A two-dimensional eddy current array–based sensing film for estimating failure modes and tracking damage growth of bolted joints

Abstract

Bolted joints are the key components for enduring primary load and play a vital role in ensuring structural safety for aircrafts. But it is very difficult to analyze the strength and failure modes of bolted joints due to their complexity and nonlinear coupling factors. Therefore, it is greatly essential to estimate potential failure mode at the early age and quantitatively track the damage parameters for calculating residual life and determining structural integrity. In this article, the concept of two-dimensional eddy current array–based sensing film is proposed to estimate the failure modes by identifying the circumferential location of the damage around the bolt hole and quantitatively track the damage parameters including the damage size in the radial direction and the damage depth in the axial direction of bolt hole. Finite element simulation is utilized to study the interaction between eddy current signals and the damage, and optimize the configuration of sensing film. Simulation result shows that a noticeable difference of eddy current signals of sensing film can be clearly seen that damage is located at different circumferential location around the hole. In addition, the exciting coil with opposite current directions at the boundary of axially adjacent coils has a better capacity of differentiating the damage sizes in the radial and axial direction than that with same current directions. The experiment is conducted to demonstrate the effectiveness of the proposed sensing film for estimating fatigue modes and quantitatively tracking damage growth.

An Eddy Current-Based Structural Health Monitoring Technique for Tracking Bolt Cracking

“…The purpose of this paper is to develop an eddy current array sensing film that can quantitatively monitor the process of bolt cracking. According to Sun and Qing's study [20,21], when the direction of the eddy current generated by the exciting coil is perpendicular to the direction of the crack in the monitored structure, there is a significant disturbance of the eddy current which can be sensed by the sensing coils. A similar concept may be introduced to monitor the bolt cracking.…”

“…Rakow and Chang [19] proposed one type of eddy current-sensing film to form the intelligent bolt by using the flexible printed circuit technique. This eddy current sensing film solved the problem of detecting the fatigue crack of thick joints or multi-layer joints, and it was optimized by Sun and Qing [20][21][22] for quantitative monitoring of the crack size and position.…”

“…However, for the bolt fracturing failure, the most common structural failure in the accidents [3,23], there are few SHM technologies. In this paper, the SHM concept of the embedding eddy current sensing films [19][20][21][22] is introduced to monitor the process of the bolt fracturing failure.…”

On-Site Health Monitoring of Composite Bolted Joint Using Built-In Distributed Eddy Current Sensor Network

“…Rakow and Chang [16] developed a flexible eddy current (EC) sensing film bonded on the bolt to detect the existence of bolt hole-edge crack and its propagation. Sun and Qing et al [17,18] further developed the EC array sensing film bonded on the bolt to quantitatively monitor the crack growth along the radial direction and axial direction of the bolt hole. Some other methods, including acoustic emission [19], acoustic-ultrasonics [20], electromechanical impedance [21], comparative vacuum monitoring (CVM) [22], and intelligent coating monitoring (ICM) [23], can also be used to inspect the damage of bolted joints.…”

A Novel Rotational Field Eddy Current Planar Probe with Two-Circular Sector Pickup Coils

“…Recently, the planar eddy current probe has become a research hotspot because it can be shaped to adapt metallic part surfaces to suppress lift-off noise and detect hard-to-reach areas [1,2]. Many structures have been proposed to design the planar flexible eddy current probe, such as the meandering winding magnetometer [3,4,5], rosette-like [6,7], parallelogram [8], mesh-winding [9], line [10], double rectangle [11], uneven step distribution [12], double-S shape [13], circular spiral [14], same direction line [4] and so on. Those structures are composed of line, circle and their spiral, so the eddy current in metallic parts with smaller direction range cannot be disturbed by the short defects in the same certain direction.…”