Friction Welding Tapered Titanium Edges to Reduce Porosity
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Solution Overview
Problem
Strain-induced porosity (SIP) formation during linear friction welding of titanium alloys, particularly at the edges of welds, leads to increased costs and material requirements due to the need for larger machining allowances and potential limitations in non-destructive examination.
Innovation Solution
The method involves tapering the workpieces away from the weld surfaces to reduce the flow rate of weld flash material during oscillation, thereby minimizing SIP and cracking at the weld edges by controlling the temperature and strain rate conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large material machining allowance is provided to remove all strain induced porosity, then the reliability of the final component is improved, but the device complexity and cost increase due to requiring larger welding tools and machines
Solution Approach 1:
The patent applies local quality by providing the tapering feature specifically at the edges of the workpiece where strain induced porosity forms, rather than uniformly throughout. This localized geometric modification redirects flash material away from problematic edge regions, reducing porosity formation precisely where it occurs most frequently during friction welding of titanium alloys.
Solution Approach 2:
The tapering of the workpiece edges is performed as a preliminary action before the friction welding process. By pre-shaping the workpiece geometry with tapered edges, the patent prevents strain induced porosity formation during welding, eliminating the need for subsequent extensive machining operations to remove defective material.
2Manufacturing precision
If a large material machining allowance is provided to ensure all strain induced porosity is removed, then the manufacturing precision is improved, but the loss of substance increases due to requiring increased forging sizes
Solution Approach 1:
The tapering modification is applied locally at the weld edges rather than to the entire workpiece. This localized approach prevents porosity formation at the critical edge regions during welding, improving weld quality without requiring increased forging sizes or excessive material removal, thus reducing material loss and cost.
3Productivity
If the workpiece is tapered to reduce strain induced porosity formation, then the productivity is improved by reducing edge clean up machining, but the manufacturing precision of the weld flash material control must be increased
Solution Approach 1:
The patent changes the geometric parameter of the workpiece by introducing a tapering feature at the edges. This parameter modification alters the flash material flow characteristics during welding, redirecting it away from the weld zone. The tapering angle and dimensions can be optimized to achieve the desired flash control, balancing productivity improvement with manufacturability.
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 results in higher quality friction welds with reduced SIP, potentially lowering the need for edge clean-up machining and minimizing material costs, while allowing for smaller welding tools and machines.
Implementation Method 1
oscillating the first and second workpieces relative to each other such that at least one of the weld surfaces of at least one of the workpieces moves relative to the other weld surface of the other workpiece such that the temperature increases at the weld surfaces to create a weld interface
Implementation Method 2
stopping the oscillating and allowing the first and second weld surfaces of the first and second workpieces to cool to weld the first and second workpieces together
Data Source
AI summary
A method of friction welding comprises providing a first workpiece having a first weld surface and a second workpiece having a second weld surface. The first workpiece is arranged such that it tapers away from the first weld surface, the first workpiece converges in a direction away from the first weld surface. The first and second workpieces are arranged such that the first weld surface abuts the second weld surface. The first and second workpieces are oscillated relative to each other such that at least one of the weld surfaces of at least one of the workpieces moves relative to the other weld surface of the other workpiece such that the temperature increases at the weld surfaces to create a weld interface. The oscillation is stopped and the first and second weld surfaces are allowed to cool to weld the first and second workpieces together. The tapering of the first workpiece reduces the flow rate of weld flash material during the oscillation of the first and second workpieces relative to each other to reduce the formation of strain-induced porosity at the edges of the weld.