Ratchet Stack for Retaining Thermal Deformation
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Solution Overview
Problem
Existing bimetallic strips cannot store repeated cycles of heating and cooling as mechanical changes in shape, as they return to their original shape upon cooling, failing to retain thermal changes as mechanical deformations.
Innovation Solution
A stack with a ratchet structure at the interface between two materials with different thermal expansion coefficients, where the first member (resin) has a higher thermal expansion coefficient than the second member (metal), satisfying specific formulas for movement and locking conditions to store mechanical changes in shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a bimetallic strip is used to convert thermal changes into mechanical changes, then the stack can respond to temperature changes with bending, but the thermal change cannot be stored as a mechanical change in shape after cooling
Solution Approach 1:
The interface between the two members is segmented into multiple engagement portions with ratchet teeth, allowing the continuous thermal expansion/contraction cycle to be converted into discrete, cumulative mechanical steps that are retained after each cycle
Solution Approach 2:
The ratchet structure employs asymmetric tooth geometry where the inclined surfaces have different angles for forward and backward movement, enabling easy movement in the heating direction while preventing return movement during cooling, thus achieving one-way mechanical deformation storage
2Reliability
If a ratchet structure is introduced to store thermal changes as mechanical changes, then shape retention is improved, but the device complexity increases
Solution Approach 1:
The ratchet structure is merged with the thermal expansion mechanism by integrating the engagement portions directly into the interface between the two thermally expanding members, combining the thermal-to-mechanical conversion function with the one-way locking function in a single integrated structure
Solution Approach 2:
The ratchet structure utilizes the thermal expansion forces themselves to drive the engagement portions into the locked position during heating, and the same thermal contraction forces during cooling are insufficient to overcome the locking engagement, making the system self-regulating without external control mechanisms
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 the storage of repeated heating and cooling cycles as mechanical changes, specifically in the form of stress, allowing the shape to be retained even after cooling, enhancing durability and reducing deformation-related issues at welds.
Implementation Method 1
two members with different thermal expansion coefficients, the two members including a first member and a second member being on each other
Data Source
AI summary
A structure capable of leaving a repetition of heating and cooling as a dynamic deformation amount. The structure retains joining performance of a laminated body made of two types of materials having different thermal properties.