Here are the Unit 1 Materials definitions:
Ultimate tensile strength / Breaking stress
Maximum stress before a material is pulled apart
Brittle
A material that shows no plastic deformation just beyond its elastic limit
Compressive force
A force applied to a material that causes compression or extension
Compressive strain
Amount of deformation per unit length of a material (ε=Δx/x) (unitless)
Compressive stress
The compressive force per unit area (σ= F/A) (Nm-2)
Density
Mass per unit volume (p=m/V) (kgm-3)
Ductile
A material that shows plastic deformation before fracturing under tension A ductile material can be pulled into wires, or threads e.g. Copper.
Elastic limit
Load on a spring beyond which the extension increases more rapidly than
expected hence the spring remains permanently deformed when the load is removed (elastic deformation ends)
Elastic deformation
Deformation after which the force is no longer applied the material will return to its original shape
Hard
Materials that resist plastic deformation by surface indentation or scratching e.g. diamond
Laminar flow / streamline flow
Smooth fluid flow in which parallel layers have a constant velocity
Limit of proportionality
Stress is proportional to strain up to this point
Malleable
Materials that show a large plastic deformation under compression. These materials can be beaten into sheets e.g. gold
Stiff
Steep gradient of a force-extension graph - High Young modulus
Stiffness
Measure of the resistance of a material to deformation by tensile force.
Strength
Ability of a material to withstand stress
Tensile strain
Extension per unit length of a material subjected to a tensile force.
Archimedes’ Principle
Upthrust is equal to weight of displaced fluid (u=Vpfg)
Fluid
A substance that can flow – usually with reference to a gas or liquid, but sometimes solids
Viscosity
A measure of a fluid's resistance to gradual deformation – inversely proportional to flow rate
Viscous drag / Stokes Force
Friction acting against movement in a fluid
Flow rate Volume of fluid that passes per second (m3s-1) (Q=V/t)
Terminal velocity
Highest attainable velocity in free fall, it occurs when weight is equal to upthrust and Stokes’ Force combined (W=u+F)
Elastic potential energy
Energy stored due to a load causing deformation (Eel=½FΔx) (Area underneath force-extension graph)
Young’s Modulus
Measure of the stiffness of an elastic material
The ratio of the stress to the strain along where Hooke's law holds (linear line)