Yr 12 - Behaviour of Materials Flashcards
Plastic Deformation
Irreversible deformation of a material.
Elastic Deformation
Reversible deformation of a material.
Stiffness
Extent to which an object resists deformation.
Hookes Law
Extension is proportional to the force applied provided the limit of proportionality is not exceeded.
F = K x
Gradient = Force constant
Force Constant
Amount of force required to produce an extension of one metre.
Describe how to find information on a Force-Extension graph.
M (Gradient) = Spring Constant
Area (Under Graph) = Elastic Potential
Therefore, Ep = 1/2 f x
Why does 1/2 appear on a Force-Extension graph?
Need to use Average force
- Average force = (Final Force - Initial Force) / 2
- Initial force = 0
- Therefore = 1/2 final force (Ep = 1/2 f x)
What happens to the Force Constant in series.
And what is a series circuit.
1/Kt = 1/K1 + 1/K2 etc
(Components connected in a single path)
What happens to the Force Constant in parallel.
And what is a parallel circuit.
Kt = K1 + K2 etc
(Current has multiple paths to flow)
F ∝ x (In opposite direction to displacement)
?? Check with Sir
Stress
Equation and unit
Force per unit cross-sectional area
(NM^-2).
Strain
Equation and unit
Strain = Deformation of a material compared to its original length.
(No units)
Youngs Modulus
Equation and unit
E = 𝛔 (Sigma) / ε (Epsilon)
- Measure of stiffness (Pa)
Ultimate Tensile Strength (UTS)
Max stress before breaking.
Elastic Limit
Max stress before irreversible deformation.
Limit of Proportionality
Max stress where Stress ∝ Strain.
Yield Point
Max stress before material becomes plastic.
Elastic Region
Region where deformation reversible.
Tough
Withstand large dynamic (moving) forces without breaking.
Strong
Withstand large static (Non-moving) forces without breaking.
Hard
Resistance to dents and scratches.
Brittle
Little deformation before fracture.
Ductile
Easily drawn into a wire.
Polymeric
Stretches under a massive strain before breaking.
Hysteresis loop
Lag between input and output due to a change in direction of force.
Describe a Stress-Strain graph. (3)
- Hysteresis loop
- Area = Energy transferred / volume
- Grad = Youngs Modulus (Indicated Stiffness)
What graph do you use to plot results from the Young Modulus experiment? (not completed)
- Extension - Tension (Mg)
- Grad = extension
