Laser Welding Inspection via Molten Pool Vibration Analysis
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Solution Overview
Problem
Existing laser beam welding quality determination systems face decreased accuracy in detecting poor welding when the laser torch is distant from workpieces, particularly due to weak electrical signals and temperature fluctuations, which can lead to missed detections of depressed welds and other poor welding types.
Innovation Solution
The system inspects the welding state based on the periodicity and intensity changes of the returned light beam, using Fourier transform or differentiation to distinguish between normal and poor welding conditions, even when signals are weak or noisy, by synchronizing the scanning period of the laser beam with the unique frequency of the molten pool's vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the laser torch is positioned at a distance from the workpieces to perform welding, then the welding process can be applied to remote or difficult-to-reach areas, but the electrical signals obtained from the received laser reflection light and welding light become weak, reducing determination accuracy of poor welding
Solution Approach 1:
The patent utilizes the natural vibration of the molten pool during laser beam welding as a diagnostic signal. By detecting the vibration frequency and characteristics of the molten pool, the system can identify poor welding conditions (such as depressed welds, unjoined welds, or holed welds) even when the laser torch is positioned at a distance from the workpieces. This transforms the previously harmful weak signal into a useful diagnostic indicator that maintains accuracy regardless of distance.
2Adaptability or versatility
If the workpiece temperature fluctuates during laser beam welding, then the welding process can adapt to varying material conditions, but the electrical signals obtained from the received laser reflection light and welding light change according to workpiece temperature, further decreasing determination accuracy of poor welding
Solution Approach 1:
The patent employs a dual-function detection approach where the same optical detection system serves both to monitor the molten pool vibration characteristics (for poor welding detection) and to track temperature-related signal variations. By analyzing the vibration frequency and pattern of the molten pool, the system can distinguish between signal changes caused by temperature fluctuations and those caused by actual poor welding conditions, maintaining determination accuracy across varying temperature conditions.
3Device complexity
If conventional optical detection methods are used to inspect welding quality, then the system structure remains simple, but the detection accuracy decreases in remote welding scenarios due to weak returned light signals
Solution Approach 1:
The patent changes the detection parameter from simply measuring the intensity of returned light to analyzing the vibration frequency and temporal characteristics of the molten pool. By focusing on the dynamic vibration parameters rather than static light intensity, the system achieves high inspection accuracy in remote welding scenarios without requiring complex additional hardware, maintaining relative system simplicity while dramatically improving measurement precision.
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 enhances the accuracy of welding state inspection by effectively differentiating between normal and poor welding conditions, even in remote welding scenarios, thereby improving the detection of defects like depressed welds and other poor welding types.
Implementation Method 1
a returned light beam L2 which is reflected from the workpieces W1, W2
Implementation Method 2
The conversion portion 3 converts, into an electrical signal, the returned light beam L2 received by the light-receiving portion 2
Implementation Method 3
a welding laser beam L1 is radiated from a welding radiation portion 1 to steel sheets W1, W2
Implementation Method 4
the welding laser beam L1...forms a molten pool Y1
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A welding laser beam (L1) is radiated along welding loci (C11, C12) set in workpieces (W1, W2), or an inspection laser beam (L5) is radiated along scanning loci (C51, C52) set in a molten pool (Y1) of the workpieces (W1, W2) that are molten by radiation of the welding laser beam (L1), a returned light beam (L2) including reflection light from the molten pool (Y1) of the workpieces, vapor light caused due to melting and evaporation of the workpieces, and thermal radiation light emitted from the molten pool (Y1) of the workpieces is received, and a welding state of a welded portion of the workpieces is inspected based on an intensity change of the returned light beam (L2) thus received.