Downloaded from https://www.everyspec.com "AMCP 70I N CHAPTERi 8 NONDESTRUCTIVE EVALUATION 8-1 INTRODUCTION Nondestructive evaluation (NDE) does not method in parallel with the development of degrade the item to which it is applied, the the system to be tested, phrase "nondestructive testing" (NDT) is used to describe similar activities, but Is usually Most NDE methods do not measure a param- considered to be Ion general than NDE. eter or characteristic directly, but measure Techniques such as infrared scanning and some more eisily observed phenomenon that X.ray radiography can be employed toэ %an be vorrelated with the desired character- Istic. For example, th, uniformity of a 1.
Prevent destruction of iteuul while material can be inferred by observing magnetic measuring properties that usually would re- flux perturbations or ultrasonic energy re- quire destruction If measured by conventional flectioni, On the other hand, methods like techniques, and/or X-ray radiography permit more direct ob- Psrvation. Table 8-2 summarizes typical char- 2. Permit certain measurements to be made acteristics of many NDE methods. more rapidly and conveniently than con- ventional techniques allow. 8.2 OPTICAL METHODS The major application areas of NDE are Optical techniques use microscopes, magni- Illustrated in Table 8.1. In research and fying glasses, interferometers, etc.
to detect development, NDE can be used to measure and the presence of surface flaws, anomallev, and evaluate special properties of materials. Use- malfunctions. A permanent record of surface ful proces control information con be gSn- conditions and outward appearance can be erated from NDE which monitors the pro- obtained by photography, This method can duction process. NDE is valuable in quality provide excellent permanent records, but can control where items and materials can be only detect and record surfice phenomena. evaluated without destructive sampling. NDE also can be used to measure wear and deteri- Microscopes provide a maximum maifp- orstion of in-service items.
'\ cation on the order of 2000 with field-of-view and depth-of-field decreasing with increasing In NDE, items art observed, measured, ex- magniflcation, Interferometer microscopes posed to X rays, magnetized, vibrated, offer depth measurements In the low micro- acoustically excited, heated, etc. No one form meter region, The capabilities of the micro- of energy nor any one NDE method can scopir approach are greatly expanded by answer all NDE requirements, Each technique using electron microscopes. has its limitations and many of the methods complement one another.
On some projects, Optical microscopy and photographic it may be necessary to develop a speoal NDE techniques can be combined to product, . .. . ....... . . ... ... . . .. .. . . . . .. .. ... .. .. .. . .... ........... .