METHOD MEASURING RATE OF INTERNAL FAILURE OF HOLLOW STRUCTURES FROM FERROMAGNETIC MATERIAL AND GEAR FOR ITS REALIZATION Russian patent published in 1999 - IPC

FIELD: nondestructive testing. SUBSTANCE: part of wall between poles of U-shaped magnetic core is magnetized to magnetic saturation, then it is demagnetized by current rising from zero and having polarity reversed to that of magnetization current and emf is tested. At moment when emf is equal to zero value of demagnetization current is recorded. After some lag additional magnetization and demagnetization operations are conducted and value of demagnetization current is found. Rate of internal failure is evaluated by relation of difference of demagnetization currents for main and additional operations to time lag. Gear for realization of method has U-shaped magnetic core with magnetization/demagnetization winding, magnetization and demagnetization units, measurement winding, meter of residual field, indicator and control unit. Magnetic core is rectangular in cross-section, size of smaller side N of it is chosen from relation N=(1.6-2.0)d, where d is initial thickness of wall of hollow structure. EFFECT: enhanced authenticity and accuracy of test. 2 cl, 2 dwg