Dual Linear SMA Wire Assembly Preventing Thermal Junction Snapping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
SMA wires in actuators for vehicle components, such as air-filled lumbar systems, often fail at the junction of bent and linear portions due to thermal differences, leading to snapping and rendering the actuator non-functional.
Innovation Solution
A dual linear shape memory alloy (SMA) wire assembly with a metallic bridge and crimps is used, where each SMA wire is fixedly coupled to the bridge via crimps, ensuring continuous linear configuration and preventing failure at the junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a bent portion is used in the SMA wire to wrap around the plastic body, then the SMA wire can engage with the actuator components, but thermal differences cause failure and breaking at the junction of bent and linear portions
Solution Approach 1:
The patent divides the SMA wire into separate segments: a linear active portion that undergoes phase transformation and a separate bent engagement portion. This segmentation prevents thermal stress concentration at junctions by eliminating the bent portion from the heated path, as the linear portion is electrically isolated from the bent portion during actuation.
Solution Approach 2:
The patent introduces an intermediary component (such as a ceramic bead or electrical insulator) at the junction between the linear and bent portions of the SMA wire. This intermediary serves as a thermal and electrical barrier, preventing heat transfer to the bent portion while maintaining mechanical continuity, thus avoiding thermal differential stress and wire failure.
2Productivity
If electrical current flows through the SMA wire to induce contraction, then the actuator operates, but thermal differences between bent and linear portions cause the wire to snap
Solution Approach 1:
The SMA wire is segmented into an electrically conductive linear portion and a separate bent engagement portion. The linear portion receives electrical current for actuation while the bent portion remains electrically isolated, preventing thermal differential stress at the junction and maintaining wire integrity during operation.
Solution Approach 2:
An intermediary component (such as a ceramic bead or electrical insulator) is placed at the junction between the linear and bent portions. This intermediary acts as a thermal and electrical barrier, allowing the linear portion to be heated for actuation while preventing heat transfer to the bent portion, thus avoiding wire snapping.
3Device complexity
If a single continuous wire is used for the SMA, then the structure is simple, but failure occurs where the bent portion meets the linear portion due to thermal stress
Solution Approach 1:
The single continuous wire is divided into separate linear and bent portions that are electrically isolated. The linear portion undergoes phase transformation while the bent portion remains cool and structurally stable, eliminating thermal stress concentration at the junction and preventing failure.
Solution Approach 2:
An intermediary component (such as a ceramic bead or electrical insulator) is introduced at the junction between the linear and bent portions. This intermediary provides thermal and electrical isolation, allowing the linear portion to be heated for actuation while protecting the bent portion from thermal stress, thus maintaining reliability without significantly increasing complexity.
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 dual linear configuration enhances the durability and reliability of SMA wires by preventing snapping, maintaining functionality of the actuator despite thermal variations.
Implementation Method 1
When electrical current flows through the SMA wire, the SMA wire undergoes solid-state phase transformation along at least one linear axis, allowing the SMA wire to contract.
Implementation Method 2
During operation, the SMA wire included in the actuator receives an electrical charge, allowing electrical current to flow through the SMA wire.
Data Source
AI summary
A shape memory alloy (SMA) wire assembly includes a first crimp, a second crimp, a metallic bridge, a first SMA wire, and a second SMA wire. The metallic bridge includes a first wire end and a second wire end opposite the first wire end. The first SMA wire is configured in a linear orientation and includes a first mounting end and a first bridge end opposite the first mounting end. The first bridge end is fixedly coupled to the first wire end of the metallic bridge via the first crimp. The second SMA wire is configured in the linear orientation and includes a second mounting end and a second bridge end opposite the second mounting end. The second bridge end is fixedly coupled to the second wire end of the metallic bridge via the second crimp.