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.
a) Brittle cracking
b) tear the bottom of the shell c) tear the upper part of the shell
Figure 5-15 Two cracked shell fragments
Figure 5-16 Interlayer phenomenon existing in the fracture surface
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Figure 5-17 Blistering phenomenon on the inner surface of the shell near the fracture
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Figure 5-18 Crack sources on the outer wall of the shell
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Figure 5-19 Crack sources on the shell
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Figure 5-20 Low-magnification structural inspection sample, crack sources and scratch damage defects on the outer wall of the shell
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Figure 5-21 High-magnification tissue image of the crack
Failure mode: brittle fracture.
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).
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Figure 5-22 Appearance of aluminum rod with shrinkage defect
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Figure 5-23 High-magnification tissue morphology of shrinkage defect
The shrinkage defects on the raw material are transferred to the shell after punching, resulting in cracks on the shell. Due to the different distribution patterns of the cracks on the shell, the shell cracks have different shapes, resulting in the shell being damaged during use. Invalid. Corrective measures: Strengthen inspection work during the inspection process after surface treatment, and remove shells with abnormalities on the surface.
Characteristic operations and practical cases of machining
This book focuses on the unique operating methods of turning processing, special fixtures, special measuring tools, testing and other manufacturing experience and knowledge, various turning processing cases, classic solutions for CNC tools, difficult parts processing cases and product failure analysis, etc. It is the crystallization of the unique skills of skill master Meng Xiangzhi and the valuable practical experience of the core members of the studio for many years. It has a very good role in promoting technical exchanges and promotion of results.
