Friction between skis and snow was studied in a variety of field laboratory measurements. Whilst tests have the drawback changing conditions, sport-specific sample sizes speeds could not be measured up to now. Hence, novel linear tribometer developed allowing studies with whole at speeds. The precision better than 2.2 %. dominant cause for imprecision variability single tracks lower speed, whilst higher also determination normal friction force speed became relevant. is high enough...

In this study, we examined the practicability of deep learning-based 2D keypoint detection applied to regular skiing and injury situations (i.e., out-of-balance fall situations) on an alpine ski racing track. We therefore created a skiing- situation-specific dataset (hereinafter called "Injury Ski Dataset"), which state-of-the-art algorithms OpenPose, Mask-R-CNN, AlphaPose DCPose were compared. The performance each detector was evaluated by calculating mean per joint position error (MPJPE)...

Modeling of ski friction requires an in-depth understanding the ski-snow contact. For this aim, we implemented Euler–Bernoulli beam equations for embedded cross-country skating ski. Apparent contact area and pressure distribution were calculated from ski's penetration depth using a hypoplastic force-penetration relation snow. In static validation experiment on elastomer foundation, difference between measured loaded was below 5.1 kPa. skis gliding snow, apparent increased normal load, softer...

Abstract In the simulation of skiing force between ski and snow is a decisive factor. We decompose reaction into penetration normal to surface, shear friction. Two portable measurement devices were developed study forces for compacted on groomed slopes. The was assessed by measuring depth ski-tool loaded surface. For tangential load measured when began fail. Overall 236 108 experiments conducted different types snow. proportional volume displaced ski-tool. failure multiplied length tool....

The temperature of snow under skating skis was studied with infrared sensors at four positions and three different velocities. To have an indication causes consequences the heating friction coefficient a linear tribometer pressure distribution were measured as well. increased velocity. highest increase 440 mm from ski end velocity 10 m/s. Temperature position 1550 independent Friction coefficient, measurements showed high reliability allowed to create model explain profile along ski.

A ski–snow interaction model is presented. The force between ski and snow decomposed into a penetration normal to the surface, shear parallel it, friction. purpose of this study was investigate benefits hypoplastic vs an elastic contact for in simulation skiing turns. To reduce number influencing factors, sledge equipped with skis considered. forward dynamic implemented. For evaluation both models, deviation simulated trajectories experimental track data computed turns 67 42 m. Maximum...

The influence of important parameters on the flight trajectory for jumps in downhill W orld C up races was investigated. To quantify impact injury risk at landing, parameter equivalent landing height ( ELH ) introduced, which considered a variable slope inclination during movement. Altogether, 145 runs four different and trainings were recorded analyzed. A simulation model developed to predict phase skier. Drag lift areas selected by identification fit two‐dimensional data from video...

The purpose of this study was to analyze the kinetic friction different combinations snowboard base structures and waxes. On a linear tribometer in cold lab 3 snowboards with were first waxed training wax. Then coefficient assessed at 2 m/s, 5 m/s 8 m/s. Subsequently boards prepared racing finish measured again. effects structure wax on snow appear be strongly interdependent. A that takes effect one board given conditions must not working structure. In addition there is strong influence...

Um den Einfluß der Skitaillierung auf Schwungradius zu untersuchen, wird im ersten Teil dieser Arbeit Radius Spur eines selbstfahrenden Schlittens ermittelt und mit Vorhersage nach Howe verglichen. Es zeigt sich, daß die Schwungradien Beginn des Schwunges zwischen 65 85 % theoretisch erwarteten Wertes betragen. Im zweiten Verlauf Carver-Fahrers bestimmt daraus, mittels Geschwindigkeitsmessung, angreifenden Kräfte berechnet. ergibt sich eine starke Reduktion Schwungradius, welche einer...

Abstract We computed reaction forces and moments acting on a skier during carved turn. performed an inverse forward dynamic analysis. For run of elite skier, marker positions skis were obtained as functions time from video analysis smoothed by splines. Linear velocities accelerations differentiating the splines, angular velocities, via rotation matrices. The at right ski measured with two Kistler force plates. dynamics, we used adapted Hanavan model for consisting upper body, left thighs,...

After falls, skiers or snowboarders often slide on the slope and may collide with obstacles. Thus, skier’s friction snow is an important factor to reduce incidence severity of impact injuries. The purpose this study was measure different fabrics ski garments respect roughness, speed, contact pressure. Three types were investigated: a commercially available overall, smooth downhill racing suit, dimpled suit. Friction measured for taped short using linear tribometer. fabrics’ roughness...

Whilst studies of the wear ski bases and wax coatings are available, few is known about change snow due to sliding ski. In this study, ski-friction-induced changes were investigated. The structure was scanned using X-ray computed tomography (CT) before after 1, 10, 20 recurring runs a cross country at temperatures −1.3, −10.7, −19.1 °C. Concurrently, friction measured. volume fraction ice as function vertical distance from surface derived CT data. Superficial compacted roughness reduced by...

Slalom skiers hit flex poles whereby an impulse is transferred from the skier to pole. Each such impact leads a speed reduction of skier, which clearly greater for relatively lighter than it heavier skiers. Additionally, there injury risk caused by and breakage For detailed analysis causes consequences this impact, three-dimensional finite element models were developed pendulum impactor. The validated comparing data experiments with impactor simulations. comparisons included flex-pole...

Introduction & Purpose The low friction coefficient of a ski on snow is due to the formation meltwater layer between base and surface. It widely accepted theory that this frictional heating (Bowden Hughes, 1939). experimental evidence regarding has been challenging task. This because dynamically created most likely refreezing immediately once heat input terminated. Ambach Mayr (1981) measured change in capacitance probe quantify thickness layer. They reported 4-20 µm during downhill...

Injury analysis may be one of the most beneficial applications deep learning based human pose estimation. To facilitate further research on this topic, we provide an injury specific 2D dataset for alpine skiing, covering in total 533 images. We propose a post processing routine, that combines rotational information with simple kinematic model. could improve detection results fall situations by up to 21% regarding PCK@0.2 metric.

In Europe and North America, approximately 150 fatalities occur as a result of avalanches every year. However, it is unclear whether certain shovel shapes are more effective than others in snow removal during avalanche victim recovery. The objective was to determine the performance parameters with developed standardized test using different sex-specific differences. Hence, several were determined for clearing from filled box (15 men, 14 women). A flat (F) deep (D) blade shaft connected...