scholarly journals Influence of the loading direction on the uniaxial compressive strength of sea ice based on field measurements

2020 ◽  
Vol 61 (82) ◽  
pp. 86-96 ◽  
Author(s):  
Shunying Ji ◽  
Xiaodong Chen ◽  
Anliang Wang
Keyword(s):  
Compressive Strength ◽  
Sea Ice ◽  
Failure Mode ◽  
Brittle Failure ◽  
Ductile Failure ◽  
Strain Rates ◽  
Vertical Loading ◽  
Loading Direction ◽  
Horizontal Loading ◽  
Nominal Strain

AbstractSea ice is composed of columnar-shaped grains. To investigate the influence of the loading direction on the uniaxial compressive strength and failure processes of sea ice, field experiments were performed with first-year level ice. Loads were applied both horizontally (parallel to the grain columns) and vertically (across the grain columns) with various nominal strain rates. Two failure modes have been observed: a ductile failure mode at low nominal strain rates, and a brittle failure mode at high nominal strain rates. However, the failure pattern of sea ice was clearly dependent on the loading direction. At low nominal strain rates (ductile failure mode), the sea-ice samples yielded due to the development of wing cracks under horizontal loading and due to splaying out at one end under vertical loading. When sea ice fails in the ductile mode, the deformation is driven by grain boundary sliding under horizontal loading and by grain decohesion and crystal deflection under vertical loading. At high nominal strain rates (brittle failure mode), the sea-ice samples failed in shear faulting under horizontal loading and in cross-column buckling under vertical loading. The nominal strain rate at the brittle–ductile transition zone is about ten times higher under vertical loading.

scholarly journals Mechanical Behavior of Cemented Sand Reinforced with Different Polymer Fibers

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Xiangfeng Lv ◽  
Xiaohui Yang ◽  
Hongyuan Zhou ◽  
Shuo Zhang
Keyword(s):  
Compressive Strength ◽  
Mechanical Behavior ◽  
Brittle Failure ◽  
Unconfined Compressive Strength ◽  
Polypropylene Fiber ◽  
Ductile Failure ◽  
Polymer Fibers ◽  
Chemical Compositions ◽  
Peak Strain ◽  
Cemented Sand

In this study, the specimens of cemented sand were prepared by reinforcing it separately with different contents (0.5%, 1.0%, 1.5%, and 2.0%) of three different polymer fibers (polyamide, polyester, and polypropylene) prepared as filaments of different lengths (6, 9, and 12 mm). Then, these specimens were tested, and the improvement effects of the three fibers on the engineering-mechanical behavior of the cemented sand were analyzed and compared. The different microstructures and chemical compositions of the fiber-reinforced cemented sand specimens were investigated using electron microscopy and X-ray diffraction. Compression tests were performed to obtain the stress-strain curves of the specimens. Comparative analysis was performed on the variation patterns of the mechanical parameters (such as unconfined compressive strength and peak strain) of the specimens. Quantitative analysis was performed on the effect of fiber content and fiber filament length on the failure mode of the specimens. It was shown that the inclusion of fibers led to a change from brittle failure to ductile failure. The macro- and microexperimental results revealed that polypropylene fiber had the best improvement effect on the mechanical behavior of the cemented sand, followed by polyester fiber and polyamide fiber. In particular, the cemented sand specimen reinforced with 1.5% polypropylene fiber prepared as 9 mm length filaments had a brittleness index of 0.0578, exhibited ductile failure (in contrast to the brittle failure of the nonreinforced cemented sand), and yielded the highest unconfined compressive strength and shear strength among the specimens.

Uniaxial Compressive Strengths of Artificial Freshwater Ice

2011 ◽  
Vol 243-249 ◽  
pp. 4634-4637 ◽  
Author(s):  
Li Min Zhang ◽  
Zhi Jun Li ◽  
Qing Jia ◽  
Guang Wei Li ◽  
Wen Feng Huang
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Uniaxial Compression Test ◽  
Strain Rates ◽  
Precise Control ◽  
Freshwater Ice ◽  
Ice Surface ◽  
Loading Direction ◽  
Maximum Value ◽  
Lower Strain

The uniaxial compression test was performed on artificial freshwater ice with a precise control-temperature unit compression tester of ice under -5, -10, -15, -20 and-30°C temperatures and strain rates ranging from 10-8 to 10-2 s-1. The loading direction was parallel to ice surface. The results showed that the compressive strength was very sensitive to the strain-rate. The uniaxial compressive strengths reached the maximum value at the ductile-brittle transition region, and the region was gradually close to the lower strain-rate with the decreasing temperature of test. Both the strain-rate and uniaxial compressive strength dependences could be expressed in terms of power function in the relevant ductile range of strain-rate. The tests also revealed that failure stress of ice increases with decreasing of temperature at the same strain rate.

scholarly journals Effect of Moisture Content on the Mechanical Properties of Watermelon Seed Varieties

2021 ◽  
Vol 2 (2) ◽  
pp. 308-320
Author(s):  
Paul Chukwuka EZE ◽  
Eze CHIKAODILI ◽  
Ide PATRICK EJIKE
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Moisture Content ◽  
Compressive Force ◽  
Deformation Energy ◽  
Vertical Loading ◽  
Watermelon Seed ◽  
Horizontal Loading ◽  
Effect Of Moisture ◽  
And Storage

The effect of moisture content on the mechanical properties of agricultural material is essential during design and adjustment of machines used during harvest, cleaning, separation, handling and storage. This study determined some mechanical properties of Black and Brown colored of watermelon seed grown in Nigeria under different moisture contents range of 6.5 to 27.8% (d.b). The results for the mechanical properties obtained ranged from 15.68-29.54 N for compressive force; 1.95-3.40 mm for compressive extension; 0.13-0.33 N mm-2 for compressive strength; and 0.17-1.93 kJ for deformation energy at vertical loading position while at horizontal loading position, results obtained ranged from 14.71-38.36 N for compressive force; 1.94-4.20 mm for compressive extension; 0.16-0.32 N mm-2 for compressive strength; and 1.47-76.39 kJ for deformation energy for Black colored watermelon seed. The compressive force, compressive extension, compressive strength, deformation energy ranged from 14.18-36.49 N, 1.85-5.20 mm, 0.19 0.76 N mm-2, 26.23-189.75 kJ at vertical loading position and 16.47-41.82 N, 1.68-11.08 mm, 0.34- 0.57 N mm-2, 27.67-319.99 kJ at horizontal loading position for Brown colored watermelon seed. The correlation between the mechanical properties and moisture content was statistically significant at (p≤0.05) level. It is also economical to load Black colored in vertical loading position at 27.8% moisture content and Brown colored in vertical loading position at 27.8% moisture content to reduce energy demand when necessary to crack or compress the seed. This research has generated data that are efficiently enough to design and fabricate processing and storage structures for Black and Brown water melon seeds.

scholarly journals Influence of Unloading Conditions of Confining Pressure on the Compressive Strength and Permeability of Deep Mudstone

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Tianyu Xin ◽  
Yashengnan Sun ◽  
Junguang Wang ◽  
Weiji Sun
Keyword(s):  
Compressive Strength ◽  
Brittle Failure ◽  
Axial Stress ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Ductile Failure ◽  
Confining Pressure ◽  
Initial Stage ◽  
Strain Change ◽  
Deep Rock

To investigate the compressive strength and permeability of deep mudstone under stress disturbance, a triaxial rheometer is used to conduct seepage experiments on mudstone specimens with different buried depths under triaxial compression and unloading conditions. The experimental results show that the compressive strength of mudstone specimen with a depth of 1000 m is much lower than that of specimen with a depth of 200 m, and the compressive strength of mudstone increases with the increase in confining pressure. Under constant axial pressure and unloading of the confining pressure, the mudstone with a depth of 200 m exhibits brittle failure, and the strain fluctuates in a pointwise manner with the increase in axial stress. In this case, the mudstone with a depth of 1000 m exhibits a transition from brittle failure to ductile failure, and the strain fluctuates linearly with the axial stress. Further, when the volumetric strain change reaches 0.01, it shows an oblique “Z” fluctuation. During the initial stage of unloading of confining pressure, the permeabilities of both the mudstone specimens (with depths of 200 and 1000 m) decrease gradually. As the confining pressure is unloaded, the permeability of mudstone with a depth of 1000 m increases. Until the specimen is completely destroyed, the permeability of mudstone increases rapidly. Overall, this study can serve as a useful reference for analyzing the engineering disasters associated with deep rock mass, tunnel ventilation, and gas storage.

Modeling snow slab failure in propagation saw test using Drucker-Prager model

2021 ◽  
Author(s):  
Agraj Upadhyay ◽  
Puneet Mahajan ◽  
Rajneesh Sharma
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Brittle Failure ◽  
High Strain ◽  
Fracture Propagation ◽  
Strain Curve ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Natural Snow

<p><strong>Abstract</strong></p><p>Fracture propagation in weak snow layers followed by the failure of overlying homogeneous snow slab leads to the formation of snow slab avalanches. The extent of fracture propagation in the weak layer and size of the avalanche release area depends on the mechanical behavior of overlying snow layers. To model the snow slab failure in slab avalanche formation process, in present work, mechanical behavior of natural snow is studied through high strain rate (1×10<sup>-4</sup> s<sup>-1</sup> or higher) uniaxial tension and compression experiments on natural snow layers. Uniaxial loading and unloading experiments are also carried out to understand the permanent strains at high strain rates. Elastic modulus of snow is derived from loading unloading test data and compared with the tangent modulus obtained from maximum slope of the stress-strain curve. Tensile and compressive strengths are derived from peak load at failure and fracture energy is derived from post peak stress-strain curve. For a density range of 100-400 Kg/m<sup>3</sup> the range of obtained mechanical properties of natural snow are: Elastic modulus: 0.1-45 MPa, Tensile strength: 0.24-20 kPa, Compressive strength: 0.1-105 kPa, Fracture energy: 0.007-0.15 J/m<sup>2</sup>. For low density snow (<150 Kg/m<sup>3</sup>) tensile and compressive strength values are quite close but for higher densities compressive strength is significantly higher than the tensile strength. At low strain rates (<1×10<sup>-4</sup> s<sup>-1</sup>) snow generally exhibit no failure and large permanent deformations whereas, at high strain rates (1×10<sup>-3</sup> s<sup>-1</sup> or higher) failure strains are generally in the range 0.05-1.5 %. In all cases a sharp decrease in load at failure suggests a near brittle failure. By fitting the experimental dataset with power law, density dependent expressions for elastic modulus, tensile and compressive strength are obtained. On the basis of the experimental observations, a continuum elastic-plastic-damage material model is considered to model mechanical behavior of snow layers. To model the asymmetry in tensile and compressive strengths, pressure dependent Drucker-Prager model is considered for yield criterion and model parameters (friction angle and cohesion) are obtained using density dependent expressions of tensile and compressive strength of snow. Effective plastic strain based damage initiation and evolution models are used to model quasi-brittle failure of snow. This model has been used for modeling the snow slab failure in two dimensional propagation saw tests and the obtained results on the influence of slab density, thickness and slope angle on slab failure have been presented.</p><p><br><br></p>

Confined Compressive Strength of Horizontal First-Year Sea Ice Samples

1991 ◽  
Vol 113 (4) ◽  
pp. 344-351 ◽  
Author(s):  
J. A. Richter-Menge
Keyword(s):  
Compressive Strength ◽  
Sea Ice ◽  
Axial Stress ◽  
Testing Machine ◽  
Constant Strain Rate ◽  
First Year ◽  
Strain Rates ◽  
Triaxial Cell ◽  
Testing Techniques ◽  
Prudhoe Bay

A total of 110 first-year sea ice samples from Prudhoe Bay, Alaska, were tested in unconfined and confined constant strain rate compression. All of the tests were performed in the laboratory on a closed-loop electrohydraulic testing machine at −10°C. The confined tests were performed in a conventional triaxial cell (σ1>σ2=σ3) that maintained a constant ratio between the radial and axial stress (σ2/(σ1)=constant) to simulate true loading conditions. Three strain rates (10−2, 10−3, and 10−5/s) and three σ2/σ1 ratios (0.25, 0.50, and 0.75) were investigated. This paper summarizes the field sampling and testing techniques and presents data on the effect of confinement on the compressive strength, initial tangent modulus, and failure strain of the ice.

Anisotropic ductile failure in titanium alloy at quasi-static and high strain rates

2003 ◽  
Vol 110 ◽  
pp. 571-576 ◽  
Author(s):  
A. A. Mir ◽  
D. C. Barton ◽  
T. D. Andrews ◽  
P. Church
Keyword(s):  
Titanium Alloy ◽  
High Strain ◽  
Ductile Failure ◽  
Strain Rates ◽  
High Strain Rates

scholarly journals Discrete Element Analysis of High-Pressure Zones of Sea Ice on Vertical Structures

2021 ◽  
Vol 9 (3) ◽  
pp. 348
Author(s):  
Xue Long ◽  
Lu Liu ◽  
Shewen Liu ◽  
Shunying Ji
Keyword(s):  
High Pressure ◽  
Sea Ice ◽  
Failure Mode ◽  
Contact Area ◽  
Loading Rate ◽  
Discrete Element ◽  
Offshore Platforms ◽  
Marine Structures ◽  
Element Analysis ◽  
Ice Pressure

In cold regions, ice pressure poses a serious threat to the safe operation of ship hulls and fixed offshore platforms. In this study, a discrete element method (DEM) with bonded particles was adapted to simulate the generation and distribution of local ice pressures during the interaction between level ice and vertical structures. The strength and failure mode of simulated sea ice under uniaxial compression were consistent with the experimental results, which verifies the accuracy of the discrete element parameters. The crushing process of sea ice acting on the vertical structure simulated by the DEM was compared with the field test. The distribution of ice pressure on the contact surface was calculated, and it was found that the local ice pressure was much greater than the global ice pressure. The high-pressure zones in sea ice are mainly caused by its simultaneous destruction, and these zones are primarily distributed near the midline of the contact area of sea ice and the structure. The contact area and loading rate are the two main factors affecting the high-pressure zones. The maximum local and global ice pressures decrease with an increase in the contact area. The influence of the loading rate on the local ice pressure is caused by the change in the sea ice failure mode. When the loading rate is low, ductile failure of sea ice occurs, and the ice pressure increases with the increase in the loading rate. When the loading rate is high, brittle failure of sea ice occurs, and the ice pressure decreases with an increase in the loading rate. This DEM study of sea ice can reasonably predict the distribution of high-pressure zones on marine structures and provide a reference for the anti-ice performance design of marine structures.

scholarly journals Static Mechanical Properties of Expanded Polypropylene Crushable Foam

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 249
Author(s):  
Przemysław Rumianek ◽  
Tomasz Dobosz ◽  
Radosław Nowak ◽  
Piotr Dziewit ◽  
Andrzej Aromiński
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Energy Absorption ◽  
Experimental Tests ◽  
Absorption Capacity ◽  
Strain Rates ◽  
Foam Density ◽  
Energy Absorption Capacity ◽  
Closed Cell

Closed-cell expanded polypropylene (EPP) foam is commonly used in car bumpers for the purpose of absorbing energy impacts. Characterization of the foam’s mechanical properties at varying strain rates is essential for selecting the proper material used as a protective structure in dynamic loading application. The aim of the study was to investigate the influence of loading strain rate, material density, and microstructure on compressive strength and energy absorption capacity for closed-cell polymeric foams. We performed quasi-static compressive strength tests with strain rates in the range of 0.2 to 25 mm/s, using a hydraulically controlled material testing system (MTS) for different foam densities in the range 20 g/dm3 to 220 g/dm3. The above tests were carried out as numerical simulation using ABAQUS software. The verification of the properties was carried out on the basis of experimental tests and simulations performed using the finite element method. The method of modelling the structure of the tested sample has an impact on the stress values. Experimental tests were performed for various loads and at various initial temperatures of the tested sample. We found that increasing both the strain rate of loading and foam density raised the compressive strength and energy absorption capacity. Increasing the ambient and tested sample temperature caused a decrease in compressive strength and energy absorption capacity. For the same foam density, differences in foam microstructures were causing differences in strength and energy absorption capacity when testing at the same loading strain rate. To sum up, tuning the microstructure of foams could be used to acquire desired global materials properties. Precise material description extends the possibility of using EPP foams in various applications.

scholarly journals Characteristics of Compressive Strength of Sea Ice at Notoro Lagoon

1997 ◽  
Vol 13 ◽  
pp. 825-830
Author(s):  
Hisao Matsushita ◽  
Toru Takawaki ◽  
Ken-ichi Hirayama ◽  
Takaharu Masaki ◽  
Hideki Honda ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Sea Ice
Sign in / Sign up

Export Citation Format

Share Document