Nonlinear viscoelastic measurements in fluids using “acoustical rheology”

Dynamic AcoustoElasticity (DAE) method was first developed to assess microcracks in trabecular bone tissue. However, the method appears to offer larger applications, especially in fluids, to investigate nonlinear rheological behaviors. The purpose of this work is to validate the technique\´s sensitivity and to characterize the viscoelasticity in fluids, and particularly in non-Newtonian fluids which exhibit complex viscoelastic properties such as shear-thinning, shear-thickening or thixotropy. DAE technique, based on the interaction of two acoustic waves (a low-frequency wave and ultrasound pulses) provides non-contact and localized measurements of viscoelastic and dissipative nonlinearities. We particularly studied several food and cosmetics products well-known for their "counterintuitive" behaviors. Nonlinear viscoelastic and dissipative measurements have shown strong asymmetry in tension/compression, hysteretic behavior and high level of nonlinearities.