Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-09 GTBL042-Callister-v3 October 4, 2007 11:53

2nd Revised Pages

312 • Chapter 9 / Failure

Impact energy (J)

100

80

60

40

20

0

100

80

60

40

20

0

–40 0 40 80 120 160 200 240 280

–40 –20 0 4020 60 80 100 120 140

Temperature (°F)

Temperature (°C)

Shear fracture (%)

Impact

energy

Shear

fracture

A

B

Figure 9.19

Temperature

dependence of the

Charpy V-notch

impact energy (curve

A) and percent shear

fracture (curveB) for

an A283 steel.

(Reprinted from

Welding Journal.

Used by permission

of the American

Welding Society.)

and, if so, the range of temperatures over which it occurs. The ductile-to-brittle

transition is related to the temperature dependence of the measured impact energy

absorption. This transition is represented for a steel by curveAin Figure 9.19. At

higher temperatures the CVN energy is relatively large, in correlation with a ductile

mode of fracture. As the temperature is lowered, the impact energy drops suddenly

over a relatively narrow temperature range, below which the energy has a constant

but small value; that is, the mode of fracture is brittle.

Alternatively, appearance of the failure surface is indicative of the nature of frac-

ture and may be used in transition temperature determinations. For ductile fracture

this surface appears fibrous or dull (or of shear character), as in the steel specimen of

Figure 9.20 that was tested at 79◦C. Conversely, totally brittle surfaces have a granular

(shiny) texture (or cleavage character) (the –59◦C specimen, Figure 9.20). Over the

 59  12 4 16 24 79

Figure 9.20 Photograph of fracture surfaces of A36 steel Charpy V-notch specimens tested

at indicated temperatures (in◦C). (From R. W. Hertzberg,Deformation and Fracture

Mechanics of Engineering Materials,3rd edition, Fig. 9.6, p. 329. Copyright©c1989 by John

Wiley & Sons, Inc., New York. Reprinted by permission of John Wiley & Sons, Inc.)