Friction Stir Welding Shoulder Movement for Surface Flatness
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Solution Overview
Problem
In friction stir welding, the outer surfaces of plate materials become recessed due to the high-speed rotation of shoulders, leading to indentations and damage to the external appearance, especially when welding hollow members with a double skin structure.
Innovation Solution
A friction stir welding method where shoulders are positioned to form a protruding portion on one surface of the plate materials, allowing for welding while avoiding indentations, and the protruding portion is removed to create a flush joint, ensuring the joint thickness is maintained and external appearance is preserved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shoulders are rotated at high speed while pressing the joint between plate materials, then welding strength is improved, but indentations occur on the outer surface of the plate materials
Solution Approach 1:
The method applies preliminary action by forming a protruding portion during the friction stir welding process itself, rather than correcting surface defects afterward. The shoulders are designed to intentionally create material accumulation (protruding portion) that prevents indentation formation on the outer surface, thereby solving the surface flatness issue while maintaining welding strength.
Solution Approach 2:
The invention changes the welding parameters by controlling the movement direction of shoulders from the other surface toward the one surface, and by managing the formation and subsequent removal of the protruding portion. This parameter control allows the outer surface to remain flat while still achieving strong welding through the friction stir process.
2Shape
If a protruding portion is formed on the joint to prevent indentations, then external appearance is preserved, but additional processing step is required
Solution Approach 1:
The method extracts the protruding portion after it has served its protective function during welding. By removing the protruding portion in a controlled manner after welding completion, the external appearance is restored to a flat surface, eliminating the need for additional surface correction processes while maintaining the benefit of indentation prevention during welding.
3Shape
If shoulders move from other surface toward one surface during friction stirring, then protruding portion is formed to prevent surface recession, but joint thickness control becomes critical
Solution Approach 1:
The invention precisely controls the movement parameters of the shoulders, specifically the direction (from other surface toward one surface) and the extent of movement. This parameter control ensures that the protruding portion is formed to the appropriate height to prevent indentation while maintaining the joint thickness within required specifications, achieving both surface flatness and dimensional precision.
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 prevents indentations on the outer surfaces, maintains a strong and aesthetically intact joint, and secures desired strength and yield strength by forming a protruding portion that can be easily processed to be flush with the surface, addressing the issue of recessed surfaces in traditional friction stir welding.
Implementation Method 1
friction heat occurs on a contact surface between the joint S between the pair of plate materials 3 and 4 and the shoulders 5 and 6
Implementation Method 2
friction heat occurs on a contact surface between the joint S between the pair of plate materials 3 and 4 and the shoulders 5 and 6, and the vicinity of the contact surface is plasticized
Implementation Method 3
structures of the ends 3a and 4a (joint S) of the pair of plate materials 3 and 4 intermix with each other due to stirring action according to high-speed rotation of the probe 2
Data Source
AI summary
In a friction stir welding method, a pair of plate materials is arranged opposing one another such that the ends thereof are butted together, after which friction stir welding is performed. A first shoulder is arranged at one surface of the pair of plate materials and a second shoulder is arranged at the other surface of the plate materials to sandwich therebetween a joint to be formed by friction stirring of the end parts of the plate materials, and the first shoulder and the second shoulder are rotated, thereby friction stirring the joint of the pair of plate materials. As the joint is friction stirred, the first shoulder and the second shoulder are moved from the other surface toward the one surface of the plate materials, thereby forming at the joint a protruding part protruding from the one surface of the plate materials as the friction stir welding is performed.