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Die Coda transmittierter Ultraschallsignale in Beton enthält Informationen zu Struktur und Zustand des Materials bzw. deren Änderung. Relevant sind u. a. Temperatur, Stress, Feuchtigkeit und verschiedene Schädigungsmechanismen. Die zahlreichen Einflussfaktoren sind nur schwer zu trennen und die Messeffekte oft zu Beginn sehr klein.Die CWI ermöglicht die Detektion kleinster Geschwindigkeitsveränderungen durch den Vergleich, der in kleinen Schritten gestauchten oder gestreckten Signalen mit eine Referenzmessung. Andere Indikatoren für Änderungen im Material sind:
• Kreuzkorrelation
• Laufzeit direkte Welle
• Energie/Amplitude
• Änderungen im Frequenzspektrum
Die beschriebene Technik wird von uns bisher primär in klein- und großskaligen Laborversuchen genutzt. Die Forschung konzentriert sich auf die Untersuchung und Trennung verschiedener Einflusseffekte. Aber auch erste reale Bauwerke wurden schon instrumentiert, z. B. Brücken und eine Tunneldecke.
Non-Destructive assessment of the National Infrastructure in Germany has been the topic of R&D at BAM since many years. In 1989 BAM has established a R&D group dedicated to the development and application of Non-Destructive Testing in Civil Engineering. Since then, this group has left has participated in numerous research projects and cooperated with many researches and institutes worldwide.
A complex system of inspection and maintenance is in place to inspect and maintain roads, bridges, tunnels and other installations. Based on visual inspection structures like bridges are inspected regularly. In case of concerns which cannot be resolved in this process, a procedure “Object Oriented Damage Analysis” has been put into place where additional inspection methods, especially NDT methods, are being utilized.
NDT methods to establish material properties such as strength, porosity, moisture, carbonation, etc need more attention to strengthen the links between engineers and inspectors. BAM and TU Berlin have established a joint Junior Professor to address this research area with gravity.
Research is currently focused on methods, data, validation, certification and standardization. Industry 4.0 has become a widely discussed topic with unforeseeable impact. Current research topics include
- Large Aperture UltraSound (LAUS) to evaluate very thick concrete elements (> 1m)
- Embedded ultrasound sensors to monitor changes in concrete
- Data fusion algorithms for honeycomb detection, corrosion localization and reinforcement diameter determination
- Reverse Time Migration to improve imaging of concrete structures
- Laser Induced Breakdown Spectroscopy (LIBS) with new applications, improved sensitivity and resolution, new devices
- RFID based humidity and corrosion sensors
- Analysis of scattered Radar waves for the classification of concrete
- Development of reference specimens for selected NDT tasks
The presentation will present examples of current research and ideas for research directions.
Vortrag über die Aktivitäten des Fachbereichs 8.2 in der zerstörungsfreien Prüfung im Bauwesen.
The presentation is #4 of the lecture series within the CE5390 NDT&E Course at the “University of Texas at El Paso”, USA (UTEP):
1. Application of NDT to Transportation Infrastructure
2. Application of NDT to Pavements
3. Application of NDT to Tunnels
4. Application of NDT to Nuclear Structures
5. Ultrasonic Methods
6. Electrical Resistivity (ER)
7. Galvanostatic Pulse Measurement (GPM)
8. Half-Cell Potential (HCP)
9. Ground Penetrating Radar (GPR) to Infrastructure
10. Ground Penetrating Radar (GPR) to Pavements
11. Impact Echo (IE)/Ultrasonic Surface Waves (USW)
12. Infrared Thermography (IR)
13. Magnetic Flux Leakage (MFL)
14. Ultrasonic Tomography (UST)
15. Falling Weight Deflectometer/Light Weight Deflectometer
16. Spectral Analysis of Surface Wave
17. Traffic Speed Deflectometer
18. Integrity of Foundations
19. Integration of Technologies
Applications of NDT for nuclear structures are presented with an overview over the special challenges for NDE in this area.
The lecture was held as a webinar on August 29, 2017
Research and Development in Non-Destructive Testing in Civil Engineering at BAM has de-veloped over more than two decades. Highlights of present research are ultrasound phase array probes, ground penetrating radar applications for the assessment of existing structures and Laser Induced Breakdown Spec-troscopy (LIBS) to determine which chemical elements on the surface of a specimen are. RFID sensor devel-opments for wireless moisture monitoring and data fusion for the combined analysis of sensor data are fast developing areas. In addition, a selection of application cases is briefly described.