Identification of dynamic material properties, non‐destructive testing and study of vibroacoustic behaviour of different structures require the use of complex, pointwise and full‐field measurements, which are capable of providing data for experimental modal analysis or model updating. Nowadays, among other techniques, optical non‐contact techniques represent the favourite choice as they do not add mass, stiffness or damping to the structure under test. When the range of vibration amplitudes allows it, most of these techniques are based on interferometric principles. Development of laser sources and detectors leads to a continuous improvement of vibration measurement techniques. However, a hard choice still has to be made between spatial resolution and temporal resolution. Another difficult choice is between space bandwidth product and energetic sensitivity of the detector. While the number of pixels of a camera is continuously increasing, the pixel size seems limited at its lower end. The paper presents a comparative study of the vibration amplitude fields as measured by two full‐field non‐contact techniques, speckle interferometry and laser Doppler vibrometry, and predicted by finite‐element model. The measurements concern the free and the forced vibrations of a thick, composite plate with free boundaries.

No abstract

The paper gives a new method for the determination of the specific addendum modifications at helical gears. The method is based on the equalization of the relative velocities at the points where the meshing of the teeth begins and ends. The numerical values were obtained for some given gears using MathCAD. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The biodynamic responses of seated occupants exposed to whole‐body vibration have been mostly investigated in terms of apparent mass characteristics, which show negligible contributions due to exposure level. Considering that the severity of vibration exposure is related to the level and duration of exposure, the apparent mass responses cannot be used for assessment of the associated risks. Alternatively, the absorbed power characteristics of the seated vibration exposed occupants show strong dependence on the level of exposure. The measured data, expressed in terms of the vertical absorbed power, are analyzed to study the effects of sitting posture on the biodynamic response under whole‐body vertical vibration. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

No abstract