Self-Reacting Friction Stir Welding Tool With Annular Gap
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Solution Overview
Problem
In self-reacting friction stir welding, the build-up of weld material between the weld pin and crown shoulder leads to inconsistent weld parameters and increased friction, resulting in weld defects and premature tool failure due to load differentials and drag forces.
Innovation Solution
A self-reacting friction stir welding tool with a central bore in the crown shoulder featuring an annular gap between the pin and the crown shoulder, which minimizes frictional drag by collecting wicked weld material and providing a path for its removal through radial bore holes, ensuring consistent axial movement and load support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If weld material is allowed to wick up into the interface between the weld pin and crown shoulder, then the seal is improved, but frictional drag force increases causing load differential and weld parameter inconsistency
Solution Approach 1:
The central bore is segmented into three distinct regions (first, second, and third regions) with different diameters. The first region has a smaller diameter that allows weld material wicking for sealing, the second region has a larger diameter that collects wicked material, and the third region provides sliding contact. This segmentation resolves the contradiction by spatially separating the sealing function from the low-friction movement function.
2Strength
If the pin and crown shoulder are in tight engagement, then structural strength is improved, but weld material build-up causes load differential and tool failure
Solution Approach 1:
Different regions of the central bore are given different local qualities (diameters) to perform different functions. The first region provides tight engagement for structural strength, the second region provides a larger diameter annular gap to collect wicked material and prevent build-up, and the third region provides sliding contact. This local differentiation resolves the contradiction between strength and reliability.
3Force
If sliding contact is provided between the pin and crown shoulder, then friction is reduced, but weld material removal capability is compromised
Solution Approach 1:
The solution moves the weld material collection function to a different dimension by creating a second region with a larger diameter that forms an annular gap. This annular gap provides a three-dimensional space for collecting and accommodating wicked weld material, separating it from the sliding contact interface. This dimensional change allows sliding contact to maintain low friction while weld material removal is handled in the annular gap space.
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 reduces weld defects and extends tool life by maintaining consistent weld parameters and minimizing frictional drag, allowing for longer, defect-free welds.
Implementation Method 1
The first region and third region have a diameter that provides sliding contact with the pin
Implementation Method 2
Some of the weld material can wick up into the tight interface between the weld pin and the crown shoulder
Data Source
AI summary
A self-reacting friction stir welding (SR-FSW) tool includes a crown shoulder having a central bore and a pin that extends through the crown shoulder's central bore. The central bore includes a first region at a first axial end of the crown shoulder, a second region axially adjacent to the first region, and a third region axially adjacent to the second region. The first region and third region have a diameter that provides sliding contact with the pin. The pin and crown shoulder have an annular gap there between at the second region of the central bore.