Friction Stir Rivet Joining for High-Strength Overlap Joints
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Solution Overview
Problem
Existing joining methods for overlapping parts, such as those in aircraft or automobile structures, often fail to achieve sufficient strength and joint quality, particularly when using resin members with continuous fibers, due to issues like interlayer peeling and deformation of fasteners like self-piercing rivets.
Innovation Solution
A joining method combining friction stir welding and a fastener, where the tool is press-fitted into the overlapping part to form a friction stirred zone, and the fastener is then press-fitted into this zone, ensuring the fastener can exert its deformation effectively and enhance the joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a self-piercing rivet is driven into resin members with continuous fibers, then the joining process is simple, but the rivet cannot be deformed sufficiently to exert an anchor effect
Solution Approach 1:
The patent applies preliminary action by performing friction stirring before fastener installation. The friction stir tool is inserted into the overlapping region and rotated to knead and soften the thermoplastic resin, creating a softened zone that facilitates subsequent fastener deformation and anchor effect formation.
Solution Approach 2:
The patent changes the physical state of the thermoplastic resin from hard to softened through friction stirring. This parameter change in material softness allows the fastener to be deformed effectively and exert its anchor effect, which would not be possible with the original hard material state.
2Strength
If a self-piercing rivet is forcibly deformed using a special lower mold, then the anchor effect is improved, but interlayer peeling occurs and base material strength deteriorates
Solution Approach 1:
The friction stirring is performed as a preliminary action before fastener installation. By softening the thermoplastic resin in advance, the material becomes more ductile and can accommodate fastener deformation without causing interlayer peeling or base material deterioration.
Solution Approach 2:
The patent changes the material state of the thermoplastic resin from hard to softened through friction stirring. This parameter change eliminates the harmful effects of interlayer peeling and base material deterioration while still achieving sufficient fastener deformation and anchor effect.
3Ease of manufacture
If friction stir welding is used alone, then the joining process is simple, but sufficient peel strength cannot be obtained
Solution Approach 1:
The patent merges friction stir welding with fastener joining into a combined process. The friction stir tool creates a softened zone, and then a fastener is installed into this zone. The combination of friction stirring and fastener anchoring achieves sufficient peel strength while maintaining relative process simplicity.
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
This method achieves a firmly joined overlapping part with high strength by softening the materials through friction stirring, allowing the fastener to apply a strong joining force without relying solely on friction stir welding, thereby improving joint quality and stability.
Implementation Method 1
press-fitting the pin member into the overlapping part to perform friction stirring
Implementation Method 2
constituent materials of the overlapping part are kneaded by friction stirring and the constituent materials are softened
Data Source
AI summary
An overlapping part of a first member and a second member is joined using a tool for friction stir spot welding and a rivet. The first member is disposed on a side where the tool is press-fitted first, and the second member is disposed on a side where the tool is press-fitted last, so that the overlapping part is formed. The tool is press-fitted into the overlapping part to perform friction stirring, thereby forming a friction stirred part in the overlapping part. The rivet is press-fitted into the friction stirred part from the first member side.