Page 270 - Fiber Fracture

FRACTURE OF SUPERFINE METALLIC WIRES 253

d

1 Metallic inclusion
U
Nonmctallir inclusion
0
1 I . I
0. 02 0. 04 0. 06 0.08 0. 1
Rcduccd diameter of wirc D, (nm)
Fig. 12. Relationship between the inclusion diameter for wire breakage and the reduced diameter of a wire.

Simulation in Which Peeling at the InclusionlMatrix Boundary is Considered

In the above analysis, the inclusion and the base material were completely bonded at
their boundary. However, in reality, the inclusion and matrix are often detached at the
boundary; therefore, the author performed simulations in consideration of this fact. The
inclusion size was set at Di/Do of 0.8, and the inclusion length was set to be L/Do of
0.78.
When an inclusion passes through a die, since tensile stress acts in the drawing
direction at the center of the wire, an internal crack occurs at the boundary in front of
the inclusion. Fig. 13 shows an example of the formation process of the internal crack,
demonstrating the growth of the internal crack with increasing drawing length. Since the

Fig. 13. Internal fracture formation and growth as the drawing length increases during wiredrawing.