Non-Contact Scanning Acoustic Microscopy for Titanium Alloys
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Solution Overview
Problem
Existing acoustic techniques for measuring material microstructure, such as scanning acoustic microscopy and slowness surface measurement, are either contact-based, slow, or lack spatial resolution, making them inadequate for quick and nondestructive evaluation of multi-grained materials like titanium alloys and aluminum.
Innovation Solution
A non-contact method using spatially modulated light to generate and detect ultrasonic waves, allowing for spatially resolved measurements of acoustic velocity by varying the generation characteristic, such as line spacing or temporal frequency, and processing these measurements to create images representing acoustic velocity distributions across the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact-based scanning acoustic microscopy is used, then acoustic velocity measurement is obtained, but the measurement process perturbs the sample and reduces spatial resolution
Solution Approach 1:
The patent replaces contact-based mechanical acoustic coupling with non-contact optical detection. A laser beam generates ultrasonic waves in the sample through optical heating, and the same optical system detects the acoustic waves without physical contact, eliminating the harmful contact perturbation while maintaining measurement accuracy through optical detection of acoustic velocity variations.
Solution Approach 2:
The patent introduces optical fields as an intermediary between the measurement system and the sample. Light serves as the mediator to both generate ultrasonic waves (through optical heating) and detect acoustic velocity changes (through optical detection of refractive index variations), eliminating the need for direct mechanical contact while preserving measurement precision.
2Loss of information
If traditional acoustic measurement methods are used, then material microstructure information is obtained, but the measurement process is slow
Solution Approach 1:
The patent enables continuous scanning of the sample surface by moving the laser beam across the sample while continuously detecting acoustic velocity variations. This continuous measurement approach allows rapid acquisition of microstructure information across the entire sample without the interruptions and sequential steps of traditional methods, significantly reducing measurement time while maintaining information completeness.
Solution Approach 2:
The patent employs periodic modulation of the laser beam parameters (such as scanning frequency and pulse duration) to efficiently generate and detect ultrasonic waves. By optimizing the periodic action parameters, the system achieves rapid measurement cycles that maintain microstructure information quality while dramatically reducing the time required to scan and analyze the entire sample.
3Measurement precision
If variable generation characteristics are swept to improve measurement accuracy, then acoustic velocity is precisely measured, but the measurement complexity increases
Solution Approach 1:
The patent implements feedback control by sweeping the generation characteristics (such as laser pulse frequency or modulation depth) and detecting the acoustic wave amplitude. The system identifies the optimal generation parameters by monitoring the feedback signal (acoustic wave strength), allowing precise acoustic velocity measurement through automated parameter optimization without manual intervention or excessive complexity in the measurement process.
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 quick, nondestructive, and spatially resolved imaging of material microstructure, avoiding perturbations from contact methods and providing high-quality images of acoustic velocity variations, which can indicate crystal states, orientations, faults, or grain size differences.
Implementation Method 1
an acoustic wave is generated in the sample; the generated wave is detected
Implementation Method 2
the acoustic wave may be ultrasonic
Data Source
Figure 1~2
Figure 3
AI summary
A sample (10) is measured by generating ultrasound at (12), for example by using a laser (22) and spatial light modulator (26). The ultrasound is detected at (16), for example by optical beam deflection techniques. A characteristic of the generation at (12) is swept across a range of values to vary the efficiency of generation of ultrasound. The value of the characteristic, which corresponds with the peak amplitude detected at (16), is identified to provide a measure of the acoustic velocity at the region (12). The method is executed at a plurality of sites (12, 20) to provide a set of spatially resolved measurements of the sample (10). This allows an image of the sample to be created.