Study On Ultrasonic Characterization Of High Temperature Characteristics Of Metal Materials

Metal materials have become one of the important symbols of social development and are widely used in many fields such as aerospace,industry and medical treatment.Metal parts that work under high temperature environment for a long time will suffer from high temperature damage and even cause major safety accidents.Therefore,the high temperature characteristics of metal materials should be estimated and evaluated before they are put into industrial use.At present,metallographic method,compression method and tensile method are commonly used to test the mechanical properties of materials.Ultrasonic nondestructive testing has the advantages of high speed,high accuracy and low cost.In this paper,the relationship between acoustic parameters and material properties is established by means of ultrasonic guided wave detection.In this paper,the basic theory of ultrasonic characterization of high temperature properties of metal materials is analyzed and studied.Based on the ultrasonic propagation theory,the ultrasonic guided wave detection method was selected to detect the high temperature characteristics of the metal material,and the size of the sample and the frequency of the probe were calculated and selected according to the ultrasonic guided wave detection principle and requirements.Combined with the principle of ultrasonic guided wave detection and the purpose of the research,an experimental platform was designed and built.The main instruments are pulse generator/receiver,ultrasonic transducer,oscilloscope,high temperature furnace,etc.In terms of ultrasonic echo signal processing,this paper adopts the methods of signal feature extraction,mathematical modeling,filtering and denoising,cross-correlation and so on.Finally,the ultrasonic guided wave detection experiments of T2 copper and molybdenumalloys were carried out at room temperature ~1000℃ and temperature ~1200℃ respectively,and the change curves of the performance parameters such as sound velocity,waveform amplitude,young’s modulus,shear modulus,bulk modulus and poisson’s ratio with the increase of temperature were obtained.The temperature variation curve of sound velocity of T2 copper,the amplitude of nodal wave and the amplitude of terminal wave all varied most obviously in the temperature range of 500 ~ 700℃,which was corresponding to the "medium temperature brittleness" zone of T2 copper,and the monotonic variation of amplitude curve in temperature environment after 700℃ corresponds to the hot working area of copper.The measured results of the elastic modulus of molybdenum alloy are consistent with the theoretical analysis and experimental data in the existing literature,and the measurement results of poisson’s ratio are within the acceptable range of ±0.01.The results show that the ultrasonic characterization method of high temperature characteristics of metal materials presented in this paper can provide an auxiliary evaluation method for the development,production,processing and high temperature use of materials.