Method for repairing an upstream rail of a turbine engine turbine casing
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Solution Overview
Problem
Existing repair methods for upstream rails in turbine engine casings face challenges in machining concave surfaces without creating geometric discontinuities, leading to material overflow and inability to repair damaged concave zones due to precision limitations and stress constraints.
Innovation Solution
A method involving TIG welding to cover both the upper and concave faces of the upstream rail with filler metal, followed by machining in one step to reform the surface up to the radial face, avoiding projections in the concave zone and eliminating wear without thickness loss, with optional additional machining to remove residues and maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the upper face of the rail is covered with filler metal by welding and then machined, then the wear on the upper face is repaired, but the filler metal overflows onto the concave surface creating a machining jump that cannot be removed
Solution Approach 1:
The method applies preliminary protection to the concave surface by covering it with a protective layer before welding. This prevents filler metal from contaminating the concave surface during the welding process, eliminating the need for subsequent machining of the concave surface and avoiding machining jumps that would compromise structural integrity.
Solution Approach 2:
The repair process segments the machining operation into distinct zones: the convex upper face is machined to remove excess filler metal, while the concave surface is protected and left untouched. This segmentation allows precise control over where material is removed, maintaining surface continuity in critical areas while achieving repair in worn areas.
2Ease of manufacture
If the concave surface is machined to remove filler metal, then the surface is cleaned, but a machining jump is created that weakens the highly stressed portion
Solution Approach 1:
The concave surface is pre-protected with a protective coating before welding occurs. This preliminary action prevents filler metal deposition on the concave surface, eliminating the need for any machining operation in this critical stress area and preserving the structural integrity of the highly stressed portion.
3Manufacturing precision
If welding precision is increased to avoid overflow, then material overflow is reduced, but the concave surface cannot be repaired when damaged
Solution Approach 1:
The concave surface is pre-coated with a protective layer that allows controlled filler metal deposition during welding. This enables the welder to work with normal precision while the protective layer prevents unwanted overflow onto the concave surface. After welding, the protective layer is removed, revealing a clean concave surface that can be further repaired if damaged, thus expanding the repair scope.
Solution Approach 2:
A protective layer acts as an intermediary between the welding process and the concave surface. This intermediary layer captures excess filler metal, allowing the welding process to proceed with standard precision while protecting the concave surface from contamination and enabling subsequent repair operations.
4Productivity
If the machining tool exits in the concave surface, then the upper face is fully machined, but a machining jump is generated that creates a geometric discontinuity
Solution Approach 1:
The concave surface is pre-protected before machining begins. This allows the machining tool to complete its path across the upper face and exit through the protected concave surface without creating harmful geometric discontinuities. The protective layer prevents material removal that would create machining jumps, while still allowing the tool to exit cleanly.
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
Enables effective repair of upstream rails by avoiding machining projections in high-stress areas, eliminating wear on concave surfaces, and maintaining the rail's structural integrity by locating machining projections on the least stressed radial face, thus preventing material overflow and ensuring precise, stress-free repair.
Implementation Method 1
A known repair process consists in covering the upper face of the rail with a filler metal by welding
Data Source
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AI summary
The invention relates to a method (40) for repairing an upstream rail (20) of a turbine engine turbine casing (19), said casing (19) including a casing body (21) extending along a longitudinal axis, said upstream rail (20) including: a base (22) including a surface, referred to as radial surface (27), extending substantially radially from the casing body (21); a plate (23) including a surface, referred to as upper surface (25), extending substantially along the longitudinal axis; and a connection portion (24) between the base (22) and the plate (23), including a concave surface (26) connecting the radial surface (27) and the upper surface (25), the concave surface (26) and the radial surface (27) extending on either side of an edge (29), said method (40) including: a step of covering (41) a surface with a solder (33), said surface including the upper surface (25) and the concave surface (26), such that said solder (33) extends substantially until the edge (29); and a step (42) of machining the covered surface, in a single action, in the direction of the radial surface (27), and at least until the edge (29), so as to reshape the surface.