What effect do cracks oriented parallel to the eddy current flow have on testing?

Cracks that are oriented parallel to the eddy current flow typically present a lower response compared to those that are perpendicular to the flow due to the way eddy currents interact with defects. Eddy current testing relies on the induced electrical currents that are generated in the conductive material being tested. When a crack is aligned parallel to the direction of these currents, the disruption in the current flow is minimized because the current can continue to flow along the crack without significant interruption.

In contrast, when cracks are perpendicular to the eddy current flow, they create a more substantial disruption in the current. This results in a stronger response signal and makes such defects easier to detect. The difference in orientation affects the impedance change that the eddy currents produce when encountering a defect; thus, their detectability and the strength of the signals recorded during testing are directly influenced by their alignment relative to the eddy current flow.

Understanding this principle is essential for interpreting eddy current test results effectively, as it allows for more accurate assessments of the material integrity being evaluated. Therefore, option B accurately reflects the relationship between crack orientation and eddy current response.