Magnetic memory method and (active) thermography

At the 11th European Conference on Non-Destructive Testing, two of the methods discussed were particularly interesting and appear to have the potential to become more mainstream NDT applications.

The first is the magnetic memory method (MMM) detecting technique. This can be used in the diagnosis of impending failure in ferromagnetic parts. The product ranges that can be tested include gear teeth, pipelines, machines and structures. The principle of the method is the ability of the application to detect a stress concentration area prior to the formation of the first micro-cracks. It does this by using sensors/transducers that measure the magnetic Barkhausen noise. There are no consumables and the power usage is minimal. It would appear that the method has some limitations but, as the very lively discussions that began in English soon became heated and in a language that I am unfamiliar with, I was unable to ascertain what was being discussed.

The second is (active) thermography, which requires the component to be thermally stimulated (heated), which can be carried out using heating lamps, lasers, ultrasounds or microwaves. With electroconductive materials, eddy currents are one of the possible heating methods. The results are viewed and captured using a thermographic camera. Recently, I saw a thermographic camera attachment for an iPhone, which appeared to work well and could help develop this application to becoming portable and site-friendly. This is a very eco-friendly method and could be a replacement for both magnetic particle (MT) and penetrant testing (PT). The disadvantages are similar to both MT and PT in that broad, shallow flaws and flaws at the bottom of a sharp profile change are difficult to detect.

The programme presentations from the 11th ECNDT provided me with some interesting facts:

  • Less than 10% of the NDT operators said the customers had NOT applied pressure on them to change the results of the inspection. Do the 90% plus customers need to sign up to a code of ethics?

  • Just over 30% of the UT operators could measure the remaining wall thickness for in-service inspection to the level of accuracy required. Does this justify additional specific on-the-job training?

  • There are nearly as many 70 plus year-olds working in NDT as there are under 30 year-olds.

Does this mean NDT keeps you fit, that NDT staff do not have suitable pension schemes or that NDT is a great occupation?

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