Piezoelectric Shear Stress Sensors for High-Temperature Flows
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Solution Overview
Problem
Current stress sensors are inadequate for measuring shear stress in high-speed and complex flows, particularly in applications involving hypersonic vehicles, as they are not temporally and spatially resolved, and cannot withstand high temperatures, and lack reliability and ease of use.
Innovation Solution
The development of solid-state shear-stress sensors with a substrate and sensing material, featuring a configuration of electrodes that generate output signals in response to shear stress, including a differential sensing cell with offset electrodes to selectively measure shear stress while being resistant to high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stress sensors are used to measure shear stress in high-speed flows, then the measurement capability is provided, but the sensors cannot withstand high temperatures and lack temporal and spatial resolution
Solution Approach 1:
The patent changes the material parameters by using piezoelectric materials (such as PZT, PVDF, or PMN-PT) that maintain their piezoelectric properties at high temperatures. This allows the sensor to operate reliably in high-temperature environments (up to 1200K) where conventional sensors fail, while still providing temporal and spatial resolution through the piezoelectric effect's inherent fast response characteristics.
Solution Approach 2:
The patent employs composite structures combining piezoelectric sensing elements with high-temperature resistant substrates and protective coatings. This composite approach enables the sensor to withstand extreme temperatures while maintaining measurement capability, resolving the contradiction between reliability and temperature resistance.
2Measurement precision
If conventional stress sensors are used, then basic stress measurement is achieved, but they lack temporal and spatial resolution required for complex flow analysis
Solution Approach 1:
The patent divides the sensing surface into multiple discrete piezoelectric sensor elements arranged in arrays. Each element provides localized shear stress measurements with high spatial resolution. The segmentation allows independent measurement at multiple points simultaneously, enhancing both spatial and temporal resolution while maintaining reliability through distributed sensing.
Solution Approach 2:
The patent utilizes the dynamic response characteristics of piezoelectric materials, which can respond to stress changes at high frequencies. This dynamic capability enables temporal resolution of unsteady flow phenomena, while the rigid substrate provides spatial stability, achieving both temporal and spatial resolution with reliable measurements.
3Measurement precision
If indirect methods such as heat flux measurements are used to measure shear stress, then measurement capability is provided, but the methods are not direct and lack accuracy
Solution Approach 1:
The patent replaces indirect thermal measurement methods with direct mechanical-to-electrical conversion using the piezoelectric effect. Shear stress applied to the piezoelectric material directly generates electrical charge, providing a direct measurement mechanism that eliminates the need for complex heat flux measurements and intermediate calculations, thereby improving accuracy while reducing system complexity.
4Temperature
If stress sensors are designed for high temperature resistance, then temperature capability is improved, but the sensors may become more complex and harder to manufacture
Solution Approach 1:
The patent designs piezoelectric sensors that serve multiple functions: they provide shear stress measurement, withstand high temperatures, and can be integrated with standard semiconductor fabrication processes. The use of piezoelectric materials and techniques compatible with existing manufacturing infrastructure enables high-temperature capability without proportionally increasing manufacturing 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 sensors provide reliable, temporally and spatially resolved measurements of shear stress, capable of withstanding high temperatures, and are easy to use, enhancing the accuracy and durability in applications such as hypersonic vehicle testing and touch sensing technologies.
Implementation Method 1
The sensor system may include a substrate, a first layer of sensing material disposed on a first layer of the substrate, and at least three electrodes forming a first and second electrode pair... The sensor system may be configured to generate an output signal in response to a shear stress within the sensing material
Data Source
AI summary
Solid-state stress sensors are presented herein. A sensor system may include a substrate, a first layer of sensing material disposed on a first surface of the substrate and at least two electrodes forming an electrode pair. The at least two electrodes may include a first electrode and a second electrode. The first and second electrodes may be offset from each other in a direction substantially parallel to the first surface. The sensing material may be a piezoelectric material and the sensor system may be configured to generate an output signal in response to shear stress experienced by the sensing material.