Non-destructive evaluation of residual stress using the collaborative robot

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In the Centre for Ultrasonic Engineering (CUE) at the University of Strathclyde, the non-destructive evaluation of residual stress in welding and Wire + Arc Additive Manufacturing (WAAM) is considered as part of a larger programme through a 5-year Chancellor's fellowship led by Dr Javadi. Therefore, an advanced robotic system for the in-process residual stress measurement will be developed within the centre's state of the art robotic facility: Sensor Enabled Automation, Robotics & Control Hub (SEARCH). The measurement process will be carried out using (i) a phased array ultrasonic system and (ii) a flexible robotic cell. The innovative idea of robotic residual stress measurement is anticipated to increase the repeatability and the accuracy of the measurement, through reducing human errors and increasing the positioning accuracy of the measurement system, and also saving the measurement time. Traditionally, the majority of residual stress measurement methods are carried out manually with some basic automation, where the whole process still requires supervision by a highly skilled operator (expert in both areas of NDE and residual stress). In this project, a collaborative robot (Cobot) similar to KUKA KMR iiwa, will be used to facilitate the transition from a manual process (residual stress measurement) to an automated process in direct collaboration with the highly skilled operator (this PhD student). Such a smart collaborative robot can help with the residual stress measurement in both (A) offline measurement on the as-built components and (B) high-temperature in-process residual stress measurement. For the offline measurement, it is expected to increase the flexibility of the measurement as the operator should reach the different sections of weld, Heat Affected Zine (HAZ) and parent material of the component for the comprehensive residual stress measurement. This flexibility is also required to deal with the variations in the size and geometry of the components because the complex geometry of WAAM components is challenging to be fully covered during a manual residual stress measurement process. Furthermore, some parts of the process are time consuming in a repetitive procedure, The cobot can be trained by the operator on one of the testing sections and then the same process will be repeated automatically for the whole measurement reaching a more accurate results and saving time/energy. For the high-temperature in-process residual stress measurement, the cobot can also allow the initial testing and experiments on the hot sample to facilitate the transition from the manual measurement to the fully automated in-process inspection. All of these developments will be considered in this project to explore the requirements of a system of cobot residual stress measurement.