Materials Flashcards
Define the density of a substance
density = mass / volume
State Hooke’s law
extension of a spring is directly proportional to the force exerted on it
Define elastic deformation
A material returns back to it’s original shape and size once forces are removed
Define plastic deformation
A material remains permanently deformed so does not return to it’s original shape when forces are removed
What is the elastic limit of a material?
the point beyond which it becomes permanently deformed
What does the area under the line of a f-e graph for an object represent?
work done on an object / total elastic potential energy stored by it
What happens to the elastic potential energy of and elastically-deformed object when the force is removed?
transfers to other energy stores
What causes an object to be under tension?
forces acting on it are stretching it
Define tensile stress on an object
stress = F/A
Define tensile strain on an object
stress = change in L / L
What is the Young modulus of a material?
Measure of the material’s stiffness in Nm^-2 or Pa
Define the limit of proportionality in a material
The point up to which stress and strain are proportional
How can the Young modulus of a material be found?
gradient of it’s initial straight line section in a stress-strain graph
What does the area under the straight line section of a material’s stress strain graph represent?
Energy stored in the material per unit volume
What does the first yield point on a material’s stress-strain graph represent?
stress at which the material suddenly weakens and stretches plastically without any additional force
