Materials Flashcards
Define Elastic Deformation?
It reforms to its original size (natural length) when force is removed
Define Plastic Deformation?
When stretched it won’t return to its original size (natural length
What is Hooke’s Law?
The extension is proportional to the force applied, up to the limit of proportionality
What is Hooke’s Law as an equation?
F = KΔL F = force K = spring constant L = extension
On a Force-Extension graph what is the Spring Constant?
The gradient of the straight part of the line
What on a Force-Extension graph indicates a material has passed the Limit of Proportionality?
The graph becomes a curve
What is the area under a Force-Extension graph?
Energy
What is the area between the Loading and Unloading line of a Force-Extension graph?
Energy lost thermaly
What is meant by a material being Non-Hookean?
It does not obey Hooke’s Law
eg. Rubber
If two springs are in Series, What happens their combined spring constant and extension?
They will extend twice the amount for the same force.
Their combined spring constant is half of the sum of the springs
If two springs are in Parallel, What happens their combined spring constant and extension?
They will extend half the amount for the same force
Their combined spring constant is the sum of the springs
Define Tensile Stress?
Force exerted per unit cross sectional area
What is the equation for Tensile Stress?
σ = F/A σ = Tensile Stress F = Force A = Cross Sectional Area
Define Tensile Strain?
Extension per unit length
What is the equation for Tensile Strain?
ε = ΔL/L ε = Tensile Strain ΔL = Extension (Change in length) L = Natural Length
What is Young Modulus?
The young modulus is the equivalent of the spring constant but scaled to the size and shape of the object so that it is a property of the material, rather than of a particular object
What is the equation for the Young Modulus?
Young Modulus = Tensile Stress / Tensile Strain
= σ/ε = FL/AΔL
What is the gradient of a Stress-Strain graph?
Young Modulus
Define Stiff?
It requires a lot of force to strech it
Define Strong?
It requires a lot of force to break it
Define Brittle?
It breaks without much plastic deformation
Define Ductile?
It can survive a lo of plastic deformation
allows it to be pulled in to thin wires
Define Malleable?
It can be beaten into shape
Define Hard?
The surface cannot be easily scratched
