Pulsed eddy current thermal imagery detecting system based on rotational magnetic field excitation

Abstract

The invention discloses a pulsed eddy current thermal imagery detecting system based on rotational magnetic field excitation. According to the pulsed eddy current thermal imagery detecting system based on the rotational magnetic field excitation, output ends of a twin-channel orthogonal excitation power supply are connected to two-road exciting coils of a combined type double U-shaped probe respectively, and the combined type double U-shaped probe is put above a sample to be tested; when currents with assigned frequency and assigned amplitude are introduced into the two-road exciting coils, vortex fields are induced on the surface and a near surface of the sample, and joule heat generated on the surface of the sample shows different distributions at different temperatures in a slit region; an infrared thermal imager is used to record temperature variation situations of the slit region of the sample to be tested, and crack characteristic signals of the surface of the sample to be tested are extracted from a thermography sequence collected by the infrared thermal imager through a computer, and detection and identification of crack defects of any angle on the surface of the sample to be tested are achieved. According to the pulsed eddy current thermal imagery detecting system based on rotational magnetic field excitation, through the adoption of the combined type double U-shaped probe, electromagnetic coupling efficiency and homogeneity of excitation are improved; meanwhile, a rotating magnetic field can be output on the surface of the sample, and thus the problem in sensitivity of crack detection direction of the surface of the sample is overcome.

Description

technical field [0001] The invention belongs to the technical field of pulsed eddy current thermal imaging non-destructive detection and evaluation technology, in particular to a pulsed eddy current thermal imaging crack detection system at any angle based on rotating magnetic field excitation. Background technique [0002] Ferromagnetic materials are widely used in petrochemical, rail transit, aerospace and other fields. Factors such as material structure discontinuity, fatigue, corrosion, and external harsh environments will cause aging and failure of material performance, which will largely affect the equipment in service. performance, and may even cause equipment failure or catastrophic consequences. In order to ensure the safe operation of equipment, it is necessary to monitor its early crack and expansion state, and non-destructive testing and evaluation technology can effectively provide useful information about the safety of the structure state. [0003] For ferroma...

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Problems solved by technology

[0003] For ferromagnetic materials, pulsed eddy current thermography has been proved to be a very potential non-destructive testing technology, combining eddy current testing and infrared thermography, with non-contact, large detection area, high spatial resolution and heat map display Intuitive and other advantages; In the pulsed eddy current thermal imaging detection system, the induction heating power supply plays a pivotal role, directly affecting the detection rate and thermal contrast of the surface cracks of the inspected object. The current induction power excitation device is mainly wound by water-cooled copper tubes For different application objects, the types of induction coils are: planar type, spiral type, special-shaped and Helmholtz type, but there is poor heating uniformity and the purpose of heating the specified area cannot be achieved. At the same time, except for Helmholtz type Induction coils other than the induction coil also have the disadvantage of blocking the field of view of the thermal imager; in order to achieve heating in a specified area, the researchers introduced an excitation coil with a U-shaped magnetic core. However, when the crack direction is small or parallel to the eddy current direction , the detection sensitivity is low or it is difficult to detect cracks; in order to detect cracks in different directions on the surface of the material to be tested, it is necessary to adjust the relative position of the excitation coil containing the U-shaped magnetic core and the material to be tested many times, and the detection efficiency is greatly reduced

Therefore, in order to achieve uniform heating, overcome the limitations of the detection field of view and the sensitivity of crack detection directions, it is necessary to develop a detection system that can meet the detection of cracks at any angle on the surface of the object to make up for the shortcomings of existing instruments and methods

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