Study On Bolt Preload Monitoring Based On Ultrasonic Energy Loss At Structural Interface

For the problem of bolt looseness in engineering practice,domestic and foreign scholars have put forwarded a variety of methods to detect bolt preload.Based on previous studies,this paper do further research on piezoelectric active ultrasonic health monitoring method for bolt structure.Studying the relationship between the transmitted ultrasonic energy which passed through bolt connection interface and bolt preload in three aspects.These aspects are theoretical analysis,finite element simulation and experimental research.Judging the health status of bolt according to the relationship between the transmitted ultrasonic energy bolt and bolt preload.The main work and conclusions of this dissertation are as follows:(1)According to the reflection and transmission characteristics of ultrasonic at steel / air interface and the G-W model of contacted rough surface,we can know that the transmitted ultrasonic energy which passed through bolt connection interface has an approximate linear relationship with the bolt preload,under the condition of light load and small deformation.(2)Using the finite element software to simulate the micro contact characteristics of rough surface and the propagation process of ultrasonic which passed through the preload bolt connection interface.Obtained the relationship between the transmitted ultrasonic energy and the bolt preload through finite element analysis results(3)Studying experiments on the basis of theoretical analysis and finite element simulation.The simulation and experimental results show that the peak to peak of response signal and peak of focusing signal have a monotonous increasing relationship with bolt preload: with the increase of bolt preload,the peak to peak of response signal and the peak of focusing signal increased rapidly at first,and then slowly increased,then tend to be stable.The results of the research show that the method of bolt preload monitoring based on ultrasonic energy loss at structural interface has a good application prospect in health monitoring of bolt connection.