Double-Sided Friction Stir Welding Without a Probe
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Solution Overview
Problem
Existing double-sided friction stir welding methods face challenges in achieving sufficient plastic flow and joint quality, particularly when welding structural steel, due to variations in temperature and plastic flow in the thickness direction, leading to defects and reduced welding speed.
Innovation Solution
A double-sided friction stir welding apparatus and method using a pair of rotating tools with end portions formed in circular and planar or convex/concave curved shapes, rotating in opposite directions, and controlled to optimize the diameter, inclination angle, and distance between end portions to ensure uniform plastic flow and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a probe is used in the rotating tool for friction stir welding, then the tool can effectively stir the metal plates, but the probe is prone to breakage and wear, reducing tool durability
Solution Approach 1:
The patent removes the probe component from the rotating tool, extracting the problematic element that caused breakage and wear. The tool now consists only of a shoulder portion, eliminating the probe while maintaining welding functionality through alternative mechanisms.
Solution Approach 2:
The patent changes the geometric parameters of the rotating tool by eliminating the probe and optimizing the shoulder portion dimensions. The diameter of the end portion is specifically controlled to satisfy 4t ≤ D ≤ 20t (where t is plate thickness), and the shoulder portion height is optimized to create effective plastic flow without probe-induced stress concentrations.
2Productivity
If high welding speed is used in friction stir welding, then productivity increases, but sufficient plastic flow and joint quality cannot be achieved
Solution Approach 1:
The patent employs a convex curved surface on the shoulder portion instead of a flat surface. This curvature design optimizes the contact area and pressure distribution during welding, enhancing material flow and plastic deformation. The convex shape creates more uniform stress distribution that facilitates adequate plastic flow even at higher welding speeds.
Solution Approach 2:
The patent optimizes specific geometric parameters including the diameter of the end portion (4t ≤ D ≤ 20t) and the height of the shoulder portion (0.05t ≤ h ≤ 0.5t). These parameter optimizations ensure sufficient plastic flow and joint quality while enabling higher welding speeds.
3Ease of operation
If the diameter of the rotating tool end portion is too small, then the tool can access narrow joints, but sufficient plastic flow and stress distribution cannot be achieved
Solution Approach 1:
The patent establishes optimal parameter ranges for the end portion diameter (4t ≤ D ≤ 20t, where t is plate thickness). This parameter optimization ensures the tool is large enough to generate sufficient plastic flow and stress distribution while remaining small enough to access narrow joints effectively.
Solution Approach 2:
The convex curved surface design increases the effective contact area between the tool and workpiece compared to a flat surface. This curvature enhancement allows for better stress distribution and plastic flow generation even when the overall tool diameter is constrained for joint accessibility.
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 approach facilitates uniform plastic flow in the thickness direction, suppressing defects and increasing welding speed, while improving tool durability by eliminating the need for a probe and optimizing the shape and size of the end portions to enhance material flow and joint strength.
Implementation Method 1
a friction stir welding method is a method in which metal plates are fixed in place and welded together by a rotating tool that moves while rotating... solid-state welding that uses plastic flow of a metal caused by frictional heat generated between a rotating tool and metal plates
Data Source
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Figure 3(a)~3(b)
AI summary
It is an object to provide rotating tools for double-sided friction stir welding that are applied to double-sided friction stir welding, which is a technique for welding two metal plates by rotating a pair of rotating tools, which oppose each other, in opposite directions, a double-sided friction stir welding apparatus that uses the rotating tools for double-sided friction stir welding, and a double-sided friction stir welding method. A pair of rotating tools for double-sided friction stir welding that are used in double-sided friction stir welding, which is a technique for welding metal plates by using a pair of rotating tools that are each disposed on one of first and second surfaces of an unwelded portion of the metal plates such that the rotating tools rotate in opposite directions, include end portions each of which is formed in a circular and planar shape. The end portions are each made of a material harder than the metal plates.