Engineering topics

Tittmann, B. R.

Publications and source records attributed to Tittmann, B. R..

25 records · Page 2

NASA NTRS1973

Internal friction of rocks and volatiles on the moon

Internal friction quality factors Q up to 2200 have been observed in a strongly outgassed terrestrial analog of lunar basalt. This was accomplished by successively cycling a bar shaped sample vibrating in its fundamental longitudinal mode at 15 kHz to higher and higher temperatures in a vacuum between 100 and 10 nanotorr. After each cycle, Q measured at room temperature in the vacuum was observed to decrease with time suggesting that gas reabsorption was taking place even at these low pressures. A study of the effect of exposing a sample to a variety of gases and vapors showed that of the volatiles most likely to be present in the lunar environment H2O was by far the most effective in lowering Q.

Tittmann, B. R.↗

NASA NTRS1972

Rayleigh wave studies in lunar rocks.

An ultrasonic surface wave technique described by the author (1971) is used to verify a hypothesis that links the seismic wave propagation velocities in lunar crust, much too low as compared to those on earth, to the extensive fracturing of lunar rock in the absence of liquids and gases which changed drastically the elastic and inelastic properties of lunar rock. Measurements on lunar rock samples and synthetic analogs suggest that the presence of microfractures have influence on both the wave velocity and Q factor in lunar rocks.

Tittmann, B. R.↗

NASA NTRS1972

Elastic velocity and Q factor measurements on Apollo 12, 14, and 15 rocks.

The Rayleigh wave velocities (vR) in one Apollo 12, one Apollo 15, and two Apollo 14 rocks were measured by the impulse technique. For 14310 vR = 1.20 km/sec; for 14321 vR = 0.9 km/sec; for 12063, on which the orientation dependence was studied, vR = 1.16-1.59 km/sec; for 15555 vR = 0.32 km/sec; and for synthetic rock 10017 analogue vR = 2.26 km/sec. This represents a larger spread by a factor of 3 than previously reported on lunar igneous rock. Absolute Q factor measurements were performed on one Apollo 14 rock by the vibrating bar technique. Under exposure to high vacuum and low temperatures, the Q factor is shown to increase towards values approaching the low end of the range of estimates from seismic data.

Tittmann, B. R.↗

NASA NTRS1971