A Novel Ski–Snow Tribometer and its Precision

Hasler, Michael; Schindelwig, Kurt; Mayr, Bernhard; Knoflach, Ch.; Rohm, Sebastian; Putten, Joost van; Nachbauer, Werner

doi:10.1007/s11249-016-0719-2

Cited by 34 publications

(36 citation statements)

References 24 publications

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“…High static friction argued against pressure melting, whereas system changes that increased interface temperatures (higher ambient temperatures, heat conducted to or trapping at the interface) reduced sliding friction, consistent with their hypothesis. Numerous subsequent studies have produced results consistent with self-lubrication theory, and it remains widely accepted (Evans and others, 1976;Colbeck, 1988Colbeck, , 1992Lehtovaara, 1989;Persson, 2000;Kietzig and others, 2010;Hasler and others, 2016;Nachbauer and others, 2016). Because snow consists of bonded ice grains, studies often assume that self-lubrication prevails on both snow and ice surfaces.…”

Section: Introductionmentioning

confidence: 83%

“…For example, short sliders are proportionally more influenced by dry-contact friction than longer ones, other conditions being the same. Nachbauer and others (2016) and Hasler and others (2016) justified development of a 24 m-long linear tribometer to test full-scale skis in part to avoid this scaling requirement. More complete understanding of the mechanics of each friction mode would aid scaling and lead to models that can predict full-scale performance from reduced-scale tests.…”

Section: Introductionmentioning

confidence: 99%

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The mechanics of snow friction as revealed by micro-scale interface observations

et al. 2017

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The mechanics of snow friction are central to competitive skiing, safe winter driving and efficient polar sleds. For nearly 80 years, prevailing theory has postulated that self-lubrication accounts for low kinetic friction on snow: dry-contact sliding warms snow grains to the melting point, and further sliding produces meltwater layers that lubricate the interface. We sought to verify that self-lubrication occurs at the grain scale and to quantify the evolution of real contact area to aid modeling. We used high-resolution (15 µm) infrared thermography to observe the warming of stationary snow under a rotating polyethylene slider. Surprisingly, we did not observe melting at contacting snow grains despite low friction values. In some cases, slider shear failed inter-granular bonds and produced widespread snow movement with no persistent contacts to melt (μ < 0.03). When the snow grains did not move and persistent contacts evolved, the slider abraded rather than melted the grains at low resistance (μ < 0.05). Optical microscopy revealed that the abraded particles deposited in air pockets between grains and thereby carried heat away from the interface, a process not included in current models. Overall, our results challenge whether self-lubrication is indeed the dominant mechanism underlying low snow kinetic friction.

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Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The mechanics of snow friction as revealed by micro-scale interface observations

et al. 2017

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“…Based on tribometer tests, they suggested that self-lubrication from frictional heating accounted for low kinetic (sliding) friction on both snow and ice substrates. Numerous subsequent studies produced results consistent with self-lubrication theory, and it remains widely accepted (Evans and others, 1976;Colbeck, 1988Colbeck, , 1992Lehtovaara, 1989;Persson, 2000;Kietzig and others, 2010;Nachbauer and others, 2016;Hasler and others, 2016). Because snow consists of bonded ice grains, studies often assume that ice is an acceptable surrogate to study the mechanics of snow friction.…”

Section: Introductionmentioning

confidence: 91%

Evidence that abrasion can govern snow kinetic friction

et al. 2018

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The long-accepted theory to explain why snow is slippery postulates self-lubrication: frictional heat from sliding melts and thereby lubricates the contacting snow grains. We recently published micro-scale interface observations that contradicted this explanation: contacting snow grains abraded and did not melt under a polyethylene slider, despite low friction values. Here we provide additional observational and theoretical evidence that abrasion can govern snow kinetic friction. We obtained coordinated infrared, visible-light and scanning-electron micrographs that confirm that the evolving shapes observed during our tribometer tests are contacting snow grains polished by abrasion, and that the wear particles can sinter together and fill the adjacent pore spaces. Furthermore, dry-contact abrasive wear reasonably predicts the evolution of snow-slider contact area, and sliding-heat-source theory confirms that contact temperatures would not reach 0°C during our tribometer tests. Importantly, published measurements of interface temperatures also indicate that melting did not occur during field tests on sleds and skis. Although prevailing theory anticipates a transition from dry to lubricated contact along a slider, we suggest that dry-contact abrasion and heat flow can prevent this transition from occurring for snow-friction scenarios of practical interest.

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“…Sliding over fresh ice has been made possible by moving the sliding object over a spiral path [10]. Other tests have used a linear tribometer for measuring the ice friction [11]- [14]. In these situations, the object is not free to move over ice, but is fixed to a mechanism that controls testing conditions (such as load and velocity) and measures the ice friction.…”

Section: Introductionmentioning

confidence: 99%

An Ice Track Equipped with Optical Sensors for Determining the Influence of Experimental Conditions on the Sliding Velocity

Lungevičs

Jansons

Gross

2018

Latvian Journal of Physics and Technical Sciences

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The ability to slide on ice has previously focused on the measurement of friction coefficient rather than the actual sliding velocity that is affected by it. The performance can only be directly measured by the sliding velocity, and therefore the objective was to design and setup a facility to measure velocity, and determine how experimental conditions affect it. Optical sensors were placed on an angled ice track to provide sliding velocity measurements along three sections and the velocity for the total sliding distance. Experimental conditions included the surface roughness, ambient temperature and load. The effect of roughness was best reported with a Criterion of Contact that showed a similar sliding velocity for metal blocks abraded with sand paper smoother than 600 grit. Searching for the effect of temperature, the highest sliding velocity coincided with the previously reported lowest coefficient of ice friction. Load showed the greatest velocity increase at temperatures closer to the ice melting point suggesting that in such conditions metal block overcame friction forces more easily than in solid friction. Further research needs to be conducted on a longer ice track, with larger metal surfaces, heavier loads and higher velocities to determine how laboratory experiments can predict real-life situations.

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A Novel Ski–Snow Tribometer and its Precision

Cited by 34 publications

References 24 publications

The mechanics of snow friction as revealed by micro-scale interface observations

The mechanics of snow friction as revealed by micro-scale interface observations

Evidence that abrasion can govern snow kinetic friction

An Ice Track Equipped with Optical Sensors for Determining the Influence of Experimental Conditions on the Sliding Velocity

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