AES

But therefore the AE ean be applied only if the materials in the structures or components are adequately stressed. 

Due to the fact, that AE by its peculiarities can be used to prevent catastrophic failure of structures and control the application of load, the higher risk of a pneumatic pressure test can be reduced significantly by the monitoring the structure during the loading by AE. 

Beside this pre-warning feature AE can be used parallel as a NDT technique to detect, locate and roughly grade any active (growing) discontinuity in the structure under test. 

Based on our practical experiences in the applieation of AE on pressure equipments since 1979, we started in the year 1994 to apply AE on steam drums in combination with pneumatic tests. Before we are able to do this, we have to perform extensive lab tests with the specific material (grey cast iron and cast steel) from which these drums are produced. 

These lab tests were done to gain a specific data base for such a brittle material compared to the normal steels used for the manufacturing of pressure equipments. In any case the application of AE was only possible due to the rapid development of the data processing and the new state-of-the-art equipment where this technique is built in.(3)... 

Before the performance of the loading we have to apply 5 up to 12 sensors, according their size, on the cylindrical part of the drums and after a short check of the required sensitivity and the wave propagation the pneumatic pressure test monitored by AE can be performed. The selection of the sensors and their positions was performed earlier in pre-tests under the postulate, that the complete cylinder can be tested with the same sensitivity, reliability and that furthermore the localisation accuracy of defects in the on-line- and the post analysis is sufficient for the required purpose. For the flat eovers, which will be tested by specific sensors, the geometrical shape is so complicated, that we perform in this case only a defect determination with a kind of zone-location. 

After the tests are finished during the post-analysis the NDT properties of AE will be used for the detection and roughly grading of defects within the material. 

The main reasons for the application of a pneumatic test in conjunction with an AE are... 

Table 1 Steam drums, which undergo a pneumatic test monitored with AE...

The only meaningful solution is a pneumatic test in conjunction with an AE. Beside the high sensitivity of an AE and its reliability in combination with an established and proven data base, the method can be performed by experienced testing agencies easily and within short shut down period. A lot of 4 up to 9 drums can be tested within one day. 

In future we will increase our data base also for the newest types of drums and are also convinced, that by the application of pattern recognition AE becomes beside its detection ability more and more also a valuation technique. 

The application of Acoustic Emission Examination (AE) during the inspection of pressure equipments, P Tscheliesnig - presented at the 3. Hungarian Conference on Safety Budapest, 1997... 

Figure 1 Amplitude distribution of AE signals from model glass epoxy specimens...

Partitional clustering using Euclidean distance as a measure of dissimilarity between pattern classes has been selected for the grouping of AE hits. 

Figure 5 Damage evolution in FRP vessel by means of characteristic AE classes.

In this study, the cumulative AE counts have been used to quantify the fatigue damage development in quasi-isotropic CFRP laminates and a model based on AE data has been formulated. 

Figure 4 Correlation plots of load versus number of cycles for the non-filtered (up) and filtered (bottom) AE data of a test at (Tna, = 80% a and R = 0.1...

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