Automatic Flaw Detection in TOFD Images for NDT During Welding

The basic approach to the inspection and repair procedure for welding has barely altered for three decades. The normal practice has continued to be to inspect a weld only after the welding programme is complete. Thus by the time a defect is detected, considerable time and money has been spent on completing the welding of a rejectable component. Furthermore, a large number of additional weld runs will generally have been deposited over the defect, thus increasing the cost of repair and decreasing the quality of the component.

There would be major cost and programme advantages for a wide range of industries if nondestructive testing (NDT) was performed during welding as an on-line operation. Rejectable welds could be identified as such before wasting time and money completing the weld. In addition, repairs could be performed more quickly and economically if performed before further weld build up, and the detection of a high incidence of flaws during welding would enable the process parameters to be appropriately adjusted prior to completion of a production run. Therefore, if NDT examinations can take place between weld runs with no resultant delay in the welding procedure, then some level of improved inspection and lack of downtime is virtually guaranteed. Furthermore, if the result of the inspection could also be automatically interpreted then comprehensive on-line control of the welding process is a foreseeable entity.