Section 1 Raw Material Defects

2. Case 4: Shell cracking

Material: 6A02-H112.

Failure background: During the inspection process of a certain model of product, two shells cracked, as shown in Figure 5-15.

Failure characteristics: The fracture modes of the two shells are brittle cracking (see Figure 5-15a) and tearing (Figure 5-15b and Figure 5-15c). There are obvious inclusions in the fracture, and there is interlayer phenomenon in the fracture, as shown in Figure 5-16; there is blistering on the inner surface of the shell in the area near the fracture, as shown in Figure 5-17. A small number of cracks on the outer wall and inner cavity of the unused shell were detected, as shown in Figure 5-18 and Figure 5-19; after low-magnification tissue inspection, there were obvious cracks in the extension direction of the shell crack source. Scratch damage, as shown in Figure 5-20; after high-magnification tissue analysis and inspection, it was found that there are inclusions in the tissue at the crack of the shell, as shown in Figure 5-21.

Figure 5-15 Two cracked shell fragments

Figure 5-16 Interlayer phenomenon existing in the fracture surface

Figure 5-17 Blistering phenomenon on the inner surface of the shell near the fracture

Figure 5-18 Crack sources on the outer wall of the shell

Figure 5-19 Crack sources on the shell

Figure 5-20 Low-magnification structural inspection sample, crack sources and scratch damage defects on the outer wall of the shell

Figure 5-21 High-magnification tissue image of the crack

Reason for failure: After sampling and analyzing 100% of the remaining raw materials for the production of tube shells, it was found that 2% of the aluminum rods had shrinkage defects, as shown in Figure 5-22 and Figure 5-23. The shrinkage defects are The length runs through the entire low-magnification sample (about 100mm).

Figure 5-22 Appearance of aluminum rod with shrinkage defect

Figure 5-23 High-magnification tissue morphology of shrinkage defect