Closed-Loop Laser Weld Geometry for Lower Stress Lap Joints
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Solution Overview
Problem
Laser lap welding in the automotive industry often results in high stress raisers, which can compromise the strength of the weld.
Innovation Solution
The implementation of closed-loop laser welds, which optimize stress raisers through symmetrical loading conditions and placement of initiation and conclusion points within the weld perimeter, reducing maximum principal stress by 20% compared to non-closed-loop welds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional laser weld paths (line, C, or staple welds) are used, then welding can be completed with standard procedures, but high stress raisers compromise the strength of the weld
Solution Approach 1:
The patent applies curvature by transitioning from linear or arcuate weld paths to closed-loop paths with radiused portions. The radiused portions replace sharp corners with curved transitions, distributing stress more evenly throughout the weld bead and eliminating stress concentration points that occur at sharp angles in conventional weld geometries.
Solution Approach 2:
The closed-loop weld path is segmented into distinct portions (starting weld path, main weld path, ending weld path) with specific geometric characteristics. Each segment serves a functional purpose: the starting path establishes the loop geometry, the main path forms the stress-distributing closed loop, and the ending path completes the weld while maintaining stress distribution benefits.
2Ease of manufacture
If multiple welding steps are used to bond substrates, then complex joints can be assembled, but the number of welding steps increases process complexity and time
Solution Approach 1:
The patent merges multiple welding operations into a single closed-loop weld path. By designing the weld path to form a closed loop that bonds multiple substrates simultaneously, the process eliminates the need for separate welding steps that would otherwise be required to achieve the same joint configuration, thereby simplifying the manufacturing process and improving productivity.
3Strength
If high energy is applied to meet performance metrics for weld joints, then weld strength is achieved, but energy consumption increases
Solution Approach 1:
The patent changes the geometric parameters of the weld path from conventional open paths to closed-loop paths with specific radius-to-length ratios. This geometric parameter change optimizes the stress distribution pattern, allowing the weld to achieve required strength performance with lower energy input by eliminating stress concentration that would otherwise require additional energy to compensate for potential weak points.
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
Closed-loop laser welds enhance the reliability and durability of laser lap joints, reduce the number of welding steps, energy requirements, and component density, while improving stress distribution and weld strength.
Implementation Method 1
Laser lap welding is used in the automotive industry to join parts
Data Source
AI summary
Systems, methods, and assemblies for forming or employing closed-loop laser-welds are described. Closed-loop laser-welds may be formed by, for example, actuating a laser on a substrate at a first point to initiate a weld and scanning the laser along a starting weld path, along a main weld path, and along an ending weld path. The starting weld path is from the first point to a second point. The main weld path is from the second point to a third point. The ending weld path is from the third point to a fourth point. The laser is scanned from the second point to the third point such that a bead of the main weld path defines an inner perimeter and an outer perimeter. The outer perimeter defines a closed-loop laser weld. The first point and the fourth points are within the inner perimeter.