3. Elastic Properties

Question 1

Elastic deformation is _____ and ____

Answer 1

non-permanent

reversible

Question 2

What is Youn’s Modulus a measure of ?

Answer 2

stiffness

Question 3

symbol for stress?

Answer 3

sigma

Question 4

symbol for strain?

Answer 4

epsilon

Question 5

Symbol for youngs modulus

Answer 5

E

Question 6

stress =

Answer 6

F/A

where F is force and A is the cross sectional area

Question 7

strain =

Answer 7

(li-lo)/lo = ∆l/lo

Question 8

what is E on the sigma vs epsilon graph?

Answer 8

the slope

Question 9

what is MOR on the sigma vs epsilon graph?

Answer 9

the area under the curve

Question 10

Define resilience

Answer 10

the recoverable energy absorbed by a material during elastic deformation

Question 11

what is youngs modulus on the stress vs strain graph?

Answer 11

the slope

Question 12

what is modulus of resilience on the stress vs strain graph?

Answer 12

the area under the curve

Question 13

what characterizes the contraction perpendicular to the extension caused by a tensile stress?

Answer 13

the poisson ratio (v)

Question 14

what does isotropic mean?

Answer 14

the material has the same properties in all directions

Question 15

what is the equilibrium interatomic distance?

Answer 15

the distance between molecules which is the lowest energy

Question 16

where is ro on the U(r) vs r graph?

Answer 16

at the minimum

Question 17

where is ro on the F(r) vs r graph?

Answer 17

at the x-intercept

Question 18

what does the slope of the line tangent to ro on the F(r) vs r graph represent

Answer 18

stiffness of the bond aka Youngs Modulus (E)

Question 19

what two things (on an atomic basis) is E a function of?

Answer 19

i) Bond Stiffness (dF/dr)

ii) density of bonds (i.e. atomic packing)