Friction-Welded Steel Joint Structure for High Cross-Tensile Strength
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Solution Overview
Problem
Existing joining techniques for steel sheets, such as spot welding and self-piercing rivets, face challenges in achieving high cross-tensile strength, especially when using high-strength steel sheets, due to reduced nugget toughness and potential cracking.
Innovation Solution
A joint structure and joining method that utilize a connecting element with a shaft portion to friction-weld both the first and second steel members, ensuring stable penetration and increased joint strength by controlling the diameters of the boundaries and the shaft portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If self-piercing rivet is used to join metal sheets, then mechanical joining without melting is achieved, but deformation of the die side metal sheet becomes extremely large causing cracking
Solution Approach 1:
A through-hole is formed in advance in the second steel member before the friction welding process. This preliminary action allows the shaft portion of the connecting element to pass through smoothly without causing extreme deformation and cracking of the die side metal sheet, while still achieving secure friction welding to both steel members.
2Strength
If connecting element is friction-welded to steel members, then cross-tensile strength increases, but control of deformation and penetration stability becomes challenging
Solution Approach 1:
The connecting element is designed with different diameter portions: a head portion with a first diameter and a shaft portion with a second diameter. The shaft portion has a controlled deformation section with specific diameter ratios (Dmax1/Dmin ≥ 0.65 and Dmax2/Dmin ≥ 1.20) that localize deformation to specific regions, ensuring stable penetration and controlled deformation while maintaining high joint strength.
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 proposed solution effectively stabilizes the joining of multiple steel members, enhancing cross-tensile strength and preventing cracking, while being applicable to vehicle members with high-strength steel sheets.
Implementation Method 1
the shaft portion of the connecting element and the second steel member are joined by friction welding, and the shaft portion and the first steel member are joined by friction welding
Data Source
AI summary
According to the present invention, provided are a joint structure (100) which joins a plurality of overlapped steel members (110, 120) using a connecting element (130) having a shaft portion (131), the joint structure including: a first steel member (110); and one or more of second steel members (120) overlapping the first steel member (110), in which the shaft portion (131) of the connecting element (130) is penetrated through the second steel member (120), and the shaft portion (131) of the connecting element (130) and the second steel member (120) are joined by friction welding, and the shaft portion (131) and the first steel member (110) are joined by friction welding, and a joining method for obtaining the joint structure.