CHAPTER 8

Question 1

What is a simple fracture?

Answer 1

The separation of a body into two or more pieces in response to static stress

Question 2

How does fracture stress vary with the size of the specimen dimension?

Answer 2

Fracture stress increases as dimension decreases

Question 3

How is it that the measured fracture strength of most materials are usually lower than the predicted?

Answer 3

Due to microscopic flaws (cracks)

Question 4

What are the types of fracture?

Answer 4

Ductile
- slow crack propagation
-accompanied by significant plastic deformation

Brittle
-rapid crack propagation
-little to no plastic deformation

Question 5

What is favoured more, ductile or brittle fracture and why?

Answer 5

Ductile…fails with more warning

Question 6

On brittle surface photographs, where do the V-shaped forms point to?

Answer 6

the crack initiation site

Question 7

What are the types brittle crack propagations

Answer 7

Intergranular - between grains
Transgranular - through grains

Question 8

When is Kc independent from the thickness of the specimen?

Answer 8

when thickness is much greater than the crack dimensiokn

Question 9

What are the conditions for brittle test

Answer 9

-High strain rate
-Deformation at low temperatures
-Presence of a notch

Question 10

How does BCC metals behave as temperature increases for impact tests?