Page 377 - Mechanical Behavior of Materials

378 Chapter 8 Fracture of Cracked Members

240
Rotor Steel : σ , MPa
ο
200
A217, 2.25 Cr-1Mo, cast : 419
200 AISI 403, 12 Cr SS : 682 160
K , Fracture Toughness, MPa m 120 A470, Cr-Mo-V : 626 120 K , ksi in Ic
A471, Ni-Cr-Mo-V : 931
A469, Ni-Mo-V : 590
160

80
80
Ic
40 40

0 0
-200 -100 0 100 200
o
Temperature, C

Figure 8.35 Fracture toughness vs. temperature for several steels used for turbine-generator
rotors. (Data from [Logsdon 76].)

Figure 8.36 Cleavage fracture surface (left) in a 49Co-49Fe-2V alloy, and dimpled rupture
(right) in a low-alloy steel. (Photos courtesy of A. Madeyski, Westinghouse Science and
Technology Ctr., Pittsburgh, PA.)

deformation along specific crystal planes that have low resistance. Dimpled rupture, also called
microvoid coalescence, involves the plasticity-induced formation, growth, and joining of tiny voids
in the material. This process leaves the rough and highly dimpled fracture appearance seen in the
photograph.