Multi-Path Ultrasonic Defect Detection Using Spatial Green's Functions
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Solution Overview
Problem
Current ultrasonic guided wave defect detection and localization methods fail to accurately identify and characterize damage in complex structures with inhomogeneous or anisotropic materials due to assumptions of homogeneous media and direct paths, leading to impractical sensor density and modeling challenges.
Innovation Solution
A method and system using a spatially distributed array of transducers to estimate combined transducer transfer functions and spatial Green's functions, leveraging multi-path reverberations for defect detection and localization, allowing for fewer sensors and improved detection capabilities in complex structures by comparing estimated signal changes to actual measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high sensor density is used to ensure sufficient direct paths between transducers and every location of interest, then defect detection reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the wave propagation paths into multiple routes (direct paths, reflected paths, mode-converted paths) that can be individually modeled and analyzed. By dividing the complex propagation problem into manageable path segments, the system can accurately track wave behavior through inhomogeneous media without requiring dense sensor coverage at every location.
Solution Approach 2:
The patent changes the modeling parameters to account for inhomogeneous and anisotropic materials by incorporating position-dependent material properties, multiple propagation modes, and path-specific velocity variations. This allows accurate defect detection using fewer sensors by compensating for complex wave behavior through advanced parameterization rather than sensor density.
2Measurement precision
If direct path assumptions are made between transducers and structure, then measurement precision is improved, but adaptability to complex structures deteriorates
Solution Approach 1:
The patent introduces an intermediate modeling layer that represents the complex structure's wave propagation characteristics. This intermediate model acts as a mediator between the simple transducer measurements and the actual defect locations, accounting for reflections, mode conversions, and material inhomogeneities to enable accurate localization in complex structures.
Solution Approach 2:
The patent adds the dimension of multiple propagation paths and modes to the analysis. Instead of assuming single direct paths, the system considers waves traveling through multiple dimensions of space and material properties, including reflected paths, mode-converted waves, and paths through different material layers, thereby achieving adaptability to complex structures while maintaining precision.
3Measurement precision
If direct modeling of ultrasonic waves in complex structures is attempted, then measurement precision is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent performs preliminary characterization of the structure's wave propagation properties before defect detection. By pre-modeling the expected wave paths, reflection patterns, and mode conversions in the specific complex structure, the system creates a reference framework that simplifies subsequent defect analysis. This preliminary action captures the complex propagation behavior once, enabling simpler and more efficient defect detection thereafter.
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
Enables efficient detection, localization, and characterization of defects in large, complex structures with fewer sensors, improving defect detection and localization accuracy by utilizing multi-path echoes and variations in propagation velocity, reducing costs and weight.
Implementation Method 1
Ultrasonic guided waves have been identified and utilized for this purpose because they travel for long distances in the plane of the structure and are sensitive to both surface and sub-surface features
Implementation Method 2
use time-of-arrival or time-difference-of-arrival information, respectively, to identify elastic scattering from defects or damage
Implementation Method 3
Each transducer 14a, 14b, etc. may, for example but not limited to, be an inexpensive piezoelectric transducer
Data Source
AI summary
A method and system of detecting, localizing, and characterizing a defect at one or more spatial points of interest on a structure. The method may include collecting first data in a first state using one or more transducers on the structure, collecting second data in a second state subsequent to the first state, computing a scattered impulse response based on the collected first data and the collected second data, comparing the scattered impulse response with an estimated scattered impulse response corresponding to the case when damage is present at one or more spatial points of interest on the structure, and combining the generated comparison results to detect, localize, and characterize a defect at the one or more spatial points of interest on the structure.