Experriment Study On Acoustic Emission Of Mortar Specimen Failure Process

Mortar is a material which commonly used in the building, and its performance directly affects the safety of the structure. From the material of the structure, the mechanical properties of the mortar material during the process of deformation and failure are studied. The acoustic emission monitoring technology is used to monitor the acoustic emission signal during the destruction of the mortar material, and the damage mechanism is explored to prevent or reduce the harm of mortar material to the structure which has important theoretical and practical value.In this paper, acoustic emission monitoring mechanism and damage theory are used as theoretical basis. The acoustic emission characteristics of mortar specimen during the process of deformation and failure are systematically studied by theoretical analysis and indoor experiment. The main research results are as follows:(1) Prefabricated mortar samples with different proportions were used to carry out uniaxial compression test. At the same time, acoustic emission monitoring system was used to monitor the signal to study the relationship between mortar ratio, loading rate and mortar sample strength.The results show that the peak strength of the mortar sample increases with the loading rate increasing, and the peak strength of the mortar sample increases with the mass ratio of cement and sand. The whole process of mortar specimen deformation and damage is divided into three stages,compressive elasticity stage, yield rise stage and failure residual stage.Based on the acoustic emission test data, a prediction index K is proposed,the clear "rebound" phenomenon of K value is appeared, which indicates that the mortar sample is about to be destroyed.(2) Prefabricated cast iron and pine wood sandwich mortar samples,acoustic emission monitoring technology was used to monitor the acoustic emission signal, the relationship between the ratio and the strength of sandwich mortar was obtained. The results show that the peak strength of the core sand mortar sample increases with the increase of the mass ratio of cement and sand, the peak strength of the cast iron sandwich mortar sample is larger than that of the pine mortar sample. The acoustic emission event counting characteristics of the sandwich mortar samples are the same as those of the acoustic emission energy characteristics. The change of the K value shows a significant "rebound" phenomenon can also predict the destruction of the core mortar sample.(3) According to the acoustic emission energy value, the damage variable is redefined, and the damage evolution equation of the mortar is given by using the two-parameter Weibull distribution theory. The parameters are determined and the damage evolution equation is modified.Finally, the constitutive model of the mortar sample is established. The results are consistent with the test results.