CPC G01N 27/82 (2013.01) [G01N 33/2045 (2019.01); G01N 27/9026 (2013.01); G01N 27/9046 (2013.01)] | 18 Claims |
14. An arrangement for determining a crack at an edge of a metallic material, the edge having a curvature with a radius, the arrangement comprising:
a transmitter coil arranged to generate a magnetic field in the metallic material,
a receiver coil arranged to detect the magnetic field,
a signal generator arranged to feed a current having a first magnitude to the transmitter coil for generating the magnetic field in the metallic material,
a control unit arranged to control the signal generator such that the current obtains a second magnitude when the magnetic field is estimated to have penetrated deeper than a deepest crack depth desired to be measured in the metallic material, and
a computing arrangement arranged to receive a signal created by the magnetic field detected by the receiver coil, and to determine a first signal value of the signal at a first time, the first time at which it has been estimated that any disturbances due to control of the current to obtain the second magnitude have ceased,
the computing arrangement being further arranged to determine a second signal value of the signal at a second time after the first time, and to determine a third signal value of the signal at a third time after the second time,
wherein the computing arrangement is further arranged to determine;
a possible presence of a crack and its crack depth based on the first, second and third signal values by means of determining a characteristic relation between at least two of the following combinations of signal values: the first signal value and the second signal value; the second signal value and the third signal value; and the first signal value and the third signal value, wherein transmitter coil, in operation, is configured to be arranged at least partly outside of the edge of the metallic material.
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