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13:30   Behavior of Alpine Skis Chair: Nicola Petrone 13:30 20 mins DEVELOPMENT OF ALPINE SKIS USING FE SIMULATIONS Fabian Wolfsperger, Szabo Denes Abstract: INTRODUCTION: The ski manufacturing industry is characterized by short product life cycles and high innovation pressure in order to meet customer's expectations of progressive improvements of skis. To reduce development time a FE model was developed and validated to simulate the influence of changes of the ski construction on its bending and torsional stiffness. METHODS: Two existing skis with identical geometry, but distinctive differences of their torsional and bending stiffness were modelled using ANSYS Workbench. The sandwich construction was modelled by 18 solid bodies with bonded contacts: core, sidewalls, edges, upper and lower face with 13 layers including 4 additional resin interlayers. Orthotropic linear elastic material properties were taken from data sheets of suppliers and from material tests of the manufacturer. Sweep meshing was used to create an all-hex mesh of solid elements. Static structural simulations of a 3-point bending test and a torsion test were run in accordance to existing laboratory tests to validate the model. Positions of the additional resin interlayers were used to calibrate the model. RESULTS: For both skis, the FE model showed good agreement with the experimental data for ski A and B. The simulated bending stiffness was, respectively 2.8% and 3.2% higher compared to the experiments. The elastic curves revealed the model as slightly too stiff at the afterbody and too soft at the forebody. The simulated torsional stiffness was, respectively 2.1% and 4.2% lower than found in the experiments. In the development process, for example, the model was then used to quantify the influence of edge profile heights on the skis bending stiffness (3% per mm edge height). CONCLUSION: A realistic representation of the different construction layers of an alpine ski is still challenging, especially due to the heterogeneity of the fibre compound layers and the resin distribution. Using bulk properties of the upper and lower face of the sandwich construction is not an alternative. To virtually test the influence of new materials and layups every single layer has to be represented. Using two skis for validation and additional resin interlayers for calibration appeared appropriate in order to achieve adequate model results. 13:50 20 mins EFFECT OF REPAIRING AND GRINDING SCRATCHED ALPINE SKIS ON THEIR FRICTION ON SNOW Lukas Kaserer, Joost van Putten, Sebastian Rohm, Michael Hasler, Werner Nachbauer Abstract: Ski base service includes filling of scratches, grinding and waxing. The aim of this study was to investigate the effect of scratched and then repaired ski bases on their kinetic friction on snow. Kinetic friction of three different types of skis (junior, women and racing skis) in four preparation steps (factory-new, standard grinded, scratched, repaired) were measured at two different velocities (4 and 8 m/s). Testing took place on a linear tribometer with defined conditions at -8°C snow temperature. The normal force was set to typical values for the particular ski type. The coefficient of friction of the scratched skis almost doubled compared to the unscratched ones. This may be caused by asperity interlocking between the snow grains and the scratches. The coefficient of friction of the repaired bases was re-established since only about 1% of the before scratched area was covered with the filling material. 14:10 20 mins A METHOD FOR MEASURING THE BENDING AND TORSIONAL STIFFNESS DISTRIBUTIONS OF ALPINE SKIS Jonas Truong, Camille Brousseau, Alexis Lussier Desbiens Abstract: A novel non-destructive method for quickly, accurately and simultaneously measuring the bending and torsional stiffness distributions of an alpine ski is presented. This method, named SMAD (Stiffness Measurement through Angular Deformations), is based on measuring the angular deformations resulting from a known combined bending and torsion load. The method’s accuracy and repeatability is investigated and are on average under 2% and 3%, respectively. The coupling in the measurement of the bending and torsional deformations during combined loading due to ski misalignment in the test machine is investigated. The measured torsional deformation was found to be independent of the bending load. The measured bending deformation was found to be dependent on the torsional load but this effect could be limited by careful alignment of the ski in the test machine.