Wave propagation in one dimensional confined granular media

Granular Media;One Dimensional;Dynamic;Split Hopkinson Pressure bar (SHPB);Confinement;Geopolymer;Shrink Fit

Lavigne, Peter ; Lambros ; John

关键词: Granular Media;    One Dimensional;    Dynamic;    Split Hopkinson Pressure bar (SHPB);    Confinement;    Geopolymer;    Shrink Fit;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/34243/LaVigne_Peter.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Ordered granular media, such as a one dimensional aligned chain of spherical particles, have unique dynamic properties arising from the contact interaction of their individual grain constituents. A primary result of this contact, the formation of solitary waves in dynamically loaded one dimensional granular arrays, has been studied at great length. This thesis is the first to consider the effects of different types of lateral confinement on the dynamic response of such one dimensional granular chains. Chains of metallic beads are placed under lateral confinement in one of two ways: (a) by having a metal tube with a diameter mismatch shrink fit around the chain and (b) by being embedded in a geopolymer matrix. A geopolymer is a room temperature curable ceramic based on earth minerals. Since the homogeneous geopolymer response is not well characterized, initially in this work a potassium-based geopolymer developed at the Department of Materials Science at the University of Illinois at Urbana-Champaign was examined to determine its dynamic properties. The dynamic response and nonlinear properties of the granular chains either laterally confined or embedded in a geopolymer were then investigated using a modified Split Hopkinson Pressure bar (SHPB). Although a dependence on granular chain length was seen, it was found that confinement does not significantly affect the primary pulse caused by the solitary wave as it passes through the chain, at least for chains exceeding 5-6 grains in length (the length necessary for the formation of a solitary wave in an unconfined chain). However, the “late-time” response, i.e. the force transmitted after the primary pulse, was seen to be strongly affected by the presence of confinement. This is explained by the alteration of the frictional characteristics on the lateral surfaces of the one dimensional bead array. In addition, curing conditions of the matrix were also seen to affect the chain response.