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- Laminography (3)
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- Damage characterization (2)
- Digital detector arrays (2)
- High-energy X-ray imaging (2)
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Grouting defects, e.g. in post-tensioned structures or piped anchors may be identified by ultrasonic imaging. Since several years experiences are carried out with false color displayed phase values, which enable distinct localization of ungrouted regions.
In this contribution we report on progress in localizing grouting defects in tendon ducts, when they are only partly grouted and the unfilled part is not orientated into the direction of the measuring surface. This is frequently the case e.g. for box girder structures.
Düring the project specimens containing different types of grouting faults are investigated in Order to optimize measuring and evaluation techniques. A handheld linear array System (commercially available) is applied for fast 2D-measurement and subsequent phase sensitive 3D-imaging (new Software development).
In a large concrete wall specimen tendon ducts and real prestressing Systems containing grouting defects were built in. The ducts are partly covered by non prestressed reinforcement bars in order to investigate its disturbing influence. These included objects were investigated afterwards with the described methods. We report on large area measuring results, which were partly verified by y-radiography. In the frame of practical application results of measuring the position and extend of a blockade within a posttensioned structure are presen ted.
Zur Planung und Durchführung umfangreicher Sanierungs- und Umbaumaßnahmen im Pergamon-Museum Berlin bestand die Erfordernis einer Bauzustandsanalyse an antiken Baudenkmälern. Bestandsunterlagen waren unvollständig vorhanden bzw. fehlten. Hieraus ergab sich die Notwendigkeit des kombinierten Einsatzes zerstörungsfreier
Prüftechnik.
Digital detectors such as phosphor imaging plates (IP) and digital detector arrays (DDA) enable radiographic inspection with higher efficiency and improved image quality in comparison to the classic film technique. The mobile mechanised tomographic system TomoCAR (tomographic computer aided radiology) was developed first for inspection of circumferential welded seams of pipes. It consists of the manipulator based position control of an X-ray tube in front of the region to inspect and a digital detector array behind it. The high contrast sensitivity technique was combined with planar tomography. The tomographic reconstruction allows the three-dimensional (3D) representation of the material structure and included defects, equivalent to a metallographic cross sectioning. The hardware design is based on a specially developed flat X-ray tube and a direct converting CMOS detector array on CdTe basis. TomoCAR is applied for sizing of volumetric and planar defects. It allows the reliable detection of planar defects with openings larger than 25µm by subpixel resolution due to the achieved high signal-to-noise ratio. TomoCAR was successfully qualified as the result of a German pilot study on the basis of the European Network of Inspection and Qualification (ENIQ) guidelines for application in the nuclear power industry. Application examples are presented. The TomoCAR design was modified for in situ inspection of large aircraft components under production conditions. A gantry gate based planar tomograph was constructed and tested for inspection of the integrity of large flat CFRP panel components of up to 3 m × 9 m size. The integrity of imbedded stringers has been successfully observed. Different trials were performed to prove the finding rate of cracks in embedded stringers, which will be presented and discussed.
The lecture includes the following topics:
- Computed Radiography with Phosphor Imaging Plates is gaining more and more importance for mobile inspection and Film Replacement.
- New High Definition CR (HD CR) systems allow the CR application for Weld and Casting inspection with low energy X-rays.
- New calibration methods enable the High Contrast Sensitivity Technology (HCS RT) for radiographic inspection. The contrast sensitivity can be enhanced by a factor of 10 in comparison to film.
- New Digital Detector Arrays (DDA) are now available for stationary and mobile testing. They are also applied for automated defect recognition (ADR), CT, Back Scatter and Dual Energy Applications.
- Back Scatter Techniques are increasingly applied for Security and NDT
- Numeric Radiographic Modelling is applied for Experiment Planning, Film replacement, POD-calculations and training
- Mobile and portable CT devices are suitable for non-destructive cross sectioning in nuclear power industry and aircraft applications.
- Neutron radiography at research reactors was enhanced for visualisation of motions.
High-energy radiography is traditionally used for the detection of defects in thick-walled, bulky components. It is also used for testing the integrity of components for civil and security-related applications, e.g. containers. The combination of high-energy sources with digital detector arrays or line cameras allows carrying out the tests either in a shorter time compared to film technique, or with higher contrast sensitivity.
The high-energy X-ray laboratory "HEXYLab" at BAM is a joint laboratory in which future users, manufacturers and scientists collaborate to initiate and develop joint development projects. The new universal manipulation system “HEXYTech” provides the engineering and technical base for meeting different requirements within HEXYLab.
Different types of trajectories for tube, object and detector can be programmed with a total of 13 rotational and linear axes. In particular, large objects with complex geometries can be examined. Measurements can be acquired as 2D images via standard radiography as well as 3D volumes from laminography or computed tomography reconstructions.
The general rules for the application of high-energy radiography with digital detectors (imaging plates, digital detector arrays) were determined within the framework of the European project "HEDRad" (High Energy Digital Radiography) and added to the standard DIN EN ISO 17636-2.
The paper gives an overview of the test technique and introduces several applications on the basis of experiments and reconstructed 3D- images.
A special 3D tomographic algorithm was developed for mobile inspection of large objects. The method is based on a coplanar movement of an X-ray tube parallel to the surface of a digital detector array (DDA). Two different designs were developed and applied for 3D testing of welded pipes in nuclear power plants and large aircraft components made from carbon fiber reinforced polymers (CFRP). The reconstructed tomo-graphic images permit the detection, characterization and measurement of the dimensions of flaws with en-hanced sensitivity compared to conventional radiography and UT.
Due to the wide range of applications, the easy production and the large field of use, reinforced concrete (RC) is a widespread building material. This variety of applications is reflected in a wide range of physical material properties. Not only therefor it still is a technical challenge to provide all necessary test conditions for experimentally reproducing dynamic effects under impact loading of RC structures. In this paper we present investigations on the thicknesses of RC plates under low and medium high velocity impact loading by a flat-tipped impactor. The planar tomography setup at BAM is used to visualize the impact damage and to characterize the damage features such as cracks, scabbing and spalling. Further, the comparison of tomography results with those of an applied numeric simulation analysis is used to verify the numeric models for future damage prognosis under impact loading. Using the results of both, the tomographic as well as the FE analysis, different damage features were investigated and compared regarding their validity. Crack damage plays a leading part and the significance of summarized crack values as well as their distribution is analyzed. The total damage value but also the determined damage distribution both provide an input for describing damage as a function of the impactor velocity and plate thickness.
Reinforced concrete (RC) is used as structural material in most diverse civil engineering applications. For the variability of its physical properties it is still an engineering challenge to meet all necessary requirements for the prediction of dynamic effects under impact loading. In this paper, investigations are shown within the scope of quantifying and evaluating the damage caused by an impact. The experimental investigations are performed in the field of low- and medium-velocity impact. The chosen flat nose shape results in small penetrations on the top side and scabbing on the bottom side. The plate is scanned with an adapted planar tomographic examination after the impact, and the damage is analysed, afterwards. Cracks and spalling are made visible with a reconstruction. The numerical model validated on the tomographic results justifies the application for further predictions of the damage description.
We examine the behavior of reinforced concrete components subjected to impact induced loading conditions which might be caused by vessels collisions such as aircraft fuel tanks The concrete plates were impact damaged at TU Dresden and shipped to BAM At BAM laminar tomography as the imaging method is used to determine and quantify the damage state An automatic crack detection method based on template matching is applied to find the cracks and we aim to develop a new method using machine learning Algorithms In addition numerical models are developed to understand the experiment and to predict the damage structures based on failure mechanisms.