Bending, Ringing, Breaking and Flowing, Ch Non-Newtonian and viscoelastic fluids
Problem
A ball of silicone putty has a Maxwell relaxation time τM=1.2s, set by the breaking and re-forming of its borate cross-links. It is struck by a hammer; the contact between hammer and putty lasts tobs=3ms and produces a local shear strain of about 0.5. Beyond a shear strain of about 0.2, the intact rubber network of the putty cannot deform further without its cross-links tearing rather than rearranging.
((a)) Compute the Deborah number for the impact.
((b)) State whether the putty responds, on this timescale, as an elastic solid or as a viscous liquid.
((c)) Predict what happens to the putty during the strike: does it flow around the hammer, bounce back intact, or shatter?