Lap Fillet Weld Joint Geometry for Thin-Plate Fatigue Strength
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Solution Overview
Problem
Existing welded joints in thin metal plates suffer from reduced fatigue strength due to geometric stress concentration, material deterioration, tensile residual stress, and root gap enlargement, which are not effectively addressed by existing methods.
Innovation Solution
A welded assembly design featuring bulging and protruding portions on overlapping metal plates, which suppress the root gap and alleviate stress concentration, maintaining base metal strength and improving joint fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If thin metal plates are used to reduce vehicle weight, then weight reduction is achieved, but joint fatigue strength deteriorates due to root gap enlargement and stress concentration
Solution Approach 1:
The invention applies preliminary action by forming bulging portions on one metal plate and protruding portions on the other metal plate before welding. These pre-formed geometric features suppress root gap enlargement during the welding process, preventing the formation of stress concentration sites that would otherwise compromise joint fatigue strength in thin plate applications
2Ease of manufacture
If conventional welding is applied to thin metal plates, then joining is achieved, but root gap enlargement occurs reducing welding performance stability
Solution Approach 1:
The bulging portions and protruding portions are formed in advance through stamping or rolling processes, creating a mechanical constraint system that maintains consistent root gap conditions during welding. This preliminary geometric configuration ensures stable welding performance without requiring complex real-time control mechanisms
Solution Approach 2:
The invention changes the geometric parameters of the metal plates by introducing bulging portions with specific curvature radii and protruding portions with controlled dimensions. These parameter modifications create a physical constraint that maintains optimal root gap spacing, transforming an unstable welding process into a controlled one
3Strength
If weld bead is formed on metal plates, then joining is achieved, but geometric stress concentration occurs at the weld toe reducing fatigue strength
Solution Approach 1:
The invention applies local quality by creating bulging portions and protruding portions at specific locations where stress concentration would occur. These localized geometric modifications redirect stress distribution away from the weld toe, reducing stress concentration factors and improving fatigue resistance without compromising overall joint strength
4Reliability
If material thickness is increased to improve joint fatigue strength, then fatigue strength improves, but vehicle weight increases
Solution Approach 1:
Instead of changing the material thickness parameter, the invention modifies the geometric parameters of the plate configuration by adding bulging portions and protruding portions. This approach improves joint fatigue strength through geometric stress distribution optimization while maintaining the original thin plate thickness, thus avoiding weight increase
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
The design effectively improves joint fatigue strength by minimizing stress concentration and root gap, stabilizing welding performance, and enhancing the structural integrity of thin metal plate assemblies.
Implementation Method 1
a part of a second edge portion 21 of the second metal plate 20 and a part of a surface 11 in the vicinity of an edge portion 12 of the first metal plate 10 are welded by arc welding or laser welding to form a first weld bead 30
Implementation Method 2
a welded assembly design featuring bulging and protruding portions on overlapping metal plates, which suppress the root gap and alleviate stress concentration
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A lap fillet weld joint and a lap fillet weld joint manufacturing method are provided which enable effectively improving joint fatigue strength easily and at low cost. On a side of a first edge (12), a first metal plate (10) is provided with a bulging portion (13) that has an internal space S of a prescribed size, and a second metal plate (20) has a protruding portion (22) that faces to the bulging portion and can be inserted into the bulging portion (13). In a state in which the protruding portion (22) has been inserted into the bulging portion (13), the first metal plate (10) and a second edge (21) of the second metal plate (20) are welded, and a first weld bead (30) is formed.