Topic 04: Materials Flashcards
Archimedes’ principle
When a body is fully or partially submerged in a fluid, it experiences an upthrust equal to the weight of the fluid it has displaced
Breaking stress
The maximum stress a material can withstand without fracturing
Brittle
A material that fractures without plastic deformation first
Density
Mass per unit volume, with units kgm^{-3}
Ductile
A material that can withstand large plastic deformation without breaking, this allows these materials to be stretched into long wires
Elastic deformation
When a material can return to its original shape, after an applied stress, without a permanent change to its shape. Any work done in elastically deforming an object is stored as elastic strain energy
Elastic limit
The maximum stress that can be applied to an object without plastic deformation
Hooke’s law
The extension of an object is directly proportional to the force being applied to the object
Laminar flow
A state of flow where layers of fluid move together in parallel with little or no mixing between layers
Limit of proportionality
The point at which the stress of an object is so great that Hooke’s law no longer applies to an object
Plastic deformation
When a material is permanently deformed after an applied stress due to the atoms moving relative to one another in the material. Work is done in plastically deforming the material and is dissipated as heat
Stokes’ law
The magnitude of the force of viscosity acting on a spherical body as it moves through a fluid is proportional to its radius, its velocity, and the fluid’s velocity. This only applies to spherical bodies travelling in laminar, non-turbulent, flow
Tensile strain
The extension of an object divided by its original length
Tensile stress
The internal resistance of an object against a force that acts to deform it. It is the force applied per unit cross-sectional area
Turbulent flow
A state of flow where layers of fluid mix together unpredictably, creating a chaotic state
