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A State of the Art instrument using the tap testing technique ‘The Woodpecker - WP-632AM’ developed by Mitsui was used to compare detectability of manufactured defects (flat bottom holes) in Perspex and aluminium specimens/coupons. A modern infrared camera the ‘T440’ developed by FLIR was also employed to perform Thermography tests on the same specimens. In this paper the authors present a comparison of the test results obtained using the above mentioned NDT techniques. The two instruments proved to be very user friendly, require very little set up time and practically no surface preparation on the specimens was required. Testing the specimens, using either technique with its respective instrument, is performed rapidly and both instruments provide instantly, permanent records of the results.

This presentation was an invited talk in the ICNDT Workshop „Use of Social Media by NDT Societies and Certification Bodies – sharing best practice, Thu 16 June, 09:00-11:00 Saal 22, 2nd floor.

Pneumatic components represent an important part of many technical devices in transportation, mechanical, automotive and power engineering etc. The proper function of these components decides not only on the correct function of production equipment, for example, but in many cases influences also the safety of passengers, operators etc. The diagnosis of these systems is currently based mainly on monitoring of vibrations, possibly also are verified devices on the principle of ultrasound. Possibilities of these methods have proven to be inadequate, less sensitive and largely unreliable. Another diagnostic procedure that is being tested is the noise analysis of activity of diagnosed devices. Also, this method proves to be unsuitable for practical use in operational diagnostics. However, the required new methods of increasing sensitivity speed and efficiency of NDT, their automation, minimizing the human factors and the reduction of operating costs. Ideally, it is the possible to consider a combination of acoustic emission with other methods, thereby ensuring high sensitivity and reliability at the same time. The paper presents the latest results obtained in the course of the project Technology Agency of the Czech Republic, which aims to create a new diagnostic system for checking the function of pneumatic valves using acoustic emission. There are compared the records of the AE signal from the undamaged pneumatic cylinders and similar entries from cylinders containing artificial defects. Records of signals are monitored by modern analysers DAKEL IPL with full sampling of the signal. Based on the analysis of large data sets are selected suitable AE signal parameters, which can be used for more accurately diagnostics of condition of tested devices which could be used for constructing of analyser for testing of pneumatic devices.

Heat treatments between RT and 1100oC and tensile tests were carried out parallel using a Gleeble 3800 thermo-mechanical simulator in weldable structural steel (S235JRG2), TRIP steel, TWIN steel and heat resistant bainitic steel (15Ch2MFA). Acoustic emission (AE) sensors were applied to monitor acoustic events along the samples under investigation including amplitudes, rate of hits and localization of AE events. Increase of rate of hits of AE was observed in phase transition at temperatures corresponding to austenite-ferrite and ferrite-bainite transitions. High amplitudes observed during heat treatments were dropped more than to half when tension started. Specific amplitudes were observed during high temperature tensile tests with growing amplitude after the start of contraction, showing that amplitudes of AE are inverse proportional to applied force. It was proven that acoustic events were generated partly and mainly by magnetic forces caused by heating with AC strong current, similarly to Barkhausen effect, in TRIP steels and baintic steel (15Ch2MFA). This opened the possibility for permanent acoustic monitoring of ferromagnetic steels

The reactive air brazing (RAB) is a relatively new brazing process, which enables to join ceramics and steel without the need of an oxygen-free atmosphere. Thus the brazing doesn’t have to be carried out in a vacuum furnace. Due to this fact, the joining process can be realized using simple and fast heating sources such as induction coils, laser- or light-beams. One challenge while using these methods is to ensure, that the integrity of the joints is sufficient enough to fulfill the needs of the later application. One fundamental challenge while brazing ceramics to metallic parts is the large difference in the coefficient of thermal of the ceramic, the filler metal and steel. Upon cooling from the brazing temperature, this mismatch can induce high internal stresses, which, especially at high cooling rates, can cause cracking of the brittle ceramic. Therefore, an online monitoring during the development of the RAB-brazing as well during the later series production is of significant importance, in order to successfully establish this method. Such a monitoring system should observe the heating, holding and cooling phases of the brazing. One possible non-destructive testing method is the acoustic emission analysis which can in principle detect cracks in the whole component during brazing in real time. In the presented study, the authors have integrated an acoustic emission analysis system into a RAB brazing system. First results of the new system will be presented for the monitoring of the brazing process with respect to the melting and solidification of the solder. Another focus is on the detection of cracks that may arise during the cooling phase. Finally, a review of the acoustic emission method with regard to a practical process monitoring is done.

The problem of delaminating of pressure vessels’s shells which operate in environment containing hydrogen sulfide is relevant. These defects have a relatively long incubation period, 10-15 years as a rule. After completion of the incubation period, growth in the size of the defect and the formation of macroscopic defects (blisters) occurs rapidly (1-2 years).That is why it is important to have the tools for the detection of the delamination at an early stage of its formation. Relations between the results obtained by various non-destructive techniques such as visual, ultrasonic and acoustic-emission are discussed on the examples of delaminating in the pressure vessels shells. The problem of the impact of the testing methods sensitivity on timely defect detection is discussed. The feasibility of early delaminating diagnosis by acoustic emission and ultrasonic inspection methods is demonstrated and new ways towards enhanced efficiency of these techniques are proposed.