How Particle Shape Affects the Stress Response
How Particle Shape Affects the Stress Response
Wednesday, October 16, 2013
We present measurements of the stress response of packings formed from a wide range of particle shapes. Besides spheres these include convex shapes such as the Platonic solids, truncated tetrahedra, and triangular bipyramids, as well as more complex, non-convex geometries such as hexapods with various arm lengths, dolos, and tetrahedral frames. All particles were 3D-printed in hard resin. Well-defined initial packing states were established through preconditioning by cyclic loading under given confinement pressure. Starting from such initial states, stress-strain relationships for axial compression were obtained at four different confining pressures for each particle type. While confining pressure has the largest overall effect on the mechanical response, we find that particle shape controls the details of the stress-strain curves and can be used to tune packing stiffness and yielding. By correlating the experimentally measured values for the effective Young’s modulus under compression, yield stress and energy loss during cyclic loading, we identify trends among the various shapes that allow for designing a packing’s aggregate behavior.
•Athanasios G. Athanassiadis, Marc Z. Miskin, Paul Kaplan, Nicholas Rodenberg, Seung Hwan Lee, Jason Merritt, Eric Brown, John Amend, Hod Lipson, and Heinrich M. Jaeger, “Particle Shape Effects on the Stress Response of Granular Packings,” Soft Matter 10, 48–59 (2014) [cover story]. pdf file
This project was started in collaboration with John Amend and Hod Lipson at Cornell. Thanasi, Paul, Nick, Seung Hwan and Jason participated as undergrads while at U Chicago. The particles were printed on Objet Connex 3D-printers (see link to Stratasys blog in 3/313 entry; .stl files of the various shapes are available at github here).