Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Tagungsband (15)
- Zeitschriftenartikel (14)
- Beitrag zu einem Sammelband (6)
- Vortrag (3)
- Forschungsbericht (2)
- Buchkapitel (1)
Schlagworte
- SAFT (11)
- Ultrasonic echo (9)
- Ultraschallecho (7)
- Beton (5)
- Modellierung (5)
- Radar (5)
- Spannbeton (5)
- Concrete (4)
- Imaging (4)
- Reconstruction calculation (4)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (3)
Ultrasonic Reflection Properties at Interfaces Between Concrete Steel and Air: Imaging and Modelling
(2006)
There is a great demand for non-destructive testing methods for quality assurance and to assess the safety and durability of wooden structures. Ultrasonic echo technique with shear waves in the frequency range of 50 kHz is one of those promising methods and is already frequently applied for usual and glued laminated timber. The article describes the development and first results for an imaging method for this purpose. The highly anisotropic properties of the ultrasonic velocity have to be considered. A 3D-SAFT (Synthetic Aperture Focusing Technique) imaging scheme is developed initially for synthetic data resulting from modelling the elastic wave propagation. The main part of the paper describes the experimental validation of this evaluation technique by experimental studies applying automated ultrasonic scanning techniques. 3D ultrasonic imaging results are described for test specimens made from pine and spruce wood. Another object of investigation was a pedestrian bridge made from siberian larch.
This paper presents the progress of successful location of grouting faults in tendon ducts with ultrasonic imaging. The examples were obtained in the research group FOR 384 funded by DFG (German Research Foundation). The co-operation of experimental research and modeling allowed imaging and identification of grouted and ungrouted areas of tendon ducts (including strands) in a large test specimen (40 m²). In addition to the criteria for indicating grouting faults in post-tensioned ducts known until now the phase evaluation of reflected ultrasonic pulses is described. Experiments and modeling of wave propagation are presented for reflections at metal plates in concrete (thickness range 0.5 mm to 40 mm) and for tendon ducts including strands.
The main part of the progress was achieved by automated measurements using dry contact transducers, 3D-SAFT reconstruction including phase evaluation and modeling considering wave propagation for typical elastic parameters and exact experimental site conditions. The results for shear waves as well as for pressure waves are compared in the frequency range from 50 kHz to 120 kHz.
Ultrasonic echo technique with shear waves in the frequency rang of 50 kHz is one of the promising methods for assessment of structural timber and is already frequently applied for this purpose. The article summarizes the state of the art of applying echo measurement via linear measurements as well as the development and first results for an imaging method for this purpose. The highly anisotropic properties of the ultrasonic velocity have to be considered. 3 D ultrasonic imaging results are described for the example of a pedestrian bridge made from Siberian larch.