Variable-Frequency Elastic Wave Defect Detection
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Solution Overview
Problem
Existing defect detection methods using speckle interferometry and speckle-shearing interferometry face challenges in determining the appropriate frequency for elastic wave induction, as users struggle to select the most effective frequency for defect detection due to multiple recommended frequencies and limitations in wavelength, which can lead to incomplete defect detection, especially for cracks and coating film separations.
Innovation Solution
A defect detection device and method that includes an input receiver for user-defined defect information, an exciter for variable-frequency elastic wave induction, a measurer for optical vibration state measurement, a wavelength determiner, and a frequency selector to choose the appropriate frequency based on the defect type and size, ensuring optimal detection by varying the elastic wave frequency and selecting the most suitable wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the oscillation frequency is set close to the resonance frequency to maximize elastic wave amplitude, then the detection sensitivity is improved, but it becomes difficult to determine the appropriate frequency without preliminary measurements and impedance analysis
Solution Approach 1:
The system performs preliminary measurements by automatically sweeping through a frequency range to identify resonance frequencies before actual defect detection. This preliminary action stores the resonance frequency information for later use, eliminating the need for users to perform manual impedance analysis and making the frequency setting process straightforward.
Solution Approach 2:
The system automatically identifies and stores its own resonance frequencies through self-measurement. The vibration generator and frequency analyzer work together to characterize the test object's resonant properties without external intervention, enabling the system to serve itself in determining optimal detection frequencies.
2Adaptability or versatility
If multiple resonance frequencies are present within the oscillation range, then more frequency options are available for detection, but it becomes difficult to select the most appropriate frequency for specific defect types and sizes
Solution Approach 1:
The system establishes quantitative relationships between defect parameters (size, type) and optimal elastic wave wavelengths. By changing the frequency parameter based on these relationships, the system automatically selects the most appropriate frequency from multiple resonance options, matching the wavelength to the defect characteristics for optimal detection.
Solution Approach 2:
The system provides feedback to the user by displaying the detected resonance frequencies and guiding the selection based on defect characteristics. This feedback mechanism helps users understand which frequency is most appropriate for their specific detection needs, reducing selection difficulty while maintaining multiple frequency options.
3Measurement precision
If the elastic wave wavelength is made short to detect small defects, then the detection coverage for small defects is improved, but the amplitude of the elastic wave decreases
Solution Approach 1:
The system dynamically adjusts the oscillation frequency to match resonance conditions for each specific detection scenario. By exploiting resonance, the system achieves large elastic wave amplitudes even at higher frequencies that produce shorter wavelengths, thereby maintaining both high amplitude and small defect detection capability simultaneously.
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 accurate and appropriate frequency setting for defect detection, enhancing the ability to identify defects such as cracks and coating film separations by selecting the frequency that maximizes amplitude and ensures correct wavelength alignment with defect size, thereby improving detection accuracy.
Implementation Method 1
an exciter Exciter 12 that induces an elastic wave in a test object S
Implementation Method 2
a defect detection method which employs speckle interferometry or speckle-shearing interferometry
Implementation Method 3
In speckle-shearing interferometry, the laser beam from the laser light source is cast onto the test area (with no reference light split from the beam), and an interference pattern is obtained from two rays of light reflected from two points located close to each other on the surface of the test object
Implementation Method 4
a beam of laser light from a laser light source is split into illumination light and reference light
Implementation Method 5
The illumination light reflected at each point on the surface of an object to be examined (which is hereinafter called the 'test object') within the test area is combined with the reference light to obtain an interference pattern
Data Source
AI summary
In a defect detection device (10), an input receiver (161) receives an input, by a user, of information concerning the kind and size of a defect expected to be present in or on a test object. An exciter (11, 12) induces an elastic wave in the test object, with the frequency of the elastic wave being variable. A measurer (15) optically measures a vibration state of the surface of the test object caused by the elastic wave. A wavelength determiner (164) determines the wavelength of the elastic wave induced in the test object, based on the vibration state obtained by the measurer. A frequency selector (165) selects an appropriate frequency from a plurality of frequencies, based on the kind and size of the expected defect as well as the wavelength acquired for each of the plurality of frequencies by the wavelength determiner by varying the frequency of the elastic wave.