Fastener Assembly for Rocket Nozzle Thermal Expansion
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Solution Overview
Problem
Connecting components made of dissimilar materials in rocket engines, such as metallic and non-metallic nozzles, poses a challenge due to significant thermal expansion mismatches, leading to stress on joints and potential structural integrity issues.
Innovation Solution
A sliding connection system using a fastener with a shank, sleeve, and resilient member, including conical spring washers, that allows for thermal expansion of one component without stressing the other, by applying a preload to structurally join the interface while permitting sliding motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid fastener connection is used to join metallic nozzle and non-metallic nozzle extension, then structural strength is improved, but thermal expansion stress increases due to mismatch between dissimilar materials
Solution Approach 1:
The fastener system transitions from a rigid static connection to a dynamic system that accommodates thermal expansion. The resilient member (spring) allows the fastener to maintain constant clamping force while adapting to dimensional changes in the metallic nozzle during thermal cycling, thereby reducing thermal expansion stress on the joint.
Solution Approach 2:
The invention changes the mechanical parameters of the connection by introducing a resilient member that can elastically deform. This allows the clamping force parameter to remain constant despite changes in the dimensional parameters of the connected components due to thermal expansion, resolving the stress issue while maintaining joint strength.
2Reliability
If a rigid bolt connection is used to secure the nozzle components, then structural integrity is improved, but bending stresses increase on the bolts due to thermal mismatch
Solution Approach 1:
The fastener system transitions from a rigid static connection to a dynamic system that accommodates thermal expansion. The resilient member (spring) allows the fastener to maintain constant clamping force while adapting to dimensional changes in the metallic nozzle during thermal cycling, thereby reducing thermal expansion stress on the joint.
Solution Approach 2:
The invention changes the mechanical parameters of the connection by introducing a resilient member that can elastically deform. This allows the clamping force parameter to remain constant despite changes in the dimensional parameters of the connected components due to thermal expansion, resolving the stress issue while maintaining joint strength.
3Adaptability or versatility
If dissimilar materials (metallic and non-metallic) are used for nozzle components to achieve functional requirements, then thermal performance is improved, but manufacturing complexity increases due to joining difficulties
Solution Approach 1:
The resilient member acts as an intermediary element between the metallic nozzle and non-metallic nozzle extension. It mediates the thermal expansion mismatch by providing a compliant connection that accommodates dimensional changes, simplifying the joining process compared to rigid mechanical fasteners or welding of dissimilar materials.
Solution Approach 2:
The invention changes the mechanical parameters of the connection by introducing a resilient member that can elastically deform. This allows the clamping force parameter to remain constant despite changes in the dimensional parameters of the connected components due to thermal expansion, resolving the stress issue while maintaining joint strength.
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 solution effectively manages thermal expansion mismatches, reducing stress on joints and ensuring structural integrity by allowing the metallic nozzle to slide relative to the non-metallic nozzle extension, maintaining a consistent clamping force across varying operating conditions.
Implementation Method 1
a resilient member received by the shank and contained by the sleeve. The resilient member is configured to press the first mating surface and the second mating surface against one another
Implementation Method 2
a significant mismatch in thermal expansion may exist between the metallic nozzle and the non-metallic nozzle extension. The thermal mismatch between nozzle and nozzle extension may act to place stresses on joints between the components
Data Source
AI summary
A sliding connection between components of dissimilar materials includes a first mating surface formed on a first component and a second mating surface formed on a second component and configured to mate with the first mating surface. The first component is connected to the second component at the first and the second mating surfaces by a fastener including a shank, a sleeve received by the shank, and a resilient member received by the shank and contained by the sleeve. The resilient member is configured to press the first mating surface and the second mating surface against one another and to permit the first mating surface to slide against the second mating surface.