Microgravity Experiments on Granular Materials

Gravity induced stresses in terrestrial laboratory specimens comprising of relatively weak and soft granular materials, are often of the same magnitude as the external tractions that are applied during investigations of constitutive behavior especially at low intergranular stress levels. The presence of heterogeneous strain and stress fields within such a specimen makes it difficult if not impossible to obtain objective and unambiguous constitutive properties and to devise relevant constitutive equations. To fill this technological gap, microgravity experiments are now planned which will be performed during future flights of the Space Shuttle, in conjunction with ground-based tests. This paper deals with analytical and experimental issues related to constitutive modeling of granular materials.