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  • 1.
    Ambrozinski, Lukasz
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Magda, P
    AGH University of Science and Technology, Kraków, Polen.
    Dragan, K
    Air Force Institute of Technology, Warsawa, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Temperature compensation based on Hilbert transform and instantaneous phase for Lamb waves-based SHM systems of aircraft structures2013In: Proceedings of the 9th International Workshop on Structural Heath Monitoring 2013 / [ed] Fu-Kuo Chang, 2013, Vol. sept, p. 1259-1266Conference paper (Refereed)
  • 2.
    Ambrozinski, Lukasz
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Packo, Pawel
    AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Experimental comparison of 2D arrays topologies for SHM of planar structures2012In: SPIE Conference Smart Structures and Materials & NDE and Health Monitoring, 2012, San Diego, CA, USA, Proceedings SPIE 8347, SPIE - International Society for Optical Engineering, 2012, p. 834717-Conference paper (Refereed)
  • 3.
    Ambrozinski, Lukasz
    et al.
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Packo, Pawel
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Ultrasonic guided waves based method for SHM: Simulations and an experimental test2011In: 5th World Conference on Structural Control and Monitoring, Tokyo, Japan, 2011Conference paper (Refereed)
  • 4.
    Ambrozinski, Lukasz
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Piwakowski, Bogdan
    Ecole Centrale de Lille, Villeneuve d'Ascq, Frankrike.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Application of air-coupled ultrasonic transducers for damage assessment of composite panels2012In: 6th European Workshop on Structural Health Monitoring, Dresden, Tyskland, 2012Conference paper (Refereed)
  • 5.
    Ambrozinski, Lukasz
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Packo, Pawel
    AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Self-focusing Lamb waves based on the decomposition of the time-reversal operator using time-frequency representation2012In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 27, p. 337-349Article in journal (Refereed)
    Abstract [en]

    Active ultrasonic arrays are very useful for structural health monitoring (SHM) of large plate-like structures. Large areas of a plate can be monitored from a fixed position but it normally requires precise information on material properties. Self-focusing methods can perform well without the exact knowledge of a medium and array parameters. In this paper a method for selective focusing of Lamb waves will be presented. The algorithm is an extension of the DORT method (French acronym for decomposition of time-reversal operator) where the continuous wavelet transform (CWT) is used for the time-frequency representation (TFR) of nonstationary signals instead of the discrete Fourier transform. The performance of the methods is compared and verified in the paper using both simulated and experimental data. It is shown that the extension of the DORT method with the use of TFR considerably improved its resolving ability. To experimentally evaluate the performance of the proposed method, a linear array of small piezoelectric transducers attached to an aluminum plate was used to obtain interelement responses, required for beam self-focusing on targets present in the plate. The array was used for the transmission of signals calculated with the DORT-CWT algorithm. To verify the self-focusing effect the backpropagated field generated in the experiment was sensed using laser scanning vibrometer.

  • 6.
    Ambrozinski, Lukasz
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Design of 2D phased array for monitoring isotropic plate-like structures using Lamb waves2012In: 6th European Workshop on Structural Health Monitoring, Dresden, Tyskland, 2012Conference paper (Refereed)
  • 7.
    Ambrozinski, Lukasz
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Self focusing of 2D arrays for SHM of plate-like structures using time reversal operator2011In: 8th Workshop on SHM, Stanford, CA, 2011, 2011Conference paper (Refereed)
  • 8.
    Ambrozinski, Lukasz
    et al.
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Ochonski, Janusz
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Klepka, Andrzej
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Development of Lamb waves-based SHM systems2012In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 518, p. 87-94Article in journal (Refereed)
  • 9.
    Dragan, Krzysztof
    et al.
    AGH University of Science and Technology, Krakow, Polen.
    Dziendzikowski, Michal
    Air Force Institute of Technology, Warszawa, Polen.
    Uhl, Tadeusz
    AGH University of Science and Technology, Krakow, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Remote monitoring of fatigue cracks growth in the aircraft structure based on active piezosensor network during the full scale fatigue test2014In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 588, p. 249-256Article in journal (Refereed)
    Abstract [en]

    One of the major issues from a structural integrity point of view of the aircraft structure is an appropriate health monitoring technology delivery for the damage tolerant philosophy. This paper presents a development of a system for fatigue crack growth monitoring and early damage detection in the PZL 130 ORLIK TC II turbo-prop military trainer aft structure. The maintenance system of the aircraft shifts from the safe-life to the hard-time. The aircraft started Full Scale Fatigue Test (FSFT) which will continue up to 2013. In the article a built block approach for the system design, signal modeling, sensing and signal processing as well as damage detection is presented. Taking into the consideration a previous experience of AGH as well as AFIT, a network of PZT transducers was deployed in the aircraft structure hot-spots. The system components are: remote monitoring unit, signal analysis, graphical user interface, sensor self-diagnostic tools, and data classification model. Description of damage detection capabilities are delivered in the paper. In particular some issues concerning the proposed damage indices and its application to crack growth estimation models are discussed. Fishers Linear Discriminant is used as a method to obtain effective crack growth predictors and one of the self-diagnostic tools used in the system. The results of the data collected from specimen fatigue tests are delivered and cross-validation technique is used to evaluate a classification model based on the damage indices derived.

  • 10.
    Dworakowski, Ziemowit
    et al.
    AGH University of Science and Technology, Krakow, Polen.
    Ambrozinski, Lukasz
    AGH University of Science and Technology, Krakow, Polen.
    Packo, Pawel
    AGH University of Science and Technology, Krakow, Polen.
    Dragan, Krzysztof
    AGH University of Science and Technology, Krakow, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    AGH University of Science and Technology, Krakow, Polen.
    Application of artificial neural networks for damage indices classification with the use of Lamb waves for the aerospace structures2014In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 588, p. 12-21Article in journal (Refereed)
    Abstract [en]

    Lamb waves (LW) are used for damage detection and health monitoring due to the long range propagation ability and sensitivity to structural integrity changes as well as their robustness in different applications. However, due to the dispersive character and multimode nature of LWs, analysis of the acquired ultrasonic signals is very complex. It becomes even more difficult when applied to a complex structure, for instance, an aircraft component with riveted joints and stringers characterized by difficult geometries. Therefore, numerous approaches to the evaluation of damage indices have been proposed in the literature. In this paper, comparison a number of damage indices applied to LWs testing in aircraft aluminum panels. The damage indices, known from the literature have been selected from the application point of view. Artificial neural network has been used for the classification of fatigue cracks and artificial damages induced in the specimens taken from a real aircraft structure. Article presents results of simulation, data analysis and data classification obtained using selected and dedicated neural network. The main aim of the presented research was to develop signal processing and signal classification methods for an aircraft health monitoring system. The article presents a part of the research carried out in the project named SYMOST.

  • 11.
    Engholm, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Adaptive Beamforming for Array Imaging of Plate Structures Using Lamb Waves2010In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 57, no 12, p. 2712-2724Article in journal (Refereed)
    Abstract [en]

    Lamb waves are considered a promising tool for the monitoring of plate structures. Active arrays employing beamforming techniques enables monitoring large areas of plate structures. Dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on standard beamforming while reducing the effects of dispersion and multiple modes through frequency selectivity and transducer design. This paper presents a minimum variance distortionless response (MVDR) approach for Lamb waves using a uniform rectangular array (URA) and a single transmitter. Theoretically calculated dispersion curves are used to compensate for dispersion. The combination of the MVDR approach and the two dimensional array improves the suppression of interfering Lamb modes. The proposed approach is evaluated on simulated and experimental data and compared to the standard delay-and-sum (DAS) beamformer. It is shown that the MVDR algorithm performs better in terms of higher resolution and better sidelobe and mode suppression capabilities. Known issues of the MVDR approach, such as, signal cancellation in highly correlated environments, and poor robustness, are addressed using methods that have proven effective for the purpose in other fields of active imaging.

  • 12.
    Engholm, Marcus
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Signal Processing. Signals and systems.
    Stepinski, Tadeusz
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Signal Processing. Signals and systems.
    Designing and evaluating transducers for narrowband ultrasonic spectroscopy2005In: 2005 IEEE Ultrasonics Symposium, 2005Conference paper (Refereed)
  • 13.
    Engholm, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signal Processing.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signal Processing.
    Designing and evaluating transducers for narrowband ultrasonic spectroscopy2007In: NDT & E international, ISSN 0963-8695, E-ISSN 1879-1174, Vol. 40, no 1, p. 49-56Article in journal (Refereed)
    Abstract [en]

    Introduction of new composite materials in aerospace applications has created a demand for an efficient NDE technique. Ultrasonic resonance inspection is especially suitable for the inspection of multilayered structures. In our previous work we have described the principle of narrowband ultrasonic spectroscopy (NBUS), where the surface of an inspected structure is scanned with a resonant transducer whose frequency response is monitored in a narrow frequency band. This paper is concerned with optimizing the NBUS setup consisting of a piezoelectric transducer coupled to a multi-layered structure. Differences in the electrical impedance of a piezoelectric transducer caused by variations of parameters of the inspected structure are estimated using an equivalent circuit model and a finite element analysis. The theoretical analysis presented in the paper results in design guidelines for NBUS transducers.

  • 14.
    Engholm, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Direction of Arrival Estimation of Lamb Waves Using Circular Arrays2011In: Structural Health Monitoring, ISSN 1475-9217, E-ISSN 1741-3168, Vol. 10, no 5, p. 467-480Article in journal (Refereed)
    Abstract [en]

     Uniform circular arrays (UCAs) with 360 degrees azimuthal coverage are very useful for structural health monitoring (SHM) of large planar structures. Difficulties encountered when working with Lamb waves include their dispersive and multi-modal nature. In this paper three different methods for estimating the direction-of-arrival (DOA) of incoming Lamb waves are compared and verified using simulated and experimental data. The previously proposed phase-mode excitation based beamformer is compared with two high-resolution spectral estimation techniques, the Capon method and the multiple signal classification method (MUSIC). Design consideration and guidelines for UCAs are presented. To experimentally evaluate the performance of the considered DOA methods a prototype array consisting of 16 separate pinducers arranged in a ring was constructed. The array was provided with an analog multiplexer that enabled recording signals received by the individual elements using a digital oscilloscope. The array was used for the reception of ultrasonic pulses sent by broadband piezoelectric transmitters and propagating in an aluminum plate. A selection of simulation and experimental results is presented showing the superior performance of the Capon beamformer.

  • 15.
    Engholm, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Using 2-D Arrays for Sensing Multimodal Lamb Waves2010In: Conference on Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2010 San Diego, CA, MAR 08-11, 2010 / [ed] Shull PJ, Diaz AA, Wu AF, 2010, Vol. 7649Conference paper (Refereed)
    Abstract [en]

    Monitoring structural integrity of large planar structures requires normally a relatively dense network of uniformly distributed ultrasonic sensors. A 2-D ultrasonic phased array with all azimuth angle coverage would be extremely useful for the structural health monitoring (SHM) of such structures. Known techniques for estimating direction of arriving (DOA) waves cannot efficiently cope with dispersive and multimodal Lamb waves (LWs). In the paper we propose an adaptive spectral estimation technique capable of handling broadband LWs sensed by 2-D arrays, the modified Capon method. Performance of the technique is evaluated using simulated multiple-mode LWs, and verified using experimental data.

  • 16.
    Engholm, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Olofsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Imaging and suppression of Lamb modes using adaptive beamforming2011In: Smart materials and structures (Print), ISSN 0964-1726, E-ISSN 1361-665X, Vol. 20, no 8, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Lamb waves have proven to be very useful for plate inspection because large areas of a plate can be covered from a fixed position. This capability makes them suitable for both inspection and structural health monitoring (SHM) applications. During the last decade, research on the use of active arrays in combination with beamforming techniques has shown that a fixed array can be used to perform omni-directional monitoring of a plate structure. The dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on conventional, delay-and-sum (DAS) beamforming, while reducing the effects of multiple modes through frequency selectivity and transducer design. The paper describes an adaptive beamforming technique using a minimum variance distortionless response beamforming (MVBF) approach for spatial Lamb wave filtering with multiple-transmitter-multiple-receiver arrays. Dispersion is compensated for by using theoretically calculated dispersion curves. Simulations are used for evaluating the performance of the technique for suppression of interfering Lamb modes, both with and without the presence of mode conversion using different array configurations. A simple simulation model of the plate is used to compare the performance of different sizes of active arrays. An aluminum plate with artificial defects is used for the experimental evaluation. The results show that the MVBF approach performs a lot better in terms of resolution and suppression of interfering modes than the widely used standard beamformer.

  • 17.
    Ericsson, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Algorithms for suppressing ultrasonic backscattering from material structure2002In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 40, p. 733-734Article in journal (Refereed)
  • 18. Hasse, L
    et al.
    Kiwilszo, M
    Smulko, J
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Quality assessment of varistor ZnO structures by resonant ultrasound spectroscopy2009In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 51, no 5, p. 262-265Article in journal (Refereed)
    Abstract [en]

    Varistors are produced from ZnO cylindrically-shaped structures whose quality depends on varying technological conditions at stages of their shape forming and firing. Therefore, the varistors art, tested at the final phase of production and faulty elements are excluded. We propose to test the quality of ZnO structures at an earlier stage of production to eliminate defective structures from further and expensive processing. The recommended method applies resonant ultrasound spectroscopy that meets the demand for limiting the costs introduced by an additional measurement procedure. This paper presents the prepared   economical measurement system. that can be used for this purpose The proposed method measures one of the lowest resonant frequencies and dimensions of the tested specimen. The measured quantities enable the estimation of a parameter that is proportional to the sound velocity,  in the tested ZnO sample and gives information about the quality of the   ZnO structure. Detailed experimental data obtained for two batches of  ZnO structures, oil purpose prepared in different ways, are analysed to confirm the usefulness of the applied procedure in industrial applications.

  • 19.
    Klepka, Andrzej
    et al.
    AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Staszewski, W J
    AGH University of Science and Technology, Kraków, Polen.
    Aymerich, F
    AGH University of Science and Technology, Kraków, Polen.
    Digital filters for extracting nonlinear modulation of elastic waves caused by damage2012In: ICAST2012: 23rd International Conference on Adaptive Structures and Technologies, Nanjing, Kina, 2012Conference paper (Refereed)
  • 20.
    Klepka, Andrzej
    et al.
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ambrozinski, Lukasz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Ichonski, Janusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Comparison of two baseline-free damage detection techniques based on Lamb waves propagation phenomena2010In: 5th World Conference on Structural Control and Monitoring, Tokyo, Japan, 2010Conference paper (Refereed)
  • 21.
    Lilliehorn, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Johansson, Linda
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Simu, Urban
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Stepinski, Tadeusz
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Johansson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science.
    Nilsson, M
    Almqvist, M
    Laurell, T
    Nilsson, J
    Array Transducer for Ultrasonic Manipulation of Particles2004In: MSW, Ystad, Sweden, 2004Conference paper (Other scientific)
  • 22.
    Lilliehorn, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science. Technology, Department of Engineering Sciences, Signal Processing.
    Simu, Urban
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science. Technology, Department of Engineering Sciences, Signal Processing.
    Nilsson, M
    Almqvist, M
    Stepinski, Tadeusz
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science. Technology, Department of Engineering Sciences, Signal Processing. Signals and systems.
    Laurell, T
    Nilsson, J
    Johansson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Materials Science. Technology, Department of Engineering Sciences, Signal Processing.
    Trapping of microparticles in the near field of an ultrasonic transducer2005In: Ultrasonics, Vol. 43, no 5, p. 289-299Article in journal (Refereed)
  • 23.
    Lingvall, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Olofsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Synthetic aperture imaging using sources with finite aperture-deconvolution of the spatial impulse response2003In: Journal of the Acoustic Society of America, JASA, Vol. 114, no 1, p. 225-234Article in journal (Refereed)
  • 24.
    Lukomski, Tomasz
    et al.
    AGH, University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Application of resonant ultrasound spectroscopy in diagnostics of rings2011In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 53, no 4, p. 192-195Article in journal (Refereed)
    Abstract [en]

    Resonant ultrasound spectroscopy (RUS) is a non-destructive technique originally developed for evaluating elastic constants of solids using resonance frequencies corresponding to the normal modes of vibration observed in samples with regular geometry. RUS can also be used for non-destructive evaluation of various metal or ceramic objects based on their resonance spectra. RUS can be used to detect deviations such as variations in dimensions and hardness or flaws in the inspected objects. This paper presents an application of RUS for monitoring the hardness of steel rings. Experimental results are presented that show a correlation between the shift of the resonant frequencies and the hardness of the inspected steel rings.

  • 25.
    Lukomski, Tomasz
    et al.
    The University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Application of resonant ultrasound spectroscopy in diagnostics of rings2010In: 11th IMEKO TC 10 Workshop on Smart Diagnostics of Structures, Kraków, Polen, 2010Conference paper (Refereed)
  • 26.
    Lukomski, Tomasz
    et al.
    Krakow, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Steel hardness evaluation based on ultrasound velocity measurements2010In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 52, no 11, p. 592-596Article in journal (Refereed)
    Abstract [en]

    Material properties such as strength, toughness or hardness are usually determined by destructive tests. However, continuous destructive measurements are generally difficult to perform during the production process, which creates a need for a fast and easy non-destructive method of material characterisation. Material elastic parameters, such as Young's modulus, bulk modulus etc, can be directly evaluated using non-destructive methods based on the measurements of ultrasonic wave velocity (shear and longitudinal). However, strength or hardness cannot be determined directly from those parameters since they also depend on material microstructure, such as grain size and orientation, as well as other factors. This paper presents an experimental evidence that hardness of rolled martensitic steel can be evaluated based on the measurements of ultrasonic wave velocity and limited information of its chemical composition.

  • 27.
    Lukomski, Tomasz
    et al.
    The University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Kowal, J
    Synthetic aperture focusing technique with virtual transducer for immersion inspection of solid objects2012In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 54, no 11, p. 623-627Article in journal (Refereed)
    Abstract [en]

    The conventional synthetic aperture focusing technique (SAFT) can improve the lateral resolution and increase signal-to-noise ratio (SNR) in ultrasonic imaging. However, the use of SAFT in immersed inspection is limited due to the issues related to the refraction effects at the boundary between the water and a solid object. The virtual transducer (VT) method employing a focused transducer or phased array is proposed as a solution to this problem. In the VT method, the focal point of a focused aperture is used as a virtual source of ultrasonic waves. If the virtual source is placed on or below the surface of an inspected solid object, SAFT can be applied in the same way as for contact inspection. Combining VT with the new phase-shift migration SAFT (PSM-SAFT) algorithm allows one to reconstruct images of multilayer objects with high resolution and high SNR. What is more, the computation efficiency of PSM-SAFT can significantly reduce the time needed for image reconstruction. Experimental validation of the proposed technique is presented in this paper. We present the results of experiments where the VT was created using a focused transducer and a phased array in the immersion inspection of a stainless steel block containing artificial defects. The performance of four different focused apertures used for generating a virtual transducer is evaluated in relation to the PSM-SAFT algorithm implemented in the frequency domain.

  • 28.
    Manka, M
    et al.
    AGH University of Science and Technology, Krakow, Polen.
    Rosiek, Mateusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Martowicz, A
    AGH University of Science and Technology, Krakow, Polen.
    Ambrozinski, Lukasz
    AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    AGH University of Science and Technology, Krakow, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Novel method for simulation of Lamb wave propagation generated by an interdigital transducer2013In: / [ed] Fu-Kuo Chang, 2013, Vol. sept, p. 2488-2495Conference paper (Refereed)
  • 29.
    Manka, M
    et al.
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Rosiek, Mateusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Martowicz, A
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Properties of interdigital transducers for Lamb-wave based SHM systems2011In: Proceeding of the 8th Workshop on SHM, Stanford, CA., 2011Conference paper (Refereed)
  • 30.
    Manka, Michal
    et al.
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Rosiek, Mateusz
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Martowicz, Adam
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Uhl, Tadeusz
    Faculty of Mechanical Engineering and Robotics, Dept of Robotics and Mechatronics,AGH University of Science and Technology, Kraków, Polen.
    Lamb wave transducers made of piezoelectric macro-fibre composite2013In: Structural Control and Health Monitoring: The Bulletin of ACS, ISSN 1545-2255, E-ISSN 1545-2263, Vol. 20, no 8, p. 1138-1158Article in journal (Refereed)
    Abstract [en]

    During recent years, an intensive research activity concerning the application of Lamb waves (LWs) for SHM has been observed. LWs may be generated and sensed using different types of transducers, and their selection is essential for the SHM system's performance. Results of the investigation of three types of transducers based on macro-fiber composite (MFC) are presented in this paper; two types of commercially available MFC actuators are compared with a novel type of custom-designed interdigital transducer also based on the MFC substrate. After a short presentation of the piezoelectric transducer designed for SHM applications, details concerning the proposed interdigital transducer design are provided. Beampatterns of the investigated transducers are first compared using numerical FEM simulations, and next, the numerically obtained beampatterns are verified experimentally using laser vibrometry. In the final part of this paper, advantages and disadvantages of the investigated transducers are discussed.

  • 31.
    Manka, Michal
    et al.
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Rosiek, Mateusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Martowicz, Adam
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Design and simulations of interdigital transducers for Lamb-wave based SHM systems2010In: 11th IMEKO TC 10 Workshop on Smart Diagnostics of Structures, Kraków, Polen, 2010Conference paper (Refereed)
  • 32.
    Ochonski, Janusz
    et al.
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Ambrozinski, Lukasz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Klepka, Andrzej
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Choosing an appropriate sensor for the designed SHM system based on Lamb waves propagation2010In: : 11th IMEKO TC 10 Workshop on Smart Diagnostics of Structures, Kraków, Polen, 2010Conference paper (Refereed)
  • 33.
    Olofsson, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Frequency-domain SAFT for the Ultrasonic Inspection of Coarse Grained Metals2009In: 7th International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, Yokohama, 2009Conference paper (Refereed)
  • 34.
    Olofsson, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Minimum entropy deconvolution of attenuated pulse-echo signals2001In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 109, no 6, p. 2831-2839Article in journal (Refereed)
  • 35.
    Olofsson, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Phase shift migration for imaging layered materials and objects immersed in water2009In: 2009 IEEE International Ultrasonics Symposium, Rome, 2009Conference paper (Refereed)
  • 36.
    Rosiek, Mateusz
    et al.
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Martowicz, Adam
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Kraków, Polen.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Lukomski, Tomasz
    The University of Science and Technology, Kraków, Polen.
    Electromechanical impedance method for damage detection in mechanical structures2010In: : 11th IMEKO TC 10 Workshop on Smart Diagnostics of Structures, Kraków, Polen, 2010Conference paper (Refereed)
  • 37.
    Skoczowski, S
    et al.
    SIGNALS AND SYSTEMS.
    Stepinski, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences.
    Approximate analysis of on-off controllers with dynamic feedback1975In: Pomiary Automatyka Kontrola, Vol. 2Article in journal (Refereed)
  • 38.
    Stepinski, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Signal Processing. Signals and systems.
    Narrowband ultrasonic spectroscopy for NDE of layered structures2004In: 16th World Congress of NDT, 2004Conference paper (Refereed)
  • 39.
    Stepinski, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. SIGNALS AND SYSTEMS.
    NDE of copper canisters for long term storage of spent nuclear fuel from the Swedish nuclear power plants2003Conference paper (Refereed)
  • 40.
    Stepinski, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. SIGNALS AND SYSTEMS.
    Ultrasonic phased arrays2003Conference paper (Refereed)
  • 41.
    Stepinski, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. SIGNALS AND SYSTEMS.
    Ultrasonic spectroscopy of adhersively bonded multi-layer structures2003Conference paper (Refereed)
  • 42.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signal Processing.
    An Implementation of Synthetic Aperture Focusing Technique in Frequency Domain2007In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 54, no 7, p. 1399-1408Article in journal (Refereed)
    Abstract [en]

    A new implementation of a synthetic aperture focusing technique (SAFT) based on concepts used in synthetic aperture radar and sonar is presented in the paper. The algorithm, based on the convolution model of the imaging system developed in frequency domain, accounts for the beam pattern of the finite-sized transducer used in the synthetic aperture. The 2D fast Fourier transform (FFT) is used for the calculation of a 2D spectrum of the ultrasonic data. The spectrum is then interpolated to convert the polar coordinate system used for the acquisition of ultrasonic signals to the rectangular coordinates used for the presentation of imaging results. After compensating the transducer lobe amplitude profile using a Wiener filter, the transformed spectrum is subjected to the 2D inverse Fourier transform to get the time-domain image again. The algorithm is computationally attractive due to the use of 2D FFT. The performance of the proposed frequency-domain algorithm and the classical time-domain SAFT are compared in the paper using simulated and real ultrasonic data.

  • 43.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group. Signals and systems.
    Assessing quality of self-piercing rivets using ultrasound2006Conference paper (Refereed)
  • 44.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Structural health monitoring of piping in nuclear power plants: A review of efficiency of existing methods2011Report (Other academic)
  • 45.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group. Signals and systems.
    Ultrasonic inspection of aerospace composite structures using narrowband ultrasonic spectroscopy2006Conference paper (Refereed)
  • 46.
    Stepinski, Tadeusz
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ultrasonic nondestructive inspection of solid objects2011Conference paper (Refereed)
  • 47.
    Stepinski, Tadeusz
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Signal Processing. Signals and systems.
    Ultrasonic Spectroscopy for the inspection of airspace structures2004In: SPIE's 9th Annual International Symposium on NDE for Health Monitoring and Diagnostics, 2004Conference paper (Refereed)
  • 48.
    Stepinski, Tadeusz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ambrozinski, Lukasz
    AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Beamforming of Lamb waves using 2D arrays: A comparative study2013In: / [ed] Fu-Kuo Chang, 2013, Vol. sept, p. 2210-2217Conference paper (Refereed)
  • 49.
    Stepinski, Tadeusz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ambrozinski, Lukasz
    AGH University of Science and Technology, Kraków, Polen.
    Uhl, Tadeusz
    AGH University of Science and Technology, Kraków, Polen.
    Designing 2D arrays for SHM of planar structures: a review2013In: Proceeding of SPIE, vol 8694, 2013, p. 86941R-Conference paper (Refereed)
  • 50.
    Stepinski, Tadeusz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Engholm, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Advanced beamforming of 2D arrays for structural health monitoring using Lamb waves2010In: 5th European Workshop on Structural Health Monitoring 2010, Sorrento, Italien, 2010Conference paper (Refereed)
12 1 - 50 of 70
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