Laser Lap-Welded Joint Geometry for Peel Strength and Accuracy
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Solution Overview
Problem
Existing laser welding technologies for automobile framework components face issues with heat input leading to increased thermal strain, reduced dimensional accuracy, and insufficient peel strength, particularly due to uncontrolled weld line shapes and sheet gaps.
Innovation Solution
A laser lap-welded joint is created by controlling the shapes of the weld line ends, sheet thickness, gap between sheets, weld position, weld ratio, and weld width, using specific formulas to ensure a sufficient peel strength and improved dimensional accuracy by reducing thermal strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous welding is performed on a portion in which the flange portion and another component are not in contact with each other, then the welding coverage is improved, but the heat input increases causing increased thermal strain and decreased dimensional accuracy
Solution Approach 1:
The continuous weld is divided into intermittent welding beads with specific ratios of weld length to pitch (0.2-0.95). This segmentation reduces the total heat input while maintaining adequate welding coverage, thereby reducing thermal strain and improving dimensional accuracy while still achieving reliable joint strength.
Solution Approach 2:
The welding process uses periodic intermittent welding instead of continuous welding. By controlling the weld pitch and weld length ratios, the process achieves periodic heat input that reduces cumulative thermal strain while maintaining adequate welding coverage for reliable joints.
2Object-generated harmful factors
If the gap between sheets is too large, then the zinc coating can be vaporized and sputtered, but burn-through occurs
Solution Approach 1:
The sheet gap is precisely controlled within a specific range (0.05-0.25mm) to optimize the welding process. This parameter control prevents zinc coating sputtering while avoiding burn-through, achieving both protection of the coating and maintenance of weld quality.
3Device complexity
If resistance spot welding is used for welding automobile structural members, then the welding process is simple, but the welding time is long, the pitch cannot be reduced due to heat value decrease from shunt current, and there are spatial limitations due to the welder gun
Solution Approach 1:
The mechanical resistance spot welding process is replaced with laser welding technology. This substitution enables faster welding speeds, reduced pitch requirements, and eliminated spatial limitations of the welder gun while maintaining process simplicity through automated laser systems.
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 solution ensures a sufficient peel strength and improved dimensional accuracy by precisely controlling the weld parameters, reducing thermal strain and preventing burn-through, while maintaining high tensile strength and workability.
Implementation Method 1
laser welding is performed on the overlap portion to form a laser-welded portion
Implementation Method 2
a laser is radiated onto a surface of the two steel sheets stacked one on top of the other in a state of being stacked one on top of the other in one-side welding to join the steel sheets to each other
Data Source
AI summary
A laser lap-welded joint being formed from stacked steel sheets and including a plurality of welded portions each having a substantially C-shaped surface, each of the welded portions being formed of a first linear portion and second linear portions having a surface having a semicircular shape. The radius R of the semicircular shape and the sheet thickness t of one of the steel sheets having a larger sheet thickness satisfy 0<R≤1.5 t. The pitch λ between the adjacent welded portions and a weld length l satisfy 0.4≤l/λ<0.7. The space X between an end of a contact portion where the steel sheets are in contact with each other and each of the welded portions satisfy 2 t≤X≤4 t. The sheet thickness t and the width W of each of the welded portions satisfy 0.3≤W/t≤1.0.