Structural Health Monitoring And Online Assessment Of Deep Sea Pressure Structure

Pressure structure is basis of the underwater vehicle safety,which provides a normal atmospheric pressure environment for the staff and instruments onboard.With the developments of science and technology and demands of scientific research,the diving depth is deeper and deeper,while,the requirements of pressure structure safety are getting higher and higher at the same time.Although the safety of pressure structure is analyzed and assessed in design stage considering,the typical load conditions,actually the deep sea pressure structure may encounter more servere and complex sea working conditions than design conditions,such as the sea water density mutation,moreover the degradation of pressure structure performance after a long time.In the absence of appropriate monitoring techniques,the staff do not know the pressure structure safety in real time,it is important to use the pressure structure health monitoring(SHM)and online assessment system to monitor and assessing the pressure structure safety.Based on engineering background above,some new ideas and practicability problems are researched in this paper,and the following study results are obtained:(1)The structural safety such as the strength and stability of the typical deep sea pressure structure are analysed,the key sensitive location which can reveal the pressure structure safety and basic strategy of sensors layout are obtained.Considering the basis condition of pressure structure at the key sensitive location,the measure error of pressure SHM system,and pressure structure design criterion,the deep sea pressure structure safety online assessment method and the prediction method for ultimate bearing pressure base on monitor data has been developed,which can be employed directly in the pressure SHM system.(2)The deep sea pressure SHM and assessment system is designed for underwater vehicle in service.The problem of long term and long distance working has been solved by using the distributed structure and low power consumption technology.The sensor data real time processing algorithm for improving the structure safety assessment accuracy which can eliminate the sensor creep data is given out.The pressure structure monitoring and assessment software is developed,which is capable of auto running,data acquisition,dataset storing,statistics and structure condition assessing in real time.(3)The long term usability,the assessment and early warning function of the deep sea pressure SHM and assessment system has been validated and verified by fatigue test of pressure structure model and collapse experiment of spherical shell model respectively.The obtained results show that the performance of SHM is steady and reliable,and the assessment results are reasonable and can be used as early warning value.(4)For the requirements for long-term monitoring of pressure structure safety,the SHM for 4500 m submersible was developed and installed in manned cabin,based on the structural analysis data and sensors layout.The results of the sea trial shows that the performance of the SHM is steady and reliable.The results of monitoring assessment are accurate.The SHM technology and online safety assessment method as well as the SHM system for deep sea pressure structure developed in this paper have been applied successfully in 4500 m submersible.They can applied to safety monitoring and assessment for various underwater vehicles,ships,and floating platforms.