Tube Bundle Fastening Assembly Without Brazed or Welded Joints
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Solution Overview
Problem
Existing fastening methods for tubular structures in turbine engines and engineering assemblies, such as brazed or welded joints, suffer from reliability issues due to stress concentrations, manufacturing defects, and difficulty in inspection and maintenance, leading to high failure rates and maintenance challenges.
Innovation Solution
A non-permanent fastening assembly using a positioning fitting and removable clamping device that bundles tubular structures without brazed or welded joints, providing low stress concentration and improved maintainability, with features like ribs to prevent axial movement and friction damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If brazed or welded joints are used to fasten tubular structures, then the assembly strength is improved, but stress concentrations and manufacturing defects occur leading to reduced reliability
Solution Approach 1:
The fastening assembly is divided into separate components: a clamping element that applies radial force and a positioning fitting that provides axial location. This segmentation eliminates the need for continuous brazed or welded joints, thereby reducing stress concentrations and manufacturing defects while maintaining assembly strength through distributed mechanical fastening points.
Solution Approach 2:
The positioning fitting acts as an intermediary component between the clamping element and the tubular structures. It provides a standardized interface that distributes loads evenly, prevents direct stress concentrations on the tubes, and facilitates precise axial positioning without requiring complex welding or brazing operations.
2Strength
If brazed or welded joints are used to fasten tubular structures, then the assembly strength is improved, but inspection and maintenance difficulty increases
Solution Approach 1:
By segmenting the fastening system into removable clamping elements and positioning fittings, the design enables easy inspection and maintenance. Each component can be independently accessed, inspected for wear or damage, and replaced without affecting other parts of the assembly, eliminating the need to cut or break welded joints for maintenance.
Solution Approach 2:
The fastening assembly transitions from a static permanent joint (weld/brazing) to a dynamic removable connection. The clamping elements can be opened and closed, allowing for easy assembly and disassembly during maintenance operations while maintaining secure fastening during operation, thus improving ease of repair without compromising strength.
3Ease of repair
If a non-permanent fastening assembly is used to bundle tubular structures, then maintainability is improved, but device complexity increases
Solution Approach 1:
The positioning fitting serves multiple functions simultaneously: it provides axial positioning for the clamping element, locates the tubular structures in the correct position, distributes radial loads from the clamping element, and prevents axial movement of the tubes. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving improved maintainability.
4Ease of manufacture
If traditional fastening methods are used, then manufacturing simplicity is maintained, but stress concentrations occur leading to high failure rates
Solution Approach 1:
The segmented design with discrete clamping elements and positioning fittings eliminates continuous welded joints that are prone to stress concentrations and manufacturing defects. Each component can be manufactured separately using simple forming and machining operations, and assembled through straightforward mechanical fastening, thereby maintaining manufacturing simplicity while significantly improving reliability by distributing stresses across multiple contact points.
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
The assembly enhances reliability, reduces stress concentrations, improves assembly and maintenance ease, and provides vibration damping, resulting in a compact and durable tube bundle with reduced failure risks and improved operational efficiency.
Implementation Method 1
The clamping element provides friction damping while allowing slippage between the tubes to minimize thermal mismatch
Data Source
AI summary
A fastening assembly for a plurality of tubular structures. The fastening assembly includes a positioning fitting member and a clamping element. The positioning fitting member is coupled to a first tubular structure of the plurality of tubular structures such that the positioning fitting member forms a part of the first tubular structure. The positioning fitting member includes a plurality of ribs. The clamping element extends around the plurality of tubular structures and around at least a portion of the positioning fitting member to bundle and to secure the plurality of tubular structures together. The clamping element is positioned between the plurality of ribs.