Materials Flashcards
What is deformation?
When a force changes the shape and size of a body
What is tensile deformation?
When 2 forces stretch a body
What is compressive deformation?
When 2 forces compress a body
What happens to a spring when tensile forces are applied?
It will extend
What happens to a spring when compressive forces are applied?
It will compress
What is Hookes Law?
The extension of the material is directly proportional to the applied force up to the limit of proportionality
What is Hookes law equation?
F = kx
F = force N
k = force constant Nm^-1
x = extension m
What is the force/spring constant a measure of?
Stiffness of the material
The larger the spring constant, the ________ the material
Stiffer
What is a brittle material?
A material that fractures after its elastic limit is exceeded
What is a ductile material?
A material that has the capacity to deform plastically, such as being drawn into wire
What is the limit of proportionality?
The point beyond which Hookes law is no longer applicable/ true when stretching a material
What is the elastic limit?
The maximum amount a material can be stretched and still return to its original length - it is always after the limit of proportionality
What does a general force-extension graph look like?
What does a force-extension graph look like for a metal wire?
What does a force-extension graph look like for rubber?
What does a force-extension graph look like for polyethene?
How do you investigate force-extension characteristics?
What is the area under a force-extension graph equal to?
The work done - this is true whether the material obeys Hookes law or not
What is elastic potential energy?
The energy stored within a material when it is stretched or compressed
What are the equations for elastic potential energy?
E = 1/2 Fx
E = 1/2 kx^2
E = elastic potential energy
F = force N
x = extension m
k = force constant
What is tensile stress?
The force extended per unit cross-sectional area
What is tensile strain?
The extension per unit length of a material
What is the equation for tensile stress?
σ = F / a
σ = stress pa
F = force N
A = area m^2
What is the equation for tensile strain?
ε= x / L
ε= strain (no units)
x = extension (m)
L = length (m)
What is ultimate tensile strength?
The maximum of load/ stress a material can handle until it fractures and breaks
What is the equation for Young Modulus?
E = σ/ ε = FL/ Ax
How do you investigate Young Modulus?
What are the features of a stress-strain graph?
What does a stress-strain graph look like for a brittle material?
What does a stress-strain graph look like for a ductile material?
What does a stress-strain graph look like for a polymeric material?
What is elastic deformation?
When the load is removed, the object will return to its original shape
What is plastic deformation?
When the load is removed, the object will not return to its original shape or length - the material is permanently deformed
