Planar Eddy-Current Sensor With Durability Pillars for Crack Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional non-destructive testing techniques, such as ultrasonic testing and eddy current sensing, face difficulties in early detection of cracks near fastener holes in aerospace components, particularly in multiple layered structures, due to penetration issues and noise from geometric variations, leading to inadequate detection and increased repair costs.
Innovation Solution
A substantially planar eddy-current sensor with durability-enhancing pillars and redundant drive/sense windings, along with a reference transformer for calibration, is used to improve detection accuracy. The sensor system includes a substrate for mechanical support and multiplexing units for coordinated excitation and response monitoring, enabling effective crack detection near fastener holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional eddy current sensors are used for crack detection near fastener holes, then the sensor can detect cracks in single-layer structures, but the sensor fails to penetrate through thick outer layers in multiple-layered structures and produces noise from geometric variations
Solution Approach 1:
The sensor is divided into multiple functional layers including drive windings, sense windings, and durability-enhancing pillars distributed across different planes. This segmentation allows each layer to perform specific functions: drive windings generate magnetic fields, sense windings detect crack signals, and pillars provide mechanical protection, collectively solving the penetration and noise problems in multi-layered structures
Solution Approach 2:
The sensor employs a composite structure combining flexible substrate materials with conductive winding materials and protective pillar materials. This composite design enables the sensor to penetrate through thick outer layers while filtering out noise from geometric variations, achieving reliable crack detection in multiple-layered structures
2Reliability
If the sensor is mounted on a component under load, then the sensor can detect cracks, but the active elements (drive winding, sense elements) are subjected to excessive mechanical stress reducing sensor durability
Solution Approach 1:
Durability-enhancing pillars are strategically positioned around the active elements before the sensor is subjected to mechanical loads. These pillars act as protective cushions that absorb and distribute mechanical stress, preventing damage to the drive winding and sense elements while maintaining sensor functionality under operational loads
3Productivity
If conventional NDT techniques are used for inspection, then the inspection can be performed, but the detection is delayed until cracks are too large for repair
Solution Approach 1:
The sensor is installed on the component before service, establishing a continuous monitoring system that detects cracks at their earliest stages. This preliminary positioning enables the sensor to capture crack initiation signals before they grow to critical sizes, allowing timely repair interventions and preventing catastrophic failures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the reliability and longevity of crack detection near fastener holes, reducing the likelihood of sensor damage and improving the probability of detection, thereby delaying component replacement and extending its service life.
Implementation Method 1
Conventional eddy current sensing involves the excitation of a conducting winding (the primary) with an electric current source of prescribed frequency. The current in the conducting winding produces a time varying magnetic field at the same frequency. By Faraday's law of induction an electromotive force is induced in a sensing winding (the secondary).
Implementation Method 2
The spatial distribution of the magnetic field which is measured by the secondary is influenced by the proximity and physical properties (e.g., conductivity and permeability) of nearby materials. When the sensor is intentionally placed in close proximity to a test material, the physical properties of the material can sometimes be deduced from measurements of the transimpedance between the primary and secondary windings.
Data Source
AI summary
A substantially planar eddy-current sensor having durability enhancing pillars in an active region is provided. The pillars are distributed and sized so as to have limited effect on the sensor's performance. When the sensor is mounted on a component such that the sensor experiences forces on a top and bottom surface, the pillars bear the load reducing the load bore by the active elements (e.g., drive winding, sense elements). A sensor with redundant drive windings and/or redundant sense elements is disclosed. The redundant elements may be connected to separate electronics. Another aspect relates to providing a reference transformer for calibration of a sensor. The secondary windings of the reference transformer are connected in series with the sense elements of the sensor to be calibrated. Transimpedance measurements are made when the drive winding of the reference transformer is excited. The measurements are used to correct transimpedance measurements made when the drive winding of the sensor is excited. A system having an impedance analyzer and a plurality of multiplexing units is disclosed for monitoring a plurality of sensor. Each multiplexing units directs an excitation signal to the drive winding of a respective sensor and returns, serially, the sense element responses back to the impedance analyzer. The system coordinates the excitation of each sensor and return of the sensor response to share a serial network. The multiplexing units may have a reference transformer for calibration of their respective sensors. Optical communication may be used.