Shape Memory Alloy Wire Phase Transformation Control
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Solution Overview
Problem
Shape memory alloys used in high-actuation temperature applications experience reduced fatigue life due to increased stress, leading to shorter operational cycles, making them less suitable for cost-effective solutions.
Innovation Solution
A device and method that utilize a primary shape memory alloy wire with a secondary wire of lower phase transformation temperature, where the secondary wire applies additional tensile load only when the ambient temperature exceeds a threshold, thereby increasing the phase transformation temperature of the primary wire and extending its operational life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If stress is increased to raise phase transformation temperature, then actuation temperature requirement is met, but fatigue life is reduced
Solution Approach 1:
The patent applies dynamic stress adjustment by introducing a variable stress element (such as a temperature-dependent mechanical element) that modifies the stress applied to the shape memory alloy wire based on ambient temperature conditions. This allows the system to meet high actuation temperature requirements only when necessary, while maintaining low stress conditions during normal operation to preserve fatigue life.
2Temperature
If high cost ultra-high transition temperature shape memory alloy wires are used, then high actuation temperature requirements are met, but device cost increases
Solution Approach 1:
The patent changes the operational parameters of a standard shape memory alloy wire by dynamically adjusting the stress applied to it. Instead of using expensive ultra-high transition temperature alloys, the system uses a more cost-effective standard alloy and modifies its transformation temperature in-situ through variable stress application, thereby achieving high actuation temperatures only when required.
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 approach allows the use of lower-cost shape memory alloy wires by maintaining low stress conditions at lower temperatures, significantly extending the operational cycle of the primary wire while increasing its phase transformation temperature as needed.
Implementation Method 1
An activation source is thermally coupled to the wire and is operable to selectively cause the wire to reversibly transform from a Martensitic phase to an Austenitic phase during a cycle
Implementation Method 2
A loading element is operatively connected to the wire and configured to selectively increase a tensile load on the primary wire when an ambient temperature is at or above a threshold temperature, thereby increasing the phase transformation temperature of the primary wire
Data Source
AI summary
A device and method for controlling a phase transformation temperature of a shape memory alloy is provided. The device includes a primary wire composed of the shape memory alloy. The primary wire defines first and second ends, the first end being attached to a fixed structure and the second end being able to displace. An activation source is thermally coupled to the wire and is operable to selectively cause the primary wire to reversibly transform from a Martensitic phase to an Austenitic phase during a cycle. A loading element is operatively connected to the primary wire and configured to selectively increase a tensile load on the primary wire when an ambient temperature is at or above a threshold temperature, thereby increasing the phase transformation temperature of the primary wire.