scholarly journals Determining the drivers for snow gliding

2018 ◽  
Vol 18 (7) ◽  
pp. 1891-1903 ◽  
Author(s):  
Reinhard Fromm ◽  
Sonja Baumgärtner ◽  
Georg Leitinger ◽  
Erich Tasser ◽  
Peter Höller
Keyword(s):  
Soil Moisture ◽  
Friction Coefficient ◽  
Soil Temperature ◽  
Slope Angle ◽  
Soil Surface ◽  
Static Friction ◽  
High Temporal Resolution ◽  
Static Friction Coefficient ◽  
Vegetation Characteristics ◽  
Snow Gliding

Abstract. Snow gliding is a key factor for snow-glide avalanche formation and soil erosion. This study considers atmospheric and snow variables, vegetation characteristics, and soil properties and determines their relevance for snow gliding at a test site (Wildkogel, Upper Pinzgau, Austria) during winter 2014/2015. The time-dependent data were collected at a high temporal resolution. In addition to conventional sensors, a “snow melt analyzer” was used. The analysis shows that the soil temperature 10 cm below the surface, the phytomass of mosses, the liquid water content in the snowpack, and the static friction coefficient of the glide shoes had significant influence on snow gliding during the whole winter. In the first period (October to January) the soil moisture at the surface and 1.5 cm below the surface and the length of the slope uphill of the glide shoes affected the snow gliding, too. In the second period (February to May) the soil temperature at the surface, the soil moisture 10 cm below the surface, and the slope angle had additional influence on snow gliding. The role of the vegetation in the snow-glide process is determined by the influence on the static friction coefficient caused by its composition and characteristics and by moss-rich and short-stemmed canopies being seemingly more interconnected with the snowpack. In addition to the soil and snow properties, the topography and the vegetation characteristics, further investigations may be focused on the freezing and melting processes in the uppermost soil layers and at the soil surface.

scholarly journals Determining the drivers for snow gliding

2018 ◽  
Author(s):  
Reinhard Fromm ◽  
Sonja Baumgärtner ◽  
Georg Leitinger ◽  
Erich Tasser ◽  
Peter Höller
Keyword(s):  
Soil Moisture ◽  
Soil Surface ◽  
Test Site ◽  
Negative Influence ◽  
Important Variable ◽  
High Temporal Resolution ◽  
Soil Layers ◽  
Key Factor ◽  
Avalanche Formation ◽  
Snow Gliding

Abstract. Snow gliding is a key factor for snow glide avalanche formation and soil erosion. This study considers atmospheric and snow variables, vegetation characteristics, and soil properties, and determines their relevance for snow gliding at a test site (Wildkogel, Upper Pinzgau, Austria) during winter 2014/15. The time-dependent data were collected at a high temporal resolution. In addition to conventional sensors a snow melt analyzer was used. The analysis shows that the soil moisture at the soil surface had the largest influence on snow gliding during the first part of the winter (October to January). The soil moisture 1.5 cm below the soil surface was the second important variable in the first part of the winter, and the most important variable in the second part of the winter (February to May). A negative influence on snow gliding had the phytomass of mosses in autumn and spring caused by lower canopy heights at these sites. Furthermore, a higher portion of dwarf shrub phytomass reduces snow gliding, because its rigid structure can transfer forces to the soil. Further investigations may be focused on the freezing and melting processes in the uppermost soil layers, and at the soil surface.

Measurements of the Static Friction Coefficient Between Tin Surfaces and Comparison to a Theoretical Model

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Rebecca D. Ibrahim Dickey ◽  
Robert L. Jackson ◽  
George T. Flowers
Keyword(s):  
Theoretical Model ◽  
Friction Coefficient ◽  
Human Error ◽  
Surface Profile ◽  
Static Friction ◽  
Quantitative Agreement ◽  
High Plasticity ◽  
Static Friction Coefficient ◽  
Experimental Apparatus ◽  
Rough Surface Contact

A new experimental apparatus is used to measure the static friction between tin surfaces under various loads. After the data is collected it is then compared to an existing theoretical model. The experiment uses the classical physics technique of increasing the incline of a plane and block until the block slides. The angle at the initiation of sliding is used to find the static friction coefficient. The experiment utilizes an automated apparatus to minimize human error. The finite element based statistical rough surface contact model for static friction under full stick by Li, Etsion, and Talke (2010, “Contact Area and Static Friction of Rough Surfaces with High Plasticity Index,” ASME Journal of Tribology, 132(3), p. 031401) is used to make predictions of the friction coefficient using surface profile data from the experiment. Comparison of the computational and experimental methods shows similar qualitative trends, and even some quantitative agreement. After adjusting the results for the possible effect of the native tin oxide film, the theoretical and experimental results can be brought into reasonable qualitative and quantitative agreement.

scholarly journals Brittle Fracture Theory Describes the Onset of Frictional Motion

2019 ◽  
Vol 10 (1) ◽  
pp. 253-273 ◽  
Author(s):  
Ilya Svetlizky ◽  
Elsa Bayart ◽  
Jay Fineberg
Keyword(s):  
Friction Coefficient ◽  
Brittle Fracture ◽  
Static Friction ◽  
Quantitative Agreement ◽  
Interface Fracture ◽  
Earthquake Dynamics ◽  
Rupture Dynamics ◽  
Static Friction Coefficient ◽  
Fracture Theory ◽  
Macroscopic Motion

Contacting bodies subjected to sufficiently large applied shear will undergo frictional sliding. The onset of this motion is mediated by dynamically propagating fronts, akin to earthquakes, that rupture the discrete contacts that form the interface separating the bodies. Macroscopic motion commences only after these ruptures have traversed the entire interface. Comparison of measured rupture dynamics with the detailed predictions of fracture mechanics reveals that the propagation dynamics, dissipative properties, radiation, and arrest of these “laboratory earthquakes” are in excellent quantitative agreement with the predictions of the theory of brittle fracture. Thus, interface fracture replaces the idea of a characteristic static friction coefficient as a description of the onset of friction. This fracture-based description of friction additionally provides a fundamental description of earthquake dynamics and arrest.

scholarly journals A Novel Process for Manufacturing High-Friction Rings with a Closely Defined Coefficient of Static Friction (Relative Standard Deviation 3.5%) for Application in Ship Engine Components

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 448
Author(s):  
Wojciech S. Gora ◽  
Jesper V. Carstensen ◽  
Krystian L. Wlodarczyk ◽  
Mads B. Laursen ◽  
Erica B. Hansen ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Friction Coefficient ◽  
Relative Standard Deviation ◽  
Static Friction ◽  
Laser Surface ◽  
Laser Surface Texturing ◽  
Textured Surface ◽  
Fibre Lasers ◽  
Static Friction Coefficient ◽  
Relative Standard

In recent years, there has been an increased uptake for surface functionalization through the means of laser surface processing. The constant evolution of low-cost, easily automatable, and highly repeatable nanosecond fibre lasers has significantly aided this. In this paper, we present a laser surface-texturing technique to manufacture a surface with a tailored high static friction coefficient for application within driveshafts of large marine engines. The requirement in this application is not only a high friction coefficient, but a friction coefficient kept within a narrow range. This is obtained by using nanosecond-pulsed fibre lasers to generate a hexagonal pattern of craters on the surface. To provide a suitable friction coefficient, after laser processing the surface was hardened using a chromium-based hardening process, so that the textured surface would embed into its counterpart when the normal force was applied in the engine application. Using the combination of the laser texturing and surface hardening, it is possible to tailor the surface properties to achieve a static friction coefficient of ≥0.7 with ~3–4% relative standard deviation. The laser-textured and hardened parts were installed in driveshafts for ship testing. After successfully performing in 1500 h of operation, it is planned to adopt the solution into production.

scholarly journals Active Sensing of Static Friction Coefficient ^|^mu; for Controlling Grasping Force

1994 ◽  
Vol 30 (10) ◽  
pp. 1188-1194 ◽  
Author(s):  
Youji YAMADA ◽  
Kenji SANDA ◽  
Kazuhide FUJITA ◽  
Nuio TSUCHIDA ◽  
Kouji IMAI
Keyword(s):  
Friction Coefficient ◽  
Static Friction ◽  
Active Sensing ◽  
Static Friction Coefficient ◽  
Grasping Force

Research for a Projectile Positioning Structure for Stacked Projectile Weapons

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Qiao Luo ◽  
Xiaobing Zhang
Keyword(s):  
Friction Coefficient ◽  
Structural Parameters ◽  
Static Friction ◽  
Element Model ◽  
Ballistic Performance ◽  
Static Friction Coefficient ◽  
Key Technologies ◽  
Contact Surfaces ◽  
Proper Material ◽  
Multibody Contact

One of the key technologies of stacked projectile weapons is projectile positioning. However, the present projectile positioning structures have their respective advantages and shortcomings. A new structure based on the self-locking principle is put forward in this paper and verified as feasible by static analysis if the proper material and structural parameters are chosen. In order to check the strength and verify the feasibility of the structure under launch conditions, the multibody contact finite element model of the structure is established, coupled with dynamic load in the interior ballistic cycle. According to simulations and analysis, the projectile positioning structure is feasible and the strength of the projectile can meet the strength requirement for launch conditions. For different maximum static friction coefficients, simulations show that an increase in the maximum static friction coefficient between the contact surfaces of the positioning ring and barrel improves the positioning performance, but an increase in the maximum static friction coefficient between the contact surfaces of the positioning ring and projectile worsens. On the basis of great computation, it is found that an increase in the upper thickness and height of the positioning ring improves the positioning performance, but an increase in the lower thickness worsens the positioning performance. Further, a lower thickness affects the positioning performance more greatly. As a result, the positioning ring will be thin and light to improve the positioning performance. Compared with other positioning structures, the new structure has little influence on the ballistic performance and is a good application prospect.

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