Research on Metal-embedded Fiber Bragg Grating In-situ Strain Measurement Technology for Intelligent Upgrading of Aerospace Large Equipment

In recent years,with the rapid development of commercial aerospace,the demand for high-density launches and long-period reliable service of reusable launch vehicles has increased significantly.Health monitoring and in-situ accurate perception of their main metal structures have become critical.Traditional adhesive-bonded sensors suffer from problems such as large strain transfer error,poor high-temperature stability,and short service life,which can hardly meet the requirements of in-situ accurate structural perception for the embodied intelligence upgrade of equipment such as digital twin systems.Firstly,ultrasonic additive manufacturing(UAM) is used to embed fiber Bragg gratings with sub-millimeter ultra-short grating length into aluminum alloy structures to solve the problem of grating chirping and realize accurate measurement of in-situ strain of metal structures.Secondly,a nonlinear Wiener stochastic degradation model is constructed to predict the reliability and service life of the sensors.Finally,tensile tests at room temperature and 120℃,as well as mechanical-thermal coupled cyclic tests,are carried out.The results show that the embedded sensor has excellent linearity of strain response.The sensitivity change at 120℃ is only 2.19% compared with that at room temperature,which is much better than 8.17% of the adhesive-bonded type.According to the life prediction model,the reliability of adhesive-bonded sensors decreases significantly to below 90% after 3406 cycles,while the reliability of embedded sensors can remain above 90% after 41 700 cycles,showing a strong service life advantage.The research results can provide a better solution for high-precision and long-period monitoring of key metal structures of aerospace equipment.