Materials Flashcards
What is 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.
Define Breaking Stress.
The maximum stress a material can withstand without fracturing.
What characterizes a brittle material?
A material that fractures without plastic deformation first.
What is Density?
Mass per unit volume, with units kgm-3.
Define Ductile material.
A material that can withstand large plastic deformation without breaking, allowing them to be stretched into long wires.
What is Elastic Deformation?
When a material can return to its original shape after an applied stress or force is removed.
What happens to the energy during elastic deformation?
Any work done in elastically deforming an object is stored as elastic strain energy.
Define Elastic Limit.
The maximum stress that can be applied to an object without plastic deformation.
State Hooke’s Law.
The extension of an object is directly proportional to the force being applied to the object.
What is Laminar Flow?
A state of flow where adjacent layers of fluid move together in parallel with little or no mixing between layers.
What is the Limit of Proportionality?
The point at which the stress on an object is so great that Hooke’s law no longer applies.
Define Plastic Deformation.
When a material is permanently deformed after an applied stress or force is removed due to the atoms moving relative to one another.
What happens to the work done in plastically deforming a material?
Work is done in plastically deforming the material and is dissipated as heat.
State Stoke’s Law.
The magnitude of viscous drag acting on a spherical body as it moves through a fluid is proportional to its radius, its velocity, and the fluid’s viscosity, as long as the movement of the sphere relative to the sphere is laminar.
What is Tensile Strain?
The extension of an object divided by its original length.
Define Tensile Stress.
It is the force applied per unit cross-sectional area.
What characterizes Turbulent Flow?
When layers of fluid cross into each other, resulting in the formation of vortices or eddy currents.
Define Viscosity.
A quantity measuring the internal friction of a fluid, acting to reduce the flow of a fluid; it is temperature dependent.
What is Upthrust?
The force felt against the weight of an object when fully or partially submerged in a fluid; equal to the weight of the fluid displaced by the object.
What is the Yield Point?
The point on a force-extension graph at which a material begins to rapidly extend without any additional stress.
Define Young’s Modulus.
The ratio of stress to strain of an object; it measures how stiff a material is, measured in Pa.
Define a fluid
a material that flows, such as a liquid or gas
Define terminal velocity
when a body moving through a fluid reaches constant velocity due to the resultant of all the force acting on the body equalling zero.
Define the coefficient of viscosity of a fluid
a measure of the resistance to flow for a fluid. It has the units Pa s.
Define elastic strain energy
the ability of a deformed material to do work as it regains its original dimensions.
Define energy density
the work done in stretching a specimen per unit volume and can be found by calculating the area under a stress-strain graph.
Define a hysteresis loop
The area enclosed by loading and unloading curves on a stress-strain graph and is a measure the work done per unit volume transferred to internal energy during each cycle.
High breaking stress =
strong
Low breaking stress =
weak
High Young Modulus =
stiff
Low Young Modulus =
flexible
High energy density (area under graph) =
tough
Low energy density (area under graph) =
brittle
