Influence of Rock Anisotropy and Time-Dependent Deformation on the Stress-Relief and High-Modulus Inclusion Techniques of

2009 ◽  
pp. 190-190-17 ◽  
Author(s):  
D S Berry ◽  
C Fairhurst
Keyword(s):  
Stress Relief ◽  
Time Dependent ◽  
High Modulus ◽  
Rock Anisotropy

An estimate of rebound potential of the Shaftesbury shales at a damsite in British Columbia

1992 ◽  
Vol 29 (3) ◽  
pp. 375-392 ◽  
Author(s):  
A. Hanna ◽  
T. E. Little
Keyword(s):  
British Columbia ◽  
Swelling Pressure ◽  
Stress Relief ◽  
Time Dependent ◽  
Swelling Properties ◽  
Deep Excavations ◽  
Hydroelectric Project ◽  
Stress Changes ◽  
Swelling Characteristics ◽  
Pressure Stress

The hydraulic structures of the proposed site C hydroelectric project in northeastern British Columbia would require deep excavations in Lower Cretaceous Shaftesbury shales. A significant stress relief would occur over most of the area to be occupied by the structures. Concerns about the magnitude and rate of time-dependent rebound and their impacts on project design, construction, and operation have been addressed. A review was made of several important case histories of other major projects constructed on Prairie shales. The properties of those shales were compared with the Shaftesbury shales. Long-term testing to establish the shale swelling characteristics was performed. Analyses were then made to evaluate potential elastic and time-dependent rebounds of the project area. A procedure for computing stress changes and time-dependent deformations due to the unloading effect of excavation followed by structural loading was developed. The procedure is useful in determining differential rebound that would occur in areas of steep topography or significant variations in the distribution of structural loads. Key words : rebound, shales, dam, swelling properties, swelling pressure, stress relief, deep excavations.

A Model for Time-dependent Microcrack Growth Due to Stress Relief and Residual Stress.

1994 ◽  
Vol 110 (7) ◽  
pp. 559-565
Author(s):  
Harumi KATO ◽  
Osam SANO ◽  
Yoshiaki MIZUTA
Keyword(s):  
Residual Stress ◽  
Stress Relief ◽  
Time Dependent ◽  
Microcrack Growth

EXELFS Studies of Carbon Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 72-73
Author(s):  
V. Serin ◽  
K. Hssein ◽  
G. Zanchi ◽  
J. Sévely
Keyword(s):  
Carbon Fibers ◽  
Energy Analysis ◽  
Electron Excitation ◽  
Complex Structures ◽  
High Modulus ◽  
Promising Technique ◽  
X Ray ◽  
Fine Structures ◽  
X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

TEM investigations of surface residual stress relaxation in A12O3 and Al2O3-SiC nanocomposite

1994 ◽  
Vol 52 ◽  
pp. 628-629
Author(s):  
J. Fang ◽  
H. M. Chan ◽  
M. P. Harmer
Keyword(s):  
Residual Stress ◽  
Single Phase ◽  
Stress Relief ◽  
Stress Recovery ◽  
Surface Residual Stress ◽  
Microscopic Mechanism ◽  
Sic Particles ◽  
Annealing Procedure ◽  
The Difference ◽  
Nano Size

It was Niihara et al. who first discovered that the fracture strength of Al2O3 can be increased by incorporating as little as 5 vol.% of nano-size SiC particles (>1000 MPa), and that the strength would be improved further by a simple annealing procedure (>1500 MPa). This discovery has stimulated intense interest on Al2O3/SiC nanocomposites. Recent indentation studies by Fang et al. have shown that residual stress relief was more difficult in the nanocomposite than in pure Al2O3. In the present work, TEM was employed to investigate the microscopic mechanism(s) for the difference in the residual stress recovery in these two materials.Bulk samples of hot-pressed single phase Al2O3, and Al2O3 containing 5 vol.% 0.15 μm SiC particles were simultaneously polished with 15 μm diamond compound. Each sample was cut into two pieces, one of which was subsequently annealed at 1300° for 2 hours in flowing argon. Disks of 3 mm in diameter were cut from bulk samples.

Autonomous self-healing polyisoprene elastomers with high modulus and good toughness based on the synergy of dynamic ionic crosslinks and highly disordered crystals

2020 ◽  
Vol 11 (41) ◽  
pp. 6549-6558
Author(s):  
Yohei Miwa ◽  
Mayu Yamada ◽  
Yu Shinke ◽  
Shoichi Kutsumizu
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Self Healing ◽  
High Modulus ◽  
Disordered Crystals ◽  
Ionic Crosslinks

We designed a novel polyisoprene elastomer with high mechanical properties and autonomous self-healing capability at room temperature facilitated by the coexistence of dynamic ionic crosslinks and crystalline components that slowly reassembled.

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