Laser Weld Inspection for Thin-Plate Internal Defect Detection
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Solution Overview
Problem
Existing ultrasonic testing methods struggle to detect internal defects in welds of thin plates during the welding process, particularly in lap fillet joints, due to the thin plate thickness and limitations in current technologies and standards.
Innovation Solution
A weld inspection device and method utilizing a combination of first and second laser irradiation devices, a laser interferometer, and a determination device to detect internal defects by generating and detecting ultrasonic waves that pass through the weld and are reflected by the base material, rather than relying on scattered waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasonic testing methods are used, then internal defects can be detected in thick plate groove welding, but the method cannot detect internal defects in thin plate lap fillet joint welding
Solution Approach 1:
The invention changes the detection parameters by switching from conventional contact ultrasonic testing to laser ultrasonic testing. This involves using laser beams to generate and detect ultrasonic waves, changing the physical state and method of ultrasonic wave generation and detection to enable application in thin plate welding where conventional methods fail
Solution Approach 2:
The invention replaces the mechanical contact method with a non-contact optical method. Instead of using physical probes that must contact the weld surface, the system uses laser beams to generate ultrasonic waves in the weld and detect reflected waves, eliminating the need for mechanical contact and enabling inspection of thin plate lap fillet joints
2Productivity
If laser ultrasonic technique with scattered wave detection is used, then in-process inspection is enabled, but detection is still difficult in thin plate welding due to plate thickness
Solution Approach 1:
The invention inverts the detection approach by not relying on scattered waves from defects, but instead detecting the reflected ultrasonic waves from the back surface of the workpiece. By measuring the attenuation of these reflected waves, the system can indirectly detect defects in thin plate welding with high precision
3Device complexity
If generation laser irradiation is performed without scanning mechanism, then simple structure is maintained, but accurate defect localization in the welding direction cannot be achieved
Solution Approach 1:
The scanning mechanism serves multiple functions: it positions the generation laser to irradiate different locations along the weld, enables defect localization in the welding direction, and allows comprehensive coverage of the inspection area. This single component achieves both simple operation and high 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
Enables the detection of internal defects in welds of thin plates during the welding process, improving the accuracy and reliability of in-process defect detection and allowing for real-time adjustments to the welding process.
Implementation Method 1
the inspection target surface is irradiated with laser (generation laser) to generate an ultrasonic wave inside an inspection target
Implementation Method 2
The laser interferometer measures interference of reflected light of the detection laser
Implementation Method 3
an ultrasonic wave (scattered wave) reflected by the defect is detected using the detection laser
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A generation laser irradiation device (12) irradiates a weld (6) after welding with a generation laser (14). A detection laser probe (18) irradiates an ultrasonic detection point (36) that passes through the weld (6) and is capable of detecting an ultrasonic wave reflected on a lower surface (5) of a base material (4) with detection laser (20). A control device (22) determines existence of an internal defect of the weld (6) based on a measurement result of a laser interferometer. The generation laser irradiation device (12) includes a scanning mechanism that scans an irradiation position of the generation laser (14) in a direction intersecting a welding direction.