Magnetostrictive Phased Array Sensor for Structural Defect Detection
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Solution Overview
Problem
Existing magnetostrictive patch transducers (MPTs) lack directional sensitivity and high resolution for precise detection of structural defects, requiring multiple transducers and relying on signal processing algorithms for directional sensing, which limits their effectiveness in structural health monitoring.
Innovation Solution
A compact magnetostrictive phased array sensor (MPAS) with a circular comb-shaped patch and a rotatable magnetic circuit device containing 3, 4, or 6 sensing coils, providing directional sensitivity through magnetic anisotropy and sensing directionality, allowing for precise detection of defects by altering the rotational orientation to acquire additional signal data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetostrictive transducers are used for structural defect detection, then measurement precision improves, but device complexity increases
Solution Approach 1:
The magnetostrictive patch is segmented into multiple comb finger members (e.g., 12 fingers) arranged radially around a central axis. Each comb finger acts as an independent sensing element that detects strain-induced magnetic property changes in specific directions. This segmentation allows a single patch to provide directional sensitivity equivalent to multiple separate transducers, resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The invention transitions from conventional single-direction or limited-direction sensing to omnidirectional sensing by arranging comb fingers radially in the planar dimension. The magnetic circuit device with coils positioned at different angular orientations around the central axis enables detection of guided Lamb waves propagating in any direction within the plate, achieving high-resolution defect detection without multiplying the number of separate transducer units
2Ease of operation
If conventional magnetostrictive transducers are used, then ease of manufacture is maintained, but directional sensitivity is lost
Solution Approach 1:
The magnetostrictive patch employs an asymmetric comb finger configuration where fingers are radially oriented at different angular positions (e.g., every 30 degrees for 12 fingers). This asymmetric arrangement creates magnetic anisotropy that provides inherent directional sensitivity. The magnetic circuit device with coils positioned at specific angular orientations further enhances directional discrimination. This asymmetric design enables directional sensing capability while maintaining manufacturability through standard fabrication processes for comb structures
Solution Approach 2:
Different regions of the magnetostrictive patch (different comb fingers) are designed with specific orientations to detect waves from different directions. Each local region (comb finger + corresponding coil) has optimized properties for its specific sensing direction. This local quality differentiation across the patch enables omnidirectional sensing capability without requiring complex overall structure
3Device complexity
If a single magnetostrictive transducer is used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The single magnetostrictive patch is segmented into multiple comb finger members (e.g., 12 radially arranged fingers), each functioning as an independent sensing element. This internal segmentation within a single transducer unit provides multiple measurement channels for phase array signal processing, achieving high-resolution damage detection without the complexity of multiple separate transducer units
Solution Approach 2:
The invention merges multiple sensing functions into a single integrated magnetostrictive patch transducer. The comb finger array combined with the magnetic circuit device creates a unified structure that performs omnidirectional guided Lamb wave detection. This merging maintains low device complexity while achieving measurement precision equivalent to multiple separate transducers through the combined output of all comb fingers
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 MPAS achieves high-resolution damage detection with improved directional sensitivity, enabling effective structural health monitoring by detecting strain-induced magnetic property changes using a single device, enhancing the accuracy and efficiency of defect identification.
Implementation Method 1
The directional sensing feature of the magnetostrictive phased array sensor (MPAS) is based on the combined effect of the magnetic anisotropy of the comb finger formation of the comb-shaped patch member and the sensing directionality of each coil sensor in the magnetic circuit device
Implementation Method 2
The magnetic circuit device is formed with a pair of biasing cylindrically shaped permanent magnets installed along a rotational axis for generating a static magnetic field induced in the patch member
Implementation Method 3
The source of ultrasonic excitation generates guided Lamb waves (GLWs) propagating in the structure under study, thus causing a deformation in the patch member attached thereto and generating a respective strain-induced dynamic magnetic field in the patch member at each of at least two predetermined directions. The generated dynamic magnetic field is coupled to the sensing coils
Data Source
AI summary
A compact directional high resolution magnetostrictive phased array sensor (MPAS) includes a magnetostrictive comb-shaped patch and a magnetic circuit device. The patch was machined with 24 comb fingers along its radial direction. The magnetic circuit device contains a sensing array of angularly spaced apart sensing coils and cylindrical biasing magnets. The individual sensing coils have distinct directional sensing preferences designated by the normal direction of the coil winding. The directional sensing feature of the developed MPAS is supported by the combined effect of the magnetic shape anisotropy of the comb finger formation in the patch and the sensing directionality of the sensing array. The MPAS detects the strain-induced magnetic property change on the comb-shaped patch due to the mechanical interaction between the patch and GLWs propagating in the structure under study. The array sensor enables to acquire signal data from different sensing sections within the patch by altering the rotational orientation of the magnetic circuit device.