Deformation field in indentation of a granular ensemble

Abstract

An experimental study has been made of the flow field in indentation of a model granular material. A granular ensemble composed of spherical sand particles with average size of 0.4 mm is indented with a flat ended punch under plane-strain conditions. The region around the indenter is imaged in situ using a high-speed charge-coupled device (CCD) imaging system. By applying a hybrid image analysis technique to image sequences of the indentation, flow parameters such as velocity, velocity gradient, and strain rate are measured at high resolution. The measurements have enabled characterization of the main features of the flow such as dead material zones, velocity jumps, localization of deformation, and regions of highly rotational flow resembling vortices. Implications for validation of theoretical analyses and applications are discussed.

Force chain and contact cycle evolution in a dense granular material under shallow penetration

“…11). The width of this dilation zone is comparable to the lateral extent of the deformed region identified in experimental studies (Murthy et al, 2012). The distance at which this inflection point occurs provides an indication of the diminishing influence of the punch.…”

“…There are other structures that emerge in penetration systems, besides those studied here. For example, vortices were recently observed in Murthy et al (2012); Hossain and Fourie (2013) in sand experiments. These merit future study, given the recent findings on the role that they play in the initiation of localised failure Tordesillas et al (2014).…”

“…Structures, vehicles and machines operate on geological materials which are granular in form, e.g. soil, rock, ice rubble, snow (Paavilainen and Tuhkuri, 2013;Estep and Dufek, 2013;Murthy et al, 2012;Calvetti et al, 2004). Laboratory tests which mimic, and are aimed at understanding the fundamentals of, deformation and dewatering processes in geological formations involve mechanical configurations where the geomaterial is loaded in fully confined or partially confined solid boundaries (e.g.…”

Deformation field evolution in indentation of a porous brittle solid

“…The deformation occurring in indentation of metals has been examined through indirect post-mortem assessments of strain-induced effects (Tabor, 1951), and more recently, the development of image based measurement techniques such as particle image velocimetry (PIV) and particle tracking velocimetry (PTV) has added a new dimension to experimental studies on the mechanics of indentation in metals (Murthy et al, 2008(Murthy et al, , 2012Sundaram et al, 2012). These image-based techniques have provided useful qualitative and quantitative insights into the evolution of deformation in indentation.…”

The impact of raindrops on sand

“…This result indicates that rather than droplet spreading it is the stress inside the granular bed that is redirected towards the free surface [61,118,119] figure 4.4b is most likely due to the post crater formation evolution.…”