Method and device for determining the neutral temperature of welded tracks

A method for determining in situ a longitudinal load acting on a beam exposed to a longitudinal load, wherein the beam is energized longitudinally in an acoustic frequency range, and a level of magnetic Barkhausen noise is measured at a surface of the energized region, then a calibration curve of Barkhausen noise versus longitudinal loading is established by measuring Barkhausen noise at different longitudinal stress states, the method comprising the steps of:

• establishing the calibration curve by measuring in situ the level of the magnetic Barkhausen noise at least at two different loadings and at least at three points on a periphery of a cross section of the beam;
• plotting a function of a value of the Barkhausen noise versus the change in Barkhausen noise for the change of the local stresses of said at least two different loadings, furtheron
• assigning the value of the Barkhausen noise belonging to zero stress to the value at the location of maximal change of the function,
• establishing the curve of Barkhausen noise versus stress by integrating the function of change of the Barkhausen noise versus Barkhausen noise,
• defining the stress at the given point of the cross section of the beam, then
• repeating the previous steps at further similarly loaded cross sections and for each point defining a weighting factor providing a weighted average of stresses in the same cross section corresponding to the given loading, and
• defining the longitudinal loading falling onto said given cross section on the basis of said calibration curve and by carrying out a weighted average calculation.