Elasticity (Lecture 2 and 3) Flashcards
What is Hookes Law?
The law states that if a tensile (stretching) force F is applied to a spring with a spring constant k, the
extension ∆L of the spring is given by: Force/Spring Constant
What is the equation of Hookes Law?
Change in Length=Force/Springs Constant
L=F/k
What is the Si unit of k?
N m^-1
What does a spring with a high value of K indicate?
It is very stiff (very hard to strech)
In a Hookes Law graph what is the y axis and x axis?
y axis is force
X axis is extension
What does the straight line in a hookes law graph represent?
It represents the springs constant
What is the straight line region called?
Elastic
What does Yield Point mean?
The point at which the material starts to deform plastically
What is the curved region of the graph called?
Plastic
For 2 springs connected in series what is the springs constant equation?
K total= K (1) x K (2)/ K (1) + K (2)
What happens if 2 springs have the same springs constant that are connected in series?
K total= K/2
What is the springs constant if 2 springs are connected in parallel?
K total= K (1) + K (2)
What is the equation if 2 springs connected in parallel have the same springs constant
K total=2k
What is stress equation and its unit?
Force/Area
Pa
What is strain equations and its unit?
Change in Length/Length
No unit
What is Young Modulus equation and its unit?
Stress/Strain
MPa or GPa
Other expressions for Young Modulus?
Young Modulus= (F/A)/(L/L)
E=FL/(Axchange in L)
Change in L=FL/AE
What is Normal Stress
Force which acts normal to the surface area that acts 90 degrees to the contact area.
What is Sheer Force?
When a force acts parallel to the surface area it is called a shear force.
What is a sheer stress?
Thus shear stress is the ratio of shear force to the surface area.
Shear strain is the (small) angle between the undeformed and deformed object after applying the shear
force.
Shear modulus G is the ratio of shear stress to shear strain.
What is Bulk Stress?
In bulk stress, the force is applied to a body equally in all directions and perpendicular to the surface.
Bulk stress is the ratio of such a force to the surface area.
Bulk strain is the ratio of change of volume to the original volume.
Bulk modulus B is the ratio of bulk stress to bulk strain.
What is Ultimate Tensile Stress
Maximum stress that an object can support in theory.
What is the equation of applied stress?
Ultimate Tensile Strength/Safety Factor
What is the value of M?
10^6
What is the value of G?
10^9
What is bending?
When a force is applied and the edges remain curved
