Shear modulus

Question 1

what unit of angle do we use?

Answer 1

radians

Question 2

what is the equation for shear strain?

Answer 2

γ = u/l0

Question 3

what is the equation for shear modulus?

Answer 3

shear stress / shear strain

Question 4

what is the symbol for shear modulus?

Answer 4

G

Question 5

what is the symbol for bulk modulus?

Answer 5

K

Question 6

what is the equation for bulk modulus?

Answer 6

K = -P / (ΔV/V0)

Question 7

what are the methods of obtaining Young’s modulus?

Answer 7

vibration frequency
speed of sound

Question 8

what does stiffness of a solid depend on?

Answer 8

stiffness of chemical bonds
number of bonds across loaded section
direction of loading relative to direction of the bonds

Question 9

what does anisotropic mean?

Answer 9

different physical properties in different directions

Question 10

what is equation for change in bond energy?

Answer 10

dU = F dr
F = force
dr = change inn distance

Question 11

what does bond stiffness relate to?

Answer 11

proportional to melting point of the bond

Question 12

what is the order of bond stiffness values?

Answer 12

covalent
metallic
ionic
hydrogen
van der waals

Question 13

what are the equations for Young Modulus?

Answer 13

E = k/r0 = 1/r0 * (dF/dr)(subscript r0)
r0 = equilibrium bond length
k = bond stiffness
F = force

Question 14

what does Young modulus depend on?

Answer 14

chemical bond strength

Question 15

what is Young’s modulus like for polymers?

Answer 15

has a large temperature dependence

Question 16

how do we predict E for polymers at low temperatures?

Answer 16

using simple van der waals forces

Question 17

what is E like for polymers at high temperatures and why?

Answer 17

much lower
van der waals linking polymer chains together are easily broken by thermal motion of molecules

Question 18

where is elastic limit for polymers?

Answer 18

can be much higher than linear portion of stress strain curve

Question 19

what is the transition between low and high temperatures?

Answer 19

glass transition temperature

Question 20

what is the symbol for glass transition temperature?

Answer 20

T subscript g

Question 21

what can happen to polymers above Tg?

Answer 21

become leathery, rubbery, viscous