A MATERIALS FAILURE RELATION OF ACCELERATING CREEP AS EMPIRICAL DESCRIPTION OF DAMAGE ACCUMULATION

Citation
Rr. Cornelius et Pa. Scott, A MATERIALS FAILURE RELATION OF ACCELERATING CREEP AS EMPIRICAL DESCRIPTION OF DAMAGE ACCUMULATION, Rock mechanics and rock engineering, 26(3), 1993, pp. 233-252
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary","Engineering, Civil
ISSN journal
0723-2632
Volume
26
Issue
3
Year of publication
1993
Pages
233 - 252
Database
ISI
SICI code
0723-2632(1993)26:3<233:AMFROA>2.0.ZU;2-5
Abstract
A general materials failure relation, OMEGA = A OMEGA(alpha), describe s accelerating creep of materials with rate coefficients alpha and A, by relating rates of deformation, OMEGA to changes in deformation rate , OMEGA (Voight, 1988). Time of failure can be extrapolated from inver se rate versus time, data, and alpha and A may be derived to permit on e to calculate the failure time. The method is of value for quantitati ve hazard assessments. Mechanisms leading to damage accumulation durin g accelerating creep include creep fracture by stress corrosion and po wer law lattice deformation. These mechanisms are examined here as phe nomenologically related to the materials failure relation. Apparently, both mechanisms favour alpha congruent-to 2, where alpha is the param eter of the materials failure relation controlling the sensitivity to accelerating activity. For pure shear governed by power law creep of p ower p, under constant load, alpha = 2.0 and A = p. Stress corrosion i s widely described by Charles' equation, relating crack velocity to st ress intensity during subcritical crack growth by the stress corrosion index n. The relationship between n and alpha is given by alpha = (2 n - 2)/n. The quantitative, predictive qualities of the general materi als failure relationship are illustrated with examples from Mount Toc, Italy, and Mount St. Helens, Washington. Six chevron-notched short ba r experiments under constant load serve as examples for accelerating c reep fracture in the laboratory. The experiments were conducted on sil tstones of the Ithaca formation, which show a mean stress corrosion in dex of n = 78 +/- 24. Analysis with regard to the materials failure re lation results in a mean alpha = 2.0 +/- 0.3, which complies with the established relationship between n and alpha.