Chapter 6 - Materials Flashcards
(17 cards)
What is tensile deformation?
When a material stretches as a result of a force.
What is compressive deformation?
When a material squashes as a result of a force.
State Hooke’s law.
The extension of a wire is directly proportional to the force acting upon it (F=kx).
What is elastic deformation?
Spring returns to original length when force is removed.
What is plastic deformation?
Spring does not return to original length after force is removed.
Define stress.
Force applied per unit cross sectional area of a wire.
Define strain.
The fractional change in the original length of the wire.
Define Young modulus.
The ratio of stress & strain for a particular material.
Define ultimate tensile stress.
The maximum stress a material can withstand before breaking.
What is the limit of proportionality on a stress-strain graph?
The point where the material stops obeying Hooke’s law and the gradient decreases.
What is the elastic limit on a stress-strain graph?
The point from where the material will no longer return to its original shape once the force is removed.
What is the yield point on a stress-strain graph?
The point at which the material starts to stretch without any extra load.
What does the stress-strain graph for a brittle material look like?
A straight line through the origin.
What does the stress-strain graph for a ductile material look like?
A straight line which then curves downwards twice before breaking.
What does the stress-strain graph for rubber look like?
A curved line when loading, with a similar line below it when unloading.
Why does the graph for rubber look like that?
Some of its elastic potential energy is converted to heat when it is stretched.
Define elastic potential energy.
The energy stored in an object when it is stretched or squashed.
