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Week 5: Material Properties (Elastic properties of solids :check: (forces…
Week 5: Material Properties
Elastic properties of solids :check:
forces are generated to counteract tensile, shear or compressive forces.
Inside the materials, there is intermolecular/ interatomic forces of particles of materials
Fluids cannot resist sheer stress as they do not deform but flow
Stress: force per unit area. same unit as pressure (N/m^2 or Pa)
:check:
4 types
Normal stress: acting perpendicular to the plane.
Tensile stress: pulls apart along an axis.
Compressive stress: pushes together along an axis.
Shear stress: pushes sideways
Bulk stress pushes inwards from all directions.
causes
Strain: Defined as the fractional change in some characteristic quantity :check:
3 types
Shear strain: fractional horizontal displacement compared to the separation of surfaces.
Bulk strain: Fractional change in volume
Tensile strain or compressive strain: fractional change in length.
Dimensional unit since it is the ratio two lengths.
Hooke's Law: Certain stress is proportional to certain strain :check:
Stress = strain x constant
(constant) Gradient of graph of stress vs strain
aka Modulus
Ductile vs Brittle :check:
Ductility is a physical property of a material associated with the ability to be hammered thin or stretched into wire without breaking
When stretched beyond the elastic limit, it experiences plastic deformation in which permanent deformation occurs
Brittle: When stretched beyond the elastic limit, it experiences little or no plastic deformation before breaking.
Fluid Behaviour :check:
Newtonian fluids: Viscosity remains constant, no matter the amount of shear applied for a constant temperature.. These fluids have a linear relationship between viscosity and shear stress.
Non-Newtonian fluids: When shear is applied to non-Newtonian fluids, the viscosity of the fluid changes.
Time-dependent
Thixotropic: decrease in viscosity when shear is applied. This is a time dependent property as well
Rheopectic:very similar to dilatant in that when shear is applied, viscosity increases. The difference here, is that viscosity increase is time-dependent
Time-independent
Dilatant (shear thickening) :Viscosity of the fluid increases when shear is applied
Pseudoplastic: the opposite of dilatant; the more shear applied, the less viscous it becomes.
