Linear Friction Welding Offset Stagnation Zones
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Solution Overview
Problem
Linear friction welding processes face challenges in removing sub-surface contaminants, particularly in safety-critical applications like aero-engine Blisks, where contaminants can lead to fatigue deficits and unexpected failures, due to the stagnation of contaminated material in the weld cross-section, which is not effectively extruded and can be below detection thresholds.
Innovation Solution
The method involves dividing the friction phase into sub-phases with offset stagnation zones, where each sub-phase forms a plasticised layer with an extrusion zone and a stagnation zone, ensuring that contaminants are extruded out by aligning the stagnation zone of one sub-phase within the extrusion zone of another, thereby ensuring complete removal of contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the total upset is increased to remove sub-surface contaminants, then contaminant removal is improved, but weld stub height increases leading to exaggerated deflections and inefficient energy transfer
Solution Approach 1:
The friction phase is divided into multiple sub-phases, each creating a plasticised layer with offset stagnation zones. This segmentation allows contaminants to be progressively extruded through offset stagnation zones without requiring excessive total upset, thereby maintaining energy transfer efficiency while achieving reliable contaminant removal.
Solution Approach 2:
The invention changes the spatial parameter of the stagnation zone by introducing offset positions in different sub-phases. This parameter change enables contaminants to be moved to extrusion zones without increasing the total upset magnitude, thus resolving the contradiction between contaminant removal and energy efficiency.
2Reliability
If the total upset is increased to remove contaminants, then contaminant removal is improved, but excessive weld flash is formed requiring more clearance and compromising tooling design
Solution Approach 1:
By segmenting the friction phase into sub-phases with offset stagnation zones, the invention achieves contaminant removal through distributed extrusion rather than a single large upset event. This reduces the volume of weld flash formed at any one time, simplifying tooling design and reducing clearance requirements.
3Reliability
If the total upset is increased to remove contaminants, then contaminant removal is improved, but material utilisation decreases leading to increased material cost
Solution Approach 1:
The invention changes the spatial distribution parameter of the plasticised layer through offset stagnation zones in different sub-phases. This allows efficient contaminant extrusion with reduced total upset, thereby minimizing sacrificial material and improving material utilization.
4Reliability
If the total upset is increased to remove contaminants, then contaminant removal is improved, but weld duration increases leading to increased machine tool wear and energy consumption
Solution Approach 1:
The invention maintains continuous useful action by implementing multiple sub-phases that progressively extrude contaminants through offset stagnation zones. This continuous process achieves thorough contaminant removal without requiring an excessively long single-phase upset, thereby reducing overall weld duration and associated wear and energy consumption.
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 ensures the removal of contaminants, enhances weld integrity, and addresses the limitations of Non-Destructive Examination (NDE) inspection, leading to improved component performance and reduced material costs by minimizing excess weld flash and energy consumption.
Implementation Method 1
Linear friction welding (LFW) is a solid-state joining process in which materials are joined using frictional heat created by relative linear motion (oscillation) between two workpieces under a compressive load
Implementation Method 2
In a second friction phase, the force between the workpieces is increased, such that a plasticised layer is formed at the interface between the workpieces and plastic material is extruded out of the interface
Data Source
Figure 1(a)~3
Figure 4(a)~6
AI summary
A method of linear friction welding, the method comprising: a friction phase comprising oscillating a first workpiece (2) relative to a second workpiece (4) with a surface of the first workpiece (2) being forced against a surface of the second workpiece (4), such that a plasticised layer is formed at the interface between the first and second workpieces (2, 4); wherein the friction phase is divided into a plurality of sub-phases, each sub-phase being configured to form a plasticised layer at the interface between the first and second workpieces (2, 4), each plasticised layer comprising a stagnation zone (10a, 10b); wherein the stagnation zone (10a) of one sub-phase is offset from the stagnation zone (10b) of another sub-phase.