Engineering topics

Perkins, Steven W.

Publications and source records attributed to Perkins, Steven W..

4 records

NASA NTRS1993

Direct tension experiments on compacted granular materials

The objective of this experiment is to determine the level of tensile strength of uncemented, dry, granular materials. The experimental apparatus does not lend itself to a direct measurement of the material's tensile strength, but must be analyzed as a stress field problem in order to arrive at a tensile strength value. The experiment, and subsequent analysis, serve to instruct the student on the influence of gravitationally induced stresses in frictional granular materials, the importance and difficulty of accurately describing the entire failure envelope for granular materials in the low mean stress range, and the fundamental principles of material modeling.

Perkins, Steven W.↗

NASA NTRS1992

Experimental, physical and numerical modeling of lunar regolith and lunar regolith structures

An extensive series of laboratory strength and deformation experiments have been performed on a lunar regolith simulant. Results of these experiments are compared to results from experiments on real lunar regolith from the Apollo and Luna missions to illustrate the suitability of this material in capturing the engineering properties lunar regolith. In addition, these results are used to calibrate a constitutive model used to describe its stress-strain behavior. This model, in conjunction with numerical analysis techniques, is used to predict the response i.e. material parameters) of lunar simulant under 1/6-g and low confining stress conditions. These tools are also used to predict the displacement response of a lunar soil embankment structure used to cover a first generation human habitat module, which might be used to accommodate the first astronauts revisiting the moon. These predictions are compared to physical models of this structure, which are tested in a geotechnical centrifuge in order to satisfy scaling relationships between prototype and model.

Perkins, Steven W.↗

NASA NTRS1990

Regolith-structure modeling of lunar facilities

The mechanical properties of lunar regolith are significantly different from terrestrial soils; at low stress levels, the ultimate strength envelope is highly nonlinear, and the material is essentially dilatant. The effects of platen friction, membrane confinement, and material self weight in triaxial tests have been shown to be of great significance in low stress level tests. An inverse identification technique has been devised to account for these effects where the load-displacement response of the entire specimen, including the boundary conditions and the self-weight, was analyzed by nonlinear finite element techniques so as to obtain true material parameters.

Perkins, Steven W.↗

NASA NTRS1989

Extraterrestrial engineering

The overall objectives and near-term (1 year) and intermediate-term (2 years) goals of the Extraterrestrial Engineering Cluster (Center of Space Construction, University of Colorado at Boulder) are presented in outline form. The Extraterrestrial Cluster objective is to develop technology needed for constructing and maintaining the outposts and bases on the Moon and Mars.

Sture, Stein↗