The Waves and Imaging Laboratory at the University of Minnesota is devoted to the development and implementation of experimental techniques for wave-based imaging, characterization, and diagnostics of complex material and structural systems.
Laser Doppler Vibrometer
Laser Doppler Vibrometer
The centerpiece of the lab is the Polytec PSV-400-3D-MScanning Laser Doppler Vibrometer (LDV). A laser vibrometer is a sensing device that provides accurate non-contact measurements of the velocities of points belonging to the surface of vibrating solid objects. Non-contact measurement techniques are non invasive and allow superior measurement accuracy (compared to standard transducer-based methods). 3D scanning vibrometers, in particular, are capable of scanning the surface of a vibrating body, thus allowing full reconstruction of the three-dimensional velocity fields associated with the wave or vibration state of the medium. Scanning lasers are agile sensing devices as a result of their ability to quickly reconfigure the spatial location and density of the scanning grid points.
PSV-400-3D-M vibrometer can detect displacements of the order of nanometers (10-9m)
The spatial resolution is ± 0.1 mm. This translates in the possibility to make O(104) measurements in a 1in x 1in region, which translates in the possibility to resolve small-scale features in the reconstructed wavefields
The frequency range is DC-1MHz, spanning across applications, from modal analysis of structures to ultrasonic-based NDE.
B&K Vibration Exciter Type 4809: electromechanical shaker with a frequency range from 10 Hz – 20 kHz.
Olympus V101 RB Piezoceramic Transducer: P-wave ultrasonic contact transducer with resonance frequency at 0.5 MHz.
Olympus V1548 Piezoceramic Transducer: S-wave ultrasonic contact transducer with resonance frequency at 0.1 MHz.
E&I 1140LA 1000 Watt Class AB amplifier: capable of providing a nominal gain of 55dB in the frequency range 9 kHz – 250 kHz.
E&I 1020L 200 Watt Class AB amplifier: capable of providing a nominal gain of 53 dB in the frequency range 10 kHz – 5 MHz.
B&K 2718 Power Amplifier: characterized by continuous variable output current from 1A to 5A.
Nicollet Sigma60 8-channel Digital Oscilloscope Workstation.
Spectral Dynamics Siglab portable dynamic signal analyzer.
Gallery of experimental setups and applications
Nuclear Graphite Block Scan
Scan of a nuclear graphite block experiencing bulk and surface wave propagation. The wavefield captured form the block surface is subsequently fed to an inverse-elasticity algorithm to reconstruct the position, size and shape of defects (e.g. internal damage due to thermal gradients) that may have developed in the interior of the block. PI: Bojan B. Guzina – Student: Roman Tokmashev.
Ultrasonic Waves In Fractured Rock
20kHz ultrasonic waves propagating across an arrested fracture in a granite slab (3-point bending configuration): in-plane (ux,uy) displacement waveforms captured by LDV. The experiment aims to better understand the fracture’s (linearized) interfacial condition, quantified in terms of the shear and normal specific stiffness distributions (kn,kt).
Department of Civil, Environmental, & Geo- Engineering
University of Minnesota
500 Pillsbury Drive SE, Minneapolis, MN 55455
Phone 612-626-0789, Fax 612-626-7750 Email