High-gradient constitutive model for granular material with random packing structure

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:175250

Chang, C S ^[1]

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1. Univ. of Massachusetts, Amherst, MA (United States)

Granular material, such as soil, powder, ceramic material, etc., can be perceived as a collection of particles. The overall mechanical properties for granular materials depend significantly on the micro-scale geometric arrangement and on the contact stiffness between two interacting particles. A second-gradient constitutive law for granular media is derived in which stress is a function of the second-order of strain gradient. The constitutive coefficients for granular materials with isotropic packing structure are derived in explicit terms of inter-particle stiffness and particle size. In the present constitutive theory, the total number of elastic constants for the isotropic granular material is four: two of them are the usual Lame constants, the other two are associated with the second-gradient of strain. The derived constitutive relationships illustrate the important role of micro-scale properties in the macro-scale behavior. The influence of inter-particle stiffness and particle size on the response of material due to second-gradient of strain is discussed. The micro structure effects become important for dynamic problems involving short wavelengths. This paper also discusses the connection between the second-gradient theory and nonlocal theory. The second-gradient theory can be regarded as the first-order approximation of nonlocal theory.

• OSTI ID: 175250
• Report Number(s): CONF-950686--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
GRANULAR MATERIALS
MECHANICAL PROPERTIES
PARTICLE SIZE
POWDERS
SOILS
STRAINS