Shape Memory Alloy Strain Sensor for Wide-Temperature Deformation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing strain sensors face limitations in their operational temperature range and sensitivity, particularly in outdoor environments, due to temperature-induced changes in electrical resistance, which affect their accuracy in measuring deformations.
Innovation Solution
A strain sensor utilizing a pseudo-elastic wire or strip-shaped electrical conductor made of a shape memory alloy, arranged in a two- or three-dimensional configuration, which exhibits significant resistance changes during phase transformation, allowing for precise deformation measurement across a wide temperature range without requiring temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional strain sensors are used in temperature-controlled environments, then measurement accuracy is maintained, but application possibilities are limited to controlled settings
Solution Approach 1:
The patent applies parameter changes by utilizing the phase transition temperature characteristics of shape memory alloys. By selecting SMAs with specific martensite start temperatures (Ms) below 10°C, the sensor maintains austenitic phase stability across a wide temperature range, eliminating temperature-induced resistance changes and enabling reliable operation in uncontrolled environments from -30°C to +80°C.
Solution Approach 2:
The patent employs composite materials by integrating shape memory alloy conductors with substrate materials. The SMA conductor exhibits pseudoelastic behavior and controlled phase transformation characteristics when combined with the substrate, enabling the sensor to maintain measurement accuracy across varying temperatures while expanding application versatility to outdoor and industrial environments.
2Temperature
If shape memory alloy conductors with lower martensite start temperatures are used, then operational temperature range is expanded, but sensitivity to temperature changes increases
Solution Approach 1:
The patent resolves this contradiction by optimizing the martensite start temperature parameter of the shape memory alloy to be below 10°C (preferably between -50°C and 0°C). This parameter selection ensures the conductor remains in the austenitic phase across the operational temperature range of -30°C to +80°C, thereby expanding the operational temperature range while minimizing sensitivity to temperature changes and maintaining measurement precision.
3Measurement precision
If pseudoelastic behavior is utilized for strain measurement, then sensitivity is enhanced, but temperature compensation requirements increase
Solution Approach 1:
The patent applies self-service by utilizing the inherent pseudoelastic properties of the shape memory alloy conductor within its austenitic phase. The material's spontaneous phase transformation behavior during deformation provides built-in sensitivity enhancement without requiring external temperature compensation mechanisms, thereby reducing device complexity while maintaining high measurement precision across a wide temperature range.
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 strain sensor achieves high sensitivity and accuracy in measuring deformations across a broad temperature range, enabling its use in various environmental conditions, including outdoor settings, with minimal temperature-induced errors.
Implementation Method 1
Shape memory alloys can exist in two different crystal structures: an austenitic structure and a martensitic structure... The austenitic and martensitic phases exhibit different crystal structures and, consequently, different electrical resistances
Implementation Method 2
Shape memory alloys can exhibit pseudoelastic behavior in certain temperature ranges... This phase transformation allows for a strain of up to 8% at relatively low stress. When the stress is removed, it can return to its original state
Implementation Method 3
the conductor with the tool is heated in a heating device at a temperature between 400 °C and 900 °C... The heat treatments were performed at temperatures of 450, 500, 550, and 600 °C
Implementation Method 4
the conductor with the tool is removed from the heating device after a heating period of 5 to 15 minutes and quenched to room temperature with a coolant
Data Source
Figure 1
AI summary
The present invention relates to a strain sensor comprising at least one pseudoelastic wire- or ribbon-shaped electrical conductor made of a shape memory alloy, which is embedded in or attached to a substrate in a two- and/or three-dimensional arrangement. The invention also relates to a method for manufacturing a strain sensor. The object of the present invention is to expand the application possibilities of a strain sensor made of a shape memory alloy. This object is achieved according to the invention in a strain sensor of the type mentioned above by the fact that the shape memory alloy has a martensite start temperature of less than 10 °C.The problem is also solved by a method of the type mentioned above, in which a wire- or ribbon-shaped electrical conductor made of a shape memory alloy is fixed on a tool in a two- or three-dimensional shape, the conductor with the tool is heated in a heating device at a temperature between 400 °C and 900 °C, the conductor with the tool is removed from the heating device after a heating period of 5 to 15 minutes and quenched to room temperature with a coolant, the conductor is then separated from the tool, inserted into a substrate and/or attached to a substrate and electrically contacted.