Deformable Brazing Spacer for Ceramic-Metal Joint Stress
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Solution Overview
Problem
Conventional assembly methods for ceramic and metal parts, such as brazing, face challenges due to significant thermomechanical and chemical differences, leading to stress-induced deformations and potential breakage, especially in high-temperature applications like aeronautics, where ceramic materials and metal alloys like titanium alloys have disparate expansion coefficients.
Innovation Solution
The introduction of a deformable intermediate connecting element with brazed flat areas and free undulations, made of materials like Ag-Mn or Ag-Cu-Ti, which absorbs expansion differentials and maintains the assembly in the elastic domain, reducing stresses and enhancing flexibility and rigidity as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional brazing is used to assemble ceramic and metal parts, then the parts are joined together, but strong stresses and deformations occur due to expansion coefficient differences
Solution Approach 1:
A deformable intermediate connecting element is introduced between the ceramic part and metal part. This intermediary layer absorbs the thermomechanical stresses generated by expansion coefficient differences, preventing direct stress transmission that would cause breakage. The intermediate element acts as a buffer zone that accommodates differential expansion while maintaining joint integrity.
Solution Approach 2:
The connecting element is designed with specific material parameters (deformability, intermediate expansion coefficient) that differ from both the ceramic and metal parts. By changing the physical parameters of the intermediate layer, the system accommodates the expansion differential without generating excessive stresses, thus resolving the contradiction between joint strength and reliability.
2Strength
If a rigid connection is used between ceramic and metal parts, then structural integrity is maintained, but thermal expansion stresses cause deformations and potential failure
Solution Approach 1:
The connecting element incorporates a deformable layer that can flex and accommodate thermal expansion differences. This flexible intermediate structure maintains structural integrity while allowing controlled deformation, avoiding the need for complex rigid assemblies with multiple stress-absorbing components.
3Ease of manufacture
If mechanical connection (riveting or bolting) is used, then assembly is straightforward, but weight and bulk increase
Solution Approach 1:
The connecting element combines multiple functions into a single component: it provides mechanical attachment, absorbs thermal stresses, and maintains structural integrity. This merged solution replaces traditional multi-component mechanical assemblies (fasteners, washers, spacers), reducing overall weight while maintaining ease of assembly through brazing.
4Adaptability or versatility
If homogeneous assembly methods for ceramic materials are used, then ceramic parts can be assembled, but heterogeneous ceramic-metal assemblies cannot be joined
Solution Approach 1:
The deformable intermediate connecting element serves as a mediator that is compatible with both ceramic and metal materials. It enables heterogeneous assembly by providing interfaces that work with both material types, overcoming the limitation of homogeneous assembly methods while maintaining manufacturing feasibility through standard brazing processes.
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 solution effectively accommodates thermomechanical expansion differentials, reducing the risk of breakage and maintaining structural integrity under thermal cycling, thereby enhancing the reliability and lifespan of ceramic-metal assemblies in high-temperature environments.
Implementation Method 1
a metal alloy based on titanium, aluminum and vanadium has an expansion coefficient approximately two to three times greater than that of ceramic materials
Implementation Method 2
the expansion differential between the part made of ceramic material and the metal is absorbed by the deformable sheet... remaining as much as possible in the elastic domain
Implementation Method 3
Brazed joint between a metal part and a ceramic part
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a joint comprising a metal part, a ceramic part and at least one connecting spacer which is assembled to each of said parts by means of brazing. The aforementioned connecting spacer (10') consists of a deformable layer having at least two flat areas (11, 12) which are brazed respectively to the above-mentioned parts. Moreover, said two flat areas (11, 12) are interconnected by a deformable area (13') having at least two non-brazed undulations (19, 20) which are oriented alternately towards the metal part and the ceramic part.