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General Rheology

This course provides an in-depth exploration of general rheology, focusing on the study of flow and deformation in materials. Participants will learn about rheometers, including shear rheometers and drag flow devices, and their role in measuring mechanical properties like stiffness and strength. The course covers fundamental concepts, including constitutive relations, the assumptions for ideal flow, and the importance of various rheological testing methods such as direct tension and bending beam tests. Ideal for senior and graduate students in materials science or engineering.

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General Rheology

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  1. Senior/Graduate HMA Course General Rheology General Rheology

  2. Rheology • Rheology: • the study of flow and deformation • Constitutive relations • fundamental relationships between force and deformation General Rheology

  3. Rheometers • Equipment used to measure rheology • Shear rheometers • Drag flow • Pressure driven flows • Rheometers for measuring stiffness and strength • Bending beam • Direct tension General Rheology

  4. Shear Rheometers General Rheology

  5. Drag Flow Rheometers • Sliding plate General Rheology

  6. Schematic of Sliding Plate Viscometer Chart Recorder (not to scale) General Rheology

  7. Assumptions • Steady, laminar flow, isothermal flow • No radial or vertical flow • Negligible gravity and end effects General Rheology

  8. Mi t Rq = 2 p Ri2 L q R g = Ro - Ri Narrow gaps: Ri / Ro > 0.99 Drag Flow Rheometers • Concentric Cylinder General Rheology

  9. Drag Flow Rheometers • Cone and Plate Similar triangles for shear flow Homogeneous flow General Rheology

  10. Drag Flow Rheometers • Parallel Plate Shear flow varies with gap height and radius Non-homogeneous flow General Rheology

  11. Assumptions • Steady, laminar, isothermal flow • Negligible body forces • Cylindrical edge General Rheology

  12. Oscillating Plate B C A Fixed Plate B Test operates at 10 rad/sec or 1.59 Hz 360o = 2 p radians per circle 1 rad = 57.3o Time A A C 1 cycle General Rheology

  13. Elastic Viscous B Strain Time A A C Strain out-of-phase d = 90o Strain in-phase d = 0o General Rheology

  14. Complex Modulus, G* Viscous Modulus, G” d Storage Modulus, G’ Complex Modulus is the vector sum of the storage and viscous modulus General Rheology

  15. Master Curves • DSR testing can be used to develop master curves • Need range of temps and frequencies at each temperature • Information • Affect of loading time on asphalt binder stiffness • Estimate of thermal coefficient of expansion General Rheology

  16. Equipment Example General Rheology

  17. Equipment Examples General Rheology

  18. Equipment Example 25 mm Plate with Sample General Rheology

  19. Pressure Driven Rheometers • Vacuum Viscometer Shear Stress Profile Velocity Profile General Rheology

  20. Viscometer Tube • Asphalt Institute Tube General Rheology

  21. Stiffness and Strength Rheometers General Rheology

  22. Bending Beam Rheometer Computer Deflection Transducer Air Bearing Load Cell Fluid Bath General Rheology

  23. Bending Beam Rheometer • S(t) = P L3 4 b h3d (t) Where: S(t) = creep stiffness (M Pa) at time, t P = applied constant load, N L = distance between beam supports (102 mm) b = beam width, 12.5 mm h = beam thickness, 6.25 mm d(t) = deflection (mm) at time, t General Rheology

  24. Bending Beam Rheometer • Evaluates low temperature stiffness properties • Creep stiffness • Slope of response (called m-value) Log Creep Stiffness, S(t) 8 15 30 60 120 240 Log Loading Time, t (sec) General Rheology

  25. Load Direct Tension Test Stress = s = P / A sf DL DLe ef Strain General Rheology

  26. Equipment Example Fluid Bath Loading Ram Cooling System General Rheology

  27. Direct Tension Test General Rheology

  28. QUESTIONS? General Rheology

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