Analysis of microcracks in dry polycrystalline NaCl by ultrasonic signal processing

Technical Report · Tue Jul 01 00:00:00 EDT 1980

OSTI ID:5181551

Sears, F M

The attenuation of energy and the change in shape of transient waveforms is a basic feature associated with the propagation of waves in crustal rocks. The dimensionless quality factor Q is observed as a useful quantity to characterize the attenuation of energy. Existing an elastic (attenuation) theories on the Q-determination problem are compared with experimental measurements to better understand rock properties. Experimental attenuation measurements were made on Avery Island (Louisiana) rock salt, Westerly (Rhode Island) granite, and Creighton (Ontario) quartz biotite gabbro. The attenuation mechanisms and how they affect the agreement between the an elastic theories were examined. Ultrasonic pulse methods were utilized of examine crack geometries as a function of frequency and thermal cycling temperature in dry polycrystalline rock salt. The attenuation of compressional (P) and shear (S) waves was studied in a thermally-induced, isotropic distribution of microcracks using ultrasonic-transmission techniques. These attenuation measurements led to the following series of generalities: ultrasonic or seismic attenuation depends on frequency in the rocks tested; thermal cycling of rock salt increases the porosity and attenuation; grain scattering seems to be the dominant loss mechanism at the higher frequencies in rocks; friction explains why the introduction of cracks into rock salt increases the attenuation; and attenuation appears to be independent of strain amplitude for low strains (10/sup -6/) such as those associated with these measurements. Much work remains to be done to adequately describe the attenuation loss mechanisms and the an elasticity of rocks both experimentally and theoretically.

• Research Organization: California Univ., Livermore (USA). Lawrence Livermore National Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5181551
• Report Number(s): UCRL-52975; TRN: 80-014755
• Resource Relation: Other Information: Thesis
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
CRACKS
DETECTION
ROCKS
WAVE PROPAGATION
SODIUM CHLORIDES
ACOUSTICS
CRYSTALS
EXPERIMENTAL DATA
FREQUENCY DEPENDENCE
HEAT TREATMENTS
MICROSTRUCTURE
STRESSES
THEORETICAL DATA
ULTRASONIC TESTING
ACOUSTIC TESTING
ALKALI METAL COMPOUNDS
CHLORIDES
CHLORINE COMPOUNDS
CRYSTAL STRUCTURE
DATA
HALIDES
HALOGEN COMPOUNDS
INFORMATION
MATERIALS TESTING
NONDESTRUCTIVE TESTING
NUMERICAL DATA
SODIUM COMPOUNDS
TESTING
420500* - Engineering- Materials Testing