Optical fiber sensor and assembly method for measuring the tensile strain of a nickel-based directionally solidified superalloy in a high-temperature environment.

Nickel-based superalloys are widely used in key hot-end components such as aero engines and industrial gas turbines due to their excellent comprehensive properties. Real-time monitoring of engine blades and other structures in high-temperature environments can promptly discover possible internal damage to the structure. Optical fiber sensing technology has unique advantages that traditional electrical sensors do not have, such as anti-electromagnetic interference, small size, light weight, and corrosion resistance. The technology is gradually replacing traditional methods and becoming an important means of structural health monitoring. We propose an optical fiber sensor and assembly method that can be used to measure the strain of a nickel-based directionally solidified superalloy in a high-temperature environment more accurately. The proposed technology is simple to manufacture and also has low cost and a high survival rate, which is of great significance for high-temperature strain measurements in aerospace and other fields.

Tensile Deformation Behavior of Typical Porous Laminate Structure at Different Temperatures.

In this study, the Ni-Cr-W superalloy GH3230 is used as the test material. According to the actual structure of the flame tube, a porous laminate structure specimen is designed. The structure consists of impact holes, overflow holes and pin fins. High-temperature tensile tests at 650 °C, 750 °C and 850 °C were carried out to study the high-temperature mechanical properties and fracture mechanism of the specimens of porous laminate structure, and the strain nephogram of the specimens were obtained by digital image correlation (DIC) technique. Due to the large number and dense arrangement of overflow holes, an obvious hole interference effect can be found from the strain nephogram. The stress concentration around the pore and the interference between the pores provide priority places and paths for the initiation and propagation of microcracks. The test found that the microcracks of the porous laminate structure first occurred around the hole, the overflow surface fractured first, after which the impact surface fractured. The strength of the alloy exhibits a significant temperature sensitivity to temperature. From 650 °C to 750 °C, the ultimate strength (σb) and yield strength (σ0.2) decrease slightly, but they decrease significantly at 850 °C. The microstructure of the fracture surface shows that all microcracks occur at the interface between the matrix and the carbides but that the fracture mode of the specimens gradually changes from intergranular fracture to transgranular fracture as the temperature increases. Due to the pinning effect of the intracrystalline diffusive solute atoms on the dislocations, the stress-strain curves of the high-temperature tensile tests at 650 °C and 750 °C showed zigzag characteristic fluctuations during the strengthening stage.