The Flow Of Strength

The current decreases in the region of the longitudinal cut and reaches the original magnitude again in the intact part of the tube. The cut in circumferential direction has apparently no influence on the current. The physical background low current consumption as long as the coil is still far away from the tube. the reason for this is the undisturbed self induction much higher current in a region where the tube is intact the reason here is the eddy current its own magnetic field and the reduced inductance of the coil. Small current consumption at the longitudinal cut because the path of the eddy current is longer. 

The eddy current is lower and its magnetic field is smaller. Full current consumption of the region with this sole cut and circumferential direction as if there were no cut at all. The flow of the eddy current is almost undisturbed obviously it is not possible to detect crack like defects that run along the flow lines of the eddy current. We observe the same phenomenon in reverse direction. This technique can be improved considerably if not only a single coil but several coils are used. The original coil which is now called the excitation coil is supplemented with the receiver coil on the left side and a receiver coil on the right side. A voltage meter is connected to each of the receiver coils. 

The improved test arrangement has been set up in the laboratory and is now in operation as can be seen from the current consumption of the excitation coil. First the materials tester picks up the right receiver coil and places it over the tube. The excitation coil is next in turn as soon as it is pushes it over the tube the current consumption increases exactly as in the previous test. Last in turn is the left receiver coil and carefully takes all three coils and moves them to the right. The point of the right voltage meter deflect then the point of the left voltage meter further to the right where the tube is intact the borders of non of the voltage meters are deflected. Unfortunately this sole cut and circumferential direction is again not detectable and more shows the physical background. The current consumption is high in an area where the tube is intact the reason for this is the undisturbed flow of the eddy current because the magnetic field of the eddy current doesn't flow through any of the two receiver coils in measure virtually no voltage on them. As soon as the excitation coil reaches the left and of the longitudinal sole cut. The current consumption decreases the reason for this is the longer path of the eddy current because the eddy current now flows partly underneath the right receiver coil it's alternating magnetic field induces a voltage there. When the excitation coil reaches the right hand of the longitudinal sole cut the eddy current partially flows under the left receiver coil and induces a voltage there. 

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