Flexible Eddy Current Sensor Array for Engine Blade Dovetail Inspection
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Solution Overview
Problem
Conventional eddy-current sensing techniques are ineffective for detecting cracks in complex-shaped components like engine blades due to limitations in curvature and geometric features, which affect the accuracy of differential coil designs and lift-off variations.
Innovation Solution
The use of flexible eddy current sensor arrays and fixtures that allow for automated scanning and accurate modeling of material properties, including the use of a carousel system for mounting components and a clamp to hold the sensor in place, enabling precise imaging of curved surfaces and accounting for lift-off variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional eddy-current sensing techniques are used, then inspection can be performed on engine blades, but detection accuracy is reduced due to curvature and geometric features in the dovetail regions
Solution Approach 1:
The patent employs flexible eddy current sensor arrays that can conform to the curved surfaces of engine blade dovetail regions. These flexible sensors maintain intimate contact with the complex geometry, enabling accurate crack detection despite the curvature and geometric features that limit conventional rigid sensor effectiveness.
Solution Approach 2:
The sensor system is divided into multiple discrete sensor elements arranged in an array across the dovetail region. This segmentation allows each element to independently measure local eddy current changes, and the collective data from all elements provides comprehensive coverage of the complex geometry, improving both detection accuracy and adaptability.
2Measurement precision
If differential coil designs are used for eddy-current sensing, then local changes in eddy current flow can be sensed, but the differential signal is significantly altered or reduced by clusters of cracks and local proximity changes
Solution Approach 1:
Instead of using a single differential coil that compares two regions, the patent employs multiple sensor elements that collectively sample the eddy current distribution across the entire dovetail region. This excessive sampling approach ensures that even if some regions contain cracks or exhibit proximity variations, the overall pattern recognition can still reliably detect and characterize crack clusters without signal cancellation.
Solution Approach 2:
The patent creates multiple copies of the sensing function through the sensor array, where each element independently measures local conditions. This redundancy allows the system to capture the spatial distribution of eddy current changes, enabling reliable detection of crack clusters by analyzing the pattern across multiple copies rather than relying on a single differential comparison that could be nullified by opposing crack signals.
3Productivity
If automated scanning systems are implemented for rapid inspection, then productivity increases, but device complexity increases due to fixtures and sensor arrays
Solution Approach 1:
The flexible sensor array is designed to be universally applicable across multiple engine blade dovetail regions and can be repositioned for different inspection locations. The array serves multiple functions: it detects cracks, maps the dovetail geometry, and compensates for lift-off variations. This multi-functionality reduces the need for multiple specialized devices, managing complexity while maintaining high productivity through rapid automated scanning.
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
This approach enables rapid, automated, and accurate detection of cracks and material properties, allowing for reliable tracking of damage progression and improved inspection efficiency across multiple components.
Implementation Method 1
Conventional eddy-current sensing involves the excitation of a conducting winding, the primary, with an electric current source of prescribed frequency. This produces a time-varying magnetic field at the same frequency, which in turn is detected with a sensing winding, the secondary.
Implementation Method 2
This produces a time-varying magnetic field at the same frequency, which in turn is detected with a sensing winding, the secondary. The spatial distribution of the magnetic field and the field measured by the secondary is influenced by the proximity and physical properties (electrical conductivity and magnetic permeability) of nearby materials.
Data Source
AI summary
A set of curved components, such as the dovetail region of engine blades, are inspected by mounting each component into a circular carousel in a vertical orientation and rotating the carousel to move each component toward and away from an inspection site. The inspection site clamps a flexible eddy current sensor array to the curved material surface, scans the array over the surface, records the sensor position. A rigid element having a surface geometry similar to the surface shape of the component can be attached to the component to facilitate scanning of the sensor array over a component edge. The response of each sense element in the array may be converted into an effective material property and sense element proximity to the component material surface to verify the quality of the inspection scan and the presence of a defect such as a crack.