Non-destructive testing device for testing a welded region of a workpiece

A non-destructive testing device, comprising:

• a magnetic flux generator having an excitation controller, and
• a detection processor, which are adapted to generate a magnetic flux density by applying a magnetic field to a measurement subject,
• said testing device further comprising a magnetic flux detection element,
• said detection processor further adapted to:
• measure magnetic flux emitted from a plurality of locations on the measurement subject by way of the magnetic flux detection element,
• calculate, after the magnetic field is discontinued, a plurality of time constants of transient change in magnetic flux, and
• detect an internal structure of the measurement subject from a distribution state of the time constants,
• wherein the magnetic flux detection element comprises a plurality of microcoils arranged in a vertical line and a horizontal line, the lines forming a cross shape,
• wherein the detection processor is adapted
• to dispose the magnetic flux detection element at a predetermined location on the measurement subject,
• to performs a first measurement using a first subset of microcoils of the plurality of microcoils arranged in the vertical line, and
• to perform a second measurement by way of a second subset of microcoils of the plurality of microcoils arranged in the horizontal line at the same location as the predetermined location, and
• wherein the detection processor is adapted to estimate a center location of a nugget formed inside of the measurement subject and/or diameter of the nugget,
• by calculating an intersection between:
• a perpendicular line passing through a central point of a connecting line of first two points extracted, by acquiring measurement results from the first measurement, and extracting from the measurement results the first two points of corresponding to two microcoils of the first subset of microcoils, the first two points corresponding to a contour line of the nugget;
• and
• a perpendicular line passing through a central point of a connecting line of second two points extracted, by acquiring measurement results from the second measurement, and extracting from the measurement results the second two points corresponding to two microcoils of the second subset of microcoils, the second two points corresponding to the contour line of the nugget;
• setting the intersection thus calculated as a center location, and calculating a diameter of a circle passing through the first two points or the second two points centering around the center location.