Continuous Ultrasonic Inspection for Local Defect Mapping
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Solution Overview
Problem
Current ultrasonic inspection techniques, such as resonant ultrasound spectroscopy and acoustic interferometry, are limited in providing local information about specimens, as they rely on temporal-frequency information and short-duration pulses, which restricts their ability to detect defects and variations within structures.
Innovation Solution
The use of steady, periodic ultrasonic excitation and continuous-scan sensing or direct imaging to extract local wave propagation properties, employing spatial-frequency information to generate maps of specimen properties, allowing for non-invasive, high-rate, high-resolution ultrasonic imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If short-duration ultrasonic pulses are used for inspection, then local information about specimen properties can be obtained, but the inspection rate is reduced due to waiting time for pulse dispersion
Solution Approach 1:
The patent applies periodic action by using continuous ultrasonic excitation at a specific frequency rather than repeated short pulses. The excitation source continuously drives the specimen at resonant frequencies, allowing the system to accumulate signal energy over time without requiring waiting periods for pulse dispersion. This periodic continuous excitation enables both high measurement precision through signal accumulation and high productivity by eliminating dead time between pulses.
Solution Approach 2:
The patent implements continuity of useful action by maintaining continuous ultrasonic excitation throughout the measurement process. Instead of interrupting excitation between pulses to allow dispersion, the system continuously applies ultrasonic energy at the resonant frequency, ensuring that the specimen remains in a steady-state vibration condition. This continuous action allows simultaneous high-resolution local property measurement and rapid inspection by eliminating idle waiting time.
2Ease of operation
If laser Doppler vibrometry is used for sensing, then non-contact measurement is achieved, but the low sensitivity in ultrasonic range requires multiple averaged measurements reducing scan rate
Solution Approach 1:
The patent resolves the sensitivity issue by using periodic excitation at the specimen's resonant frequencies. By continuously exciting the specimen at these specific frequencies, the vibration amplitude is significantly amplified compared to broadband pulsed excitation. This resonant amplification produces strong, consistent signals that laser Doppler vibrometers can detect with high signal-to-noise ratio in a single measurement, eliminating the need for multiple averaged measurements and restoring high scan rates.
Solution Approach 2:
The patent changes the frequency parameter of excitation to match the specimen's resonant frequencies. This parameter change transforms the excitation from broadband random noise (typical of pulsed excitation) to narrowband resonant frequencies where the specimen naturally amplifies vibrations. The resulting enhanced vibration amplitudes are easily detectable by laser Doppler vibrometers without requiring signal averaging, thus maintaining high scan rates while preserving non-contact measurement capability.
3Measurement precision
If resonant ultrasound spectroscopy is used, then bulk properties such as elastic moduli can be determined, but local information about defects and irregularities cannot be provided
Solution Approach 1:
The patent applies segmentation by dividing the specimen into multiple localized measurement regions through spatially resolved scanning. Instead of measuring only global resonant modes, the system scans the laser Doppler vibrometer across different locations on the specimen surface, collecting vibration data from each local region. This spatial segmentation allows simultaneous determination of bulk properties from overall resonant behavior and local defect detection from position-specific vibration characteristics, preserving both types of information.
Solution Approach 2:
The patent adds the spatial dimension to the frequency domain analysis. By scanning the measurement point across the specimen surface and recording vibration amplitudes and phases at each location, the system creates a two-dimensional map of local properties. This dimensional extension from single-point bulk measurement to spatially-resolved surface scanning enables concurrent extraction of both bulk material properties (from frequency content) and local defect information (from spatial variation in vibration response).
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 the detection of defects and variations within structures by providing detailed, local information on properties like thickness, density, and material composition, significantly improving the sensitivity and speed of ultrasonic inspections.
Implementation Method 1
application of a continuous periodic signal to a specimen to induce a steady state wave response
Implementation Method 2
A laser Doppler vibrometer (LDV) then measures the response at each inspection point
Data Source
AI summary
Methods and apparatus are disclosed for analyzing structures by applying a continuous ultrasonic excitation and measuring steady state response of the structures using laser Doppler vibrometery, or other techniques. In one example, a method comprises applying a continuous signal having one or more periodic tones to the structure, generating measurements of wave response to the signal at each of a plurality of inspection points of the structure, and, for each of the periodic tones, estimating wavenumbers for a number of the inspection points of the structure based on the wave response measurements and the frequency of the periodic tones. The estimated wavenumbers can be used to determine properties of the structure, including defects, damage, or variation in thickness.