Measurement And Experimental Study Of Internal Temperature Distributions In Solid Structures Based On Ultrasonic

The measurement and control of the internal temperature distributions in solid structures are of great significance in industrial production,people's daily life and new technology research.The internal temperature distribution measurement is a complex problem.The existing internal temperature measurement methods,such as the thermocouple temperature measurement,fiber grating temperature measurement and neutron resonance spectrum have many great limations.Or the needs for the contact measurement and damage the structural stability,or temperature measurement conditions are lacking and difficult to promote.Therefore,it becomes one of the most important research direction in the field of temperature measurement and control to develop a technique which can realize the non-destructive measurement of temperature in solid structures.Ultrasonic temperature tenchnology is widely concerned because of the characteristics of non-contact,fast response,no radiation,no temperature drift,large temperature range,high sensitivity and so on.According to the demands of non-destructive detection of the internal temperature,the internal temperature destributions measurement and experiment by ultrasonic thermometry in solid structures are studied from two aspects:ultrasonic temperature measurement mechanism and internal temperature distributions reconstruction method based on the theoretical analysis,numerical simulation and experimental verification and exploring the development of ultrasonic detection technology in solid structures of the inernal temperature distributions.This paper mainly completed the following work:(1)The experimental platform is designed and set based on the principle of ultrasonic temperature measurement.According to the research contents,four parts of the ultrasonic system,the temperature measurement system,the temperature control system and the auxiliary parts are designed,and the selection and precision evaluation of equipments in the system are carried out.(2)Based on the study of the law of ultrasonic propagation,the three factors that affect the ultrasonic velocity are analyzed,and the ultrasonic velocity equation based on temperature correction is established.Through the numerical simulation and experimental design,the metal aluminum and steel are selected to analyze the relationship between the propagation time and temperature,and the relationship between the propagation velocity and the temperature of the ultrasonic wave in different temperature materials,and the "time-shift characteristics" of the temperature induced by the temperature are studied.The analysis model of the internal temperature distribution of the ultrasonic sensing structure is constructed.Finally,combined with the simulation and experimental data analysis,the validity and accuracy of the proposed modified equation are verified,and the numerical method is modified.(3)Based on the analysis of thermal/acoustic coupling problems,a one-dimensional steady-state temperature distribution reconstruction model based on cold boundary condition is established according to the propagation characteristics of ultrasonic waves and the internal heat conduction equation.It is proved that this method can reconstruct the one-dimensional steady-state temperature field inside the solid structures by means of numerical simulation and experimental verification,and has better reconstruction precision for the obvious region of temperature gradient,whch provides a new research direction for the study of temperature field reconstruction.