Propagation of glacier surges

1969 ◽  
Vol 6 (4) ◽  
pp. 969-977 ◽  
Author(s):  
G. de Q. Robin ◽  
P. Barnes
Keyword(s):  
Shear Stress ◽  
Melting Point ◽  
Strain Rate ◽  
Experimental Results ◽  
Shear Stresses ◽  
Rate Data ◽  
Stress Strain ◽  
Glacier Surface ◽  
Glacier Surges ◽  
Tensile Zone

Propagation of glacier surges has been discussed in terms of stresses acting in the three major zones of the surge. The steeply sloping front of a surge appears sufficient to explain the thickening of a glacier and the rise in velocity of ice motion which takes place across this zone in terms of accepted stress–strain rate data for ice. Explanation of the high velocities which occur in the next zone in spite of little change in the available shear stress is more difficult, but the experimental results of Barnes and Tabor on ice close to the melting point appear to offer an explanation of the unusually high rates of flow. In the tensile zone, where velocities slow down, the net lowering of the glacier surface after the surge has passed is explained in terms of the depth of crevassing and easier flow of ice at melting point when under tensile and shear stresses.

scholarly journals A Strain Rate-Dependent Damage Evolution Model for Concrete Based on Experimental Results

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Bin Xu ◽  
Xiaoyan Lei ◽  
P. Wang ◽  
Hui Song
Keyword(s):  
Strain Rate ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Model ◽  
Evolution Model ◽  
Experimental Results ◽  
Strain Rates ◽  
Compression Tests ◽  
Stress Strain ◽  
Actual Damage

There are various definitions of damage variables from the existing damage models. The calculated damage value by the current methods still could not well correspond to the actual damage value. Therefore, it is necessary to establish a damage evolution model corresponding to the actual damage evolution. In this paper, a strain rate-sensitive isotropic damage model for plain concrete is proposed to describe its nonlinear behavior. Cyclic uniaxial compression tests were conducted on concrete samples at three strain rates of 10−3s−1, 10−4s−1, and 10−5s−1, respectively, and ultrasonic wave measurements were made at specified strain values during the loading progress. A damage variable was defined using the secant and initial moduli, and concrete damage evolution was then studied using the experimental results of the cyclic uniaxial compression tests conducted at the different strain rates. A viscoelastic stress-strain relationship, which considered the proposed damage evolution model, was presented according to the principles of irreversible thermodynamics. The model results agreed well with the experiment and indicated that the proposed damage evolution model can accurately characterize the development of macroscopic mechanical weakening of concrete. A damage-coupled viscoelastic constitutive relationship of concrete was recommended. It was concluded that the model could not only characterize the stress-strain response of materials under one-dimensional compressive load but also truly reflect the degradation law of the macromechanical properties of materials. The proposed damage model will advance the understanding of the failure process of concrete materials.

scholarly journals The distortion of crystals of aluminium under compression. Part III.―Measurements of stress

1927 ◽  
Vol 116 (773) ◽  
pp. 39-60 ◽  
Keyword(s):  
Shear Stress ◽  
Large Range ◽  
Experimental Results ◽  
The Other ◽  
Shear Stresses ◽  
Measurable Difference ◽  
The Relationship ◽  
Do So

Several experiments were devised to find out whether it is possible to measure the internal shearing stresses in a compressed disc, and the conditions under which it is possible to do so. Equations are developed for analysing shear stresses parallel to planes of slip and distortion due to double and single slipping. The relationship between shear stress and amount of shear is found for tensile and for compression specimens, when slipping is confined to one plane. The experimental results in the two cases are identical. The fact that the component of force normal to plane of slip is a pressure in one case and a tension in the other makes no measurable difference to resistance to slipping for given amount of slip. During double slipping resistance to shear increases more rapidly for a given total amount of slipping than when all slip is confined to one plane. The experiments cover a large range and show that resistance to shear goes on increasing up to greatest amounts of distortion used.

On the Determination of Stress, Strain, Strain-Rate Relations From Dynamic Beam Tests

1969 ◽  
Vol 36 (3) ◽  
pp. 632-634 ◽  
Author(s):  
P. P. Gillis ◽  
J. M. Kelly
Keyword(s):  
Strain Rate ◽  
Dynamic Testing ◽  
Direct Method ◽  
Bending Moment ◽  
Experimental Results ◽  
Stress Strain ◽  
Analytical Technique ◽  
Flexural Response ◽  
Flexural Tests

A direct method is proposed for the determination of stress, strain, strain-rate relations from dynamic flexural tests in which bending moment is given in terms of curvature and curvature rate, or any other suitable deformation parameter and deformation rate parameter. The method is demonstrated by application to published experimental results. It is found that the stress, strain, strain-rate relations that are derived from the flexural test data are in significantly better accord with uniaxial data on the same material, than moment, curvature, curvature-rate relations predicted from the uniaxial data correspond with the experimental results. It appears that the process of reducing flexural data to uniaxial relations by the method proposed is much less sensitive than that of predicting flexural response from uniaxial data. Since flexural tests have many experimental advantages over uniaxial tests this analytical technique seems to open up possibilities for improved dynamic testing methods.

scholarly journals Non-coaxiality of sand under bi-directional shear loading

2018 ◽  
Vol 5 (5) ◽  
pp. 172076 ◽  
Author(s):  
Yao Li ◽  
Yunming Yang
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Simple Shear ◽  
Shear Test ◽  
Shear Loading ◽  
Shear Behaviour ◽  
Shear Stresses ◽  
Simple Shear Test ◽  
Principal Axes ◽  
Angle Difference

This study aims to investigate the effect of consolidation shear stress magnitude on the shear behaviour and non-coaxiality of soils. In previous drained bi-directional simple shear test on Leighton Buzzard sand, it is showed that the level of non-coaxiality, which is indicated by the angle difference between the principal axes of stresses and the corresponding principal axes of strain rate tensors, is increased by increasing angle difference between the direction of consolidation shear stress and secondary shearing. This paper further investigated the relation and includes results with higher consolidation shear stresses. Results agree with the previous relation, and further showed that increasing consolidation shear stresses decreased the level of non-coaxiality in tests with angle difference between 0° and 90°, and increased the level of non-coaxiality in tests with angle difference between 90° and 180°.

Deformation of ice under high internal shear stresses

1969 ◽  
Vol 6 (4) ◽  
pp. 963-968 ◽  
Author(s):  
John J. Jonas ◽  
Fritz Müller
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Polarized Light ◽  
Shear Stresses ◽  
Strain Rates ◽  
Transparent Plastic ◽  
Cross Section Area ◽  
Section Area ◽  
Polycrystalline Ice ◽  
Glacier Surges

By means of transparent plastic dies, cylindrical samples of single crystal and polycrystalline ice were extruded into rods of one quarter the original cross-section area. The deformation was carried out at −5 °C and a mean strain rate of about 10−2 s−1. With the aid of polarized light, the formation of cracks and the occurrence of dynamic recrystallization were studied. The experiments of Steinemann, and more recent results in metals suggest that, during such plastic flow, two types of dynamic recrystallization are involved. At low strain rates, the recrystallization is periodic, leading to rapid increases in strain rate at constant applied stress; at higher strain rates, the recrystallization is continuous and the strain rate is constant. The possibility that dynamic recrystallization of the periodic type is associated with glacier surges is discussed.

The Effects of Strain Rate and Thickness on the Response of Thin Layers of Solder Loaded in Pure Shear

1997 ◽  
Vol 119 (2) ◽  
pp. 81-84 ◽  
Author(s):  
A. Gilat ◽  
K. Krishna
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Strain Rate ◽  
Mechanical Response ◽  
Pure Shear ◽  
Strain Curve ◽  
Thin Layers ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Stress And Deformation

A new configuration for testing thin layers of solder is introduced and employed to study the effects of strain rate and thickness on the mechanical response of eutectic Sn-Pb solder. The solder in the test is loaded under a well defined state of pure shear stress. The stress and deformation in the solder are measured very accurately to produce a reliable stress-strain curve. The results show that both the stress needed for plastic deformation and ductility increase with increasing strain rate.

scholarly journals The Sliding Velocity of Athabasca Glacier, Canada

1970 ◽  
Vol 9 (55) ◽  
pp. 55-63 ◽  
Author(s):  
W. S. B. Paterson
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Longitudinal Strain ◽  
Shear Stresses ◽  
Sliding Velocity ◽  
Flow Law ◽  
Basal Shear ◽  
Longitudinal Strain Rate

AbstractA method of estimating siding velocity is presented. It rests on few assumptions, one of which is that longitudinal strain-rate varies linearly with depth. The flow law of ice is not used. To apply it, the sliding velocity at one point must be known. The method is used to calculate the sliding velocity at twelve points on Athabasca Glacier. These values are not related to calculated basal shear stresses. Thus one or more of the following statements must be true: (1) basal shear stress cannot be calculated by the conventional formula, (2) the roughness of the glacier bed varies from place to place, (3) sliding velocity does not obey Weertman's formula. Analysis of seven published measurements of sliding velocity leads to the same conclusion.

scholarly journals Measurement of Pure Shear Constitutive Relationship from Torsion Tests under Quasi-static, Medium and High Strain Rate Conditions

2021 ◽  
pp. 1-26
Author(s):  
LongHui Zhang ◽  
David Townsend ◽  
Nik Petrinic ◽  
Antonio Pellegrino
Keyword(s):  
Shear Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
Digital Image ◽  
High Strain ◽  
Pure Shear ◽  
Rate Sensitivity ◽  
Constitutive Relationship ◽  
Stress Strain ◽  
Strain Relationship

Abstract Torsion tests provide important shear stress and shear strain relationships to reveal the fundamental plastic flow response of a material. Bespoke torsion techniques complemented by Digital Image Correlation are developed to accurately measure the shear stress-strain relationship at quasi-static, medium rate 9/s and high strain rate above 1000/s. The equipment used includes a screw driven mechanical system, a hydraulic Instron machine and a Campbell thin-walled tube split Hopkinson torsion bar equipped with an ultra-high speed camera. A near alpha Ti3Al2.5V alloy was used as a model material in this study. A four camera digital image system has been constructed to monitor the material deformation and failure during a low rate torsion test, to gain further insight into plastic deformation of the tubular specimen. Shear stress-strain relationship of the Ti3Al2.5V alloy exhibits noticeable strain rate sensitivity. Observations of the strain hardening rate evolution indicate that the hardening capacity of Ti3Al2.5V is both strain and strain rate dependent. High strain rate torsional stress-strain relationship shows lower strain hardening, compared to the response obtained from a shear compression specimen. The present techniques are demonstrated to be suitable for the measurement of pure shear constitutive relationship, including rate sensitivity and failure of the material.

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