Mechanical properties of mater Flashcards
What is the symbol for tensile stress?
sigma
What is the equation for tensile stress?
sigma = F/A
What does strain tell us?
How much something has changed by compared to it’s original length.
What is the symbol for strain?
Epsilon
What is the equation for strain?
Epsilon = x/L where x is the extension and L is the original length.
What are the units for stress?
Nm^-2
What are the units for strain?
Doesn’t have any units.
What is the symbol for Young’s modulus?
E
What is the equation to calculate Young’s modulus of a material?
E = stress/strain
What is the typical YM of steel?
210GPa
What is Young’s modulus a measure of?
The stiffness or a material.
What are the units for YM?
Pa or Nm^-2
Define Tensile stress.
The tension force per unit cross-sectional area of a material.
Define Tensile strain.
The extension per unit length of a material
Define Young’s modulus.
The tensile stress per unit tesnile strain.
Sketch a stress-strain graph labelling with the elastic limit, yield point, limit of proportionality and UTS.
Look at notes!
Define UTS.
Ultimate Tensile strength- the maximum stress a material can withstand before fracture.
Define Elastic limit.
The value if stress or force beyond which elasrtic deformation becomes plastic deformation; the material will not retun to its original shape and size when the stress or force is removed.
What can strain of 0.012 be written as?
1.2%
How would you describe copper?
Ductile
Define brittle.
A material that distorts very little even when subject to a large stress and does not exhibit much plastic deformation; for example, concrete or glass.
Define polymetric.
Materials that consist of long molecular chains; they experience a high strain beofre braking.
Define ductile.
Materials that have a large plastic region and therefore they can be drawn into a wire; for example copper.
Draw a hysterisis loop for: rubber, polyethene and a matal wire.
Look at notes!
Define a hysteresis loop.
A loop-shaped plot obtained when loading and unloading a material produce different deformations.
When determining the YM what do you do with the diameter of the wire?
Measure it in 3 different places along the wire using vernier callipers.
What is the best value for L which is the length from the block to the marker?
The longest possible value you can get will give you more accurate results.
How would you clauclate the YM using the gradient from the graph x against mg?
E = L/A x gradient.
