X-Ray Computed Tomographic Inspection of Castings
Casting is an economical way to manufacture parts. On average, complex aerospace castings incur about one-fourth the cost of forgings. However, castings can not be used as primary structure in aircraft because of poor control over design allowables for the material strength and ductility. They can be used as secondary structure, but must include significant safety factors — usually between 3 and 6. The safety factor increases the overall weight of the casting, which defeats the cost and weight savings that castings offer. Finally, the criteria for accepting castings has very little to do with their ability to provide operational service. That is, the present inspection criteria are not requirements on casting performance, but rather comparison to a qualitative standard. If a method of nondestructive evaluation of castings could be implemented that would allow a quantitative analysis of the casting suitability for service, then a significant increase in casting utilization with a reduction in design weight and overall product cost may be possible.
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