TY - JOUR A1 - Heideklang, René A1 - Shokouhi, Parisa T1 - Multi-sensor image fusion at signal level for improved near-surface crack detection N2 - This study aims at improving the detection of near-surface defects in magnetizable and conductive specimens by combining the measurements of eddy current, magnetic flux leakage and thermography testing. Different signal processing methods for data normalization are proposed to enable data fusion at the pixel level. These methods are applied to a test specimen which contains 10 variably-sized defects. We quantitatively evaluate the performances of a total of 29 detection methods with respect to false alarm reduction at a fixed level of true positive rate. We report that false positive rate could be reduced from 1.65% down to 0.28% by the best multi-sensor method compared to the best single-sensor performance on the smallest defect, when 50% found flaw pixels are required for successful detection. KW - Data fusion KW - Image processing KW - Surface flaw KW - Detection PY - 2015 DO - https://doi.org/10.1016/j.ndteint.2014.12.008 SN - 0963-8695 VL - 71 SP - 16 EP - 22 PB - Elsevier Ltd. AN - OPUS4-32577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - White, J. A1 - Hurlebaus, S. A1 - Shokouhi, Parisa A1 - Wimsatt, Andrew T1 - Use of ultrasonic tomography to detect structural impairment in tunnel linings - Validation study and field evaluation N2 - Tunnel inspection is a challenging problem because of high-volume traffic and routine operations in naturally aggressive environments. The need to keep tunnels open during inspection and minimize tunnel closures and user delays must be carefully balanced with the need to conduct in-depth lining inspections to ensure the safety of drivers. This paper describes the laboratory validation and field performance of a recently developed in-depth nondestructive testing technology for the detection of impairments in tunnel lining: linear array shear wave tomography, typically referred to as ultrasonic tomography (UST). Before this equipment is used in the field, the system is first evaluated through the use of laboratory specimens with artificial defects that mock common structural problems, such as air- and water-filled voids, delaminations, and other potential abnormalities. The device is also used to determine concrete thickness and reinforcement depth and spacing. The test results are discussed to determine the device's capabilities and limitations in locating defects in concrete structures. After the system is evaluated on the basis of its ability to detect these simulated defects, the system is taken to the field to inspect a public tunnel for natural structural defects. Potential regions of interest are first identified through high-speed air-coupled ground-penetrating radar (GPR) and visual inspection and subsequently inspected with UST. This paper shows that the combination of preliminary inspection procedures (GPR surveys and visual inspection) and an in-depth technique like UST is powerful for the assessment of the condition of tunnel linings and can detect potential anomalies, such as delamination, reinforcement depth and layout, and lining thickness. KW - Evaluierung KW - Tunneluntersuchung KW - Ultraschall-Tomografie KW - Validierung PY - 2014 DO - https://doi.org/10.3141/2407-03 SN - 0361-1981 VL - 2 IS - 2407 SP - 20 EP - 31 PB - National Research Council CY - Washington, DC AN - OPUS4-31520 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heideklang, René A1 - Shokouhi, Parisa T1 - Application of data fusion in nondestructive testing (NDT) N2 - Applying contemporary data fusion techniques, the multi-modal nondestructive testing (NDT) data sets can be combined to obtain more reliable results. The reliability can be quantified in terms of the probability of detection of sought material defects. A concise review of the published studies on NDT data fusion is provided here and the key concepts and anticipated challenges are discussed. The detailed steps involved in the NDT fusion process are explained with reference to a case study. The presented data set includes the results of three different NDT techniques on a test specimen with built-in defects. Several pixel-level fusion algorithms were applied and their performances are quantitatively compared. T2 - FUSION 2013 - 16th International Conference on Information Fusion CY - Istanbul, Turkey DA - 09.07.2013 PY - 2013 SN - 978-605-86311-1-3 SP - 835 EP - 841 AN - OPUS4-30033 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shokouhi, Parisa A1 - Wolf, Julia A1 - Wiggenhauser, Herbert T1 - Detection of delamination in concrete bridge decks by joint amplitude and phase analysis of ultrasonic array measurements N2 - The accuracy and precision of low-frequency (center frequency of approximately 55 kHz) ultrasonic testing for detection and characterization of delamination in concrete bridge decks were evaluated. A multiprobe ultrasonic testing system (with horizontally polarized shear-wave transducers) was used to detect built-in delamination defects of various size, depth, and severity (i.e., thickness) in a test specimen—a 6.1 m × 2.4 m × 216 mm (20 ft × 8 ft × 8.5 in.) reinforced concrete slab-built to simulate a concrete bridge deck. The collected data sets were reconstructed applying synthetic aperture focusing technique (SAFT). The reconstructed measurement results were then used to assess the condition of the concrete slab at individual points [point-by-point data collection and two-dimensional (2D) reconstruction] as well as along lines, where data were collected at smaller steps and reconstructed in a three-dimensional (3D) format. The local-phase information was also calculated, superimposed on the reconstructed images and used as complementary information in condition assessment. The precision and accuracy of condition assessments were evaluated. The results indicated that, using the multiprobe ultrasonic array, delamination defects as small as 30 cm² (1 ft²) could be reliably detected. Deep delaminations [i.e., those deeper than 150 mm (6 in.)] were directly detected and characterized, whereas shallow delaminations [shallower than 65 mm (2.5 in.)] were detected only indirectly. The precision of the measurements was demonstrated by comparing repeated measurements at several test points. Similar measurement results obtained on a delaminated portion of a real bridge deck support the conclusions of the validation study. KW - Concrete bridge deck KW - Bridge deck evaluation KW - Delamination KW - Nondestructive testing (NDT) KW - Ultrasonic testing PY - 2014 DO - https://doi.org/10.1061/(ASCE)BE.1943-5592.0000513 SN - 1084-0702 VL - 19 IS - 3 SP - 04013005-1 EP - 04013005-11 PB - Soc. CY - Reston, Va. AN - OPUS4-31261 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heideklang, René A1 - Shokouhi, Parisa T1 - Quantitative multi-modal NDT data analysis N2 - A single NDT technique is often not adequate to provide assessments about the integrity of test objects with the required coverage or accuracy. In such situations, it is often resorted to multi-modal testing, where complementary and overlapping information from different NDT techniques are combined for a more comprehensive evaluation. Multimodal material and defect characterization is an interesting task which involves several diverse fields of research, including signal and image processing, statistics and data mining. The fusion of different modalities may improve quantitative nondestructive evaluation by effectively exploiting the augmented set of multi-sensor information about the material. It is the redundant information in particular, whose quantification is expected to lead to increased reliability and robustness of the inspection results. There are different systematic approaches to data fusion, each with its specific advantages and drawbacks. In our contribution, these will be discussed in the context of nondestructive materials testing. A practical study adopting a high-level scheme for the fusion of Eddy Current, GMR and Thermography measurements on a reference metallic specimen with built-in grooves will be presented. Results show that fusion is able to outperform the best single sensor regarding detection specificity, while retaining the same level of sensitivity. T2 - Quantitative nondestructive Evaluation conference 2013 (QNDE) CY - Baltimore, MD, USA DA - 2013-07-21 KW - Data fusion KW - Multi-sensor KW - Reliability PY - 2013 SP - 1 EP - 5(?) AN - OPUS4-30058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Shokouhi, Parisa A1 - Zoëga, Andreas A1 - Wiggenhauser, Herbert ED - Thompson, D.O. ED - Chimenti, D.E. T1 - Nondestructive evaluation of damage in concrete under uniaxial compression N2 - Surface wave velocities over the sonic frequency range (<20 KHz) were measured on concrete specimens undergoing various cycles of loading and unloading. Acoustic Emission test (AE) was conducted simultaneously to monitor the microcracking activities. The sonic surface wave velocity was found to be highly stress-dependent. The observed changes in surface wavespeed are repeatable and follow a particular trend. By measuring the wave velocities in both loading and unloading phases, the effects of stress and stress-induced damages could be distinguished. The observed trend could be explained by a combination of acoustoelasticity and microcracking theories. T2 - 36th Annual Review of Progress in Quantitative Nondestructive Evaluation CY - Kingston, RI, USA DA - 2009-07-26 KW - Nondestructive testing (NDT) KW - Microcracking KW - Sonic wave velocity KW - Concrete KW - Load KW - Stress PY - 2010 UR - http://link.aip.org/link/?APCPCS/1211/1525/1 SN - 978-0-7354-0748-0 SN - 0743-0760 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings SP - 1525 EP - 1532 CY - Melville, NY AN - OPUS4-22642 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shokouhi, Parisa A1 - Wöstmann, Jens A1 - Schneider, Gerhard A1 - Milmann, Boris A1 - Taffe, Alexander A1 - Wiggenhauser, Herbert T1 - Nondestructive detection of delamination in concrete slabs - multiple-method investigation N2 - The delamination of concrete slabs is the separation along a plane roughly parallel to, and generally near, the surface. Corrosion-induced delamination is a common problem in old concrete bridge decks. If undetected, delaminations could expand, reach the surface, and result in spalling. Early detection of delamination is necessary for planning timely repairs that prevent costly deck replacement projects. Most bridge owners rely on routine visual and traditional surveys of bridge deck conditions. These surveys are highly subjective and can locate only large shallow delaminated zones. Several nondestructive testing (NDT) techniques have recently been employed for bridge deck evaluation to obtain more objective and comprehensive assessment. The reliability of applicable methods needs to be established before a greater role for NDT in routine inspections can be encouraged. This paper presents a validation study aimed at evaluating the effectiveness of three NDT techniques, namely impact echo, ultrasound (US) echo, and US linear array, in detection of delamination. This study is unique because the subject test specimens were deteriorated bridge deck segments preserved from the demolition of a prestressed box girder bridge. The results of the tests conducted on one of the specimens are presented and discussed here: impact echo provided satisfactory overall assessment, but the individual results were often difficult to interpret; US echo detected deep delaminations but not shallow ones; and US linear array located the extent of deep delaminations and provided indications of shallow ones. KW - Delamination KW - Concrete KW - Ultrasonic testing KW - Impact echo KW - Scanning PY - 2011 DO - https://doi.org/10.3141/2251-11 SN - 0361-1981 VL - 2251 SP - 103 EP - 113 PB - National Research Council CY - Washington, DC AN - OPUS4-25552 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kolkoori, Sanjeevareddy A1 - Shokouhi, Parisa A1 - Höhne, Christian A1 - Rahman, Mehbub-Ur A1 - Kreutzbruck, Marc A1 - Prager, Jens T1 - A comparative study of ray tracing and CIVA simulation for ultrasonic examination of anisotropic inhomogeneous austenitic welds N2 - Ultrasonic examination of anisotropic inhomogeneous austenitic welds is challenging, because of the columnar grain structure of the weld leads to beam skewing and splitting. Modeling tools play an important role in understanding the ultrasound field propagation and optimization of experimental parameters during the ultrasonic testing of austenitic welds as well as the interpretation of the test results. In this contribution, an efficient theoretical model based on the ray tracing concepts is developed to calculate the ultrasonic fields in inhomogeneous austenitic welds quantitatively. The developed model determines the ultrasound fields by taking into account the directivity of the ray source, the inhomogenity of the weld as well as ray transmission coefficients. Directivity of the ray source in columnar grained austenitic materials (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. Ray energy reflection and transmission coefficients at an interface between two general columnar grained austenitic materials are calculated in three dimensions. The ray tracing model predictions on inhomogeneous austenitic weld material are compared against those from CIVA, a commercial non-destructive modeling and simulation tool. The ultrasonic modeling tools in CIVA are based on semi-analytical solutions. For beam propagation simulation, a so-called 'pencil method' is used, which involves modeling the probe as a set of individual source points, each radiating 'a bundle' of diverging rays into the medium and integrating those elementary contributions. Inhomogenity in the weld region is approximated by mapping the grain orientations on weld macrograph. Simulation results for ultrasonic field profiles for an austenitic weld are shown to be in good agreement with the corresponding experimental results. T2 - 39th Annual review of progress in quantitative nondestructive evaluation CY - Denver, Colorado, USA DA - 15.07.2012 KW - Crystal microstructure KW - Ray tracing KW - Ultrasonic materials testing KW - Ultrasonic propagation KW - Ultrasonic reflection KW - Ultrasonic transmission KW - Welds PY - 2013 SN - 978-0-7354-1129-6 DO - https://doi.org/10.1063/1.4789158 SN - 0094-243X SN - 1551-7616 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1511 SP - 1043 EP - 1050 PB - AIP Publishing AN - OPUS4-27736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shokouhi, Parisa A1 - Zoëga, Andreas A1 - Wiggenhauser, Herbert A1 - Fischer, G. T1 - Surface wave velocity-stress relationship in uniaxially loaded concrete N2 - The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface wave velocity proved to be direction-dependent. The velocity increases and decreases the most when measured parallel and perpendicular to the loading axis, respectively. KW - Acoustic emission KW - Acoustoelasticity KW - Microcracking KW - Surface waves KW - Velocity measurement PY - 2012 SN - 0889-325x VL - 109 IS - 2 SP - 141 EP - 148 PB - ACI CY - Farmington, Mich., USA AN - OPUS4-27999 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Shokouhi, Parisa A1 - Bruno, Giovanni T1 - Stress- and damage-induced changes in coda wave velocities in concrete N2 - Diffuse ultrasonic measurements are used to monitor progressive stress-induced damage in a number of concrete specimens. Each specimen was subjected to uniaxial compression, applied in small steps over one or several load cycles. At each step, the loading was held constant and a series of ultrasonic measurements parallel and perpendicular to the loading were obtained. The measurements were taken during both the loading and unloading phases. The time scale of the signals was chosen such that the diffuse ultrasonic regime could be recorded. Using Coda Wave Interferometry (CWI), the corresponding changes in the velocity of diffuse ultrasonic waves were monitored. The evolution of the slope of the CWI velocity-stress curve with the increased level of damage in concrete is demonstrated. T2 - 39th Annual review of progress in quantitative nondestructive evaluation CY - Denver, Colorado, USA DA - 2012-07-15 KW - Ultrasonics KW - Ultrasonic velocity KW - Interferometry KW - Velocity measurement PY - 2013 SN - 978-0-7354-1129-6 DO - https://doi.org/10.1063/1.4789073 SN - 0094-243X SN - 1551-7616 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1511 SP - 382 EP - 389 AN - OPUS4-31386 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -