Damage Research Of Toughening Ceramic Based On Acoustic Emission Technology

In the field of modern material science, with its excellent characteristics such as high temperature resistance, corrosion resistance, wear resistance and small density, alumina ceramic has become the research focus of modern material science. Since its non-tension characteristics, the domestic and foreign researchers are committed to improve tenacity and ability to resist damage, of which the difficulty is how to capture the position of the internal crack and determine the degree of danger of the crack. As a new nondestructive testing technology, for the study of ceramic material fracture mechanics and damage, acoustic emission testing technology provides a favorable tool. As one of the noise reduction method in recent years, wavelet transformation noise reduction effectively weakens the influence of the noise signals of the acoustic emission signal, which help to accurately further analyze the damage mechanism of ceramic materials.In order to study the crack nucleation, the development law of crack and the toughening mechanism of ceramic materials, this paper designed verification experiment to verify the reliability of the combine of the wavelet transformation noise reduction technology and the acoustic emission technology. The acoustic emission signals of alumina ceramic and toughening ceramic(15% and 25% 2ZrO toughening ceramics) in the Brazilian splitting experiment are monitored and analyzed separately in this paper. In this paper, the main research contents are as follows:(1) By analyzing the time-domain characteristic parameters(amplitude, hitting counts, energy counts, ringing counts) of acoustic emission signals produced during the Brazilian splitting experiments, the damage process of alumina ceramics and zirconia toughened alumina ceramics can be divided into four stages: ceramic material micro crack closure phase stage, ceramic material micro crack nucleation stage, ceramic material micro crack extension stage and ceramic materials critical buckling stage.(2) After processing the acoustic emission signals produced during the Brazilian splitting experiments by the wavelet transform, energy eigenvalues of acoustic emission signals produced during the Brazilian splitting experiments can be acquired to estimate frequency feature of the acoustic emission signals. With the energy eigenvalues of acoustic emission signal of ceramic material failure process, it is concluded that the frequency of acoustic emission signal and the dimension of micro crack have an inverse relationship.(3) Denoising the acoustic emission signals produced during the Brazilian splitting experiments by wavelet transformation noise reduction, combined with Geiger algorithm, acoustic emission source location can be acquired. It has been verified by experiment that this method is effective and has a certain degree of accuracy, the location results are in conformity with the actual situation of the ceramic specimens damage. Based on different period of acoustic emission source location, the process of fracture crack formation of ceramic materials can be described...