Numerical Simulation And Analysis Of Acoustic Emission Characteristics In The Damage Process Of Nano-concrete

Nano-concrete is a non-homogeneous material constituted by the multi-material, compared with the ideal brittle material, the damage mechanism of Nano-concrete is far more complex. Application of Acoustic Emission (AE) testing technology, can real-time recording and reflect the development and change of the internal cracks of the Nano-concrete materials. However, the AE technology is one of the few subjects of the theory behind the practice, resulting in its practical application in the absence of strong theoretical support. This paper, combining with the JiangXi province graduate student innovation projects (NO:YC10A034)"Study on the fatigue damage mechanism of Nano-concrete pavement and its AE characteristics.", the AE characteristics in the damage process of Nano-concrete and Kaiser Effect is analyzed on the basis of Nano-concrete uniaxial compression test and circulating loading and unloading test. Based on the concrete damage constitutive model of Weibull distribution, the quantitative relationship between the mechanic parameters and AE parameters is given theoretically.Application with RFPA software, the damage process of Nano-concrete is simulated, which reappeares the thougly physical process of its damage fracture, and reference for the further study on the mechanism of damage fracture of Nano-concrete is provided. Specific study content is as follows:(1) The uniaxial compression test of Nano-concrete with different nano-SiO2content is conducted, as well as different strength grade and different curing age. Use of counting, amplitude, energy and other AE characteristic parameters, the process of its damage failure is analyzed thoroughly, and the failure mechanism of Nano-concrete and the precursory features of destruction is explored;(2) The circulating loading and unloading test of Nano-concrete with the SiO2content of3%is conducted, and the AE Kaiser Effect under different loading methods is studied as well. The existence of the Kaiser Effect of nano-concrete is verified. It is also pointed out that the influence of friction type AE and rupture type AE to the Kaiser Effect memory stability and accuracy;(3)Use of Ohstu model and Dai model, respectively, to nonlinear fitting the AE data of Nano-concrete with different SiO2content, and the applicable condition of the two models also is pointed out. Combined with the results of this test, the coupling relationship between AE cumulative energy and strain is derived on the basis of the time parameter as an intermediate variable. Further, based on distribution of Weibull concrete damage constitutive model, the coupling relationship between AE cumulative energy and stress and damage is deduced.(4) The uniaxial compression process and circulating loading and unloading process of Nano-concrete is simulated using the RFPA2D software. The final rupture location can be given by its stress figure and AE figure, which can dynamic demo the process of crack propagation. Also, the AE Kaiser Effect of Nano-concrete is reappeared.