Page 334 - Mechanical Behavior of Materials

Section 8.1 Introduction 335

Figure 8.1 Photographs from a propane tank truck that exploded due to fracture from
initial environmental cracks in welds. Typical initial cracks are shown from a region that did
not participate in the final failure. (Photos courtesy of H. S. Pearson, Pearson Testing Labs,
Marietta, GA, lower left, upper and lower right, published in [Pearson 86]; copyright
c ASTM; reprinted with permission.)

In addition to cracks themselves, other types of flaws that are cracklike in form may easily
develop into cracks, and these need to be treated as if they were cracks. Examples include deep
surface scratches or gouges, voids in welds, inclusions of foreign substances in cast and forged
materials, and delaminations in layered materials. For example, a photograph of a crack starting
from a large inclusion in the wall of a forged steel artillery tube is shown in Fig. 8.2.