Lecture 7- failure

Question 1

What TWO main things can happen to
materials beyond elastic deformation?

Answer 1

-Fracture
-Plastic deformation

Question 2

Define Elastic Recovery

Answer 2

if load is removed before yield stress, material returns to original dimensions

Question 3

Define Yielding and plastic deformation

Answer 3

permanent change of shape

Question 4

Define Creep

Answer 4

increase of strain at constant stress

Question 5

define fracture

Answer 5

cracking and separation of 2 or more parts

Question 6

define wear

Answer 6

removal of material from surfaces that are in contact due to friction

Question 7

define fatigue

Answer 7

failure under repeated (cyclic) loading

Question 8

How can you find yield stress on a stress-strain curve?

Answer 8

0.2% offset from linear region or when the graph peaks

Question 9

How can you find ultimate tensile stress on a stress strain curve?

Answer 9

highest point on the curve

Question 10

if a metal has a yield drop, how does that show on the material?

Answer 10

luder bands or stretcher strains, are formed

Question 11

What is the relationship between strength and ductility for alloys?

Answer 11

the stronger the metal, the less ductile it is.

Question 12

What are the 4 ways we can change the shape of a metal through stressing them beyond their yield point?

Answer 12

• rolling
  -extrusion
  -forging
  -sheet forming

Question 12

what enables plastic deformation?

Answer 12

defects in the structure