Laser Acoustic Resonance Defect Detection for AM Metal Parts
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Solution Overview
Problem
There is a need for non-destructive quality control techniques to ensure high reproducibility and detect internal defects in additively manufactured metal alloy parts, particularly those with unconventional geometric shapes, as existing methods are inadequate for rapid and reliable characterization.
Innovation Solution
Laser Acoustic Resonance Spectroscopy (LARS) using a laser doppler vibrometer to measure vibrational frequency responses, analyze spectra, and determine frequency shifts to identify defects such as voids, cracks, or porosity in metal objects, enabling non-destructive validation and authentication of parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional non-destructive testing methods are used, then they can detect some defects, but they are inadequate for rapid investigation of additively manufactured parts with unconventional geometric shapes
Solution Approach 1:
The patent applies mechanical vibration by exciting the test object with a broadband impulse and measuring its vibrational response. The resonant frequency spectrum obtained from this vibration analysis serves as a unique fingerprint that reveals internal defects such as voids, cracks, and porosity, enabling both rapid testing and reliable defect detection in complex geometries.
Solution Approach 2:
The patent replaces traditional mechanical contact-based NDT methods with acoustic resonance spectroscopy. By using acoustic excitation and optical measurement (laser Doppler vibrometry), the system eliminates the need for physical contact probes, enabling rapid scanning of complex geometries while maintaining high defect detection reliability through spectral analysis.
2Reliability
If existing non-destructive characterization techniques are used, then they can provide some quality control, but they are insufficient for ensuring high reproducibility in additive manufacturing
Solution Approach 1:
The patent establishes a reference resonant frequency spectrum from a known defect-free object before testing. This preliminary reference spectrum enables rapid comparison with test objects, allowing quality control decisions to be made quickly based on spectral deviations, thus reducing inspection time while maintaining high reliability through systematic comparison.
Solution Approach 2:
The system provides feedback by comparing the measured resonant spectrum of each test object against the reference spectrum. Defects are identified through spectral shifts and changes in resonant frequencies, providing immediate quality control feedback that ensures high reproducibility without requiring lengthy inspection procedures.
3Difficulty of detecting and measuring
If conventional measurement methods are used on additively manufactured parts, then they can measure external dimensions, but they cannot effectively detect internal defects in parts with unconventional geometric shapes
Solution Approach 1:
The resonant frequency spectroscopy system serves multiple functions: it detects internal defects (voids, cracks, porosity), characterizes material properties, and works with any geometry. The same acoustic excitation and spectral analysis apparatus handles all these tasks universally, reducing the need for multiple specialized devices while improving internal defect detectability.
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
LARS effectively detects internal defects as small as 0.10 mm to 0.6 mm, ensuring high reproducibility and identifying defective or counterfeit items by analyzing frequency shifts, facilitating rapid and efficient quality control in additive manufacturing processes.
Implementation Method 1
Laser Acoustic Resonance Spectroscopy (LARS) using a laser doppler vibrometer to measure vibrational frequency responses
Implementation Method 2
measuring a first vibrational frequency response of a first object produced via a first process; measuring a second vibrational frequency response of a second object produced via a second process; performing a spectra analysis of the first vibrational frequency response and the second vibrational frequency response; identifying a first plurality of peaks from the first vibrational frequency response as resonant frequency modes of the first object; identifying a second plurality of peaks from the second vibrational frequency response as resonant frequency modes of the second object
Data Source
AI summary
A system and a method for non-destructive characterizations of objects using Laser Acoustic Resonance Spectroscopy (LARS)-based diagnostic techniques are provided. The system includes using a laser doppler vibrometer to measure vibrational responses of objects. The method includes measuring vibrational frequency responses of a first object and a second object, performing a spectra analysis of the vibrational frequency responses, determining a frequency shift based on the spectra analysis, and indicating a difference between the first object and the second object or a presence of a defect in the second object if the determined frequency shift exceeds a predefined threshold value. The difference between the first object and the second object may indicate the presence of a void, a crack, or a plurality of pores in the second object, or can be used for validating or authenticating the second object as a defective or counterfeit item, in various embodiments.