DYNAMIC TESTING OF MATERIALS /WITH DISCUSSION/

DYNAMIC TESTS OF BOTH SONIC VELOCITY AND RESONANT FREQUENCY TYPES ARE DESCRIBED. SONIC VELOCITY TESTS WERE MADE TO EVALUATE THE EFFECT OF BOTH AIR-FILLED AND WATERFILLED CRACKS ON TRANSMITTAL OF SIGNALS THROUGH CONCRETE. LOW-FREQUENCY SIGNALS, ESPECIALLY THOSE GROUPS CAUSED BY HAMMER BLOWS, SHOWED LITTLE EFFECT FROM EITHER NARROW OR WATER-FILLED CRACKS. AS WOULD BE EXPECTED, ANY ATTENUATION OR DELAY WAS INCREASED AS THE CRACK SIZE INCREASED. AN INCREASE IN THE FREQUENCIES COMPOSING THE SIGNAL ALSO INCREASED THE EFFECT OF BOTH AIR- AND WATER FILLED CRACKS. ANOTHER SERIES OF INVESTIGATIONS CONSISTED OF SONIC-VELOCITY MEASUREMENTS ON MASSES OF SAND, GRAVEL, COMBINATIONS OF SAND OR GRAVEL WITH WATER, AND FRESHLY MIXED CONCRETE. DECREASING PARTICLE SIZE REDUCED THE MEASURED SONIC VELOCITIES. THE PRESENCE OF WATER IN THE ABOVE MIXTURES INCREASED THE SONIC VELOCITY IN ALL CASES. MEASURED VELOCITIES IN THIS SERIES WERE MUCH BELOW VELOCITY OF SOUND IN AIR AND, WHEN COMPARED TO DATA PRESENTED BY OTHER INVESTIGATORS, LED TO THE CONCLUSION THAT THE APPARENT VELOCITY THROUGH A LOOSE MASS IS DEPENDENT UPON THE CHARACTER AND FREQUENCY OF THE SIGNAL. THESE RESULTS LED TO THE INVESTIGATION OF VARIOUS PICKUPS AND CIRCUIT COMPONENTS WHICH DEMONSTRATED THAT ORDINARY EQUIPMENT COMPONENTS ALWAYS PRODUCED TIME DELAY FACTORS IN THE MEASUREMENT. SOME OF THESE VARIABLES ARE CAUSED BY SURFACE CONDITIONS, POWER AND TYPE OF THE ORIGINAL SIGNALS AND THE MOUNTING OF PICKUP COMPONENTS. RESONANT-FREQUENCY DYNAMIC TESTS WERE COMPARED TO SONIC VELOCITIES. FLEXURAL AND TORSIONAL RESONANT FREQUENCY TESTING ON ROCK CORES REVEALED UNUSUAL REACTIONS. SOME INDICATIONS OF HETEROGENEITY AND LOOSE STRUCTURE WERE EVIDENT EVEN IN APPARENTLY SOUND SPECIMENS. IRRATIONAL VALUES OF POISSON'S RATIO, WHICH WERE FREQUENTLY INDICATED BY THESE CORES, ARE DISCUSSED. /AUTHOR/

  • Supplemental Notes:
    • Vol 33, pp 242-258, 10 FIG, 5 TAB, 10 REF, 1 APP
  • Authors:
    • Mitchell, L J
    • Mccoy, E E
    • Mather, B
  • Publication Date: 1954

Media Info

  • Monograph Title: Proceedings of the Thirty-Third Annual Meeting of the Highway Research Board, Washington, D.C., January 12-15, 1954
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00213965
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 22 1972 12:00AM