- Tensile Deformation
- Compressive Deformation
- Elastic Deformation
- Plastic Deformation
- Elastic Limit
Tensile Deformation: Changes shape under tension.
Compressive Deformation: Changes shape under compression.
Elastic Deformation: Goes back to its original shape.
Plastic Deformation: Permanent change in shape.
Elastic Limit: Stretched beyond the elastic limit, causes plastic deformation.
What is the equation for HOOKE'S LAW?
F = kx
k is the spring constant
k = F ÷ x
Gradient of a Force vs Extension graph.
State HOOKE'S LAW.
The extension of a spring is directly proportional to the force applied.
This is true as long as the elastic limit of the spring has not been exceeded.
What is this?
A hysteresis loop.
What DOES NOT obey HOOKE'S LAW?
Rubber bands do not obey Hooke's Law.
What is the equation for STRESS and what are its UNITS?
σ = F ÷ a
Units : Nm² or Pa
What is the equation for STRAIN and what are its UNITS?
Σ = Extention ÷ Original Length
Σ = x ÷ L
Strain has no units, it is a ratio or a percentage.
State what each point on the graph represents.
P : Limit of proportionality - Hooke’s Law no longer obeys at this point.
E : Elastic limit.
Y1 & Y2: The yield point - The wire is about to give
UTS (Ultimate Tensile Strength) : Stress at its limit - About to break - The wire begins to thin out.
What is the equation for THE YOUNG MODULUS and what are its UNITS?
σ ÷ Σ
Stress ÷ Strain
Units: Pa or Nm²
How do you calculate the GRADIENT on a STRESS vs STRAIN GRAPH?
σ ÷ Σ
The Young Modulus is the gradient, which relates to te stiffness of the material.
What is the equation for ELASTIC POTENTIAL ENERGY?
For a spring that obeys Hooke's Law:
F = ½kx²