Refill Friction Stir Spot Welding with Post-Weld Joint Compression
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Solution Overview
Problem
Friction stir spot welding methods face challenges in improving the fatigue strength of joint portions without compromising manufacturing efficiency.
Innovation Solution
A friction stir spot welding method using a device with a rotary tool and clamp member that applies pressure to both surfaces of the workpiece after welding, utilizing a pressing tool set to compress the joint portion and enhance residual stress, thereby improving fatigue strength without requiring additional dedicated equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pressing step is added after friction stir spot welding to improve fatigue strength, then the fatigue strength of the joint portion is improved, but the manufacturing efficiency decreases due to additional process time
Solution Approach 1:
The patent combines the pressing operation with the existing friction stir spot welding device by utilizing the clamp member's pressing capability. The clamp member presses the workpiece during the welding process and can continue pressing during a subsequent cooling period, merging two functions (welding and pressing) into one device operation sequence, thereby avoiding the need for separate dedicated pressing equipment and reducing overall process time
Solution Approach 2:
The pressing action is performed during the cooling period that naturally follows the welding process. By utilizing this idle time for the pressing operation, the patent performs the fatigue strength improvement action during a period when no additional equipment is needed, effectively overlapping the pressing process with the natural cooling cycle of the welded joint
2Strength
If a dedicated pressing device is introduced to apply compression after welding, then the residual stress and fatigue strength are improved, but the device complexity increases
Solution Approach 1:
The clamp member is designed to perform multiple functions: it clamps the workpiece during the friction stir spot welding process and subsequently serves as a pressing device to apply compression to the welded joint during the cooling period. This multi-functionality eliminates the need for separate dedicated pressing equipment, maintaining device simplicity while achieving the desired fatigue strength improvement
Solution Approach 2:
The friction stir spot welding device performs the pressing operation itself using its own clamp member, rather than requiring an external dedicated pressing device. The device serves its own additional function of applying compression to improve fatigue strength, thereby reducing overall system complexity and equipment investment
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 method efficiently enhances the fatigue strength of the joint portion by applying residual stress through compression, reducing the need for separate pressing devices and maintaining manufacturing efficiency.
Implementation Method 1
friction stir spot welding of the workpiece by using the pin member and the shoulder member
Implementation Method 2
partially stirs the workpiece
Implementation Method 3
pressing step of causing the friction stir spot welding device to press an obverse surface and a reverse surface of at least one of a friction-stirred region of the workpiece and an adjacent region
Data Source
AI summary
A friction stir spot welding method includes a welding step of performing friction stir spot welding of a workpiece by using a pin member and a shoulder member while the workpiece is supported and pressed by the end face of a clamp member and a pressing step of causing a friction stir spot welding device to press an obverse surface and a reverse surface of at least one of a friction-stirred region of the workpiece and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side after the welding step while the pin member and the shoulder member are accommodated in an accommodation space of the clamp member.