Automated system for laser ultrasonic sensing of weld penetration

An on-line sensor is required for real-time control of penetration depth in robotic welding. Currently, no on-line techniques exist for direct penetration depth measurement. The development of a penetration control system will significantly reduce the costs associated with repairing or scrapping defective welds. Laser array generated ultrasound is a noncontact, nondestructive method that can potentially be used to measure weld penetration. This paper will discuss the design and implementation of an automated system that was used to measure the depth of simulated solidified welds. The system consists of a laser array generation source and an electromagnetic acoustic transducer (EMAT) receiver. Measured penetration results for the simulated weld are compared with the exact results. Experimental results will also be shown for array gain measurements in order to demonstrate the power of the array. This automated system is being modified in readiness for use in actual robotic welding.

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