The advantages and challenges of linking industrial needs with academic research

Dunhill, Ally; Thayer, P. J.; Newton, Kathryne

doi:10.1784/insi.2011.53.1.12

Cited by 2 publications

(4 citation statements)

References 4 publications

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“…Industry has consistently highlighted the need for improved eddy current and electromagnetic testing capabilities [1], and the ability to detect small surface breaking defects in safety critical applications such as in jet engine components is extremely important for safety but also potentially for cost savings in asset management. One can increase the sensitivity to small surface defects by reducing the depth to which eddy currents flow in the sample surface.…”

Section: Introductionmentioning

confidence: 99%

“…One can increase the sensitivity to small surface defects by reducing the depth to which eddy currents flow in the sample surface. This electromagnetic skin depth for an electromagnetic plane wave is often defined by the equation given below (1) where  is the electrical conductivity of the sample,  is the magnetic permeability of the sample and is the frequency of the electromagnetic wave from the eddy current coil. It is worth noting that this equation is a simplification and approximation for a plane wave up to MHz frequencies [2].…”

Section: Introductionmentioning

confidence: 99%

“…Metal components with high electrical conductivity such as aluminium, or high magnetic permeability tend to have relatively electromagnetic small skin depths at MHz frequencies, and using equation (1) above, at 1 MHz we would obtain skindepths of 83 m and 650 m, in aluminium and a titanium alloy (Ti-6Al-4V) respectively . Approximately 63% of the total eddy current in the sample is confined to within one skindepth, and at one skindepth deep the current lags the current at the surface by 57˚.…”

Section: Introductionmentioning

confidence: 99%

“…Target defects include fatigue cracks, stress corrosion cracking or even inclusions that may effectively present themselves as surface breaking cracks. The ability to improve early stage detection and increase sensitivity to smaller defects is a key industrial requirement that fits in with the strategic priorities of industry [1]. In industrial use, eddy current sensor stand-off is likely to vary, but if care is taken this can be controlled to a large extent, but cannot be completely avoided.…”

Section: Introductionmentioning

confidence: 99%

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High-frequency eddy current measurements using sensor-mounted electronics

Hughes¹,

Day²,

Tung³

et al. 2016

Insight

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Eddy current techniques are used widely for the detection of surface breaking cracks in metal samples and the detection of such defects on metals with low electrical conductivity is challenging. For good sensitivity to small surface cracks, the electromagnetic skin-depth of the eddy current needs to be small, which often means operating at MHz frequencies. One of the major challenges in high frequency eddy current testing is that the capacitance of the cable between the instrument electronics and the sensor head becomes significant in the MHz range, making the system unstable and introducing noise into the system as the cable moves and electrically interacts with objects close to it. There are significant benefits to locating the electrical circuitry directly behind the eddy current sensor coils, reducing issues with cable induced electrical noise, enabling one to detect smaller defects at earlier stages of growth. Materials such as nickel based super-alloys, titanium, austenitic steel and carbon fibre composites are often used in safety critical applications, where the ability to detect surface cracks at the earliest possible stage is vital. Examples are presented that show detection of small defects on a range of challenging materials at eddy current frequencies to over 15 MHz.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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