Search for dissertations about: "Lamb waves"

Showing result 1 - 5 of 11 swedish dissertations containing the words Lamb waves.

  1. 1. Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves

    University dissertation from Uppsala : Acta Universitatis Upsaliensis

    Author : Marcus Engholm; Uppsala universitet.; [2010]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; imaging; array processing; guided waves; Lamb waves; dispersive waves; multi-modal waves; spatial filtering; mode suppression; resonant ultrasound; transducer design; direction of arrival estimation; adaptive beamforming; TECHNOLOGY Information technology Signal processing; TEKNIKVETENSKAP Informationsteknik Signalbehandling; TECHNOLOGY Electrical engineering; electronics and photonics Electronic measurement and instrumentation; TEKNIKVETENSKAP Elektroteknik; elektronik och fotonik Elektronisk mät- och apparatteknik;

    Abstract : Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures. READ MORE

  2. 2. Lamb wave evaluation of concrete plates

    University dissertation from Department of Biomedical Engineering, Lund university

    Author : Oskar Tofeldt; Lunds universitet.; Lund University.; [2017-09-01]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Lamb waves; guided waves; impact-echo; concrete; non-destructive evaluation;

    Abstract : This thesis is about the application of Lamb waves for non-destructive evaluation of plate-like concrete structures under one-sided access test condition using a portable equipment consisting of an accelerometer and impact hammer. With this type of equipment and based on array signal processing, the impact-echo (IE) method can be extended with measurements of surface waves; this extension allows an evaluation with Lamb waves. READ MORE

  3. 3. Air-coupled microphone measurements of guided waves in concrete plates

    University dissertation from Stockholm : KTH Royal Institute of Technology

    Author : Henrik Bjurström; KTH.; [2014]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Non-destructive testing; Lamb waves; surface waves; air-coupled microphones; non-contact measurements;

    Abstract : Quality control and quality assurance of pavements is today primarily based on core samples. Air void content and pavement thickness are parameters that are evaluated. However, no parameter connected to the stiffness is evaluated. READ MORE

  4. 4. Detecting Inclusions in a Silicone Rubber Phantom Using Standing Lamb Waves and Multiple Frequency Footprints

    University dissertation from Umeå : Umeå Universitet

    Author : Ulf G Jonsson; Umeå universitet.; Umeå universitet.; [2014]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Piezoelectric; Silicone rubber; Impedance; Resonance; Lamb waves; Phantom; Electronics; elektronik;

    Abstract : The thesis deals with one major question: is it possible, using one piezoelectric sensor/vibrator, to detect a hard inclusion in a silicone rubber phantom? The question was approached with an open mind and the task was subdivided into three clearly identifiable parts: characterization of the piezoelectric sensor/vibrator (paper I), creating a model of the visco-elastic properties of a tissue-like material (phantom) in contact with the sensor/vibrator (paper II), and to detect the presence of a hard inclusion in the phantom (paper III). All vibrations of the sensor/vibrator and phantom was modeled using a finite element method (FEM). READ MORE

  5. 5. Non-contact surface wave measurements on pavements

    University dissertation from Stockholm : KTH Royal Institute of Technology

    Author : Henrik Bjurström; KTH.; [2017]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; seismic testing; asphalt concrete; dynamic modulus; non-contact measurements; rolling measurements; surface waves; Lamb waves; MEMS microphones; Civil and Architectural Engineering; Byggvetenskap;

    Abstract : In this thesis, nondestructive surface wave measurements are presented for characterization of dynamic modulus and layer thickness on different pavements and cement concrete slabs. Air-coupled microphones enable rapid data acquisition without physical contact with the pavement surface. READ MORE