Athermal Mirror Mount Using Composite Bracket Assemblies
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Solution Overview
Problem
Conventional mirror mounts experience thermal expansion-induced stresses due to distinct thermal expansion coefficients in structural materials, leading to physical distortions and instability in optical applications, particularly in military settings where this can degrade focus and impact performance.
Innovation Solution
A mirror-mount platform with an annular back plate made of Ti-6Al-4V titanium alloy and a mirror structure of silicon carbide, connected by bracket assemblies of aluminum alloy Al 6061-T6, which have a higher coefficient of thermal expansion, providing a geometric triangular restraint to counteract thermal expansion forces and maintain rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional mirror mounts use structural materials with distinct thermal expansion coefficients, then the mount provides structural support, but thermal expansion induces stresses causing physical distortions and degraded focus
Solution Approach 1:
The patent applies parameter changes by selecting materials with specific thermal expansion coefficients. The mount uses aluminum alloy brackets (higher CTE) combined with a titanium alloy backplate (lower CTE) to create a composite structure whose overall thermal expansion matches that of the silicon carbide mirror, thereby eliminating thermal stress-induced distortions while maintaining structural support
Solution Approach 2:
The invention employs composite materials by combining aluminum alloy bracket assemblies with a titanium alloy backplate. This composite construction allows the mount to achieve both structural strength and thermal expansion compatibility with the mirror, resolving the contradiction between providing robust support and maintaining focus precision under thermal conditions
2Object-affected harmful factors
If flexible mirror mounts are used, then some thermal stress is reduced, but low harmonic frequency and instability issues arise under operational conditions
Solution Approach 1:
The patent changes the rigidity parameter of the mount structure by using rigid aluminum alloy bracket assemblies with triangular geometric restraints rather than flexible mounting mechanisms. This rigid construction maintains operational stability and high harmonic frequencies while still accommodating thermal expansion through material selection, thereby resolving the contradiction between reducing thermal stress and ensuring operational reliability
3Reliability
If rigid mirror mounts are used, then stability is improved, but thermal expansion forces create stress concentrations and potential mirror damage
Solution Approach 1:
The patent changes the thermal expansion parameter by selecting aluminum alloy and titanium alloy materials whose combined expansion characteristics match the mirror's expansion. This allows the rigid mount to remain stable while preventing thermal stress concentrations that could damage the mirror, as the entire assembly expands uniformly together
Solution Approach 2:
The composite construction of aluminum alloy brackets with a titanium alloy backplate creates a graduated thermal expansion structure. The aluminum brackets accommodate higher expansion, the titanium backplate provides structural rigidity with lower expansion, and together they match the mirror's thermal characteristics, preventing stress concentrations while maintaining stability
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 minimizes thermal stress on the mirror, maintaining athermal-rigidity and stability, preventing harmonic resonance and stress concentrations, while being easier to manufacture and cost-effective compared to traditional designs.
Implementation Method 1
Each bracket assembly is composed of a second material that has a higher coefficient of thermal expansion than the first material
Data Source
AI summary
A mirror-mount platform is provided for securing a mirror surface to a substrate to mitigate distortion from thermal expansion. The platform includes an annular back plate as the substrate composed of a first material, a mirror structure having an obverse reflective surface and a reverse attach surface, and a plurality of bracket assemblies that connect the back plate to the reverse attach surface. Each bracket assembly is composed of a second material that has a higher coefficient of thermal expansion than the first material.