| Refractory materials is often used in the production of high-temperature industry,the reliability of its structure affects the stability and safety of industrial production.It is a kind of multiphase heterogeneous composite material and it is usually divided into particle phase and matrix phase on the micro scale.Due to the refractory materials has been enduring the extreme environment of high temperature and high pressure for a long time,the particle phase and the matrix phase both bear large loads.Although the mechanical properties of the refractory materials are isotropic on the macro level,they are anisotropic on the micro level due to the great difference in the material properties of the matrix phase and the particle phase.In order to explore the micro structure characteristics of refractory materials,it is necessary to study the stress distribution and the generation and development of micro cracks in the internal structure of refractory materials under thermal-mechanical loads.In addition,the growth and interpenetration of meso-scale crack damage will lead to macroscopic crack defects,which will seriously affect the mechanical properties of refractory materials,so it is necessary to conduct quantitative detection and analysis of macroscopic defects.In view of the above aspects,this paper firstly explores the stress distribution state and interfacial debonding under thermal-mechanical coupling loads at the micro scale,and adopts ultrasonic to detect the internal crack size on the macro scale,including the following aspects:1.Monte Carlo method is used to generate random numbers,and these numbers are used to generate the micro heterogeneous model of refractories.The stress distribution is studied from the point of view of thermal-mechanical coupling,and the results of thermal-mechanical coupling field are compared with the stress field of single thermal load or mechanical stress load.2.The representative volume unit is adopted,the particle phase is set to be a circle or a random polygon,cohesive elements are inserted at the interface between the particle phase and the matrix phase,and strain is applied to the model to study the failure of cohesive elements of particles of different shapes at the interface.3.Establish the kinematic and dynamic sound field mathematical model of ultrasonic propagation in refractories,use the finite difference method to solve the soundfield value,and explore the numerical relationship between the changes of ultrasonic detection signals and the size of defects of refractories according to time-domain amplitude and frequency-domain energy characteristics.In this paper,the thermal-mechanical coupling analysis is carried out by constructing the micro heterogeneous model of refractories.It is found that the stress concentration usually occurs at the corners of the particle phase,and the position of the single stress extremum is different from the position of the stress extremum under the coupling loads,and the number of the stress extremum is not equal to the sum of the stress under the single loads.When the representative volume element is used to study the interface damage of particles,it is found that the stress extremum around the polygonal particles is larger than that around the circular particles.The internal defects of refractories cause the time-domain amplitude and frequency-domain energy index attenuation of ultrasonic testing signals,and the signal propagation time and defect size change linearly.The work in this paper provides valuable research ideas for the microstructure damage mechanism and macroscopic defect detection of refractories. |
