Fakih et al., [16] developed a flaw detection system in FSW using ultrasonic guided waves. A damage index was defined using the acquired signals and computer tomography scan was used to verify the damage. Hugget et al., [17] employed Phased array ultrasonic testing and X-ray radiography to detect defects in FSW joint. The result reveals that phased array ultrasonic testing performs better as it detects defects less than 0.2 mm whereas Xray radiography fails to detect this defect. These non-destructive testing methods discussed are post weld inspection process and incur high cost which may result in increased production time and cost. Further these methods may not be effectively implemented for inspection while performing welding operation.