Накладний індуктивний перетворювач для магнітної дефектометрії

Abstract

Сутність електромагнітних методів неруйнівного контролю феромагнетиків полягає у виявленні магнітного поля, що виступає над внутрішніми і підповерхневими дефектами. Для виявлення такого локального поля запропоновано новий варіант накладного давача у вигляді індуктивного елемента на тороїдальному осерді з додатковими магнітопроводами. Цей давач має просту конструкцію, його висока чутливість підтверджена експериментально. Такий давач може використовуватись для контролю зварних з’єднань запропонованим методом, що ґрунтується на вимірюванні магнітного опору ділянки зварювання. Сущность электромагнитных методов неразрушающего контроля ферромагнетиков состоит в выявлении магнитного поля, выступающего над внутренними и подповерхностными дефектами. Для выявления локального магнитного поля предложен новый вариант накладного датчика в виде индуктивного элемента на тороидальном сердечнике с дополнительными магнитопроводами. Этот датчик имеет простую конструкцию и высокую чувствительность, подтвержденную экспериментально. Такой датчик может использоваться для контроля сварных соединений предложенным методом, основанным на измерении магнитного сопротивления участка сварки. The essence of electromagnetic methods of nondestructive ferromagnets testing consists in identifying the lines of ledge of the external magnetization constant magnetic field that is scattered on interior and subsurface defects. Existing electromagnetic methods differ only by ways of local magnetic inhomogeneity detections. For detecting the local magnetic field the new variant of the plated sensor for nondestructive testing of ferromagnetic materials in the form of an inductive element on a toroidal core with magnetoconductive elements was proposed. The sinusoidal audio frequency voltage from the generator with amplitude at which the core material begins to enter into the saturation stage is supplied in winding. The magnetic field of an internal defect straying through internal lining magneto conductive linings sub magnetizes the ferrite core, and is summed up with the field from the generator, that is leading to saturation of the core coil, losses the inductance and increase current in the coil. To measure the saturation current series with the winding turns on the low resistor, which voltage is measured, and it determines the size of the defect. Inductive sensor has a simple design and high sensitivity (output voltage increase more than 5 times), confirming by the experimental investigation of its model. The proposed sensor is insensitive to the presence of extraneous ferromagnetic objects, and only responds to a magnetic field and can be used for monitoring welds of steel elements by measuring the magnetic resistance of some consecutive areas of the consistent weld in the transverse direction. The magnetic resistance value of the weld at most depends on the presence of cracks, cavities, pores and other non-magnetic inclusions having negatively affect on the strength of the connection. The magneto motive force determination in the control area is carried by means of the inductive magnetic field sensor. The internal high magnetic resistance of the sensor is much larger than its poles contact resistance and resistance of the defect area, and therefore does not affect on its stray field. It does not matter how the intensity of the ledge field in the section of the seam changes because the welding defect has increased magnetic resistance and the quality of welding is defined by the range of this resistance The magnetic flux of the applied field to determine the magnetic resistance control areas is measured by means of an optional magnetic flux sensor installed in one of the pole pieces of the magnetized device. Since the pole piece has a constant value of the magnetic resistance, the output voltage of the additional sensor further will depend on the magnitude of the magnetic flux of the magnetized device. This means that irregularities of detail surfaces will be taken into account in determining the magnetic resistance of the defect area.