ISSN:
1434-453X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Architecture, Civil Engineering, Surveying
,
Geosciences
Notes:
Summary A general materials failure relation, $$\ddot \Omega = {\rm A}\dot \Omega ^\alpha$$ , describes accelerating creep of materials with rate coefficients α andA, by relating rates of deformation, $$\dot \Omega$$ , to changes in deformation rate, $$\ddot \Omega$$ (Voight, 1988). Time of failure can be extrapolated from inverse rate versus time data, and α andA may be derived to permit one to calculate the failure time. The method is of value for quantitative hazard assessments. Mechanisms leading to damage accumulation during accelerating creep include creep fracture by stress corrosion and power law lattice deformation. These mechanisms are examined here as phenomenologically related to the materials failure relation. Apparently, both mechanisms favour α≅, where α is the parameter of the materials failure relation controlling the sensitivity to accelerating activity. For pure shear governed by power law creep of powerp, under constant load, α=2.0 andA=p. Stress corrosion is widely described by Charles' equation, relating crack velocity to stress intensity during subcritical crack growth by the stress corrosion indexn. The relationship betweenn and α is given by α=(2n−2)/n. The quantitative, predictive qualities of the general materials failure relationship are illustrated with examples from Mount Toc, Italy, and Mount St. Helens, Washington. Six chevron-notched short bar experiments under constant load serve as examples for accelerating creep fracture in the laboratory. The experiments were conducted on silstones of the Ithaca formation, which show a mean stress corrosion index ofn=78±24. Analysis with regard to the materials failure relation results in a mean α=2.0±0.3, which complies with the established relationship betweenn and α.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01040117
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