Friction Stir Joining Control for Anchor-Formed Three-Member Joints
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Solution Overview
Problem
Existing methods for manufacturing vehicle bodies using steel and light metal plate materials face challenges in effectively joining three different members with varying melting points and hardness levels, resulting in inadequate joint strength.
Innovation Solution
A friction stir joining device and method that uses a cylindrical tool capable of rotation and reciprocation, with a control system to position and process the members such that the member with higher hardness extends material above the second member, forming an anchor part that enhances tensile-shear and peel strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional friction stir joining method is used to join three different members, then the joining process can be performed, but the joint strength is insufficient due to inadequate material flow and anchoring
Solution Approach 1:
The joining process is segmented into distinct phases: initial pressing to soften the first member, extension of the third member above the second member, and tool withdrawal. This segmentation allows each phase to be optimized independently, ensuring proper material flow and anchoring for maximum joint strength.
Solution Approach 2:
The tool performs preliminary pressing action on the joined part before complete penetration, softening the first member in advance. This preliminary action prepares the material for subsequent flow and anchoring, ensuring adequate joint strength without requiring excessive force during the main joining phase.
2Strength
If the tool presses deeply into the joined part to soften the first member, then material flow improves, but the third member cannot extend properly above the second member
Solution Approach 1:
The tool performs periodic pressing and withdrawal actions. During the pressing phase, the first member is softened; during the withdrawal phase, the third member extends above the second member. This periodic action sequence ensures both adequate material flow and proper extension shape are achieved.
Solution Approach 2:
The tool's pressing force and position are dynamically adjusted during the joining process. The force is increased during pressing phases to soften material, then reduced during withdrawal phases to allow extension. This dynamic control enables both good material flow and proper third member extension.
3Productivity
If the tool is withdrawn quickly from the joined part, then productivity increases, but the third member does not extend sufficiently above the second member
Solution Approach 1:
The tool withdrawal is performed in periodic cycles rather than as a single continuous motion. Each cycle includes a pressing phase followed by a controlled withdrawal phase, allowing the third member to extend progressively above the second member while maintaining overall high productivity through efficient cycle timing.
4Strength
If the joining process is optimized for members with different melting points and hardness, then joint strength improves, but the device complexity increases due to multiple process parameters
Solution Approach 1:
The control device dynamically adjusts multiple parameters including pressing force, tool rotation speed, and withdrawal rate based on the specific properties of the three members. These parameter changes are coordinated to account for different melting points and hardness levels, ensuring optimal joint strength without requiring overly complex device architecture.
Solution Approach 2:
The control device incorporates feedback mechanisms to monitor the joining process in real-time and adjust parameters accordingly. This feedback system ensures that the pressing force and withdrawal rate are optimized for the specific material properties being joined, achieving high joint strength while keeping the control system manageable through intelligent regulation.
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 enables full joining of three members with increased tensile-shear and peel strength, providing a strong joint structure by forming an anchor part with the harder material extending above the second member.
Implementation Method 1
locally softening the light metal plate material and causing a plastic flow thereof by frictional heat of a rotary tool being pressed from the light metal plate material side
Data Source
AI summary
A friction stir joining device includes a tool, a rotary driver, a linear-movement driver, and a control device. The control device is adapted to (A) dispose so that a first member opposes to the tool, and the first member, a second member and a third member are located in this order, (B) control the linear-movement driver and the rotary driver so that a tip-end part of the tool presses a joined part of a to-be-joined object while the tool is rotated, (C) control the linear-movement driver and the rotary driver so that the third member softened extends above an upper surface of the second member, and the tip-end part of the tool reaches a first position, and (D) control the linear-movement driver and the rotary driver so that the tool is drawn out from the joined part while the tool is rotated.