Asymmetric Spot Welding Electrode for Crash-Resistant Dissimilar Joints
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Solution Overview
Problem
Resistance spot welding of high-strength metallic materials, such as aluminum and austenitic stainless steels, in crash-relevant structural components faces challenges with weldability, particularly in dissimilar material combinations, leading to brittle failures and non-acceptable fracture behavior due to the limitations of rotationally symmetric weld nuggets and inadequate heat management.
Innovation Solution
A non-axially symmetrical resistance spot welding electrode cap with specific geometric features, such as angled web and shank portions, is used to create a desired weld nugget shape that deflects crash forces into uncritical areas, enhancing power transmission and load dissipation, and allowing for the use of adhesive materials in combination with welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rotationally symmetric electrode caps are used for resistance spot welding, then standard welding processes can be applied, but the weld nuggets have limited tolerable loads under cross tensile direction and peeling conditions
Solution Approach 1:
The patent applies asymmetry by replacing the conventional rotationally symmetric electrode cap with a non-rotationally symmetric electrode cap having a specific geometric shape. This asymmetric shape creates a corresponding asymmetric weld nugget geometry that can better withstand cross tensile loads and peeling forces, directly resolving the limitation of symmetric weld nuggets under these loading conditions.
2Strength
If high-strength press-hardening steel grades with high carbon content are used, then high ultimate strength is achieved, but weldability decreases and brittle failure behavior occurs
Solution Approach 1:
The patent applies local quality by using a non-rotationally symmetric electrode cap shape that creates a weld nugget with optimized local stress distribution. The asymmetric geometry concentrates heat and stress in specific regions, improving weldability of high-strength materials while maintaining their high ultimate strength properties and preventing brittle failure.
3Power
If standard copper or copper alloy electrode caps are used, then good current transmission with low resistance is achieved, but controlled heat management and deep welding effect are limited
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the electrode cap from a standard rotationally symmetric shape to a non-rotationally symmetric shape with specific dimensions. This geometric parameter change alters the heat distribution pattern during welding, enabling controlled heat management and deeper welding effects while maintaining good current transmission through the copper or copper alloy material.
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 non-axially symmetrical weld nugget design improves crash energy absorption and reduces the risk of 'zipping' failures, enabling targeted load dissipation and increased tolerable loads under crash conditions, while allowing for combined resistance welding and bonding methods.
Implementation Method 1
Because of that effect the transition resistance between the two sheets is by far the highest, the thermal energy is at this the highest, too. At the end the thermal energy at this point reaches the melting temperature of sheets and a spot weld nugget results.
Implementation Method 2
At the end the thermal energy at this point reaches the melting temperature of sheets and a spot weld nugget results.
Data Source
AI summary
A resistance spot welding electrode for forming dissimilar welded lap joints in crash-relevant structural components of the automotive industry made of high-strength materials. The resistance spot welding electrode includes a cap having, at an end portion of the electrode in contact with materials to be welded together during welding, a non-axially symmetrical contact area in order to form, between the materials being welded, a weld nugget with an essentially similar non-axially symmetrical shape.