MATERIALS ENGINEERING FOR COLD REGIONS AND THE BRITTLE FRACTURE PROBLEM
ARMY MATERIALS RESEARCH AGENCY WATERTOWN MA
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Most rubber and plastics materials lose flexibility and become dangerously embrittled in cold regions, although certain classes of these nonmetallic engineering materials are available which are serviceable even at extremely low temperatures. Low temperature mechanical behavior of a metal can be correlated with its intrinsic crystallographic structure. In addition to crystal structure, factors such as chemical composition, purity, heat treatment and processing variables influence behavior of metallic materials at low temperatures. In cold environment, most engineering metals actually become stronger, but they lose ductility and become dangerously brittle. Thus, the major problem at low temperatures is brittle fracture. The presence of notch defects, particularly in the case of high strength alloys, plays a predominant role in contributing to sudden brittle fracture. The V-notch Charpy impact test has been used effectively as an inspection criterion for screening brittle materials for armor, cannon and other military applications. Parameters based on rational fracture mechanics concepts, although not yet adequate for prevention of brittle behavior.
- Properties of Metals and Alloys