Fatigue Crack Length Sizing Using a Novel Flexible Eddy Current Sensor Array

Abstract

The eddy current probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar eddy current sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM), the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm.

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

“…Note that each of the 32 axial channels covers 11.25° around the circumference of the tube, and each circumferential channel covers 22.5°. Data are collected as the probe is pulled along the axis of the pipe, giving circumferential and axial defect information at each axial and circumferential location in the tube [ 35 , 36 ]. Thus, the data collected are in the form of a 2D image.…”

Flexible Sensors—From Materials to Applications

“…Parametric FE analysis was conducted to identify the best geometry of the pillars of a PDMS pressure sensor under bi-axial stress and to analyse the performance of the sensor's final configuration under bending and twisting at 180° (Figure 14a) [22]. Simulations have also been applied to study the distribution of magnetic fields and current densities (Figure 14b) to optimize the design of an Eddy current sensor array used to identify fatigue cracks in aircrafts' elements, proving consistency with tests [574]. Simulations were also used in a parametric analysis aid in the fabrication of a curled sensor to identify the most rigid structure arrangement [571].…”

“…Finite Element Analysis (FEA) has been the most common numerical method used for simulations, specially using commercial software such as Abaqus [136,451,[568][569][570] or Comsol [571][572][573][574]. These tools have been used to better understand the mechanical behaviour of the sensors prior to the fabrication [568], perform parametric analysis of geometries under adverse mechanical loadings [22,136,[569][570][571], understand electrical behaviour of the components [569,[573][574][575], and to analyze the electrical response under a deformed state [569,573]. Besides, numerical simulations have been proved to be a practical tool in the analysis of changes in capacitance with the effect of strain [576] and for the analysis of electrical performance and mechanical stability of flexible circuits with different configurations under bending loads [572].…”

“…These materials have a non-linear elasticity and their simulation have reached a complexity by using hyperelastic models such as the Neo-Hookean [136,451,569] or the Mooney-Rivlin [570] models. However, it has been observed that simplified models can achieve an accurate prediction of the stress-strain distribution with linear elastic material properties [568,571,574]. Parametric FE analysis was conducted to identify the best geometry of the pillars of a PDMS pressure sensor under bi-axial stress and to analyse the performance of the sensor's final configuration under bending and twisting at 180° (Figure 14a) [22].…”

Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique

“…Defects may occur in the stress concentration areas of in-service components or systems. Generated defects gradually grow due to stress and pose a severe threat to the structural integrity of in-service parts or systems [ 1 , 2 , 3 ]. Therefore, it is essential that periodic inspection be implemented nondestructively for safe and efficient operation.…”