Materials Flashcards
(17 cards)
Malleable
Material can be hammered or beaten into flat sheets and will show extensive plastic deformation when subjected to compressive forces
Brittle
Material will break with little/no plastic deformation
Hard
Material will resist plastic deformation by surface indentation/scratching
Stiffness
Abilitis of a material to resist tensile force
Polymeric
Material is made of long chains of molecules called polymers
Ultimate tensile strength
Maximum stress it can withstand while being pulled/stretched, before it fail/breaks
Ductile
Material can be drawn into wires and will show plastic deformation under tensile stress before breaking
Elasticity
The property of a body to resume its original shape/size once the deforming force/stress has been removed as
Deformation
The change in shape/size of an object. If the material returns to its original shape then the deformation is elastic; if not, then it’s deformation is plastic
Describe plastic behaviour
When the deforming force is removed -> material remains stretched ∵ exceeded its elastic limit
What’s Hooke’s law?
States that the extension of an object is proportional to the force that causes it, provided the elastic limit is not exceeded
F=kx
What is stress?
The force per unit area
Nm-² or Pa
Strain
Extension per unit length
Describe the graph of a rubber material
- elastic
- doesn’t obey Hookes law
- loading + unloading graphs are different ∴ showing heat has been lost
What’s the assumption when using the eqt Y = Fl/eA
Hooke’s law obeyed ∴ elastic limit not exceeded
Explain why the force constant of 2 identical springs in series is k/2
Extension is doubled
Force is the same
∴ k is halved
Explain why k of 2 springs in parallel is 2k
extension is halved ∵ force on each spring is halved
∴ k doubles
