Large-Scale Dilatant Dynamics of Silly Putty
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Large-Scale Dilatant Dynamics of
Silly Putty A Report by the Alfred Unlversity Chapter Introduction
Dow-Corning 3179 Dilatant Compound™, or "Silly Putty™" as commonly known in less scientific circles, is a coralpink silicone polymer with unique rheological properties. It exhibits dilatant behavior, meaning that as shear increases its viscosity increases. This property allows the compound to exhibit high elastic rebound in addition to ease of formation. Patented in 1947 by McGregor and Warrick,' Dow-Corning 3179 has important uses as a therapeutic stress reliever, low gravity fastener (on the Apollo 8 Mission), and stabilizer of wobbly tables. In the novelty toy market, an offshoot of this technology accounts for annual sales of approximately 75 tons of this material. Extensive informai research has investigated the effects of small, 13.3 g (egg-sized) samples striking a hard surface. Surprisingly little data, however, are available on the rebound behavior of larger samples (i.e. >45,000 g). The goal of the Alfred University Chapter's research is to spark interest in the new field of Large-Scale Dilatant Dynamics (LSDD).
observed on the lower surface at the point of impact. The second impact resulted in catastrophic failure of the sample. The sphère fractured into four large portions and numerous small fragments. Post-experimental fractography indicated that fracture initiated due to voids beneath the surface. Discussion
The manufacturer spécifies an 80% rebound for Dilatant Compound 3179. This would correspond to a recoil of 8.9 m after primary impact. The observed 2.0 m correspondstoa rebound value of only 17.9%. The déviance between the specified and observed values can be attributed to brittle fracture. It is hypothesized that the energy was dissipated in the création of new surfaces, thus reducing energy available for rebound. Plastic déformation was not observed and was not considered to be a significant mechanism of energy dissipation. The brittle failure can be attributed to localized régions of high stress intensified by
It can be concluded that as the impact force is increased, brittle fracture becomes more probable. It can also be concluded that air voids in the sample provide fracture origins, which should be minimized for best elastic behavior. This clearly has ramifications in sample préparation techniques used for future research. Infinitely more important than the scientific value of this experiment was the witnesses' gênerai consensus that hurling a big wad of coral-pink Silly Putty off the tellest building in town was a fine way to spend a cold November afternoon in Alfred, New York.
One hundred pounds (45.4 kg) of 3179 Dilatant Compound were obtained from Dow-Corning in two 50-lb lots. The two lots were joined together and kneaded to ensure homogeneity. The sample was formed to a near spherical shape by continuous rolling on a hard surface. The sample diameter measured 42 cm. The spherical sample was accelerated by gravity from a height of 11.3 m onto a hard surface. The estimated velocity a
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