Keyhole Welding Interferometry for Real-Time Weld Stability
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Solution Overview
Problem
Current laser welding technologies face challenges in controlling the phase change region (PCR) during keyhole welding, leading to instability, internal voids, and high weld porosity due to the turbulent and stochastic nature of the light-matter interaction, which results in poor weld quality and requires expensive and destructive testing for verification.
Innovation Solution
The implementation of low-coherence interferometry to characterize the morphology of the keyhole and surrounding material by directing an interferometry measurement beam into the PCR, using an imaging optical source, optical combiner, and interferometry output processor to determine keyhole characteristics such as length, width, depth, and aspect ratio in real-time, allowing for dynamic control of the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If keyhole welding is used to achieve deep penetration and high aspect ratio features, then the depth of the phase change region increases, but the process becomes unstable and produces internal voids and high weld porosity
Solution Approach 1:
The patent applies optical coherence tomography (OCT) to provide real-time feedback on keyhole morphology and phase change region characteristics during laser welding. By continuously monitoring the keyhole depth, width, and stability, the system enables closed-loop control of welding parameters to maintain stable keyhole formation and prevent defects such as porosity and voids, thereby resolving the contradiction between achieving deep penetration and maintaining weld quality
Solution Approach 2:
The patent replaces destructive mechanical testing methods with non-invasive optical measurement (OCT) to verify weld integrity. Instead of using expensive and destructive ex-situ testing to assess weld quality, the system uses light-based interferometry to continuously monitor the welding process and keyhole characteristics, enabling quality verification without compromising the weld or requiring sample destruction
2Device complexity
If conventional imaging methods are used to monitor the weld joint, then the system complexity is reduced, but the capability to characterize keyhole dynamics and phase change region morphology is limited
Solution Approach 1:
The patent introduces optical coherence tomography as an intermediary measurement technique that bridges the gap between simple imaging and complex material characterization. OCT uses low-coherence light interferometry to provide three-dimensional cross-sectional imaging of the keyhole and phase change region, enabling precise measurement of keyhole morphology, depth, and dynamics without requiring overly complex imaging systems or invasive sensors
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 real-time monitoring and control of keyhole formation, reducing instability and porosity, improving weld quality, and eliminating the need for destructive testing by providing continuous, non-invasive verification of weld integrity.
Implementation Method 1
an optical combiner that combines the reflection component and at least another component of the imaging light to produce an interferometry output, the interferometry output based on a path length taken by the first component and the reflection component compared to a path length taken by the at least another component of the imaging light
Implementation Method 2
at least one input-output port that outputs a first component of the imaging light to an optical access port of the material processing system and that receives a reflection component of the imaging light
Data Source
AI summary
A method, apparatus, and system are provided to monitor and characterize the dynamics of a phase change region (PCR) created during laser welding, specifically keyhole welding, and other material modification processes, using low-coherence interferometry. By directing a measurement beam to multiple locations within and overlapping with the PCR, the system, apparatus, and method are used to determine, in real time, spatial and temporal characteristics of the weld such as keyhole depth, length, width, shape and whether the keyhole is unstable, closes or collapses. This information is important in determining the quality and material properties of a completed finished weld. It can also be used with feedback to modify the material modification process in real time.