Snow, an Intriguing, Complex, and Changeable Solid

2020 ◽  
pp. 5-13
Author(s):  
Francois Louchet
Keyword(s):  
Stress Distribution ◽  
Granular Material ◽  
Snow Cover ◽  
Volume Ratio ◽  
External Pressure ◽  
Ice Crystals ◽  
Formation Mechanisms ◽  
Grain Surface ◽  
Topological Concept ◽  
Complex Arrangement

This chapter provides basics of snow structure and topology. As snow is a complex arrangement of ice crystals, themselves found in oodles of geometrical shapes, sizes, and formation mechanisms, we essentially focus on those that are more directly involved in avalanche release. Three snow peculiarities are also outlined. Snow being made of ice, it inherits its particular propensity to melt under external pressure. Since snow cover results from accumulation of snowflakes, it may be considered as a granular material, with quite original properties due to the unusually large grain surface vs volume ratio, and to their related tendency to change shapes and to heal. Snow being also a mixture of ice, air, and water, the topological concept of percolation is of interest to deal with stress distribution in the snow cover, and is briefly discussed.

Numerical study of stress distribution in sheared granular material in two dimensions

2000 ◽  
Vol 62 (3) ◽  
pp. 3882-3890 ◽  
Author(s):  
S. G. Bardenhagen ◽  
J. U. Brackbill ◽  
D. Sulsky
Keyword(s):  
Stress Distribution ◽  
Granular Material ◽  
Numerical Study ◽  
Two Dimensions

scholarly journals Separation of the Formation Mechanisms of Residual Stresses in LPBF 316L

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1234
Author(s):  
Alexander Ulbricht ◽  
Simon J. Altenburg ◽  
Maximilian Sprengel ◽  
Konstantin Sommer ◽  
Gunther Mohr ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
Formation Mechanisms ◽  
Micro Computed Tomography ◽  
Solidification Shrinkage ◽  
Stainless Steel 316L ◽  
Heat Accumulation ◽  
Cooling Rates

Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured parts and important factors for the residual stress formation. This study examined the influence of heat accumulation on the distribution of residual stress in two prisms produced by Laser Powder Bed Fusion (LPBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two different border fill scan strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. The goal was to reveal the effect of different heat inputs on samples featuring the same solidification shrinkage. Residual stress was characterised in one plane perpendicular to the building direction at the mid height using Neutron and Lab X-ray diffraction. Thermography data obtained during the build process were analysed in order to correlate the cooling rates and apparent surface temperatures with the residual stress results. Optical microscopy and micro computed tomography were used to correlate defect populations with the residual stress distribution. The two scanning strategies led to residual stress distributions that were typical for additively manufactured components: compressive stresses in the bulk and tensile stresses at the surface. However, due to the different heat accumulation, the maximum residual stress levels differed. We concluded that solidification shrinkage plays a major role in determining the shape of the residual stress distribution, while the temperature gradient mechanism appears to determine the magnitude of peak residual stresses.

Research of Reinforce Stress on the Pressure Structure of Submersible Vehicle

2014 ◽  
Vol 496-500 ◽  
pp. 590-593
Author(s):  
Guan Nan Chu ◽  
Qing Yong Zhang ◽  
Guo Chun Lu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Hoop Stress ◽  
External Pressure ◽  
Finite Element Models ◽  
Cylinder Pressure ◽  
Simulation Experiments ◽  
Element Analysis ◽  
Load Carrying

In order to improve the load-carrying properties of pressure structure, a new method to improve the external bearing limit is put forward and residual stress is used. Based on finite element analysis, finite element models of cylinder pressure structure of submersible vehicle are established to produce hoop residual stress in the process of outward expansion. According to a lot of data of simulation experiments, the result indicates that hoop residual stress is compressive on the outer surface of the pipe and the hoop stress keeps tensile on the inside surface. This kind of stress distribution is helpful to the cylinder structure and can improve its bearing capacity of external pressure. Moreover, the rules of the residual stress are got. The influences of physical dimension, yield strength of material and the expansion rate to the stress distribution are analyzed. The measures to produce the stress distribution are also presented.

Penetrations in Shells Under External Pressure

1970 ◽  
Vol 92 (2) ◽  
pp. 269-274
Author(s):  
R. C. DeHart ◽  
L. F. Greimann
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Stress Condition ◽  
External Pressure ◽  
Experimental Stress ◽  
Spherical Shells ◽  
Premature Failure ◽  
Resistant Structure ◽  
Theoretical Results ◽  
Stress Analyses

Penetrations, in the pressure-resistant structure of a submersible, disturb the stress condition in the shell and may cause a premature failure. In this paper, two types of finite-element solutions are used to predict the stress distribution near view port openings in spherical shells under external pressure. Results of experimental stress analyses are also given and compared to the theoretical results.

scholarly journals Systematically Peculiar Molecular Composition in M 82: Regarding the Formation Mechanisms

2005 ◽  
Vol 13 ◽  
pp. 875-878 ◽  
Author(s):  
S. Takano ◽  
N. Nakai ◽  
K. Kawaguchi ◽  
T Takano ◽  
P. Schilke ◽  
...  
Keyword(s):  
High Temperature ◽  
Molecular Composition ◽  
Formation Mechanisms ◽  
Starburst Galaxy ◽  
Surface Formation ◽  
Nearby Galaxies ◽  
Grain Surface

AbstractA systematically peculiar molecular composition has been found in a nearby starburst galaxy M 82. Molecules related to grain surface formation and to production reactions favorable at high-temperature are deficient in M 82 among nearby galaxies with rich gas. These molecules are SO, SiO, NH3, HNCO, CH3OH, and CH3CN. Possible reasons for this peculiarity are discussed.

scholarly journals Recrystallization of snowpack at sites with different degrees of humidity

2012 ◽  
Vol 53 (61) ◽  
pp. 27-30
Author(s):  
Valentina A. Lobkina
Keyword(s):  
Snow Cover ◽  
Sea Of Okhotsk ◽  
Structural Changes ◽  
Sakhalin Island ◽  
Ice Crystals ◽  
The South ◽  
Snow Layer ◽  
Rate Of Evolution ◽  
Rate Of Growth ◽  
Separate Layer

AbstractThe results of monitoring the rate of recrystallization of snow cover at sites with different degrees of humidity are presented. Observations were carried out at two sites within the same stratigraphic complex of snow cover in the south of Sakhalin island, Sea of Okhotsk. The basic structural changes in snowpack were traced. We determined the rate of growth of the diameter of the crystals in the snow layer. The structure of the snowpack was studied using E.G. Kolomyts’s technique. On the basis of stratigraphic observations, diagrams of the stratification of the snow cover were created, to determine the rate of evolution of ice crystals in a separate layer from its inception.

scholarly journals The Effect of Bionic Brake Drum Striped Unit Body on Friction and Wear of Brake Pad

2020 ◽  
Vol 213 ◽  
pp. 02012
Author(s):  
Haiyan Hu ◽  
Haiyang Yang ◽  
Jiandong Yang ◽  
Qingnian Wang ◽  
Ti Zhou
Keyword(s):  
Stress Distribution ◽  
Contact Stress ◽  
Friction And Wear ◽  
Normal Pressure ◽  
External Pressure ◽  
Brake Pad ◽  
Distribution Law ◽  
Contact Surfaces ◽  
Brake Drum ◽  
Contact Stress Distribution

In this paper, the contact mechanics is applied to analyse the interaction between the striped unit body on the bionic brake drum and the brake pad. The contact stress distribution law of two objects interaction is obtained. According to the stress distribution law the change of the friction and wear of the striped unit body on the brake pad is derived. Considering the change of the surface feature regardless of other factors, the friction wear of the striped unit body on the brake pad has increased by more than 27%. It is found that small convex striped unit bodies are added on the surface of the bionic brake drum, which makes the contact surface between the brake drum and the brake pad no longer the original plane contact. Therefore, the pressure and direction between the contact surfaces are various. Besides, even if the external pressure does not change, the contact normal pressure between the contact surfaces will be increased which increases the friction wear on the brake pad accordingly.

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