| The aero engine is known as the "Pearl of the Industrial Crown" and is an important symbol of the country's core competitiveness.High-pressure turbine blades convert gas heat energy into kinetic energy,which is the most critical core component in the engine and the short-board that restricts engine development.Thermal Barrier Coating(TBC)is recognized at home and abroad to effectively block the heat transfer between the gas and the blade substrate to significantly reduce the blade substrate temperature,which is the most practical to significantly improve the engine's thrust-toweight ratio,thermal efficiency and service life.Method.In this paper,a new method for non-destructive measurement of thermal barrier coating thickness by eddy current testing is proposed.The thickness measurement model of thermal barrier coating is deduced and constructed.The experimental platform of eddy current testing is built.The model-based thickness detection method is proposed.The model calibration method is finally evaluated by the Monte Carlo algorithm for the reliability of the model.The main results and innovations are as follows:Firstly,the integral analytical model of the eddy current field of single-layer conductive structure excited by multi-turn coils is derived based on Maxwell's equations and vector magnetic bits.The integral analytical model of multi-layer conductive structure eddy current field is established by means of superposition principle.At the same time,in order to determine the accuracy of the detection model,it was numerically verified by Ansys Maxwell.Then,the influencing factors of the impedance signal were explored through simulation.Secondly,the thermal barrier coating test piece was fabricated,and the eddy current testing experimental platform was built.The FPGA-based experimental system was designed and developed.The platform consists of hardware and software.The hardware part includes FPGA control module,probe drive module,signal processing module,power supply module and wireless communication module;the software part is composed of upper computer software and lower computer software,and the lower computer software is mainly responsible for receiving detection probe signals,controlling transmission of detection signals and Processing;and the main function of the host computer is to coordinate the normal operation of the entire system.Furthermore,an analytical model based thermal barrier coating thickness detection method is proposed,and the optimization strategy is selected to determine the downhill simplex algorithm as the solution method.Then the thermal barrier coating is experimentally studied,and the measured impedance is substituted into the thickness.The detection algorithm shows that the detection error is large.The relationship between model error and impedance signal is explored by means of model simulation and experiment.Based on this,a calibration coefficient based method is proposed to calibrate the model and improve the detection accuracy.Finally,Monte Carlo algorithm is used to evaluate the uncertainty of the thermal barrier coating thickness detection method.The results show that when the detection signal obeys the Gaussian distribution,the thickness detection result also approximates the Gaussian distribution,and the ceramic layer and the thickness of the bonding layer are average.Consistent with the true value,and the standard deviation is 0.0056 and 0.0035,respectively.The uncertainty analysis results verify the reliability of the proposed algorithm.The research in this paper is involved in the detection of thermal barrier coating thickness,detection model construction,calibration method exploration,reliability evaluation,etc.,and has important theoretical and practical value. |
PDF Full Text Request