Destructive Testing
Destructive testing is any method of evaluating failure properties of materials and structures which requires loss or failure of the specimen or system. In many ways the only "true" way to fully know and verify at what limits something will fail is to destroy it. In many cases however, it is not practical to destroy something to determine what it can withstand. For larger structures, the creation alone of scale copies of skyscrapers for destructive testing purposes would be infeasible due to cost, space, and time. There are cases of destructive testing being performed on large structures or systems, like the aircraft crash tests such as those performed by NASA or scale aircraft structure tests, but overall large systems are not tested destructively. Even in smaller complex systems, the cost and time for creating and destroying a copy of the final product may be impractical.
Destructive testing is very applicable on a component basis, rather than on the entire system of components. For testing individual, small, inexpensive parts, it is reasonable to test a number of the parts to failure to characterize the part's behavior. In cases where individual parts are too large or expensive to waste in destructive testing, material properties can be estimated for the part by destructively testing a small representative sample of the materials. One example is the methods for tensile testing of metals as prescribed by the American Society of Testing and Materials (ASTM)[1]. The document ASTM-E8 provides appropriate destructive testing methods for determining yield strength, tensile strength, elongation, and area reduction from representative specimens. It is important to keep in mind that these are based on representative specimens and there may be some variation in materials even from batch to batch.
In the end, the best-case scenario from destructive testing, is an estimation of how a part may fail. However, this does not provide detailed information about the state of a current part in service. This is where nondestructive evaluation is essential. Nondestructive evaluation can provide information about a specific part or system that is in service without damaging it, and it can be applied in cases where there is only a single instance of the part or system of interest.
References and Resources
- ASTM, "E8 Standard Test Methods of Tension Testing of Metallic Materials", Annual Book of ASTM Standards, American Society for Testing and Materials