Bridges are regularly inspected and monitored. Methods of non-destructive testing are used, such as visual inspection, radar, ultrasound, radiographic testing, thermography, leakage tests or monitoring with sensors. Non-destructive testing methods play a special role for bridges. Damage to infrastructure must be detected and monitored at an early stage so that safety problems do not arise in the first place.
Three engineers inspect the Köhlbrand Bridge. During a bridge inspection, even a simple visual inspection can detect damage, e.g. moisture damage, corrosion on surfaces or cracks in concrete.
© BAM, division Non-destructive Testing Methods for Civil Engineering
Radar and ultrasound are electromagnetic and acoustic methods of NDT, respectively. They use signals to detect cracks and other critical areas in buildings or structures. If the instruments indicate initial damage, measures can follow, e.g. more frequent inspections or monitoring with sensors. Most of the radar and ultrasonic devices are mobile. They are suitable, for example, for investigations on concrete ceilings in buildings.
A mobile LIBS system is used to measure the exposure of a dam on the North Sea with chlorides from seawater. This enables a quick and well-founded assessment of the remaining service life (laser-induced breakdown spectroscopy, LIBS). With laser-induced breakdown spectroscopy (LIBS) the element-specific chemical composition can be determined.
© BAM, division Thermographic Methods
X-ray based computed tomography can be used to detect and evaluate the smallest defects. This method illuminates the objects and makes their inner structures visible (computed tomography, CT). Materials research, 3D-printig, aerospace and medical technology require spatial information about internal structures in the micrometer range. A micrometer is a millionth of a meter.
The sensors of a drone developed by BAM "sniff" for explosive or toxic gases. In certain accident situations, human helpers have to protect themselves especially. If the sniffer drone does not indicate dangerous gases, the helpers can approach without danger.
© BAM, division Surface Analysis and Interfacial Chemistry
The scanning electron microscope (SEM) shows gold particles in a size of a few nanometres. Scanning electron microscopy plays a central role in nanotechnology. It is used for investigating smallest particles and their properties. One nanometre is a billionth of a metre.
Adolf Martens, one of the founders of materials research, investigated metal structures already at the end of the 19th century. To do this, he used a light microscope that he had developed himself. He made the most precise drawings, e.g. of samples made from crucible steel. In this way, Martens documented scientific findings or damage. Along the way, he created drawings of special aesthetics. Today "Tiegelstahl", a historical method of manufacturing steel, is no longer use
Raman spectroscopy (red) and laser-induced breakdown spectroscopy, LIBS (green) are indispensable methods of non-destructive testing in materials research. Spectroscopic methods can be used to determine the chemical elements and element compounds of a material sample. These methods use light sources and spectra for analysis.
© BAM, division Biodeterioration and Reference Organisms
The picture shows a grid electron image of carbon steel. The upper particle was treated with corrosive, methane-forming microorganisms, the lower particle remained untreated. Scanning electron microscopy (SEM) is a particularly powerful method for making surfaces and structures visible. SEM images impress with their special depth of focus.
© BAM, division Materialography, Fractography and Ageing of Engineered Materials
The picture shows deformations in the structure of an iron meteorite. Shockwaves, which are produced when colliding with other fragments in the asteroid belt, have left clear traces. The colours representation was created by mixing the signals from three detectors making the slightest deformation in the material visible.
© BAM, division Materialography, Fractography and Ageing of Engineered
The fine structure of materials becomes visible under the light microscope. Here, island-like precipitations in a nickel alloy can be seen. The image width is approx. 0.1 mm. Light microscopes are optical microscopes. They have been used in science for centuries. Today, it is impossible to imagine materials research without light microscopes in an advanced form.
© BAM, division Thermographic Methods
Themograms are thermal images. Red signals a high temperature, yellow less, green less and blue indicates minimal heat differences. In this way, with the help of heating by sun radiation, high temperature islands on facades can be identified as plaster detachments. Infrared thermography is an imaging method. It is used, for example, in building restoration for the protection of Cultural Heritage.
© BAM, division Glas
Using high-resolution high-speed camera technology and 3D microscopy, the growth and closing of cracks in glass can be observed very well. This makes it possible to fathom the mechanisms of these processes and to extend the service life of glass components. This technique documents extremely fast dynamic processes and enables the four-dimensional mapping of changes in surface profiles.
The ultrasound of a LAUS device can be used to detect damage inside large concrete structures (Large Aperture Ultrasonic, LAUS). The LAUS is used on site, e.g. to investigate invisible damage in concrete bridges or buildings. Even vertical surfaces are no problem for LAUS.