Call number:
ZSP-201-87/10
In:
CRREL Report, 87-10
Description / Table of Contents:
Uniaxial constant-stress and constant-strain-rate compression tests were conducted on more than 200 remolded, saturated, frozen specimens of Fairbanks silt under various conditions. A series of curves of stress vs strain rate for various temperatures of strain rates ranging from about 6x10-2 to 10-8s-1show a close strength correspondence between the constant-stress and-costant strain-rate tests. All of these "complete" stress vs strain rate curves could not be described by a single power law or exponential equation, indicating that different deformation mechanisms are dominant within different ranges of strainrate Two critical strain rates for distinguishing between the different deformation mechanisms were ob-served to be near 10- 3 and 10-6 s-1 for the medium-dense frozen Fairbanks silt. The former indicates the transition from ductile failure to moderate brittle fracture as strain rate increases, while the latter indicates the transition from dislocation creep to glide creep (by the authors' definition). Based on the change in flow law, two fundamental creeps were classified: short-term creep, which is governed by glide creep, and long-term creep, which is governed by dislocation creep. The failure criterion of frozen silt has a general form of em x tm = Ef, where m depends only on density, and tm is in minutes if m is not 1. The failure strain Ef was not sensitive to temperature and strain rate over a certain range of strain rates, but it was very sensitive to density. Assur's creep model (1980) for ice was used to fit the creep data in this study. It works well for short-term creep but does not fit as well for long-term creep. The rate process theory was applied to the creep data. A very high value of experimental activation energy was obtained for lower stresses, and a very high value of apparent activation energy was observed for higher temperatures. The peak compressive strength was very sensitive to temperature and strain rate but relatively insensitive to density. While the initial tangent modulus is not-sensitive to strain rate, it increases with decreasing temperature and density.
Type of Medium:
Series available for loan
Pages:
vi, 75 Seiten
,
Illustrationen
Series Statement:
CRREL Report 87-10
URL:
https://apps.dtic.mil/dtic/tr/fulltext/u2/a184816.pdf
URL:
https://hdl.handle.net/11681/9029
Language:
English
Note:
CONTENTS
Abstract
Preface
Introduction
Review of previous work
Specimen preparation
Material
Molding
Testing procedure and apparatus
Test results
Definition of strain and stress
Definition of creep failure
Definition of failure in constant-strain-rate tests
Definition of initial yield strength
Determination of initial tangent modulus and 50% peak strength modulus
Creep behavior
General nature of the creep process and the failure mode
Minimum creep rate
Time to creep failure
Relationship between t, and tm
Creep failure strain and failure criterion
Creep model and prediction of creep strain
Strength behavior
General stress-strain behavior and failure mode
Peak compressive strength
Initial yield strength
Failure strain
Initial yield strain
Initial tangent modulus
50% peak strength modulus
Correspondence between constant-stress tests and constant-strain-rate tests
Conclusions
Literature cited
Appendix A: Unfrozen water content data
Appendix B: Physical properties of samples tested
Location:
AWI Archive
Branch Library:
AWI Library
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