The early stages (<180 min) of cavitation erosion of silicon surfaces were studied for three different crystallographic orientations. We introduce a quantity defined as the ratio of the relative eroded area to the number of pits, a p , to evaluate the evolution of erosion among the different substrates used. Different erosion evolution was observed for (100), (110), and (111) silicon surfaces when exposed to cavitation bubbles generated by an ultrasound signal of 191 kHz. (100) silicon substrates showed the most erosion damage, with an eroded area 2.5 times higher than the other two crystallographic orientation substrates after 180 min sonication. An apparent incubation period of 50 min was measured. The number of erosion pits increased monotonically for (110) and (111), but for (100) no increase was detected after 120 min. The collapse of a spherical bubble was simulated using an axisymmetry boundary integral method. The calculated velocity of the jet from the collapsing bubble was used to estimate the pressure P that is induced by the jet upon impact on the silicon substrate. V C 2013 American Institute of Physics. [http://dx.

This paper presents the analysis of pressure dependence of three thermoplastic polyurethane (TPU) materials on vibration isolation. The three TPU Elastollan R materials are: 1190A, 1175A and 1195D. Aim of this investigation was to analyze how much the performance of isolation can be enhanced using patented Dissipative bulk and granular systems technology. The technology uses granular polymeric materials to enhance materials properties (without changing its chemical or molecular composition) by exposing them to 'self-pressurization', which shifts material energy absorption maxima towards lower frequencies, to match the excitation frequency of dynamic loading to which a mechanical system is exposed. Relaxation experiments on materials were performed at different isobaric and isothermal states to construct mastercurves, the time-temperature-pressure interrelation was modeled using the Fillers-Moonan-Tschoegl model. Dynamic material functions, related to isolation stiffness and energy absorption, were determined with the Schwarzl approximation. An increase of stiffness and energy absorption at selected hydrostatic pressure, compared to its stiffness and energy absorption at ambient conditions, is represented with κ k (p, ω), defining the increase of stiffness and κ d (p, ω), defining the increase of energy absorption. The study showed that close to the glassy state, moduli of 1190A and 1195D is about 6-9 times higher compared to 1175A, whereas, their properties at ambient conditions are for all practical purposes the same. TPU 1190A turns out to be most sensitive to pressure: at 300M P a its properties are shifted for 5.5 decades, while for 1195D and 1175A this shift is only 3.5 and 1.5 decades, respectively. In conclusion, the stiffness and energy absorption of isolation may be increased with pressure for about 100 times for 1190A and 1195D, and for about 10 times for 1175A. a) Dedicated to dr. David Binding for his contributions to the field of Rheology.