Multiparameter Detection Of The Stainless Steel Frame Under Vacuum Condition Based On Fiber Bragg Grating

The stainless steel structure,with advantages such as anti-corrosion,high strength,high temperature resistance,is widely used in different fields like architectural engineering,aerospace and energy facilities.Compound loads of heat and force effect the stainless steel structure and lead to internal performance changes.Applying proper sensors can exclude risks immediately.A 304 stainless steel frame,as the research object,is similar to the support structure of the vacuum chamber of the Tokamak devices.The rules of thermal transmission,temperature distribution,strain and displacement are studied with loads of temperature and force under vacuum condition.Fiber Bragg grating sensor has advantages such as small volume,anti-electromagnetic interference,multiplexing networks and high accuracy.So it can achieve the parameter detection of stainless steel structures in the Tokamak devices or under other similar extreme working conditions.The main contents of this thesis are as follows:1.The development and application status of the fiber grating are introduced.The surveys of parameter measurement of stainless steel structures,including thermodynamics and dynamics,are stated.2.The temperature and strain sensing principles of fiber Bragg grating and signal demodulation based on the filter method are analyzed briefly.Thermal transmission,including thermal conduction,thermal convection,thermal radiation,and mechanics of materials are presented particularly.3.The steady-state thermal simulation of 304 stainless steel frame under normal pressure and vacuum condition,and statics simulation under vertical and horizontal force condition are conducted separately by using ANSYS Workbench.The measurement points are confirmed according to the simulation results.It is shown that values of four temperature measurement points decrease in turn.Temperature values under vacuum condition are higher than that under normal pressure condition because of thermal convection dissipation.Applying vertical force load,?₁ is stretching strain,?₂,?₃,?₄ are compression strain;Applying horizontal force load,?₁,?₂ is stretching strain,?₃,?₄are compression strain.The displacement caused by horizontal force load is larger than that caused by vertical force load.4.A measurement system of multiple parameters of the stainless steel frame under vacuum condition based on fiber Bragg grating is established.First,temperature distribution results of the frame under normal pressure and vacuum condition areobtained,temperature values under vacuum condition are higher than that under normal pressure condition and it is found that thermal convection leads to thermal losses under normal pressure condition.Thermal convection doesn't exist under vacuum condition.The heat flux by the way of thermal conduction in the support part under vacuum condition is 34.99 W,while the radiant heat flux from heating plate to foundation is1.74 W.Thermal conduction has higher heat transmission efficiency than thermal radiation under vacuum condition;secondly,the strain and displacement values caused by vertical and horizontal force?77.6kg?in the lab are measured.The corresponding values caused by vertical force?62kg?under vacuum condition are also obtained.Strain and displacement schedules are drew and the errors of results are analyzed.This thesis verifies the reliability of obtaining information of structures' thermal transmission,strain and displacement based on fiber Bragg grating under vacuum condition and provide a feasible method for the structure parameter detection under complex working condition.