- Conference date: 3–8 August 2008
- Location: Monterey (California)
Suspensions containing rigid monodisperse spherical particles in a Newtonian carrier liquid are investigated experimentally, providing evidence for solid and liquid states in transient controlled shear rate (TCSR) experiments starting from the state of rest and experiments in controlled shear deformation (CSD) oscillatory flows. In TCSR experiments it has been found that between solid and liquid states a transition takes place. The dynamics of the transition is shown, with the material in this regime reacting as a highly nonlinear system. A key feature of the transition regime is an intrinsic material instability with a negative slope of the flow and deformation curves in a certain range of shear rates and shear strains, respectively. For the same suspension CSD oscillatory shear experiments have been carried out with varying shear strain amplitudes and angular frequencies. The raw input strain and stress response signals were analyzed by the method of Fourier transform rheology. At low amplitudes only the fundamental frequency component is relevant. At higher shear strain amplitudes the intensity of the higher harmonic overtones increases and reaches a maximum at a given shear strain amplitude. In this case, the whole frequency spectrum must be taken into account to calculate the complex modulus. Comparison of this result with that of the TCSR experiments shows that the amplitude range of maximum non‐linearity corresponds to intrinsic material instability region in TCSR experiments.
- Solid liquid phase transitions
- Liquid solid interfaces
- Flow instabilities
- Shear deformation
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