Investigation of Indirect Thermal Resistance/Conductance Measurements Utilizing Ultrasonic SHM Sensors

Researchers have been working on methods for truncating assembly, integration, and testing timelines for satellites without significantly reducing system reliability and incurring unacceptable mission risk. Structural Health Monitoring has been pursued as a means for validating workmanship, which is considered an area of high uncertainty. Embedded ultrasonic piezoelectric wafer active sensors have been utilized with local and global inspection capabilities and have shown promise in detecting structural changes that may occur during a build and test cycle, specifically focused on interface qualification. This paper will focus on investigations into the capability of the same sensors to indirectly quantify thermal resistance across an interface as a means to validate system thermal conductance without the need for thermal vacuum testing. Ultrasonic waveforms will be analyzed across simple joints for the detection of features related to the impedance of thermal transmission. Analysis will be conducted on the influence of atmosphere and the impact it has on ultrasonic impedance of guided waves through a solidsolid interface and compare the results with those known for thermal testing.