Guided Wave Remnant Thickness Evaluation via Cut-Off Properties
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Solution Overview
Problem
Current non-destructive evaluation methods for structural health monitoring, particularly in industries concerned with wall thinning, face challenges in accurately quantifying defects in inaccessible locations due to limitations in detectable remnant wall thickness and complexity from multiple wave modes and mode conversions, leading to inefficient and costly inspections.
Innovation Solution
The method employs the cut-off property of higher order guided wave modes to determine remnant thickness by coding excitation to generate a range of wavelengths and frequencies, allowing for the identification of cut-off frequency through transmission or reflection analysis, enabling precise thickness evaluation without the need for complex transducer arrays or time-consuming wavelength adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional guided wave methods using low frequency modes are used, then long-range inspection is enabled, but the range of detectable remnant wall thickness is minimal
Solution Approach 1:
The invention changes the frequency parameter by using high frequency guided wave modes instead of conventional low frequency modes. This parameter change enables the system to detect a broader range of remnant wall thicknesses (from 10% to 90% of original thickness) while maintaining long-range inspection capability, thus resolving the contradiction between inspection range and measurement precision.
2Loss of information
If multiple wave modes are used for defect detection, then substantial information concerning defects is provided, but mode conversions create complexity in isolating a single mode
Solution Approach 1:
The invention extracts and utilizes only the essential cut-off frequency information from multiple wave modes, rather than attempting to analyze and isolate each individual mode. By focusing on the cut-off frequency property which is common to all modes, the system obtains substantial defect information while avoiding the complexity of mode conversion analysis.
3Measurement precision
If coded excitation is used to expand detectable thickness range, then more thickness values can be measured, but the complexity of transducer arrays and wavelength adjustments increases
Solution Approach 1:
The invention uses a simple single-element transducer instead of complex transducer arrays. The system achieves expanded thickness detection range through signal processing of cut-off frequency information from multiple modes rather than through physical complexity of multiple transducers, effectively replacing complex hardware with simpler computational approaches.
4Device complexity
If 2D-FFT approach is used to eliminate mode conversion complexity, then mode identification is simplified, but the need for array transducers and time-consuming wavelength adjustments remains
Solution Approach 1:
The invention replaces the mechanical complexity of array transducers and wavelength adjustment mechanisms with a simple single-element transducer. The system uses signal processing techniques to extract cut-off frequency information that inherently provides mode identification without requiring the mechanical complexity of 2D-FFT approaches with multiple transducers.
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 allows for rapid, precise, and cost-effective evaluation of remnant thickness in structures, overcoming limitations of existing methods by simplifying the inspection process and improving accuracy and speed, while reducing equipment complexity and inspection time.
Implementation Method 1
One of the experiments involves measuring the amplitude of a wave mode transmitted through a defect by sweeping the input frequency. This experiment gives the cut-off frequency using which defect thickness can be determined.
Implementation Method 2
Guided wave techniques using Electro-Magnetic Acoustic Transducers (EMAT) further extends the advantage of rapid inspection because of it's non-contact no couplant nature.
Data Source
AI summary
This invention provides a method for finding the remnant thickness of a structure. A feature of guided waves known as the cut-off property is used to determine the remnant thickness of structures. Fundamental guided wave modes do not possess cut-off property, but higher order modes do. The cut-off thickness of a particular mode is the minimum thickness required for that mode to travel through the guided medium. The invention uses a wide-bands of frequency and wavelength to generate the modes using appropriate magnets and excitation signal shape to provide a low cost and rapid evaluation of remnant thickness of structure.