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14:40   Instrumentation and surface interaction of various types of shoes Chair: Kenta Moriyasu 14:40 20 mins PARAMETRIC STUDY OF SIMULATED TENNIS SHOE TREADS John Goff, Daniel Ura, Luke Boswell, Matt Carre Abstract: We report on friction properties between simulated tennis shoe treads created in house and a hard court tennis surface approved by the International Tennis Federation. To simulate tennis shoe tread, we use the compound N70-Nitrile (NBR-Butadine Rubber), which possesses similar physical characteristics as commercial tennis shoe treads, namely hardness, tensile strength, and elongation percentage. Into that compound we have created a series of tread patterns with various shapes, spacing, and heights. An in-house traction rig allows for the maintaining of a constant vertical load while a horizontal load is monotonically increased until our tread slips on the hard court tennis surface. Our experimental apparatus allows us to test a range of rubber compound areas and tread patterns. We performed experiments with different vertical loads and extracted both static and dynamic friction coefficients using force data supplied by load cells mounted vertically and horizontally. Variations in the compound’s tread geometry lead to different friction coefficients. We also rotated our tread patterns over a range of angles and extracted associated friction coefficients. Our results have moved us closer to a better understanding of optimal tread patterns on a tennis shoe. Such results are especially of interest to us as sliding is becoming a more prominent feature of elite tennis play on hard courts. 15:00 20 mins THE INSTRUMENTED RUNNING SHOE Stefan Schwanitz, Stephan Odenwald Abstract: Typical studies investigating the biomechanics of running are conducted in laboratories (Odenwald 2006). Subjects are requested to perform repeated running trials i.e. with a certain running shoe condition. Force platforms, camera systems, accelerometers and other measurement techniques are then applied to obtain variables used to describe each running trial. Oriwol et al. (2012) have demonstrated that the arithmetic mean of such variables obtained in repeated measures with a low number of replications (n < 10) did not serve as a valid estimator for the true value of a subject. Hence it was concluded the necessity to explore alternative measurement techniques that might be applied in field-testing in order to obtain objective data of higher number of gait events for each subject. In this paper a measurement system will be described that is able to overcome some of the limitations of laboratory based running shoe research described before. Therefore, the heel part of a commercial running shoe was equipped with five Hall-Effect sensors and the same number of permanent magnets. Due to a specific calibration routine is was possible to calculate the local deformation of the midsole at each of the five positions from the sensor output voltage. To perform running trials in the laboratory the sensor shoe was connected by wire to a measurement amplifier that is synchronized with the force plate data acquisition system and the kinematic data recording system. For testing in the field a small data recorder was worn by the subject. In order to compare lab and field testing absolute values of local midsole deformations, timing of midsole compressions and deformation velocities will be discussed. Furthermore, an approach to correlate information of midsole deformation to the ground reaction forces will be shown. REFERENCES Oriwol, D., Milani, T. L., & Maiwald, C. (2012). Methodological issues associated with the mean value of repeated laboratory running measurements. Footwear Science, 4(3), 183-190. Odenwald, S. (2006). Test methods in the development of sports equipment. In The Engineering of Sport 6 (pp. 301-306). Springer New York. 15:20 20 mins SKI BOOT SOLES BASED ON GLASS FIBER/RUBBER COMPOSITES WITH IMPROVED GRIP ON ICED AND WET SURFACES Martino Colonna, federico de Bon, Matteo Moncalero, Claudio Gioia Abstract: Slips and falls are very common when walking with ski boots and they are often the cause of serious injuries. For this reason, we have previously reported1 the factors influencing the friction coefficient of the materials used for the production of soles on wet floors and icy surfaces. The results of our study1 have pointed out that the stiffness and the roughness of the material used for the sole have a fundamental effect on grip performances. However, even the most performing thermoplastic polymer or rubber tested in our previous study (complying with ISO 5355 standard for ski boots) did not possess a coefficient of friction on icy surfaces above 0.15 and therefore the soles present on the market do not posses an efficient grip on those surfaces. For this reason, in the last few years ski boot producers have started to study the application of composite materials in order to improve the grip performances of rubber on ice. In particular, one of the most promising approaches consists in the use of a composite material based on a rubber matrix containing aligned glass fibers that are perpendicular to the base of the sole. The rigid glass fibers should increase the mechanical grip on ice and snow while the creation of a structured surface should have an effect on grip performances on wet surfaces, since it should modify the water repellency of the surface. However, no studies on this type of composites have ever been reported in the literature. For this reason, we have performed a study in order to assess the performances of this type of composite materials and to understand the effect of the size, amount, orientation and distribution of the fibers in the rubber matrix. Rubber/glass fiber composites with different content and distribution of the fibers have been prepared and the surface has been analyzed using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and optical profilometry. The hydrophobicity of the soles has been analyzed using contact angle measurement and the coefficient of friction has been measured on various substrates. The results obtained indicate a significant effect of the glass fibres on the grip, in particular on icy surfaces, and that the dimension and distribution of the fibres has a fundamental effect on the grip performances. FEM modelling has also been used to determine the optimal characteristics of the composite.