In-Situ Uniaxial Compression Tests of Level Ice: Part I — Ice Strength Variability Versus Length Scale

2006 ◽  
Author(s):  
Svetlana Shafrova ◽  
Per Olav Moslet
Keyword(s):  
Uniaxial Compression ◽  
Ice Cores ◽  
Length Scale ◽  
Horizontal Distance ◽  
Compression Tests ◽  
Strength Determination ◽  
Level Ice ◽  
Ice Strength ◽  
Strength Variability

Field programs of the ice strength determination through the uniaxial compression tests were carried out on the landfast level ice both in the Van Mijenfjorden and in the Adventfjorden on Svalbard, Norway in 2004 and 2005. The ice strength was examined in relation to the different length scales. The step (horizontal distance) between the ice samples was continuously reduced in order to find out how the ice strength variability develops. The spatial variation of the physical properties of the ice such as temperature, salinity, density has been measured. The typical ice strength variability for the areas larger than 40 m2 is found about 20–30 % for the vertical ice cores of the certain depth from the ice cover surface. For the horizontal ones it is slightly less about 10–20 %.

In-Situ Uniaxial Compression Tests of Level Ice: Part II — Ice Strength Spatial Distribution

2006 ◽  
Author(s):  
Svetlana Shafrova ◽  
Per Olav Moslet
Keyword(s):  
Spatial Distribution ◽  
Field Tests ◽  
Ice Cover ◽  
Strength Distribution ◽  
Test Area ◽  
Compression Tests ◽  
Level Ice ◽  
Ice Strength ◽  
Strength Variability

Part I of this paper describes in-situ field tests of ice strength estimation in relation to the different length scales. Part II deals with the spatial heterogeneity of the ice strength in landfast level ice for the different tests areas. The paper presents a statistical analysis of the ice strength distribution for a Point-area, for a line and for an area in the ice cover. The ice strength distribution for a Point-area varied seasonally. It was estimated in terms of the coefficient of variation about 24.9% at the end of the season. For the coldest months the ice strength variability was around 40%. For the test area the strength spatial variability for the ice samples from the certain ice depth below the ice cover surface was about 19.4% for warm ice and 35.8% for cold ice. The ice strength heterogeneity for a line was determined of 14.4% in case of warm ice.

scholarly journals Flow-Law Parameters of the Dye 3, Greenland, Deep Ice Core

1988 ◽  
Vol 10 ◽  
pp. 146-150 ◽  
Author(s):  
H. Shoji ◽  
C.C. Langway
Keyword(s):  
Uniaxial Compression ◽  
Ice Core ◽  
Depth Interval ◽  
Physical Parameters ◽  
Compression Tests ◽  
Axis Orientation ◽  
Cold Room ◽  
Entire Depth ◽  
Made In

Uniaxial compression tests under constant crosshead speed were carried out on 22 new specimens from the 268, 1890, 1944 and 2006 m depths of the Dye 3, Greenland, ice core. The measurements were made in a laboratory cold-room, using an Instron model 1131 apparatus. Test temperatures were held constant between −17° and −13° C, the approximate sample in-situ temperature. Specimens were prepared with various test orientations in relation to the long vertical core axis. The specimens were analyzed in terms of the content of dust, Cl−, NO3 − and SO4 2− concentrations and various other physical parameters, such as ultrasonic wave velocities, c-axis orientation patterns and grain-size. The results of the previous uniaxial compression tests show that most of the flow occurs in the Wisconsin-age ice between 1786 m and the bottom of the ice sheet. This entire depth interval is strongly anisotropic, with a vertical c-axis fabric pattern. The enhancement factor, E, which was calculated from these tests ranges from 0.03 to 17. The Wisconsin-age ice is about ten times softer (Es = 10) than artificially made laboratory ice (E = 1). The combined results of the multi-parameter correlation analyses show that E is controlled primarily by the orientation strength of c-axes and that the impurity concentration-level variations contribute to a lesser degree.

scholarly journals Flow-Law Parameters of the Dye 3, Greenland, Deep Ice Core

1988 ◽  
Vol 10 ◽  
pp. 146-150 ◽  
Author(s):  
H. Shoji ◽  
C.C. Langway
Keyword(s):  
Uniaxial Compression ◽  
Ice Core ◽  
Depth Interval ◽  
Physical Parameters ◽  
Compression Tests ◽  
Axis Orientation ◽  
Cold Room ◽  
Entire Depth ◽  
Made In

Uniaxial compression tests under constant crosshead speed were carried out on 22 new specimens from the 268, 1890, 1944 and 2006 m depths of the Dye 3, Greenland, ice core. The measurements were made in a laboratory cold-room, using an Instron model 1131 apparatus. Test temperatures were held constant between −17° and −13° C, the approximate sample in-situ temperature. Specimens were prepared with various test orientations in relation to the long vertical core axis. The specimens were analyzed in terms of the content of dust, Cl−, NO3− and SO42− concentrations and various other physical parameters, such as ultrasonic wave velocities, c-axis orientation patterns and grain-size. The results of the previous uniaxial compression tests show that most of the flow occurs in the Wisconsin-age ice between 1786 m and the bottom of the ice sheet. This entire depth interval is strongly anisotropic, with a vertical c-axis fabric pattern. The enhancement factor, E, which was calculated from these tests ranges from 0.03 to 17. The Wisconsin-age ice is about ten times softer (Es = 10) than artificially made laboratory ice (E = 1). The combined results of the multi-parameter correlation analyses show that E is controlled primarily by the orientation strength of c-axes and that the impurity concentration-level variations contribute to a lesser degree.

scholarly journals Hot Workability of 300M Steel Investigated by In Situ and Ex Situ Compression Tests

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 880 ◽  
Author(s):  
Rongchuang Chen ◽  
Haifeng Xiao ◽  
Min Wang ◽  
Jianjun Li
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Hot Working ◽  
Ex Situ ◽  
Lower Strain Rate ◽  
Hot Workability ◽  
Compression Tests ◽  
300M Steel ◽  
Lower Strain

In this work, hot compression experiments of 300M steel were performed at 900–1150 °C and 0.01–10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

scholarly journals Investigation of Microcrack Propagation and Energy Evolution in Brittle Rocks Based on the Voronoi Model

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2108
Author(s):  
Guanlin Liu ◽  
Youliang Chen ◽  
Xi Du ◽  
Peng Xiao ◽  
Shaoming Liao ◽  
...  
Keyword(s):  
Uniaxial Compression ◽  
Damage Evolution ◽  
Rock Sample ◽  
Rock Fracture ◽  
Damage Threshold ◽  
Crack Development ◽  
Energy Evolution ◽  
Shear Cracks ◽  
Compression Tests ◽  
Microcrack Propagation

The cracking of rock mass under compression is the main factor causing structural failure. Therefore, it is very crucial to establish a rock damage evolution model to investigate the crack development process and reveal the failure and instability mechanism of rock under load. In this study, four different strength types of rock samples from hard to weak were selected, and the Voronoi method was used to perform and analyze uniaxial compression tests and the fracture process. The change characteristics of the number, angle, and length of cracks in the process of rock failure and instability were obtained. Three laws of crack development, damage evolution, and energy evolution were analyzed. The main conclusions are as follows. (1) The rock’s initial damage is mainly caused by tensile cracks, and the rapid growth of shear cracks after exceeding the damage threshold indicates that the rock is about to be a failure. The development of micro-cracks is mainly concentrated on the diagonal of the rock sample and gradually expands to the middle along the two ends of the diagonal. (2) The identification point of failure precursor information in Acoustic Emission (AE) can effectively provide a safety warning for the development of rock fracture. (3) The uniaxial compression damage constitutive equation of the rock sample with the crack length as the parameter is established, which can better reflect the damage evolution characteristics of the rock sample. (4) Tensile crack requires low energy consumption and energy dispersion is not concentrated. The damage is not apparent. Shear cracks are concentrated and consume a large amount of energy, resulting in strong damage and making it easy to form macro-cracks.

scholarly journals Quantitative 3D imaging of partially saturated granular materials under uniaxial compression

2021 ◽  
Author(s):  
Marius Milatz ◽  
Nicole Hüsener ◽  
Edward Andò ◽  
Gioacchino Viggiani ◽  
Jürgen Grabe
Keyword(s):  
Granular Materials ◽  
Uniaxial Compression ◽  
Water Clusters ◽  
Local Strain ◽  
Confining Pressure ◽  
Mechanical Effect ◽  
Compression Tests ◽  
Initial Water ◽  
Interfacial Areas ◽  
Membrane Effects

AbstractGauging the mechanical effect of partial saturation in granular materials is experimentally challenging due to the very low suctions resulting from large pores. To this end, a uniaxial (zero radial stress) compression test may be preferable to a triaxial one where confining pressure and membrane effects may erase the contribution of this small suction; however, volume changes are challenging to measure. This work resolves this limitation by using X-ray imaging during in situ uniaxial compression tests on Hamburg Sand and glass beads at three different initial water contents, allowing a suction-dependent dilation to be brought to the light. The acquired tomography volumes also allow the development of air–water and solid–water interfacial areas, water clusters and local strain fields to be measured at the grain scale. These measurements are used to characterise pertinent micro-scale quantities during shearing and to relate them to the measured macroscopic response. The new and well-controlled data acquired during this experimental campaign are hopefully a useful contribution to the modelling efforts—to this end they are shared with the community.

Failure Process of Rock Sample Observed by AE Source Locating Technique under Uniaxial Compression

2006 ◽  
Vol 324-325 ◽  
pp. 567-570
Author(s):  
Yuan Hui Li ◽  
Rui Fu Yuan ◽  
Xing Dong Zhao
Keyword(s):  
Uniaxial Compression ◽  
High Speed ◽  
Failure Process ◽  
Compression Tests ◽  
Temporal And Spatial Distribution ◽  
Primary Stage ◽  
Brewing Process ◽  
Ae Signal ◽  
Failure Location ◽  
Low Amplitude

A series of uniaxial-compression tests were conducted on some representative brittle rock specimens, such as granite, marble and dolerite. A multi-channel, high-speed AE signal acquiring and analyzing system was employed to acquire and record the characteristics of AE events and demonstrate the temporal and spatial distribution of these events during the rupture-brewing process. The test result showed that in the primary stage, many low amplitude AE events were developed rapidly and distributed randomly throughout the entire specimens. In the second stage, the number of AE increased much slower than that in the first stage, while the amplitude of most AE events became greater. Contrarily to the primary stage, AE events clustered in the middle area of the specimen and distributed vertically conformed to the orientation of compression. The most distinct characteristic of this stage was a vacant gap formed approximately in the central part of the specimen. In the last stage, the number of AE events increased sharply and their magnitude increased accordingly. The final failure location coincidently inhabited the aforementioned gap. The main conclusion is that most macrocracks are developed from the surrounding microcracks existed earlier and their positions occupy the earlier formed gaps, and the AE activity usually becomes quite acute before the main rupture occurs.

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