Non-Destructive, Non-Contact Materials Testing
Using the right material in the right place is crucial to the quality, durability, and weight of an end product—and ultimately to its success. Optomet laser Doppler vibrometers make important contributions worldwide to the systematic pursuit of new insights in materials research. Whether determining material parameters or performing non-destructive testing/non-destructive inspection (NDT or NDI), non-contact measurement methods are particularly valuable because they do not affect material properties and, unlike contact-based methods such as accelerometers, enable unaltered materials testing.
Non-Destructive Testing of Materials (NDT)
Fiber-reinforced composites are becoming increasingly important in component manufacturing, helping to reduce weight while achieving high specific stiffness. Examples include aircraft wings in the aerospace industry and body components in the automotive industry. Delaminations or cracks must be detected early during production or maintenance inspections to prevent premature material fatigue. When thin-walled fiber-reinforced composite panels are excited at high frequencies, for example by piezoelectric elements, Lamb waves (short-wavelength surface waves) are generated, among other phenomena. These waves interact with imperfections in the material, causing irregularities in wave propagation or local resonances (Local Defect Resonance - LDR).
SMART-series laser Doppler vibrometers can detect the in-phase propagation of waves at every measurement point on the material surface, revealing defects that are invisible to the naked eye. The internal signal generator can produce arbitrary waveforms for exciting the components, such as pulses or frequency sweeps. OptoSCAN software manages the entire measurement process, from configuring the measurement channels and defining the measurement points to visualizing and analyzing measurement data in the frequency and time domains. The export function allows data to be exported in standard formats such as UFF, HDF5, and MAT-files (MATLAB) for further processing.
Practical Example
The Optomet Scanning Vibrometer detects defects on the rear side of a CFRP plate. The internal signal generator produces a rectangular pulse that excites a piezo actuator attached to the CFRP plate. The waves propagating from the piezoelectric element (bottom center) interact with the two defects, revealing them in the time and frequency domains through locally elevated amplitudes (local defect resonances).
Split Hopkinson Bar (SHPB)
The split Hopkinson bar test is a materials testing method used to determine material properties under dynamic conditions. The specimen (e.g., a concrete cylinder or composite material) is placed between two bars: the incident bar and the transmission bar. An accelerated striker impacts the incident bar, generating an impact pulse. The resulting wave travels through the first bar and reaches the material specimen. It then propagates through the specimen and into the second bar (transmission bar).
Thanks to their high sampling rate of 160 MSamples/s and dynamic range of over 220 dB, Optomet laser Doppler vibrometers (LDVs) are the ideal instruments for measuring the time response of these highly dynamic impact pulses.
Split Hopkinson Bar (SHPB)
Vibration measurement in research, development and industry – Optomet offers the right solution for your requirements.
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