High-temperature Strain Sensor Research Articles

Cascaded Fabry-Perot cavity and fiber Bragg grating on sapphire fibers for high-temperature strain sensing

High-temperature strain sensors are key elements for several applications. Key issues of the existing devices include the difficulties of sensor operating above 1000°C as well as the very strong thermal effect under high temperatures introducing significant bias on the strain measurement. Here we developed a cascaded Fabry-Perot cavity and fiber Bragg grating strain sensor fully integrated on sapphire fibers, permitting a sufficient temperature compensation and strain measurement up to 1150°C temperature. A three-point adhesive bonding process is proposed to greatly improve the adhesion performance, and hence the robustness of the device at high temperatures. Experimental results show that the fabricated strain sensor can achieve a measurement range of ±1000 με at temperature up to 1150°C. The experimental results show that the measurement accuracy is not more than 5% at room temperature. the measurement accuracy is significantly decreased at high temperature, and the maximum strain measurement error is 14% at 1150°C.

High-temperature thin-film strain sensors with low temperature coefficient of resistance and high sensitivity via direct ink writing

High-temperature thin-film strain sensors are advanced technological devices for monitoring stress and strain in extreme environments, but the coupling of temperature and strain at high temperature is a challenge for their use. Here, this issue is addressed by creating a composite ink that combines Pb2Ru2O6 and TiB2 using polysilazane (PSZ) as a binder. After direct writing and annealing the PSZ/Pb2Ru2O6/TiB2 film at 800 °C in air, the resulting thin film exhibits a low temperature coefficient of resistance (TCR) of only 281 ppm/°C over a wide temperature range from 100 °C to 700 °C, while also demonstrating high sensitivity with a gauge factor approaching 19.8. This exceptional performance is attributed to the intrinsic properties of Pb2Ru2O6, which has positive TCR at high temperature, and TiB2, which has negative TCR at high temperature. Combining these materials reduces the overall TCR of the film. Tests showed that the PSZ/Pb2Ru2O6/TiB2 film maintains stable strain responses and significant signal output even under varying temperature. These findings provide valuable insights for developing high-temperature strain sensors with low TCR and high sensitivity, highlighting their potential for applications in high-temperature strain measurements.

High-temperature strain sensor based on sapphire fiber Bragg grating.

Sapphire fiber Bragg grating (SFBG) is a promising high-temperature strain sensor due to its melting point of 2045°C. However, the study on the long-term stability of SFBG under high temperature with an applied strain is still missing. In this paper, we reported for the first time to our knowledge on the critical temperature point of plastic deformation of the SFBG and demonstrated that the SFBG strain sensor can operate stably below 1200°C. At first, we experimentally investigated the topography and the spectral characteristics of the SFBG at different temperatures (i.e., 25°C, 1180°C, and 1600°C) with applied 650 µε. The reflection peak of the SFBG exhibits a redshift of about 15 nm and broadens gradually within 8 h at 1600°C, and the tensile force value decreases by 0.60 N in this process. After the test, the diameter of the SFBG region decreases from 100 to 88.6 µm, and the grating period is extended from 1.76 to 1.79 µm. This indicates that the plastic deformation of the SFBG happened indeed, and it was elongated irreversibly. Moreover, the stability of the Bragg wavelength of the SFBG under high temperature with the applied strain was evaluated. The result demonstrates the SFBG can be used to measure strain reliably below 1200°C. Furthermore, the strain experiments of SFBG at 25°C, 800°C, and 1100°C have been carried out. A linear fitting curve with high fitness (R2 > 0.99) and a lower strain measurement error (<15 µε) can be obtained. The aforementioned results make SFBG promising for high-temperature strain sensing in many fields, such as, power plants, gas turbines, and aerospace vehicles.

High-sensitivity interferometric high-temperature strain sensor based on optical harmonic vernier effect

We present a fiber optic vernier harmonic sensor for simultaneous detection of temperature and strain in high temperature conditions based on a parallel dual fiber Fabry-Perot interferometers (FPI). Two air-cavity FPIs were assembled from SMF, MMF and a hollow silica tube (HST). A fiber Bragg grating (FBG) is inscribed in one of the arms of the Fabry-Perot interferometers (FPIs) for temperature compensation. Based on the fiber optic vernier harmonic effect, the strain sensitivity of the sensor is further increased to 178.75 pm/µε, with a good linear response to strain and temperature in the range of 24 ℃-900 ℃. And the fabrication is straightforward and economy. It is a potential tool for micro strain measurements under extreme high temperature conditions.

Test and Analysis of SAW High Temperature Strain Sensor Based on Langasite

In this study, we fabricate a surface acoustic wave strain sensor based on langasite. By constructing a temperature-strain composite testing platform, we examine this sensor for the strains of 0 to 500 <inline-formula> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> at temperatures ranging from 18 to <inline-formula> <tex-math notation="LaTeX">$700~^{\circ }\text{C}$ </tex-math></inline-formula>. The value obtained from the tests for the strain sensitivity of the sensor is 20.09 Hz/<inline-formula> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> at 700 &#x00B0;C, and the maximum relative error and hysteresis error are 3.35&#x0025; and 6.98&#x0025;, respectively. Moreover, the sensor exhibits a stable response at high temperatures. Considering the sensitivity of the temperature and strain of the sensor at high temperatures, a temperature - strain decoupling method is proposed. The strain values obtained after the calculation agreed well with the reference strain values, and the maximum error was between &#x2212;4.2&#x0025; and 5.425&#x0025;. Therefore, the proposed temperature - strain decoupling method could help eliminate the influence of temperature on the strain measurements of this sensor.

Polyimide Encapsulation of Spider-Inspired Crack-Based Sensors for Durability Improvement

In mechanical sensory systems, encapsulation is one of the crucial issues to take care of when it comes to protection of the systems from external damage. Recently, a new type of a mechanical strain sensor inspired by spider’s slit organ has been reported, which has incredibly high sensitivity, flexibility, wearability, and multifunctional sensing abilities. In spite of many of these advantages, the sensor is still vulnerable in harsh environments of liquids and/or high temperature, because it has heat-vulnerable polyethylene terephthalate (PET) substrate without any encapsulation layer. Here, we present a mechanical crack-based strain sensor with heat, water and saline solution resistance by alternating the substrate from polyester film to polyimide film and encapsulating the sensor with polyimide. We have demonstrated the ability of the encapsulated crack-based sensor against heat, water, saline solution damage through experiments. Our sensor exhibited reproducibility and durability with high sensitivity to strain (gauge factor above 10,000 at strain of two percent). These results show a new potential of the crack-based sensory system to be used as a wearable voice/motion/pulse sensing device and a high-temperature strain sensor.

High temperature strain sensor based on a fiber Bragg grating and rhombus metal structure.

In this paper, a novel high temperature strain sensor based on a polyimide-coated fiber Bragg grating (FBG) and a rhombus metal structure is presented and experimentally demonstrated. By heating low softening point glass via a micro torch, the polyimide-coated FBG could be fixed into the rhombus metal structure. Consequently, when the rhombus structure is stretched and compressed, respectively, then the FBG will be subjected to a reverse state. Moreover, the strain sensitivity is controllable and enhanced by adjusting the dimension of the rhombus metal structure appropriately. The experiment was then carried out by using an equi-intensity cantilever beam and high temperature chamber, and the result showed that the proposed high temperature strain sensor could be used at the high temperature of 300°C. A resolution of ∼10 με has been experimentally achieved. The average wavelength strain sensitivity at 300°C is 1.821 and 1.814 pm/με, for the compressed and stretched states, respectively.

Research on FBG High Temperature Sensor Used for Strain Monitoring

Strain sensing is widely used in safety monitoring of high temperature pressure pipes in oil companies and power plants. A novel high-temperature strain sensor was researched based on FBG(Fiber Bragg Grating) and the elastic high-temperature alloy in this paper. First, high-temperature Polyimide fiber FBG was prepared and tested in high temperature chamber. Second, a novel T strain gauge structure of three FBG was designed and fabricated on the elastic high-temperature alloy. This strain gauge could be applied in measurement of two-dimensional high-temperature strain sensing. In the end, a equi-intensity cantilever was adopted to test the high-temperature FBG strain sensor and testing results verified that the T type FBG strain sensor was suitable for high-temperature strain sensing with reliable performance in 300°C environment.

Fabrication and characterization of carbon nanotube–polyimide composite based high temperature flexible thin film piezoresistive strain sensor

A high temperature strain sensor based on polyimide/single-wall carbon nanotube (SWCNT) composites was proposed. Sensors with different SWCNT contents ranging from 0.07 to 2.0wt% were prepared. The electrical property of the composites was investigated by direct current (DC) resistance and electrical impedance spectroscopy. A simple equivalent model was used to estimate the resistance of the composite, and percolation theory was adopted to analyze the electrical property transition from insulator to conductor. The experiment results suggested the percolation threshold to be 1wt%. Several strain sensors with different CNT concentrations in and above the percolation threshold range are characterized, and the test results show the optimum CNT concentration for the sensor to be 1.4wt%. The strain sensors are also characterized under different temperature up to 265°C for future high temperature application.

基于空芯光子晶体光纤的法-珀干涉式高温应变传感器

基于空芯光子晶体光纤的法-珀干涉式高温应变传感器

Effect of doping on silicon carbide based high temperature strain sensor

Effect of doping on silicon carbide based high temperature strain sensor

High temperature strain gages based on reactively sputtered AlN x thin films

Thin film strain sensors based on reactively sputtered aluminum nitride are being developed for a variety of advanced aerospace applications, where the measurement of both static and dynamic strain is required at elevated temperatures. The non-stoichiometric AlN x thin films are particularly attractive for strain sensor applications at elevated temperatures since they exhibit a relatively large gage factor G, and a relatively low temperature coefficient of resistance (TCR), and they are electrically stable at high temperature, “c” axis oriented (0002) AlN x thin films were prepared by reactive r.f. sputtering from high purity aluminum targets. By varying the nitrogen content in the plasma, AIN x films useful for strain gage applications were produced. The resulting films exhibited room temperature resistivities in the range 1 × 10 −3 Ω cm to 5 × 10 2 Ω cm, were semi-transparent in the visible spectrum (optical band gaps in the range 4.6–5.8 eV) and tested “p” type by hot probe. TCRs ranged from +825 to −1200 ppn °C −1 after repeated thermal cycling to 1100 °C, depending on the nitrogen content in the film and the room temperature resistivity. Sputtering parameters were adjusted to yield a minimum value of +109 ppm°C −1. Large positive gage factors were measured at room temperature for all semiconducting AlN x films and the films exhibited a nearly linear piezoresistive response with little or no hysteresis when cycled from tension to compression. Gage factors on the order of 15 were realized for the AlN x films (gage factors of 2 are normally observed for refractory metal alloys). Annealing the AlN x films in argon at temperatures up to 1100 °C had minimal effect on the gage factor. This suggests that the piezoresistive response was more dependent on the defect structure of the as-deposited films than on the resistivity or subsequent thermal processing. Both the TCR and gage factor were correlated with the as-deposited resistivity and the nitrogen content in the films. The relationship between processing parameters and properties of these A1N x films is reviewed here, and prospects of using such films as high temperature strain sensors are discussed.

Preparation and piezoresistive properties of reactively sputtered indium tin oxide thin films

Oxygen deficient thin films of indium tin oxide (ITO) were prepared by r.f. reactive sputtering from a high-density ITO target (90 wt.% In 2O 3 and 10 wt.% SnO 2 in various Ar:O 2 mixtures for the purpose of investigating their use in a variety of strain gage applications. The resulting thin films were transparent in the visible spectrum (optical bandgap of 3.3-3.4 eV), tested n-type by hot probe and exhibited room-temperature resistivities in the range 0.01 to 0.10 ω cm after annealing. Room-temperature gage factors ( G = ΔR/ R o1/ ε) as large as −77.71 were measured on patterned ITO films. These gage factors are considerably larger than those reported for refractory metal alloys ( G = 2). A large, negative piezoresistive response (negative gage factor) was observed for all ITO films similar to the responses observed for n-type silicon. The piezoresistive response was reproducible and linear, with little or no hysteresis observed with strains up to 700μ m m − . Additionally, optical gage factors based on changes in the ITO bandgap due to strain were established for these films using UV-Vis spectroscopy. Temperature coefficients of resistance (TCRs) of ITO films as low as +230 ppm °C −1 were realized in nitrogen ambients at temperatures up to 500 °C. In oxygen-bearing ambients, two distinct regions were observed; one having a TCR as low as −429 ppm °C − and another, at temperatures up to 1100 °C, having a TCR of −1560 ppm °C −1. Large gage factors combined with relatively low TCRs make these ITO films excellent candidates for use as high-temperature strain sensors. The relationship between processing parameteers and piezoresistive properties of these ITO films is reviewed and prospects using these films as high-temperature strain sensors is discussed.

Protective Coatings for High Temperature Strain Sensors

Protective Coatings for High Temperature Strain Sensors