PSI - Issue 17

Ekaterina M. Zubova et al. / Procedia Structural Integrity 17 (2019) 822–827 Ekaterina M. Zubova et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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3. Results and discussions

3.1. The results of mechanical tests and signal processing AE

The authors were proposed and implemented the following technique to study the damage accumulation process in the ceramic coating deposited on the composite material: • carrying out mechanical tests of metal samples and metal samples with the TBC with the registration of AE signals, • processing and comparative analysis of the AE data obtained for metal samples and metal samples with coating with the use methods AE and DIC, • identification of parameters of AE caused by the destruction of the ceramic coating, • carrying out mechanical tests on composite samples with ceramic coating with the registration of AE signals and using method DI С , • processing of the AE data (peak frequency and amplitudes) by using for this the data identified in the process of AE processing of metallic samples, • plotting the dependencies of parameters characterizing the AE behavior of the coating during the damage process, analyzing the results obtained and describing the process of damage accumulation in the coating applied to the composite material. The first three points are described by the authors in work [Zubova et al. (2019)]. The ranges of amplitudes and frequencies that characterize the damage accumulation and destruction of the ceramic coating applied on the metal samples were determined in this work. It was determined that during the failure of a ceramic coating AE signals are recorded with the amplitude range of 60 – 100 dB and in the frequency range of 150 – 200 kHz. These results are applied to the process of AE obtained during the samples ’ testing of C/C composite material with a coating. Graphs of dependences of some parameters of the AE signal (amplitude, peak frequency, energy) were plotted. Diagram of the amplitudes distribution above 60 dB are shown at Fig. 4, a. It can be noted that most of the recorded signals are in the range of up to 80 dB. Thus, the amplitude range of 60-80 dB is used for further studying of the coating. Peak frequency distribution is shown at Fig. 4, b. For it four frequency ranges can be distinguished: 20 – 50 kHz, 150 – 200 kHz, 500 – 580 kHz, 780 - 850 kHz. Thus, for further studies of coating, we apply the frequency range 150 – 200 kHz. In addition, it can be noted that this range is present on samples with coating and is absent on samples without coating.

Hits

Hits

a

Peak frequency, kHz

Amplitudes, dB

b Fig. 4. Diagram of the amplitudes distribution ( а ), diagram of the Peak frequency distribution (b).

The energy distribution of all AE signals shown at Fig 5, a (red line), and the energy distribution of AE signals with selected parameters: amplitude range 60 – 80 dB, frequency range 150 – 200 kHz shown at Fig. 5, b (blue line).