Photo-Acoustic Layer Testing for Faster Additive Defect Detection
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Solution Overview
Problem
Existing non-destructive photo-acoustic tomography systems for defect testing in additive manufacturing are complex, expensive, and time-consuming, making them inefficient for scanning parts.
Innovation Solution
A method using laser-generated hammer and read-out beams with adjustable pulse lengths and patterns, combined with spatial light modulators, to induce surface movement and capture interferograms for rapid defect detection and volumetric analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional photo-acoustic tomography systems are used for defect testing, then defect detection capability is achieved, but system complexity and cost increase
Solution Approach 1:
The patent combines the hammer beam and read-out beam into a single integrated optical system that uses a spatial light modulator to generate multiple beams simultaneously. This merging of functions reduces system complexity while maintaining defect detection capability, as the single system performs both excitation and measurement functions that traditionally required separate systems.
Solution Approach 2:
The optical system is designed to perform multiple functions: generating hammer beams for acoustic excitation, generating read-out beams for surface displacement measurement, and potentially both functions simultaneously. This multi-functionality reduces the need for separate specialized systems, thereby reducing overall system complexity and cost.
2Reliability
If traditional photo-acoustic tomography systems are used for defect testing, then defect detection capability is achieved, but scanning time increases
Solution Approach 1:
The patent segments the measurement process by using multiple read-out beams that can simultaneously measure different regions or aspects of surface displacement. This parallel measurement approach reduces the total scanning time compared to sequential measurement methods, while maintaining comprehensive defect detection capability through the combined data from all beam segments.
Solution Approach 2:
The system enables continuous scanning by maintaining simultaneous operation of hammer and read-out beams across multiple regions. The continuous acquisition of interferogram data from multiple beams reduces idle time between measurements and accelerates the overall scanning process while preserving detection sensitivity.
3Productivity
If multiple hammer beams and read-out beams are used, then measurement speed increases, but system complexity increases
Solution Approach 1:
The spatial light modulator serves as an intermediary device that simplifies the generation and control of multiple hammer and read-out beams. Instead of requiring complex independent control systems for each beam, the SLM provides a unified interface for generating patterned light fields, thereby reducing control complexity while enabling multi-beam operation for accelerated measurement.
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 fast and efficient detection of sub-surface defects and surface topography in additive manufacturing, allowing real-time corrections and improving the quality of manufactured parts.
Implementation Method 1
A short pulse laser (i.e. a hammer or ping pulse) is directed incident onto the surface of the PUT to locally heat the surface of the PUT during the pulse width of the laser pulse. This launches an acoustic pulse into the PUT as a result of differential heating, plasma generation or local expansion
Implementation Method 2
The acoustic response is launched, causing the surfaces of the PUT to minutely move. This motion causes a phase modulation on the read-out beam which can be detected by taking the reflection of the read-out beam and processing it through a Michelson interferometer.
Data Source
AI summary
An additive manufacturing method supporting layer by layer testing includes a layer test including generating a hammer beam using laser light having a first wavelength, generating a read-out beam using laser light having a second wavelength, directing the generated hammer beam toward a first layer on a part to provide an acoustic hammer pulse that induces surface movement of the part, and reading the surface movement of the part using the read-out beam directed to a second position on the part. Layers can be added and the layer test repeated.