Materials Flashcards
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
