1. Goal: To understand some simple stress- strain relationships Rheology

2. Relationship between stress and strain Why did various types of putty deform differently? –Was stress constant in these experiments? –Was temperature constant? –What other variables exist?

3. Rheology: The study of relationship between stress and strain in deforming materials –The term rheology is also used as a noun for a material property. For instance: The rheology of glacial ice. –If two materials have different rheologies, we say they are rheologically (adverb) different

4. Elastic rheologies Example — rubber band Exhibit recoverable strain Elastic deformation is strain-rate independent

5. Elastic behavior described by Hook’s Law σ d = E x e E = Young’s modulus e = elongation Can draw strain/time and stress/strain curves for this

6. Viscous rheologies Viscous materials deform by flowing Examples: Honey, motor oil, water, and Lava. Silly Putty is an approximately viscous material. Exhibit permanent, nonrecoverable strain. Strain-rate dependent: Deform Silly Putty as an example

7. Viscous flow is described by ė = σ d /η η = material’s viscosity Can draw strain/time and stress/strain-rate curves for this

8. Real rocks.... Combination of elastic/frictional-brittle and nonlinear-viscous behavior The transition is dependent on both temperature (T) and strain rate (ė) Can use silly putty as an example the effects of both T and ė