The Research For Damage Characterization Of Brittle Material Based On The Acoustic Emission Data

Material with only small deformation under the action of external force occurs broken fracture, such materials are known as brittle material, such as rock, etc. Brittle material breakage occurs suddenly when its stress reaches to a certain degree,and such destruction will bring serious disaster engineering, so using acoustic emission technique for monitoring brittle material damage in time and studying its internal damage process are of great significance.The stability of the rock can be greatly affected by water, the mechanical properties of the rock soaked by water can be affected, which results in that the strength of the rock decreases and the plastic deformation increases. The acoustic emission regularity of the hydrous rock and dry rock is different, and the acoustic emission characteristics of the same sample under different saturation is also different. The acoustic features of same sample under the saturation and dry state have bigger difference, and the difference will change as the change of moisture content.In the article, the uniaxial compression experiment with acoustic emission of rock is done, and the rock acoustic emission signals in different saturation state are proceeded with wavelet transform, in addition, the damage characterization of rock is studied by acoustic emission parameter.(1)According to the theory of wavelet transform, the method of extracting energy of acoustic emission signal in different frequency band is studied by using wavelet transform. The acoustic emission signal of the uniaxial compression test of sandstone and the sandstone with initial damage in different saturation is processed and the energy of acoustic emission signal in different frequency band is exacted by using this method. Analyzing the energy of each frequency band obtains the feature band that can show the regularities of acoustic emission energy distribution and the main frequency band of acoustic emission signal, at the same time, the regularities of frequency band energy of acoustic emission signal are got.(2) The data that gets from the uniaxial compression experiment with acoustic emission of diorite is analyzed.First, the characteristics of acoustic emission signals of diorite are analyzed:The movements of the acoustic emission signal reflect the damage situation of the whole failure process of rock, the activity of the early damage, damage evolution and buckling failure with each phase of acoustic emission signal is analyzed.Secondly,The acoustic emission signal of diorite is processed by using the method of wavelet transform,the frequency band of main energy distributions of acoustic emission signal of the diorite is obtained. Finally, According the quantitative relation of rock damage variable and strain and acoustic emission parameter as well as the date of the accumulated count of relative acoustic emission energy and the corresponding strain of diorite, the damage variable formula of diorite and the stress-strain relations of its damage are obtained with MATLAB fitting. According to that the stress-strain curves of its damage in theory is relatively consistent with the experiment, the accuracy of the formula of diorite damage variable is verified.