Experimental study of elasto-plastic wave propagation in one-dimensional and two-dimensional disk arrays

Waymel, Robert

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https://hdl.handle.net/2142/46770 Copy

Description

Title

Experimental study of elasto-plastic wave propagation in one-dimensional and two-dimensional disk arrays

Author(s)

Waymel, Robert

Issue Date

2014-01-16T18:01:53Z

Director of Research (if dissertation) or Advisor (if thesis)

Lambros, John

Department of Study

Aerospace Engineering

Discipline

Aerospace Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• granular media
• disk
• cylinder
• plastic
• wave propagation

Abstract

In this work, a drop-weight tower setup and a modified split Hopkinson pressure bar (SHPB) are used to dynamically load one- (1D) and two-dimensional (2D) arrays of disks in contact. The disks are made of aluminum 6061 T6 and are selected because of their rate-independence, thus allowing static contact force-displacement laws to be used in the dynamic case. Although differing considerably between each other, the loading magnitudes in the drop tower and SHPB setups, 2 kN to 30 kN respectively, cause the arrays to deform plastically at the contact points between disks where stress concentrations exist. This allows for elasto-plastic wave propagation to be studied in ordered 1D and 2D elasto-plastic arrays. Additionally, the loading pulse durations from the two experimental setups are sufficiently different that the effect of the loading time can be studied. The drop tower load times are of the order of milliseconds and are much longer than the solitary wave duration, while the SHPB time scales are in the microseconds regime and are comparable to the solitary wave time scales. Imaging techniques are also used to capture the deformation process and post mortem residual strains. The wave speed is seen to be dependent on force and ranges between 1000 and 2000 m/s. It was also found that there was not a monotonic relationship with respect to force in the drop tower setup, but there was decreasing force and yielding along the 1D disk chain in the SPHB. The difference was attributed to the longer time scales involved in the drop tower experiments. This research is the first to investigate the propagation of elasto-plastic waves in 1D and 2D arrays of disks and will form the basis of subsequent studies.

Graduation Semester

2013-12

Permalink

http://hdl.handle.net/2142/46770

Copyright and License Information

Copyright 2013 Robert F. Waymel

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