Stiffened Plate Laser Welding Residual Stress Reduction
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Solution Overview
Problem
Arc welding of stiffener materials onto steel plates results in thermal contraction-induced residual stress, leading to deteriorated tensile and fatigue strength, and the challenge of preventing melt-through causes welding residue issues, which can lead to crack formation and reduced fatigue strength.
Innovation Solution
The use of laser welding or hybrid laser-arc welding to join stiffener materials to steel plates, with controlled laser output, irradiation direction, and welding speed, eliminates melt-through and welding residue, improving weld quality and fatigue strength by minimizing stress concentration and residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If arc welding is used to join stiffener materials to steel plates, then the welding operation can be performed from the external side of closed cross-sectional structures, but welding residual stress is generated causing deteriorated tensile strength, compressive strength, and fatigue strength
Solution Approach 1:
The patent changes the welding method from arc welding to laser welding, which fundamentally alters the thermal process parameters. Laser welding uses concentrated optical energy to create a keyhole effect, resulting in deeper penetration and significantly reduced heat input compared to arc welding. This parameter change eliminates welding residual stress while maintaining welding accessibility from the external side.
Solution Approach 2:
The patent replaces the arc welding process (thermal-mechanical system) with laser welding (optical-thermal system). By substituting the arc discharge mechanism with a focused laser beam, the welding process achieves precise energy delivery with minimal heat affected zone, thereby preventing residual stress generation while maintaining operational ease.
2Ease of operation
If arc welding is used on closed cross-sectional structures, then welding can be performed from the external side, but melt-through control is difficult causing welding residue portions in root portions
Solution Approach 1:
The patent changes the welding process parameters by using laser welding with controlled power density, pulse duration, and beam focus. These parameter changes enable precise control of the melting and vaporization process, creating a clean weld without residue portions while maintaining external side accessibility for closed cross-sectional structures.
Solution Approach 2:
The patent implements feedback control in the laser welding process by monitoring weld pool characteristics, penetration depth, and material vaporization rate. This feedback mechanism allows real-time adjustment of laser power and speed to prevent both melt-through and insufficient welding, ensuring high manufacturing precision for closed cross-sectional structures.
3Reliability
If welding residue portions are present in root portions of closed cross-sectional structures, then stress concentration occurs leading to crack formation, but preventing melt-through causes welding residue
Solution Approach 1:
The patent uses laser welding with optimized parameters (power density, pulse width, focus position) to achieve complete penetration without residue. The keyhole effect in laser welding creates a self-cleaning mechanism that prevents welding residue formation while ensuring complete fusion, thereby eliminating stress concentration points and improving fatigue strength.
Solution Approach 2:
The patent converts the potential harm of excessive melting (melt-through) into a beneficial keyhole effect. By controlling the laser parameters, the vaporization of material creates a keyhole that promotes deep penetration and complete welding, while the controlled nature of this process prevents residue formation, thus improving both weld completeness and fatigue strength.
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 weld quality and fatigue strength of stiffened plates by preventing melt-through and reducing welding residue, thereby reducing the risk of cracks and maintaining assembly accuracy and strength.
Implementation Method 1
edge portions of stiffener materials which are in contact with a steel plate are laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon
Implementation Method 2
a laser having a predetermined output being irradiated from a predetermined direction thereon
Data Source
AI summary
A method of forming stiffened plate by welding a plurality of stiffener materials and a steel plate, so that closed cross-sectional structures are secured onto a surface of the steel plate. The stiffener materials are joined to the steel plate as a result of edge portions of the stiffener materials which are in contact with the steel plate by being laser welded at a predetermined welding speed as a result of a laser having a predetermined output being irradiated from a predetermined direction thereon from the external side of the closed cross-sectional structures. Accordingly, it is possible to achieve an improvement in the weld quality when welding stiffener materials onto a steel plate, and to achieve an improvement in fatigue strength.