Techniques for processing remote field eddy current signals from bend regions of steam generator tubes of prototype fast breeder reactor

Study on Remote Field Eddy Current Testing Technology for Crack-like Defects in Long Truss Structure of Aircraft

Detection of hidden defects of aircraft long truss structures (aluminum alloy) is a challenging problem. The shape of the aircraft truss structure is complex, and the crack defects are buried in a large depth. Without the restriction of skin effect, remote field eddy current (RFEC) has great advantages in detecting buried depth defects. In this paper, in order to detect the hidden defects of the aluminum alloy aircraft long truss structure, the remote field eddy current probe is improved from two aspects of magnetic field enhancement and near-field signal suppression using the finite element method. The results show that indirect coupling energy is greatly enhanced when the connected magnetic circuit is added to the excitation coil. By adding a composite shielding structure outside the excitation coil and the detection coil, respectively, the direct coupling energy is effectively restrained. As a result, the size of the probe is reduced. By optimizing the coil spacing and probe placement position, the detection sensitivity of the probe is improved. The simulation is verified by experiments, and the experimental results are consistent with the simulation conclusions.

Development of ultrasonic guided wave inspection methodology for steam generator tubes of prototype fast breeder reactor

An ultrasonic guided wave based methodology is developed for inspection of steam generator tubes of the prototype fast breeder reactor. To this aim, axisymmetric longitudinal mode (L(0,2)) at the frequency of 250 kHz is optimized using 3D-finite element simulation and experiments. The group velocity of mode L(0,2) at 250 kHz is found to be 5387 m/s. First, the long range propagation of the L(0,2) mode at 250 kHz is examined and the mode is found to propagate over a distance of 45.6 m with a sufficiently good SNR. Secondly, the detection of multiple defects such as circumferential, axial, partial-pinholes and tapered defects lying in the same line of sight is investigated using 3D-finite element simulation and the results obtained are validated experimentally for the first three cases. The sensitivities achieved are 0.23 mm depth (10%WT) for circumferential, axial and tapered defects and for partial-pinholes: 1 mm diameter and 1.38 mm depth (60%WT). Thirdly, 3D-FE simulations with ID and OD pinhole defects are performed which show that the ID and OD defects are detected by L(0,2) with a fairly similar sensitivity. Finally, study on the thermal expansion bend (with three successive bends) shows that the bend does not have much influence on the mode and the multiple circumferential defects considered in the bend are detected with good sensitivity.

Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications

Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper.