Measurement of surface strain rates in glaciers using embedded wire strain gages

1974 ◽  
Vol 14 (1) ◽  
pp. 24-28 ◽  
Author(s):  
G. Warner ◽  
G. Cloud
Keyword(s):  
Surface Strain ◽  
Strain Rates ◽  
Strain Gages ◽  
Wire Strain

scholarly journals Ice-divide flow at Hans Tausen Iskappe, North Greenland, from surface movement data

2001 ◽  
Vol 47 (156) ◽  
pp. 78-84 ◽  
Author(s):  
C. S. Hvidberg ◽  
K. Keller ◽  
N. Gundestrup ◽  
P. Jonsson
Keyword(s):  
Global Positioning System ◽  
Average Rate ◽  
Horizontal Velocity ◽  
Surface Strain ◽  
Surface Velocity ◽  
Strain Rates ◽  
Ice Cap ◽  
Movement Data ◽  
Global Positioning ◽  
North Greenland

AbstractSurface strain rates around the southeastern dome of Hans Tausen Iskappe in Peary Land, North Greenland (82.5° N, 27.5° W), are determined from global positioning system surveys of a strain net. Average longitudinal surface strain rate increases towards the dome, from (1.4 ± 0.2) × 10−4 a−1 at 5–10 ice thicknesses from the divide to (2.4 ± 1.0) × 10−4 a−1 within 1 ice thickness from the divide. Analysis of the data shows that the ice cap is presently building up within the strain net with an average rate of 〈∂H/∂t〉 = + 0.04 ± 0.02 m a−1. Assuming a uniform thickening, the shape factor of the horizontal velocity (the ratio between the vertically averaged horizontal velocity and the horizontal surface velocity) decreases towards the dome, from 0.9 at a distance of 10 ice thicknesses from the dome to 0.5 at the dome based on application of the continuity equation. Our results indicate that a region with anomalous flow is formed around the dome, supporting recent indications reported by Vaughan and others (1999). It is not possible from our data to constrain parameters of the flow law, because there is no independent estimate of the significant present thickening of the central part of the ice cap and its pattern around the dome.

Accounting for the transverse sensitivity of wire strain gages

1972 ◽  
Vol 15 (9) ◽  
pp. 1316-1318
Author(s):  
O. N. Ivanov ◽  
I. Kh. Sologyan ◽  
A. Kh. Baliullin ◽  
F. D. Chegolyaev
Keyword(s):  
Strain Gages ◽  
Transverse Sensitivity ◽  
Wire Strain

scholarly journals Strain Rates On Rutford Ice Stream, Antarctica (Abstract)

1986 ◽  
Vol 8 ◽  
pp. 207
Author(s):  
N. Stephenson ◽  
C.S.M. Doake
Keyword(s):  
Strain Rate ◽  
Velocity Gradient ◽  
Surface Strain ◽  
Lateral Strain ◽  
Strain Rate Tensor ◽  
Strain Rates ◽  
Average Value ◽  
Divergent Flow ◽  
Ice Stream ◽  
Thickness Variations

In a study of the Rutford Ice Stream, strain rates were measured on a transverse section. Magnitudes ranged up to 40 × 10−3 a−1 but were typically in the order of 3 × 10−3 a−1 with an error of 0.1 χ 10−3 a−1. Variations in the strain rate between adjacent stakes of 0.2 χ 10−3 a−1 to 2 × 10−3 a−1 were matched to the thickness variations on the glacier. For each set of three adjacent stakes, the velocity gradient components of the surface strain rate tensor were calculated by assuming that the gradients were linear over the distance between adjacent stakes. When plotted against distance across the ice stream, each strain rate component revealed different aspects of the flow field. The longitudinal strain rate was compressive, with an almost constant magnitude of 10−3 a−1. The lateral strain rate is extensive, with an average value of 1.1 × 10−3 a−1 which agreed with the angle between the divergent flow lines observed on a Landsat image. Peaks in the lateral strain rate, corresponding to longitudinal bands of thicker ice, showed that these thicker bands were spreading more rapidly at the expense of thinner areas. The two velocity gradient components of the shear rate tensor also reflected differences in ice thickness.

scholarly journals Constant Strain-Rate Tensile Testing of Natural Snow

1980 ◽  
Vol 26 (94) ◽  
pp. 519 ◽  
Author(s):  
H. Singh ◽  
F.W. Smith
Keyword(s):  
Strain Rate ◽  
Strain Gage ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Strain Rates ◽  
Strain Gages ◽  
Compression Tests ◽  
Snow Sample ◽  
Stress Strain ◽  
Natural Snow

Abstract In conducting tension and compression tests on snow samples, strains and strain-rates are usually determined from the displacements of the ends of the samples. In this work, a strain-gage which mounts directly onto the snow sample during testing, was developed and was found to give accurate and direct measurements of strain and strain-rates. A commercially available 0-28 pF variable capacitor was modified to perform the required strain measurements. It is a polished metallic plunger sliding inside a metal-coated glass tube. The plunger and tube were each soldered to the end of a spring-steel wire arm. To the other end of these arms were soldered to 10 mm square pads made of thin brass shim stock. The whole device weighs 2.5 g and the low coefficient of friction in the capacitor resulted in a very low actuation force. To mount the strain gage, the pads are wetted and frozen onto the snow sample. A high degree of sensitivity was achieved through the use of “phase-lock-loop” electronic circuitry. The capacitance change caused by the strain in the sample, changes the frequency of output signal from an oscillator and thus causes the change in output from the system. In the locked state, to which the system is constantly driven by a feed-back loop, the system output is almost ripple free. The strain gages were calibrated in the field in order to take into account the effects of very low field temperatures. The calibration curves were almost linear over the travel of 15 mm, the maximum limit. The sensitivity of the system is 4 mV per strain unit, but this could be increased by an order of magnitude by minor adjustments in the circuit. Constant strain-rate tensile tests were performed on natural snow at Berthoud Pass, Colorado, U.S.A., in the density range of 140-290 kg m-3. Four strain gages were mounted onto the samples to sense any non-uniform deformation which otherwise would have gone unnoticed or caused scatter in the data. The average indication of these gages was used to construct stress—strain curves for various types of snow at different strain-rates. The effect of strain-rate on the behavior of snow was studied. “Ratcheting” in the stress-strain curve in the region where the snow becomes plastic was observed first by Kinosita in his compression tests. A similar phenomenon was observed in these tension tests. It was found that directly measured strain is quite different from that which would be calculated from sample end movement. Strain softening was not observed in these tests up to total strains of 8%. The strain-rate effects found were comparable to the results of other investigators.

scholarly journals Ice deformation very close to the ice-sheet margin in West Greenland

1992 ◽  
Vol 38 (128) ◽  
pp. 3-8 ◽  
Author(s):  
Peter G. Knight
Keyword(s):  
Detailed Analysis ◽  
Flow Direction ◽  
Surface Strain ◽  
Small Scale ◽  
Strain Rates ◽  
Glacier Surface ◽  
West Greenland ◽  
Small Areas ◽  
Strain Pattern ◽  
Fine Resolution

AbstractThis paper describes fine-resolution measurements of glacier surface strain rates very close to the margin of Russell Glacier, West Greenland. Measurements at a small scale make possible detailed analysis of strain patterns close to the glacier margin, and suggest that strain rates vary over small areas. The strain pattern is determined by ice flexure over subglacial obstacles as well as by seasonally variable marginal retardation and by the orientation of the ice margin relative to the flow direction.

Development of High Temperature Semiconductor Strain Gages for Thermal Power Plant Applications

2018 ◽  
Author(s):  
Christopher A. Suprock ◽  
Joseph J. Christian ◽  
Stan T. Rosinski
Keyword(s):  
Power Generation ◽  
High Temperature ◽  
Thermal Power ◽  
Surface Strain ◽  
Strain Gages ◽  
Working Temperature ◽  
Monitoring Applications ◽  
Field Deployment ◽  
Structural Strain ◽  
Semiconductor Strain

This paper discusses a specially developed semiconductor strain cell that allows sensitive measurement of surface strain in environments with temperatures up to 1050F (566C). There is an unmet industry-wide need in the manufacturing and power generation fields for monitoring material mechanics and component degradation at temperatures exceeding the maximum working temperature of traditional strain gage technologies. This technology advances attachment methodology of the semiconductor gage to allow field deployment and a physically reliable interface with structural strain. Measuring strain at these temperatures is useful both in the laboratory and in practical monitoring applications. The technology provides a way to monitor changes in materials exposed to heat and stress and give plant engineers tools to predict and avoid critical failures.

scholarly journals Mass Balance of the Greenland Ice Sheet at Dye 3

1985 ◽  
Vol 31 (108) ◽  
pp. 198-200 ◽  
Author(s):  
Niels Reeh ◽  
Niels S. Gundestrup
Keyword(s):  
Mass Balance ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Bottom Layer ◽  
Surface Strain ◽  
Ice Thickness ◽  
Strain Rates ◽  
Confidence Limits ◽  
Rate Of Increase

AbstractThe mass balance of the Greenland ice sheet at Dye 3 is estimated on the basis of observations of ice thickness, accumulation rate, surface velocities, and surface strain-rates. The calculations indicate a rate of increase of surface elevation of 3 cm/year, with 95% confidence limits of −3 cm/year and +9 cm/year. Previous estimates of the mass balance of the Greenland ice sheet by the same method reported large imbalances; these are most probably due to lack of precise data and the use of quantities measured at the surface as representative of depth-averaged quantities. The most reliable observations indicate that the interior regions of the Greenland ice sheet are at present thickening at a rate of a few centimetres per year; a contributing cause for this may be the slow thinning of a bottom layer of relatively soft Wisconsin ice.

Sign in / Sign up

Export Citation Format

Share Document