SMA Bimorph Actuator Layout for Lower Weld Joint Stress
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Solution Overview
Problem
Existing shape memory alloy (SMA) actuators experience reduced resiliency at weld joints due to high wire exit angles and stress concentrations, necessitating additional resource-intensive processes like adhesive application to enhance reliability.
Innovation Solution
Affixing SMA wires at the bottom surface of the actuator reduces wire exit angles and stress at weld joints, improving reliability without the need for additional processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If SMA wires are affixed at traditional locations with higher wire exit angles, then the actuator can achieve adequate actuation force, but the weld joints experience high stress concentrations reducing resiliency
Solution Approach 1:
The patent applies local quality by positioning SMA wires at the bottom surface of the actuator where the wire exit angle is naturally reduced. This localized structural modification creates favorable stress distribution at the weld joints while maintaining adequate actuation force, eliminating the need for adhesive application at high-stress locations
2Reliability
If additional processes like adhesive application are used to enhance weld joint reliability, then weld joint resiliency improves, but manufacturing complexity and resource consumption increase
Solution Approach 1:
Instead of adding adhesive to protect weld joints from stress, the patent inverts the approach by designing the wire attachment location at the bottom surface where the geometry itself produces lower stress concentrations. This structural inversion eliminates the need for additional protective processes while maintaining or improving weld joint reliability
3Reliability
If wire exit angles are reduced by changing wire placement geometry, then weld joint stress decreases improving reliability, but actuator design complexity increases
Solution Approach 1:
The patent merges the wire attachment function with the bottom surface structure of the actuator. By integrating the wire placement geometry into the existing actuator housing design rather than adding separate components or complex mounting mechanisms, the solution reduces wire exit angles and stress concentrations without significantly increasing overall design 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 bottom surface configuration enhances SMA actuator resilience and reduces stress on weld joints, improving reliability and eliminating the need for additional process steps like adhesive application.
Implementation Method 1
The SMA actuator can be configured to actuate responsive to providing an electrical current to the SMA wire
Implementation Method 2
a first end of an SMA wire can be engaged at a fixed end fixed to an actuator. Further, a second end of the SMA wire can be engaged to a free end configured to move in response to the actuation of the SMA wire
Data Source
AI summary
The present embodiments relate to a shape memory alloy (SMA) actuator with a joint between an SMA wire the SMA actuator being disposed at a bottom surface of the SMA actuator. The SMA actuator can include at least one fixed end configured to be fixed to a carriage, at least one free end, at least one beam connecting the fixed end and the free end, and at least one SMA wire. The at least one SMA wire can be electrically connected to the at least one fixed end and the at least one free end via electrical contact portions. The position of the at least one SMA wire being affixed to the bottom surface can allow for reduced stress and a wire exit angle at the weld joint between each SMA wire and the actuator, improving resiliency of the SMA actuator.