Improved nondestructive testing of 60 mm M720 mortar projectile magnetic flux leakage inspection system of M720 mortar

Abstract

Abstract : The objective of this project was to provide basic outline drawings (BOD) for the concept design (level 1) and specifications of an automated magnetic flux leakage inspection system (AMFLIS) for detecting anomalies/flaws within the projectile body of the 60 mm mortar. The inspection of the M720 mortar projectile body for anomalies was performed by magnetic particle inspection (MPI) followed by visual inspection before and after painting the projectile using normal light. MPI cannot indicate the depth of a crack (anomaly); therefore, as per the item specification, no cracks in the projectile body shall be accepted and thereby increase the cost of the projectile body due to false rejects. The basic principles of MFL are shown in figure 1. The item tested was rotated in the field of a magnet and was magnetically saturated. In the absence of defects (discontinuities), the magnetic flux lines (saturated) continue to be contained and flow within the interior of the test item. If any defects were present, they forced some of the flux lines to flow external to the surface of the test item producing a leakage field.