Friction Stir Weld Assembly Distortion Mitigation
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Solution Overview
Problem
Friction stir welding introduces distortion, such as bowing and buckling, in welded assemblies due to strain and residual stress, which complicates assembly and reduces the strength of the resulting joint, especially in thinner materials, and existing techniques to mitigate this distortion are either ineffective or require high temperatures and specialized equipment.
Innovation Solution
A method and apparatus that utilize a friction stir weld assembly with a roller to apply compressive force along the weld path after joint formation, inducing plastic deformation to reduce distortion, where the roller is directed by a controller to follow a predefined path and apply a predetermined force, potentially using a hardened cylindrical roller with chamfered edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If friction stir welding is performed on thin materials, then welding capability is achieved, but distortion increases significantly
Solution Approach 1:
The patent applies preliminary counter-bending to the workpiece before friction stir welding to pre-compensate for expected distortion. By calculating and applying the reverse deformation in advance, the workpiece is positioned such that post-weld distortion will return it to the desired flat configuration, thereby resolving the contradiction between achieving weldability in thin materials and maintaining manufacturing precision.
Solution Approach 2:
The patent modifies process parameters including welding speed, tool rotation speed, and plunge depth to optimize the thermal cycle and plastic deformation characteristics. By carefully controlling these parameters, the heat input and residual stress distribution are optimized to minimize distortion while maintaining weld quality in thin materials, thus resolving the contradiction between welding capability and distortion control.
2Adaptability or versatility
If friction stir welding is performed on thin materials, then welding capability is achieved, but assembly difficulty increases due to distortion
Solution Approach 1:
By applying preliminary counter-bending before welding, the workpiece is pre-positioned to account for expected distortion. This ensures that after welding, the assembly maintains proper alignment and fit, thereby eliminating assembly difficulties while preserving welding capability in thin materials.
Solution Approach 2:
Optimizing welding parameters such as travel speed, rotation speed, and tool design controls the magnitude and distribution of distortion, ensuring that the welded thin materials remain within acceptable tolerances for subsequent assembly operations, thus improving ease of operation without sacrificing welding capability.
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 effectively reduces or eliminates distortion in friction stir weld joints, enhancing the strength and assembly efficiency of the welded assembly by inducing plastic deformation along the weld path, while maintaining alignment and precision throughout the process.
Implementation Method 1
applying force to the workpiece following formation of and along at least a portion of the friction stir weld joint in order to reduce the distortion of the workpiece, wherein applying force comprises inducing plastic deformation along at least a portion of the friction stir weld joint
Implementation Method 2
Frictional heat is generated as a result of the interaction of the rotating friction stir weld tool and the workpieces through which the friction stir weld tool is advanced
Data Source
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AI summary
A method of mitigating distortion in a friction stir weld joint as well as an associated friction stir weld assembly for mitigating distortion in a friction stir weld joint are provided. In this regard, a workpiece having a friction stir weld joint and associated distortion may be provided. Force may then be selectively applied to the workpiece along at least a portion of friction stir weld joint. The application of force induces plastic deformation along at least the portion of the friction stir weld joint in order to reduce the distortion of the workpiece. Force may be applied, for example, by moving a roller, such as a hardened cylindrical roller having chamfered edges, along at least a portion of the friction stir weld joint in order to apply a compressive force.