Bera P K, Kandar A K, Krishnaswamy R, Sood A K
Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
J Phys Condens Matter. 2019 Dec 18;31(50):504004. doi: 10.1088/1361-648X/ab4235.
We investigate the response of the two-dimensional (2D) continuous non-particulate film of surfactant sorbitan tristearate confined at the air-water interface under oscillatory shear deformation. The time dependence of various rheological parameters show critical-like behavior at a value of strain amplitude close to the crossover point of elastic ([Formula: see text]) and viscous ([Formula: see text]) shear moduli. Imposing oscillatory shear of different strain amplitudes ([Formula: see text]) above and below the crossover strain amplitude ([Formula: see text]) over a large number of cycles, we quantify the temporal dependence of interfacial viscous modulus, phase angle ([Formula: see text]) as well as higher harmonic components of stress. The number of shear cycles ([Formula: see text]) required for these quantities to reach the steady state value diverges near [Formula: see text]. The steady state values of the third harmonic ([Formula: see text]) show order parameter like behavior indicating the importance of higher order harmonics near the nonequilibrium transition. We further show that the energy dissipation per cycle per unit volume has a marked change near [Formula: see text], consistent with continuum level nonequilibrium shear-transformation-zone model of amorphous viscoplasticity.
我们研究了在振荡剪切变形下，限制在空气-水界面的二维（2D）连续非颗粒状脱水山梨醇三硬脂酸酯表面活性剂薄膜的响应。各种流变参数的时间依赖性在应变幅值接近弹性（[公式：见正文]）和粘性（[公式：见正文]）剪切模量的交叉点时表现出临界样行为。在大量循环中，在交叉应变幅值（[公式：见正文]）之上和之下施加不同应变幅值（[公式：见正文]）的振荡剪切，我们量化了界面粘性模量、相角（[公式：见正文]）以及应力的高次谐波分量的时间依赖性。这些量达到稳态值所需的剪切循环数（[公式：见正文]）在[公式：见正文]附近发散。三次谐波（[公式：见正文]）的稳态值表现出类似序参量的行为，表明在非平衡转变附近高次谐波的重要性。我们进一步表明，单位体积每循环的能量耗散在[公式：见正文]附近有显著变化，这与非晶粘塑性的连续水平非平衡剪切转变区模型一致。
