How does surface roughness affect the results in ET?

Surface roughness plays a significant role in eddy current testing (ET) as it can influence the flow of eddy currents and thus impact measurement accuracy. When a surface is rough, it can cause variations in the electromagnetic field used during the inspection. This can lead to unexpected changes in the impedance of the probe, which directly affects the measurement readings. Particularly, the roughness might create additional noise in the signal, making it more challenging to discern the true characteristics of the material being tested.

Moreover, increased surface roughness can alter the depth of penetration of the eddy currents, which may lead to erroneous assessments of the material properties. Factors like crack detection and material thickness measurements become less reliable if the surface is not adequately smooth, as rough surfaces can mask defects or lead to false indications.

In contrast, the other options do not accurately reflect the influence of surface roughness in eddy current testing. For instance, claiming that it does not affect results would ignore the fundamental principles of how eddy currents operate. Similarly, restricting the effects to only external surface inspections overlooks the comprehensive impact roughness can have across various testing scenarios. Lastly, suggesting that rough surfaces make detection easier contradicts the practical experiences where clarity and accuracy of readings are diminished in the presence