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A platform for research: civil engineering, architecture and urbanism
Imaging of defects in concrete components with non-contact ultrasonic testing
The building industries require NDT- methods for the quality control and damage detection. The high specific inhomogeneity of concrete causes scattering and large sound attenuation so that the pulse parameters have to be optimised very carefully. In dependence of the size of the aggregates frequencies in the range of 50 to about 150 kHz can penetrate concrete components. Using immersion technique most of pores and internal holes will be filled with water so that their indication is very difficult. Therefore the coupling usually is carried out with pastes or even with honey. The point to point inspection and the cleaning of the component is very time consuming. New developments open the possibility of non-contact ultrasonic testing with air- coupling without increasing the air pressure. The new technique is very easy to handle and delivers images of the interior of concrete components in a few minutes. This paper reports on the new developments for such a system: high effective and broadband transducers, matched ultra low noise amplifiers, freely programmable high power pulser and an imaging software for A-, B-, C- and D- scans including full-wave scans and shows on the other hand typical results of applications on concrete components e. g. with a crack plane, a gravel nest and bore holes. The airborne inspection of concrete components like stilts, pillars and columns can be carried out without any problems. Further investigations will show the possibility of monitoring the hardening process with non-contact ultrasonic testing. The automatic evaluation of the frequency spectrum will give further details about the status of components and buildings. Possible options are chirp- and codes signals which provide an increase of the signal to noise ratio up to 8 dB. However, the longer pulse lengths decrease the PRF. Therefore, special transmitter excitations should only be used for the inspection of components thicker than 1 m. A testing from one side is possible in pitch and catch technique. This method is being used in application for natural stone plates.
Imaging of defects in concrete components with non-contact ultrasonic testing
The building industries require NDT- methods for the quality control and damage detection. The high specific inhomogeneity of concrete causes scattering and large sound attenuation so that the pulse parameters have to be optimised very carefully. In dependence of the size of the aggregates frequencies in the range of 50 to about 150 kHz can penetrate concrete components. Using immersion technique most of pores and internal holes will be filled with water so that their indication is very difficult. Therefore the coupling usually is carried out with pastes or even with honey. The point to point inspection and the cleaning of the component is very time consuming. New developments open the possibility of non-contact ultrasonic testing with air- coupling without increasing the air pressure. The new technique is very easy to handle and delivers images of the interior of concrete components in a few minutes. This paper reports on the new developments for such a system: high effective and broadband transducers, matched ultra low noise amplifiers, freely programmable high power pulser and an imaging software for A-, B-, C- and D- scans including full-wave scans and shows on the other hand typical results of applications on concrete components e. g. with a crack plane, a gravel nest and bore holes. The airborne inspection of concrete components like stilts, pillars and columns can be carried out without any problems. Further investigations will show the possibility of monitoring the hardening process with non-contact ultrasonic testing. The automatic evaluation of the frequency spectrum will give further details about the status of components and buildings. Possible options are chirp- and codes signals which provide an increase of the signal to noise ratio up to 8 dB. However, the longer pulse lengths decrease the PRF. Therefore, special transmitter excitations should only be used for the inspection of components thicker than 1 m. A testing from one side is possible in pitch and catch technique. This method is being used in application for natural stone plates.
Imaging of defects in concrete components with non-contact ultrasonic testing
Fehlerabbildung in Betonkomponenten mit berührungsloser Ultraschallprüfung
Hillger, W. (author)
2004
6 Seiten, 5 Bilder, 1 Tabelle, 7 Quellen
(Nicht paginiert)
Conference paper
Storage medium
English
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