Robotic residual stress measurement using phased array ‎ultrasonic method

Residual Stress (RS) in engineering components can lead ‎to unexpected and dangerous ‎structural ‎‎failures, and thus ‎represent a significant challenge to quality assurance in both ‎‎welding and metal ‎‎additive manufacturing (AM) processes.‎ ‎The RS ‎measurement using the ‎Phased Array Ultrasonic ‎Testing (PAUT) system, ‎rather than the single element ‎ultrasonic ‎method, is a new Non-Destructive Evaluation (NDE) method developed by the Center for ‎Ultrasonic Engineering (CUE) to improve the measurement accuracy and allow the robotic ‎measurement. Traditionally, the majority of RS measurement methods are carried out ‎manually with some ‎basic ‎automation, where the whole process still requires supervision by a ‎highly skilled operator. This ‎paper aims to study the feasibility of the development of an ‎innovative robotic system for RS ‎measurement using the PAUT method. Using 6-axis KUKA ‎robots in Sensor Enabled Automation, Robotics & Control Hub (SEARCH)‎, the robot ‎programming and path planning for the RS measurement in the component with the complex ‎geometries, like Wire Arc Additively Manufactured (WAAM) samples, and with the ‎complications of the unknown position of Heat Affected Zone (HAZ) and weld, which ‎requires more accurate positioning compared with the base metal, was developed. The ‎feasibility of integrating this new system with the in-process high-temperature inspection ‎system was also discussed and a new method for the measurement of the acoustoelastic ‎coefficient was studied. The robotic RS ‎measurement was shown to increase the ‎‎measurement ‎repeatability and ‎PAUT sensor positioning accuracy as well as allow the in-process RS ‎measurement in the WAAM and welding components. ‎