Laser Weld Seam Thermal Decay Analysis for Defect Detection
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Solution Overview
Problem
Existing laser welding processes struggle to reliably detect welding defects, particularly in lap joints with I-seams, as visual inspection from the top view is inadequate for identifying gaps or missing connections between welded workpieces, which can compromise the mechanical and electrical integrity of battery cells.
Innovation Solution
A method involving thermal excitation of the weld seam with a laser pulse and analysis of the decay characteristic of thermal radiation emitted by the weld seam to determine the presence of defects, using photodiodes to measure and evaluate the intensity and cooling rate of thermal radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If visual inspection from top view is used to detect welding defects, then the inspection method is simple and quick, but the detection reliability is insufficient for identifying gaps or missing connections in lap joints with I-seams
Solution Approach 1:
The patent replaces visual inspection (optical system) with thermal excitation and measurement (thermal system). A laser pulse thermally excites the weld seam, and the resulting thermal radiation decay characteristic is measured to detect welding defects. This substitution enables reliable detection of gaps and missing connections in lap joints while maintaining quick inspection capability.
Solution Approach 2:
The patent changes the detection parameter from visual appearance to thermal radiation decay characteristic. By measuring how the thermal radiation intensity decays over time after laser pulse excitation, the system can identify welding defects based on differences in thermal conductivity between sound welds and defective welds, achieving both speed and reliability.
2Reliability
If thermal excitation with laser pulse and analysis of thermal radiation decay is used to detect welding defects, then the detection reliability is improved, but the device complexity increases compared to visual inspection
Solution Approach 1:
The laser source serves multiple functions: it performs the actual welding operation and subsequently provides the thermal excitation pulse for defect detection. This multi-functionality reduces device complexity by eliminating the need for separate inspection equipment while maintaining high detection reliability through thermal radiation analysis.
Solution Approach 2:
The weld seam itself serves as the measurement object and the source of information. The thermal radiation emitted by the excited weld seam provides the decay characteristic that reveals defect information. This self-service approach eliminates the need for external probes or complex sensing systems, achieving reliable detection with minimal additional device complexity.
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, easy, and reliable detection of welding defects without physical contact, allowing differentiation between good and bad welds by analyzing the material properties and structural integrity of the weld seam.
Implementation Method 1
thermally exciting the weld seam by radiating at least one laser pulse onto the weld seam
Implementation Method 2
acquiring a decay characteristic of thermal radiation emitted by the weld seam
Implementation Method 3
using photodiodes to measure and evaluate the intensity and cooling rate of thermal radiation
Data Source
AI summary
A method for analyzing a weld seam formed by a laser welding process includes thermally exciting the weld seam by radiating at least one laser pulse onto the weld seam, acquiring a decay characteristic of a thermal radiation emitted by the weld seam, and determining whether a welding defect is present based on an evaluation of the acquired decay characteristic.