STEEL - Materials for Civil and Construction Engineers - page 121

Notch Notch

Ductile, shear area
(dull, grey)

Brittle, cleavage area
(shiny, salt and pepper)

(a) (b)

FIGURE 3.20 Fracture surface of Charpy V notch specimen: (a) at high
temperature and (b) at low temperature.

shows that the required energy is high at high temperatures and low at low
temperatures. This indicates that the material changes from ductile to brit-
tle as the temperature decreases.
The fracture surface typically consists of a dull shear area (ductile) at
the edges and a shiny cleavage area (brittle) at the center, as depicted in
Figure 3.20. As the toughness of the steel decreases, due to lowering the
temperature, for example, the shear area decreases while the cleavage area
increases.

Sample Problem 3.5

A Charpy V Notch (CVN) test was performed on a steel specimen and produced the
following readings:

Temperature Toughness

( F) (ft.lb)

°

- 40

5

30 7

100 28

170 66

240 79

310 80

Plot the toughness-versus-temperature relation, and determine the temperature
transition zone between ductile and brittle behavior.

Solution
The toughness-versus-temperature relation is as shown in Figure SP3.5. From the fig-
ure, the temperature transition zone between ductile and brittle behavior can be seen
to be 30 to 240F.