Limits of ToFD technique 1

[fakhmed]

Dear All,

As far as ToFD has many advantages for identification of defects and traceability, are there possible defects type for which ToFD is not effective and can be blind ?

Best regards

 

[stanweld]

Shallow surface defects are difficult to find. It is noted that improvements have been made in this area.

 

[ndeguy]

fakhmed

I dont agree with the first part of your opening sentence -identification of defect-type is not easy from the grey scale image. Most TOFD technicians can reasonably say is that the indicated flaw is either planar (measurable length and vertical height, threadlike (measurable length but no measurable vertical height)or a point reflector (no measurable length or height). To discriminate between say LOF, slag and crack takes a very skilled and experienced interpreter.

I dont understand what your reference to "traceability" implies - the usual concept of this is that there is a verified chain of information relating a finished product back through its manufacture to the various points of origin. How this relates to TOFD i dont understand.

In terms of type of defects to which it is blind, well following the laws of physics the longitudinal waves may be either diffracted or reflected so it is hard to imagine a particular type of defect being systematically missed. Of course say there is a small defect masked by a larger defect above it, then that will be missed.