Engineering topics

Lograsso, T. A.

Publications and source records attributed to Lograsso, T. A..

7 records

NASA NTRS1988

Isothermal dendritic growth: A low gravity experiment

The Isothermal Dendritic Growth Experiment is an active crystal growth experiment designed to test dendritic growth theory at low undercoolings where convection prohibits such studies at 1 g. The experiment will be essentially autonomous, though limited in-flight interaction through a computer interface is planned. One of the key components of the apparatus will be a crystal growth chamber capable of achieving oriented single crystal dendritic growth. Recent work indicates that seeding the chamber with a crystal of the proper orientation will not, in and of itself, be sufficient to meet this requirement. Additional flight hardware and software required for the STS flight experiment are currently being developed at NASA Lewis Research Center and at Rensselaer Polytechnic Institute.

Glicksman, M. E.↗

NASA NTRS1988

Isothermal dendritic growth - A proposed microgravity experiment

This paper describes an isothermal dendritic growth experiment (IDGE), a microgravity-oriented spaceborne scientific experiment designed to obtain 'convection-free' dendritic growth and thereby provide a test of dendritic growth theory. The apparatus includes a controlled thermostatic bath capable of providing + or - 2 mK stability, a photographic data collection system, a crystal growth chamber ensuring 'free' dendritic growth, and an optical RAM camera for crystal growth detection. The experiment will be carried on essentially automatically aboard the Materials Science Laboratory in the cargo bay of the Space Shuttle. The results of preliminary ground-based studies are presented.

Glicksman, M. E.↗

NASA NTRS1988

Dendritic solidification under microgravity conditions

The Isothermal Dendritic Growth Experiment is undergoing development in cooperation with NASA-Lewis in order to test dendritic growth theory at small supercoolings in low earth orbit. The apparatus encompasses four major subsystems: a temperature-controlled thermostatic bath capable of millikelvin stability, a photographic data collection system, a crystal-growth chamber, and a start-detection system which initiates data collection. Comparisons are made with ground-based study methods for dendritic growth.

Glicksman, M. E.↗

NASA NTRS1988

A facility for precise temperature control applications in microgravity

The general design, main components, and operation of the isothermal dendritic growth apparatus (IDGA) designed for microgravity experimentation are described. The four major subsystems of the IDGA are a temperature controlled thermostatic bath capable of milli-kelvin stability, a photographic data collection system, a crystal growth chamber, and a growth detection system to initiate data collection. Some of the specific experiments that could utilize the capabilities of the IDGA are dendritic growth in alloys, monotectic systems, life science experiments, and technological applications.

Glicksman, M. E.↗

NASA NTRS1987

Isothermal dendritic growth - A low gravity experiment

The Isothermal Dendritic Growth Experiment has been designed to test dendritic growth theory at low undercoolings, under microgravity conditions in the Space Shuttle Cargo Bay-borne Material Science Laboratory. The experiment will be essentially autonomous, although limited in-flight interaction through a computer interface is planned. A crystal growth chamber able to yield oriented single-crystal dendritic growth will be incorporated; 'seeding' the chamber with a crystal of the requisite orientation will not in itself meet this requirement.

Glicksman, M. E.↗

NASA NTRS1987

Solidification under microgravity conditions - Dendritic growth

The experimental approach and apparatus of a zero-gravity active crystal growth experiment to test dendritic growth theory at low supercoolings are discussed. The experiment consists of 20 experimental cycles. Estimates have been made as to how low gravitational accelerations would have to be reduced to observe convection-free dendritic growth at supercoolings from 0.01-1.0 K. The experiment requires temperature control of + or - 2 mK and photographic resolution of a few microns with a depth of field of + or - 6 mm. The thermostatic bath and temperature control system, photographic system, growth chamber, and dendrite detection system are described in detail.

Glicksman, M. E.↗

NASA NTRS1984

The solidification of monotectic alloys - Microstructures and phase spacings

The microstructures of directionally grown monotectic alloys in metallic and organic systems fall into two categories those which can form aligned fibrous composite structures with even phase spacings and fiber sections, and those in which the phase distribution is coarser and less regular. This division appears to relate to the form of the phase diagram and has been rationalized by Cahn (1977, 1979) in terms of the relative surface energies between solid and two liquids to give steady state or nonsteady state profiles. The transition in growth behavior occurs when the ratio of the monotectic temperature to that of the upper consolute temperature is approximately 0.9. Differences in phase spacings between a range of monotectic and eutectic systems are discussed in terms of the expected growth interface shapes and the factors which will influence them.

Grugel, R. N.↗