Steel Sheet Lap Weld Bead Layout for Torsional Stiffness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lap weld joints of high-strength steel sheets face challenges in maintaining joint strength and torsional stiffness due to torn-open deformation, particularly when subjected to tensile stress or torsional moments, as the nuggets are formed away from the standing wall portions, leading to stress concentration at the nugget ends.
Innovation Solution
A lap welding method that combines spot welding and laser welding to form nuggets and weld beads, where the weld beads are positioned between the nuggets and the R stop of the standing wall portions, with specific dimensions and configurations to enhance joint strength and torsional stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spot welding is used to join steel sheet members with hat shape, then the welding process is simple and widely applicable, but the nuggets are formed away from the standing wall portions causing stress concentration and reduced joint strength
Solution Approach 1:
The patent combines spot welding and laser welding processes to create a hybrid welding method. Spot welding forms initial nuggets, and laser welding subsequently forms weld beads that extend from the nugget ends toward the R stops, creating a continuous welded path that eliminates stress concentration points while maintaining manufacturing feasibility
Solution Approach 2:
The welding process is divided into two distinct stages: first, spot welding creates discrete nuggets at specific locations; second, laser welding creates continuous weld beads connecting the nuggets to the R stops. This segmentation allows each process to optimize its function while achieving the overall goal of improved joint strength
2Ease of operation
If nuggets are formed at locations away from the standing wall portions to avoid electrode interference, then the welding operation can be performed, but torn-open deformation occurs under tensile stress and torsional moment
Solution Approach 1:
The laser-welded beads act as intermediary elements that connect the spot-welded nuggets to the R stops. These beads serve as stress-distributing bridges that prevent direct stress concentration at the nugget ends, thereby preventing torn-open deformation while maintaining the feasibility of the welding operation
Solution Approach 2:
Spot welding is performed first to create initial nuggets at safe locations away from the R stops, avoiding electrode interference. Subsequently, laser welding is applied to extend the welded path from these pre-formed nuggets to the R stops, preparing the joint structure to resist future mechanical loads
3Power
If the welding electrode has a taper portion to concentrate current, then nugget formation is effective, but the nugget is formed at a distance from the standing wall portion reducing torsional stiffness
Solution Approach 1:
The solution extends the welding from a point-source (spot welding creating nuggets) to a line-source (laser welding creating continuous beads). This dimensional transition allows the welded path to reach the R stops, improving the structural distribution of forces and thereby enhancing torsional stiffness while maintaining effective current concentration through the laser beam
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 method improves joint strength and torsional stiffness by distributing stress more evenly across the weld joint, reducing the likelihood of torn-open deformation and enhancing the overall structural integrity.
Implementation Method 1
the tip end surface 94a of the taper portion 94 comes into contact with the flange portion 72 of the steel sheet member 70, whereby electric currents flow in the flange portion 72, and the nugget 80 is formed
Implementation Method 2
a weld bead 120 having a length L that is equal to or greater than a diameter Dn of the nugget 110 and a width W that is 0.5 to 3.0 mm is formed by laser welding
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A lap welding method of a steel sheet includes spot welding in a state in which the flange portion of a second steel sheet member having the flange portion and a standing wall portion is overlapped with the first steel sheet member, thereby forming a nugget between a first steel sheet member and a flange portion; and, after the spot welding, laser welding a region between an R stop of the standing wall portion and the nugget, thereby forming a weld bead, and, in the weld bead, a length dimension is equal to or longer than a diameter of the nugget, and a width dimension is 0.5 to 3.0 mm.