TY - JOUR A1 - Shokouhi, Parisa A1 - Zoëga, Andreas A1 - Wiggenhauser, Herbert T1 - Nondestructive investigation of stress-induced damage in concrete JF - Advances in civil engineering N2 - The changes in the sonic surface wave velocity of concrete under stress were investigated in this paper. Surface wave velocities at sonic frequency range were measured on a prismatic concrete specimen undergoing several cycles of uniaxial compression. The loading was applied (or removed) gradually in predefined small steps (stress-controlled). The surface wave velocity was measured at every load step during both loading and unloading phases. Acoustic Emission (AE) test was conducted simultaneously to monitor the microcracking activities at different levels of loading. It was found that the sonic surface wave velocity is highly stress dependent and the velocity-stress relationship follows a particular trend. The observed trend could be explained by a combination of acoustoelasticity and microcracking theories, each valid over a certain range of applied stresses. Having measured the velocities while unloading, when the material suffers no further damage, the effect of stress and damage could be differentiated. The slope of the velocity-stress curves over the elastic region was calculated for different load cycles. This quantity was normalized to yield a dimensionless nonlinear parameter. This parameter generally increases with the level of induced damage in concrete. KW - Nondestructive testing (NDT) KW - Surface wave velocity KW - Concrete KW - Acoustoelasticity KW - Microcracking PY - 2010 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-215943 UR - http://downloads.hindawi.com/journals/ace/2010/740189.pdf DO - https://doi.org/10.1155/2010/740189 SN - 1687-8094 SN - 1687-8086 VL - 2010 IS - Article ID 740189 SP - 1 EP - 9 PB - Hindawi Publ. Corp. CY - New York, NY, USA AN - OPUS4-21594 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Völz, Uwe A1 - Mrasek, Heinz A1 - Matthies, Klaus A1 - Kreutzbruck, Marc ED - Mazal, Pavel T1 - Visualization of sound propagation with electrodynamic probes T2 - 5th International workshop of NDT experts - NDT in progress 2009 (Proceedings) T2 - 5th International workshop of NDT experts - NDT in progress 2009 CY - Prague, Czech Republic DA - 2009-10-12 KW - Ultrasonic KW - Sound field KW - Visualization KW - Electrodynamic probe KW - Nondestructive testing (NDT) KW - Nickel alloy KW - Anisotropic weld KW - Narrow-gap weld PY - 2009 SN - 978-80-214-3968-9 SP - 321 EP - 328 AN - OPUS4-20334 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Völz, Uwe A1 - Mrasek, Heinz A1 - Matthies, Klaus A1 - Kreutzbruck, Marc T1 - Visualization of sound propagation with electrodynamic probes T2 - ECNDT 2010 - 10th European conference on non-destructive testing (Proceedings) N2 - When dealing in ultrasonic testing with inhomogeneous material structure data interpretation can be rather difficult. This is especially the case when using anisotropic dissimilar welds made from austenitic steel or nickel based alloys, which are currently used for modern power plant concepts. For better understanding of the complex interaction between the sound field and the component under test, the visualization of sound propagation in solids is a substantial task to increase the probability of detection of relevant defects. However, there exist only a small number of appropriate techniques published today, such as scanning laser interferometer, piezoelectric and optical approaches in case of transparent solids. In this work we present an electrodynamic technique providing a simple use and a high signal to noise ratio. By detecting the grazing beam with an electrodynamic probe with a size smaller than 10 mm, we measured the particle displacement as a function of time with a spatial resolution in the order of 1 mm. Adapting the electrodynamic probe and its coil alignment allows for measuring the displacement components in all three dimensions. This comprises the detection of the horizontal and vertical particle displacement with respect to the surface and thus also the transformation from longitudinal waves into transversal waves and vice versa is possible. A SNR of higher than 36 dB could be achieved within ferromagnetic and high conductive chrome steel when using a transversal wave generated by an angled beam transducer. We report on measurements of the sound field in complex weld joints. One example shows a 10 mm thick narrowgap weld joining a nickel alloy with a chrome steel yielding a substantial anisotropy of the weld structure. The test system enables us to visualize the wave propagation within the weld and indicates the reflection scenario and the energy losses due to both the anisotropic structure and material defects. T2 - ECNDT 2010 - 10th European conference on non-destructive testing CY - Moscow, Russia DA - 2010-06-07 KW - Ultrasonic KW - Sound field KW - Visualization KW - Electrodynamic probe KW - Nondestructive testing (NDT) KW - Nickel alloy KW - Anisotropic weld KW - Narrow-gap weld PY - 2010 SN - 978-1-617-82791-4 SP - 1 EP - 8 AN - OPUS4-22974 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -