Holographic Characterization of Ceramics. Part 2. (Observation of Static Fatigue)
Final rept. 15 May 1970-15 Jun 1971
TRW SYSTEMS GROUP REDONDO BEACH CA
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An experiment is described which uses live fringe holographic interferometry to observe static fatigue in glass. A characteristic holographic fringe pattern has been observed which indicates the existence and location of minute flaws propagating in a glass specimen subjected to a constant load. The fringe pattern is observed continuously as the crack propagates through the material thereby permitting detection of impending failure as much as 20 minutes prior to spontaneous fracture. The results of the experiments demonstrate that live fringe holographic interferometry offers the investigator a new technique for the detection, observation, and control of flaw growth in brittle materials. Due to the complexity of rigorous fringe analysis and the lack of a usable mathematical model for deflections caused by a crack in a bending beam, the results of these experiments are discussed in a semi-quantitative fashion. The ability of holographic interferometry to obtain both qualitative and quantitative data coupled with the highly coherent pulsed ruby laser system discussed in Part I of this program could permit the application of these techniques to design oriented failure problems as well as theoretical fracture studies.
- Ceramics, Refractories and Glass
- Test Facilities, Equipment and Methods