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Title: Active doublet method for measuring small changes in physical properties

Small changes in material properties of a work piece are detected by measuring small changes in elastic wave velocity and attenuation within a work piece. Active, repeatable source generate coda wave responses from a work piece, where the coda wave responses are temporally displaced. By analyzing progressive relative phase and amplitude changes between the coda wave responses as a function of elapsed time, accurate determinations of velocity and attenuation changes are made. Thus, a small change in velocity occurring within a sample region during the time periods between excitation origin times (herein called "doublets") will produce a relative delay that changes with elapsed time over some portion of the scattered waves. This trend of changing delay is easier to detect than an isolated delay based on a single arrival and provides a direct measure of elastic wave velocity changes arising from changed material properties of the work piece.
Inventors:
 [1];  [1];  [2];  [2]
  1. (Los Alamos, NM)
  2. (Santa Fe, NM)
Issue Date:
OSTI Identifier:
869629
Assignee:
United States of America as represented by United States (Washington, DC) LANL
Patent Number(s):
US 5369997
Contract Number:
W-7405-ENG-36
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM
Country of Publication:
United States
Language:
English
Subject:
active; doublet; method; measuring; changes; physical; properties; material; piece; detected; elastic; wave; velocity; attenuation; repeatable; source; generate; coda; responses; temporally; displaced; analyzing; progressive; relative; phase; amplitude; function; elapsed; time; accurate; determinations; change; occurring; sample; region; periods; excitation; origin; times; called; doublets; produce; delay; portion; scattered; waves; trend; changing; easier; detect; isolated; based; single; arrival; provides; direct; measure; arising; changed; elapsed time; relative phase; physical properties; time period; material properties; time periods; wave velocity; accurate determination; elastic wave; direct measure; source generate; delay based; /73/