Transient Dynamics of Concentrated Particulate Suspensions Under Shear (Springer Theses)

Description

This thesis demonstrates the first use of high-speed ultrasound imaging to non-invasively probe how the interior of a dense suspension responds to impact. Suspensions of small solid particles in a simple liquid can generate a rich set of dynamic phenomena that are of fundamental scientific interest because they do not conform to the typical behavior expected of either solids or liquids. Most remarkable is the highly counter-intuitive ability of concentrated suspensions to strongly thicken and even solidify when sheared or impacted. The understanding of the mechanism driving this solidification is, however, still limited, especially for the important transient stage while the response develops as a function of time. In this thesis, high-speed ultrasound imaging is introduced to track, for the first time, the transition from the flowing to the solidified state and directly observe the shock-like shear fronts that accompany this transition. A model is developed that agrees quantitatively with the experimental measurements. The combination of imaging techniques, experimental design, and modeling in this thesis represents a major breakthrough for the understanding of the dynamic response of dense suspensions, with important implications for a wide range of applications ranging from the handling of slurries to additive manufacturing. Supervisor's Foreword Acknowledgments Parts of This Thesis Have Been Published in the Following Journal Articles Contents 1 Introduction 1.1 Steady-State Rheology of Suspensions 1.2 Shear Jamming in Dry Granular Materials and Dense Suspensions 1.3 Wyart–Cates Model for Steady-State Rheology 1.4 Dynamic Jamming and Transient Flows Under Impact, Extension, and Shear 1.5 The Scope of This Thesis 2 Ultrasound Techniques for Studying Suspensions 2.1 Introduction 2.2 Introduction to the Ultrasound System 2.3 Speed of Sound Measurements 2.4 Measurement of Porosity and Bulk Modulus of Microparticles in Liquids 2.5 Ultrasound Imaging 2.6 Visualizing Flows of Dense Suspensions 3 Investigating Impact-Activated Fronts with Ultrasound 3.1 Introduction 3.2 Impact Experiment with Ultrasound 3.3 Measurement of Flow Field 3.4 Invariant Packing Fraction During Front Propagation 3.5 Impact-Activated Fronts Are Shear Fronts 3.6 Conclusions 4 Modeling Shear Fronts in One Dimension 4.1 Introduction 4.2 Quasi-One-Dimensional Wide Gap Shear Experiment 4.2.1 Features of Dynamic Shear Fronts 4.2.2 Flow Profile at Slow Boundary Speed 4.2.3 Front Speed and Accumulated Strain 4.2.4 Relation Between Applied Stress and Front Speed 4.2.5 Maximum Shear Rate 4.3 Validating the Original Wyart–Cates Model with Steady-State Rheology 4.4 Generalized Wyart–Cates Model for Transient Flows 4.4.1 Generalize the Wyart–Cates Model 4.4.2 Numerical Calculations 4.4.3 Transition from Slow to Fast U0 4.5 Validation of the Generalized Model 4.5.1 Qualitative Predictions of the Model 4.5.2 Quantitative Comparison with Experiments 4.6 Conclusions 5 Rheology in the Shear Jamming Regime 5.1 Introduction 5.2 Limitations of Narrow-Gap Steady-State Rheology 5.3 Steady-State Rheology Using One-Dimensional Transient Flows 5.4 Boundary of Shear Jamming in Suspensions 5.5 Conclusions 6 Conclusions and Outlook 6.1 Conclusions 6.2 Outlook A Effective Density of Non-density-Matched Suspensions B Preparation of Suspensions C Relation Between k Value and Accumulated Strain in 2D D Relation Between kl and kt in 3D E Some Calculations Regarding the Generalized Model References