Fatigue Crack Propagation in Freshwater Ice
The study describes an investigation of the fracture toughness and fatigue behavior of granular and columnar S2 freshwater ice. A four point bend single edge notched beam was used throughout. The fracture toughness of columnar ice was found to be temperature independent between -5 and -45 deg C. In...
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| Format: | Text |
| Language: | English |
| Published: |
1993
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| Subjects: | |
| Online Access: | http://www.dtic.mil/docs/citations/ADA271086 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA271086 |
| Summary: | The study describes an investigation of the fracture toughness and fatigue behavior of granular and columnar S2 freshwater ice. A four point bend single edge notched beam was used throughout. The fracture toughness of columnar ice was found to be temperature independent between -5 and -45 deg C. In contrast, granular ice exhibited a higher toughness than columnar ice between -5 and -20 deg C. At -45 degrees C, granular ice had the same toughness as the columnar ice. The differences in behavior are due to micro-structural differences in the two ice types, as shown by scanning electron micrography. The internal friction response of the granular and columnar ice was determined as a function of both frequency and amplitude. The results are consistent with a Granato-Lucke type dislocation damping model. A new technique has been developed to measure sub- critical crack growth in ice, using a low powered laser mounted on an X-Y vernier. Fatigue crack growth in ice has been observed and Quantified. Three stages are evident: Initial growth may be termed classic ductile fatigue. This is followed by a period of brittle fatigue, then finally by crack arrest. The final two stages develop as the crack becomes shielded by cycling dislocations. |
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