Accession Number : ADA118679

Title :   Ultrasonic Pulse Propagation in Constant-Group-Velocity Media.

Descriptive Note : Interim rept. Mar-Jul 82,

Corporate Author : NAVAL SURFACE WEAPONS CENTER SILVER SPRING MD

Personal Author(s) : Edwards,Palmer L

PDF Url : ADA118679

Report Date : 01 Jun 1982

Pagination or Media Count : 30

Abstract : Results are presented of calculations made of distortion experienced by ultrasonic pulses in transmission through dispersive constant-group-velocity media, and the effects that it may have on velocity measurements. Three types of pulses were considered; a pulsed sine wave of constant amplitude, a pulsed sine wave with amplitude varying as sine-squared, and a rectangular pulse. It is shown that the individual waves in the pulsed sine waves move with the phase velocity of a continuous wave, and the envelope moves with the group velocity. It was also found that a pulsed sine wave in going a certain distance in a constant-group-velocity medium repeats itself, and midway between these distances is the negative of the values at the repetition distances. Because of this repetition phenomenon it is seen that the pulses do not spread as is normally the case in dispersive media. The envelopes of the propagated waves were also calculated, an in agreement with Brillouin's results (Wave Propagation and Group Velocity, Academic, New York, l960) it was found that if the envelope contains negligible frequency components above the carrier frequency then the envelope is not distorted in passing through a dispersive constant-group-velocity medium.

Descriptors :   *Pulses, *Ultrasonic radiation, *Wave propagation, Velocity, Signals, Distortion, Dispersions, Nondestructive testing, Composite materials, Carrier frequencies, Velocity, Repetition rate

Subject Categories : Laminates and Composite Materials
      Crystallography
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE