Laser Ultrasonic Weld Inspection for Thin Plate Lap Fillet Joints
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Solution Overview
Problem
Current ultrasonic testing methods, such as UT and laser ultrasonic techniques, face challenges in detecting internal defects in thin plate welds during the welding process due to the high temperature and thickness limitations, making it difficult to apply these methods effectively for lap fillet joints in thin plates.
Innovation Solution
A weld inspection device utilizing first and second laser irradiation devices, a laser interferometer, and a determination device that scans the generation laser in a direction intersecting the welding direction, detecting ultrasonic waves that pass through the weld and are reflected by the base material's lower surface to determine internal defects, allowing for in-process inspection of lap fillet joints in thin plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional ultrasonic testing methods are used for weld inspection, then internal defects can be detected in thick plate groove welding, but the method cannot be applied to thin plate lap fillet joint welding due to plate thickness limitations
Solution Approach 1:
The patent 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 non-contactly, which enables effective inspection of thin plate welds where conventional methods fail due to the 6mm thickness limitation specified in JIS Z 3060 and other standards.
Solution Approach 2:
The patent replaces the mechanical contact probe system with an optical laser system. Instead of physically contacting the weld surface with ultrasonic probes, the system uses laser beams to generate ultrasonic waves in the weld and detect reflected waves from defects, eliminating the mechanical contact requirement and enabling inspection of thin plate lap fillet joints.
2Loss of time
If in-process weld inspection is attempted during welding, then real-time defect detection is possible, but the high temperature during welding prevents direct probe access to the inspection target surface
Solution Approach 1:
The patent replaces the mechanical probe system with a non-contact optical laser system that can withstand high temperatures. The laser beams pass through the hot environment without being affected by temperature, enabling in-process inspection during welding operations where conventional probes would be damaged or unable to access the target surface.
Solution Approach 2:
The patent introduces laser beams as an intermediary medium to transfer energy and information through the high-temperature welding environment. The generation laser creates ultrasonic waves in the weld, and the detection laser receives reflected signals, acting as a thermal barrier that protects the inspection system from direct exposure to high temperatures.
3Measurement precision
If scattered wave detection method is used for internal defect detection, then the method works for thick plate groove welding, but it cannot detect defects in thin plate lap fillet joints due to insufficient scattered wave signal
Solution Approach 1:
The patent changes the detection dimension by instead of detecting scattered waves reflected from defects (conventional method), it detects the transmitted ultrasonic waves that pass through the weld and are reflected from the lower surface of the base material. This dimensional shift in detection approach enables defect detection in thin plate lap fillet joints where scattered wave signals are insufficient.
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 thin plate welds during the welding process, improving the accuracy and reliability of weld inspection by using the attenuation degree of ultrasonic waves to determine defect presence, thereby ensuring the quality of thin plate welds.
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
Data Source
AI summary
A generation laser irradiation device irradiates a weld after welding with a generation laser. A detection laser probe irradiates an ultrasonic detection point that passes through the weld and is capable of detecting an ultrasonic wave reflected on a lower surface of a base material with detection laser. A control device determines existence of an internal defect of the weld based on a measurement result of a laser interferometer. The generation laser irradiation device includes a scanning mechanism that scans an irradiation position of the generation laser in a direction intersecting a welding direction.