ISO 9934-1:2015 pdf free

ISO 9934-1:2015 pdf free.Non-destructive testing一Magnetic particle testing一General principles
When using multidirectional techniques, the current used shall be purely sinusoidal or phase controlled but the phase cutting shall not be more than 90°. Practical demonstration that the technique is effective in all directions shall be carried out (e.g. using sample parts with known defects or shim type indicators).
Provided the permeability is in the normal range and the current measurement methods are controlled as described, calculations based on the use of 2 kA/m can provide a valuable method of technique preparation. The use of either peak current or True RMS current is acceptable if the crest factor is known. Knowing the entire waveform of the magnetizing curve would be optimal, but knowing the crest factor is a good practical approximation. For pure sinusoidal waveforms, the relationship between peak, mean, and RMS is shown in Annex A. Techniques based on calculation shall be verified before implementation.
NOTE 1 For steels, with low relative permeability, a higher tangential field strength might be necessary. If magnetization is too high, spurious background indications can appear, which could mask relevant indications.
If cracks or other linear discontinuities are likely to be aligned in a particular direction, the magnetic flux shall be aligned perpendicular to this direction where possible.
NOTE 2 The flux can be regarded as effective in detecting discontinuities aligned up to 60° from the optimum direction. Full coverage can then be achieved by magnetizing the surface in two perpendicular directions.
Magnetic particle testing should be regarded as a surface NDT method, however discontinuities close to the surface can also be detected. For time varying waveforms, the depth of magnetization (skin depth) will depend on the frequency of the current waveform. Magnetic leakage fields produced by imperfections below the surface will fall rapidly with distance. Therefore, although magnetic particle testing is not recommended for the detection of imperfections other than on the surface, it can be noted that the use of smooth DC or rectified waveforms can improve detection of imperfections just below the surface.ISO 9934-1 pdf download.