Double-pulsed Holography Research Articles

Tire Vibration Studies: The State of the Art

Abstract General principles of mechanical vibration enigneering are used to discuss the total tire vibration problem in terms of three necessary factors: an excitation force, a transmitter, and a receiver of the vibratory force. The present state of knowledge for each of these factors is discussed and an overall goal for reduction of vehicle vibration is formulated. Current experiments for investigating tire vibration transmissibility are described and the results presented: the first used an electrohydraulic shaker; the second used time average holography, in order to see tires, and investigated impact wave propagation in tires with double-pulsed laser holography. Results show that it is difficult to reduce tire transmissibility and to shift resonant frequencies; however, this may be accomplished by introducing small amounts of body ply crown angles in radial tires (0–20 deg). Results of the impact wave propagation tests are beginning to reveal the true nature of what happens when a tire strikes a sharp bump.

An application of high-speed microholography: the mertology of fogs

Holograms of fogs produced in a high-altitude propeller test cell were recorded in the following condition: Pressure 0,5 atm; temperature 0 °C; velocity of the fog 100 m/s. The droplet diameters ranged between 5 and 50 μm. Reconstructed images were enlarged X 1000 and visualized with the help of a TV-system. Individual measurements on the particules porvided the local concentration and diameter repartition. Moreover, the use of double-pulse holography gives the three components of the speed vector for each particle. The optical arrangement and apparatus are described. The influence of experimental parameters upon the precision of measures is discussed.