5. Materials Flashcards
(17 cards)
What is Hooke’s law?
F=kx
The extension of a stretched wire is proportional to the load or force, F.
What is the limit of proportionality?
The point at which the material no longer obeys Hooke’s law.
What is the elastic limit?
The point at which the material is permanently stretched.
What is an elastic deformation?
When a stretched material has its load removed, it will return to its original extension.
What is plastic deformation?
The material is permanently stretched.
What is breaking stress?
When an object is under stress to the extent that it breaks.
What is ultimate tensile stress (UTS)?
The maximum stress that a material can withstand.
How is the elastic strain energy in a stretched material calculate graphically?
It is the are under the graph of force against extension.
How is the elastic strain energy calculated?
It is the are under the graph of force against extension.
What are elastic and plastic deformations?
In elastic, the material is not permanantly stretched whereas in plastic deformations, it would not return to its initial position.
What is breaking stress?
When the stress on an object is enough to break it.
What is ultimate tensile stress (UTS)?
The max stress that a material can withstand.
How can elastic strain energy be calculated graphically?
Area under a force extension graph.
What is the equation for the work done in extending a string?
E = 0.5kx^2
What is Young’s modulus?
Below the limit of proportionality, it is a constant that is equal to stress / strain.
How do you calculate the energy per unit volume (under the limit of proportionality)?
Energy per unit volume = 0.5 x stress x strain
What are brittle materials?
They simply break after they are deformed too much.
