mechanical properties

Question 1

how is stiffness measured

Answer 1

k=stiffness (N/m)

amount of force required to stretch material by L

Question 2

what is wrong with the measure for k (stiffness)

Answer 2

depends on geometry but we want to know about the material only

Question 3

engineering stress

Answer 3

o- = F/A

Question 4

engineering strain

Answer 4

e= delta L/L

Question 5

slope of stress-strain curve

Answer 5

young’s elastic modulus (E)

Question 6

what is the transition called from elastic to plastic deformation

Answer 6

yield stress/strength

Question 7

yield stress/strength is used for what?

Answer 7

• indicates the transition from elastic to plastic

- represents the 0.2% offset we use for metals

Question 8

what happens as you continue to stretch a material past the proportional limit

Answer 8

necking

Question 9

true stress compared to engineering stress after the proportional limit

Answer 9

-true will be the higher curve because its based on instantaneous A and L

Question 10

brittle materials

Answer 10

-has some plastic deformation but fails quickly

Question 11

ductile materials

Answer 11

much more plastic deformation compared to brittle

Question 12

resilience

Answer 12

energy absorbed per unit V to proportional limit

Question 13

toughness

Answer 13

energy absorbed per unit V to failure

Question 14

brittle and ductile materials have the same/diff resilience?

Answer 14

same resilience

Question 15

viscoelasticity is dependent on what

Answer 15

time

Question 16

creep

Answer 16

constant stress, different strain

Question 17

stress relaxation

Answer 17

diff stress, constant strain

Question 18

fast fracture

Answer 18

stress reaches ultimate strength

Question 19

fatigue fracture

Answer 19

a force below ultimate strength that is applied until fast fracture occurs