Stiffness Definition

The material shape doesn't change when a force is applied to

Brittle Definition

The material cracks easily

Elastic Definition

The material goes back to its original shape when F=0

Plastic Definition

The material stays deformed when F=0

Ductile Definition

The material can be pulled in to a longer and thinner shape

Malleable Definition

The material can be deformed under compression (Ductile can be Malleable but not other way around)

Hooke's Law definition

An elastic object opposes deformation forces (Forces proportional to extension) within the limit of proportionality

Hooke's Law Equation

F = -kx k = Spring Constant (kgm-1) x = Extension (m)

Spring Constant (k) definition

A measure of how to stretch / bend material dependant on object / size / shape

Tensile Definition

That the material is under tension

Stress Equation

Force (N) /Area (m^2)

What does high Strength mean for a material

How much Force a material can support

What does high toughness mean for a material

How much Force a material can absorb before rupturing

Stress Definition

A measurement of the force applied over the cross-sectional area of a material

Strain Equation

Extension (m) / Original Length (m)

Strain Definition

The ratio of the extension and original length of the sample

Young's Modulus Definition

The number which represents how easy it is to deform a material (Independent of shape)

Young's Modulus Equation

F L / A (Change in L) OR Stress / Strain

Workdone Equation

Force (N) * Extension (m)

Average Force

Force max /2

Elastic Strain Energy

1/2*F*Change in L

Strain Energy Density

E = 1/2*F*(Change in L) And Volume = AL 1/2*(Stress*strain)

Hardness Definition (Not Absolute Value)

Resistance to indentation or scratching of the material

Moh's Scale What is it

Scratch test used by geologists 1-10 intervals of 1

Brinell's Hardness What is it

(Spherical indenter used to compress the material) Has standardised D and F [think stress equation]

Fracture Energy Equation

Total Energy used to fracture / Area (If it's High material is tough)

Tensile Strength Equation

Breaking Force / Area (If it's high material is strong)

Polycrystalline structure definiton

Atoms not lined up correctly (Metal structure)

Stiffness and elasticity Metal microstructure

Need to pull apart the positive protons from e- seas

4 faults in the metal

Missing Atoms Small Atom thinks it ion of metal Small Atom just chilling there Large Atom thinking it a metal ion

Polymer Microstructure

Amphorus- Polymer Chains tangled Crystalline- Polymer chains folded regularly

Polymer Stiffness

Different rings shape make it difficult and crosslinks stop the chains unfolding

Polymer Elasticity

Stretching rotates and/or elongates the bonds

Density

Mass (kg) / Volume (m^3) Water P = 1000kg/m^-3 Air P = 1.2kg/m^-3

Laminar Fluid

Liquid moved smoothly and adjacent layers within fluid and mix only on a molecular scale

Turbulent Fluid

Adjacent layers mix and small eddies are produce in the fluid

Viscosity Definition

Resistance to flow a measure of the resistance to gradual deformation by shear/stress/tensile strength

Stoke's Law (Viscous Drag)

6*π*r*n*v

n = co-efficient of viscosity

Terminal Velocity with Stoke's Law (ball)

- Weight = Upthrust + Drag force
- P
_{f}= Fluid Density P_{b}=Material Density

4πr^{3}P_{b}g/3 = 6πrnv + 4πr^{3}P_{f }/3

Viscosity Tests (3)

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- Line Spread Test
- Bostwick Consistometer (Put fluid in contraption open trap there is a ruler)
- Falling Ball Viscometer (Measures the time taken for ball to fall through transparent liquid)

Flowing Fluid

The fluid is sheared as it flows

- Faster the fluid flows the higher the shear rates
- The smaller the gap the higher the shear rate

Newtonian Fluid

Constant viscosity regardless of shear rate

Non-Newtonian Fluid

Velocity changes with shear rates