A shear failure strength law of rock in the brittle-plastic transition regime

1995 ◽  
Vol 22 (1) ◽  
pp. 25-28 ◽  
Author(s):  
Mitiyasu Ohnaka
Keyword(s):  
Shear Failure ◽  
Transition Regime ◽  
Failure Strength

The Effect of Notches on the Failure of Two-Dimensional Nonwoven Fiber Networks

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Yinglong Chen ◽  
Thomas Siegmund
Keyword(s):  
Fiber Orientation ◽  
Shear Failure ◽  
Fiber Material ◽  
Failure Strength ◽  
Double Edge ◽  
Unnotched Specimen ◽  
Notch Geometry ◽  
Notch Length ◽  
Nonwoven Fiber ◽  
Tearing Strength

Abstract The tearing response of sheets of nonwoven fiber material is investigated. It addresses the question on how notch length and notch geometry is related to the tearing strength and tearing processes. The system considered consists of elastic-brittle fibers connected by strong interfiber bonds. Fiber fracture is the only failure mechanism. For a random fiber orientation case, deformation of the unnotched specimen occurs by long-range fiber chains connecting the load inducing boundaries, and failure is by tearing the cross section. The strength of the notched random fiber sheets is well described by a net section criterion, independent of the notch geometry. For a fiber orientation with symmetry relative to the loading direction, tensile loading is transferred by formation of the X-shaped fiber chains centered in the specimen. The subsequent failure occurs along the fiber chain by shear. Thus, the tearing strength is independent of the notch depth in double-edge notched and single-edge notched specimens, when the presence of shallow notch does not disrupt the force chains in the model. As the notch disturbs the fiber chains, alternative shear failure path forms near the notch tip, leading to a dependence of failure strength on the notch geometry. Then, the failure strength of notched nonwoven networks is described by a shear strength and a notch geometry term.

Thermal Damage, Cracking and Rapid Erosion of Cannon Bore Coatings

2003 ◽  
Vol 125 (3) ◽  
pp. 299-304 ◽  
Author(s):  
John H. Underwood ◽  
Anthony P. Parker ◽  
Gregory N. Vigilante ◽  
Paul J. Cote
Keyword(s):  
Thermal Damage ◽  
Shear Failure ◽  
Low Cycle Fatigue ◽  
Steel Substrate ◽  
Zone Model ◽  
Open Crack ◽  
Failure Strength ◽  
Closed Crack ◽  
Cyclic Shear ◽  
Coating Failure

Thermal damage observed at the bore of fired cannons has increased noticeably in the past decade, due to the use of higher combustion gas temperatures for improved cannon performance. Current authors and coworkers recently have described cannon firing damage and proposed new thermo-mechanical models to gain understanding of its causes, with emphasis on the severe damage that occurs in the steel beneath the chromium plating used to protect the cannon bore. Recent refinements in the models will be used here to characterize some additional damage observations in the area beneath the protective coating of fired cannons. Model results validated by microstructural observations give predictions of near-bore temperature and stress distributions and good agreement with observed depths of hydrogen cracking in the high strength steel substrate. Interest in damage and failure within a coating is also of concern for cannons, since coating failure leads to extremely rapid erosion of coating and substrate. The slip zone model of Evans and Hutchinson is adapted here to predict failure strength of cannon coatings based on observed crack spacing and microhardness of thermally damaged areas. Results are described for electroplated chromium coatings from fired cannons and for sputtered chromium and tantalum coatings with laser-heating damage to simulate firing. Coating mechanics analysis of fired and laser-heated samples provides an insitu measurement of coating failure strength, showing that sputtered chromium has more than twice the failure strength of electroplated chromium. An analysis of cyclic shear failure of a coating interface at an open crack shows a six-fold decrease in low cycle fatigue life compared to the life of a closed crack. Recommendations are given for preventing rapid coating failure and catastrophic erosion of fired cannon, with emphasis on methods to prevent deep, open cracks in coating and substrate.

Transport Path in Hydrogenated Microcrystalline Silicon

2002 ◽  
Vol 715 ◽  
Author(s):  
N. Wyrsch ◽  
C. Droz ◽  
L. Feitknecht ◽  
J. Spitznagel ◽  
A. Shah
Keyword(s):  
Raman Spectroscopy ◽  
Volume Fraction ◽  
Conductivity Measurement ◽  
Dark Conductivity ◽  
Transition Regime ◽  
Conductivity Data ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Crystalline Fraction ◽  
Transport Path

AbstractUndoped microcrystalline silicon samples deposited in the transition regime between amorphous and microcrystalline growth have been investigated by dark conductivity measurement and Raman spectroscopy. From the latter, a semi-quantitative crystalline volume fraction Xc of the sample was deduced and correlated with dark conductivity data in order to reveal possible percolation controlled transport. No threshold was observed around the critical crystalline fraction value Xc of 33%, as reported previously, but a threshold in conductivity data was found at Xc≈50%. This threshold is interpreted here speculatively as being the result of postoxidation, and not constituting an actual percolation threshold.

INTERPRETATION OF SURFACE EROSION AS SHEAR FAILURE OF SOIL CAUSED BY SURFACE FLOW

2018 ◽  
Vol 74 (5) ◽  
pp. I_901-I_906
Author(s):  
Yosuke HIGO ◽  
Shinichiro ONDA ◽  
Daiki TAKANO ◽  
Toshiki YAMAUCHI
Keyword(s):  
Shear Failure ◽  
Surface Flow ◽  
Surface Erosion
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