ski pole design
116605790
Improved ski pole design by thin ply composite reinforcement
For cross country skiers, the ski poles are an essential tool for propulsion. To minimize the energy required for handling, the ski poles are to be light and stiff. The pursuit of lighter and stiffer ski poles has introduced Carbon Fiber Reinforced Plastics (CFRP) as the material class of choice. It has superior weight to stiffness properties compared to aluminum which is used for more basic ski poles. However, CFRP ski poles suffer from increased brittleness, whereby even small impacts may lead to sudden ski pole failure when it is used. By experimentally analyzing two generations of Skigo race 2.0 ski poles, the mechanical behavior in terms of stiffness and impact resistance has been characterized. The behavior from the experiments was captured using Finite Element (FE) simulations. The simulations were then used as a tool for generating new concept ski poles. Experiments were also conducted on the reference ski poles to obtain material properties used in the FE models. The project resulted in two concepts for more impact resistant ski poles which both have maintained weight and stiffness properties compared to the reference ski poles. To achieve this, the concept ski poles utilizes thin ply CFRP and are arranged with and without a foam core. The intention of the concepts is to prove the benefits of using thin ply CFRP to achieve increased impact resistance. Proceeding from the concept, prototypes need to be manufactured and tested to verify performance and before a potential commercialization the concepts suitability for mass manufacturing has to be evaluated. Keywords: ski pole, carbon fiber, CFRP, impact resistance, thin ply, finite elements
Martin Granlund Gustav Grasberg
204688881
Design of Device for Measuring the Load of Cross Country Ski Poles
Monitoring of physical activity allows the optimization of physical exercise and sports performance. Currently, there are a number of wearable devices designed to measure the acceleration of body segments. However, there are only a small number of experimental systems for evaluation of load and movement of cross country skiing and Nordic Walking poles. The system proposed in the article allows to measure the force which user is applying on the pole, the pole linear and angular acceleration and the tilt of the pole. The system uses a pair of strain gauge bridges and inertial measurement unit mounted on each pole. The measured data are subsequently processed by the capturing and recording unit, transmitted via Wi Fi interface and stored on an integrated SD card. Developed software allows analysis of the determined quantities including poling detection. The verification measurement has shown the usability of the system for assessing biomechanical parameters, particularly with regard to the evaluation of training methods and running styles for cross country skiing and Nordic running. The limitation of the proposed system is the disruption of the structural integrity of the pole due to the bonding of the strain gauge bridges and the associated greater susceptibility to damage in the event of extreme load, e.g. in top sports.
IFMBE Proceedings
Jan Hejda Petr Volf Jakub Mejstrik Jan Hybl Ales Tvrznik David Gerych Tomas Michalek Cestmir Oberman Emil Bolek Patrik Kutilek
755636
Multidisciplinary Design Process of a 6 Slot 2 Pole High Speed Permanent Magnet Synchronous Machine
High speed permanent magnet synchronous machines (HS PMSMs) are a popular topology among modern electrical machines. Suitable applications for such machines are low power vacuum pumps, compressors, and chillers. This paper describes a systematic design methodology for an HS PMSM using two case studies. The design process for such high speed (HS) machines is multidisciplinary and highly iterative due to the complex interaction of the many design variables involved. Consequently, no single optimum solution exists, and multiple possible solutions can meet the customer requirements. Practical solutions should be within acceptable thermal limits, should be energy efficient, and should be rigid enough to withstand the forces exerted during operation. The proposed design flow is divided into steps that are presented in this paper in the form of a flowchart with emphasis on mechanical aspects. Each step represents a task for a thermal, mechanical, or electrical engineer. The features of each step and the prerequisites for moving to the next step are discussed. The described methodology was implemented in the design of two HS PMSMs. The output performance results of the design flow are compared with measured results of the prototypes. The design process described in this paper provides a straightforward procedure for the multidisciplinary design of HS permanent magnet electrical machines.
IEEE Transactions on Industrial Electronics
Nikita Uzhegov Emil Kurvinen Janne Nerg Juha J Pyrhonen Jussi T Sopanen Sergey Shirinskii
44065210
Increased Impact Resistance of Cross Country Ski Poles by Improved, Simulation Assisted Composite Design
High end carbon fibre reinforced polymer (CFRP) ski poles of today are lighter and stiffer than previous generations, explained by the higher specific stiffness (stiffness to density ratio) for CFRPs in the range of 0.1 0.13 GPa m3/kg compared to approximately 0.03 GPa m3/kg for aluminium. In this study, we have analysed different CFRP pole designs on the market by mechanical testing and microscopy. We conclude that the strive for optimised weight and bending stiffness has generally driven the pole design to be sub optimal towards stiffness making them unnecessarily sensitive to transverse and impact loads. Based on the experimental findings, we have developed numerical simulation models to predict the bending and stress state in CFRP ski poles under axial as well as transverse (impact) loading conditions. These numerical model has then been used to find a new conceptual pole design with similar weight and stiffness but with seemingly higher impact resistance.
Martin Granlund Gustav Grasberg Hana Zrida Martin Fagerstrom Andreas Karlsson
218910598
Examining ski area padding for head and neck injury mitigation.
OBJECTIVES The injury mitigation capabilities of foam, ski area padding was examined for headfirst impacts. DESIGN AND METHODS A custom made pendulum impactor system was constructed using an instrumented, partial 50th percentile male Hybrid III anthropomorphic testing device (ATD) For each test, the ATD was raised 1.0m, released, and swung into a 20 cm diameter wooden pole. Test trials were conducted with the wooden pole covered by ski area padding (five conditions of various foam types and thicknesses) or unpadded. Linear (linear acceleration and HIC15) and angular (angular velocity, angular acceleration, and BrIC) kinematics were examined and used to estimate the likelihood of severe brain injury. Cervical spine loads were compared to the injury assessment reference values for serious injury. Further tests were conducted to examine the changes produced by the addition of a snowsport helmet. RESULTS 38 test trials were recorded with a mean sd) impact speed of 4.2 0.03) m/s. Head, resultant linear acceleration, HIC15, and associated injury likelihoods were tempered by ski area padding at the impact speed tested. Ski area padding did not reduce brain injury likelihood from rotational kinematics (p>0.05 for all comparisons) or reduce the cervical spine compression below injury assessment reference values. The addition of a helmet did not reduce significantly the likelihoods of brain or cervical spine injury. CONCLUSIONS At the impact speed tested, ski area padding provided limited impact protection for the head (for linear kinematics) but did not protect against severe brain injuries due to rotational kinematics or serious cervical spine injuries.
Journal of science and medicine in sport
Irving S Scher Lenka L Stepan Jasper E Shealy Ryan W Hoover
119300121
The 10 Meter South Pole Telescope
ABSTRACT.The South Pole Telescope (SPT) is a 10 m diameter, wide field, offset Gregorian telescope with a 966 pixel, multicolor, millimeter wave, bolometer camera. It is located at the Amundsen Scott South Pole station in Antarctica. The design of the SPT emphasizes careful control of spillover and scattering, to minimize noise and false signals due to ground pickup. The key initial project is a large area survey at wavelengths of 3, 2, and 1.3 mm, to detect clusters of galaxies via the Sunyaev Zel'dovich effect and to measure the small scale angular power spectrum of the cosmic microwave background (CMB) The data will be used to characterize the primordial matter power spectrum and to place constraints on the equation of state of dark energy. A second generation camera will measure the polarization of the CMB, potentially leading to constraints on the neutrino mass and the energy scale of inflation.
J E Carlstrom P A R Ade K A Aird Bradford A Benson Lindsey E Bleem Sonia Busetti C Chang E Chauvin H-M Cho Thomas M Crawford Abigail Crites M A Dobbs N W Halverson Stephen J Heimsath W L Holzapfel J Dana Hrubes Marshall K Joy Ryan Keisler Trevor Lanting A T Lee Erik M Leitch Jonathan Leong W X Lu M Lueker Daniel M Luong-Van Jeff J McMahon Jared Mehl S S Meyer Joseph J Mohr Thomas Montroy Stephen Padin Thomas J Plagge Clement L Pryke John E Ruhl K K Schaffer Dan Schwan E Shirokoff H Spieler Zachary Staniszewski Antony A Stark C E Tucker Keith Vanderlinde Joaquin D Vieira Ross Williamson
112318252
Entwurf robuster strukturbeschrankter Zustandsregelungen durch Polgebietsvorgabe mittels Straffunktionen Design of robust structurally constrained state feedback controllers by pole region assignment using penalty functions
Ausgangspunkt des Verfahrens ist eine Multi Modell Beschreibung der parameterabhangigen Strecke. Das Entwurfsziel besteht dann in der simultanen Polgebietsvorgabe fur alle Systemmodelle mit Hilfe eines fest eingestellten Reglers. Dazu wird die Entwurf sauf gabe zunachst mittels Straffunktionen in ein Optimierungsproblem uberfuhrt, welches dann durch numerische Minimierung gelost werden kann.
Ulrich Konigorski
114758691
A review of stress concentration factors in tubular and non tubular joints for design of offshore installations
Abstract Tubular structures are widely used in offshore installations, trusses, high rise buildings, towers for wind turbines, ski lift installations, lightning, road pole signals etc. owing to their excellent structural performance and attractive appearance. Stress concentration, especially in the welded joints of these structures, is an important design consideration particularly for fatigue design. In the context of tubular and non tubular joints, this paper provides a review of the experimental and numerical studies that have been carried out so far to determine the stress concentration factor (SCF) Emphasis is also placed on the complexity of capturing different types of stresses in tubular/non tubular joints for estimation of SCF. Present code provisions for evaluation of SCF are also discussed. Further, a few issues, which require significant research effort to advance our understanding and to improve the current design guidelines, have been identified.
Dikshant Saini Debasis Karmakar Samit Ray-Chaudhuri
33281564
Mechanics of pole vaulting: a review
A good understanding of the mechanics of pole vaulting is fundamental to performance because this event is quite complex, with several factors occurring in sequence and/or in parallel. These factors mainly concern the velocities of the vaulter pole system, the kinetic and potential energy of the vaulter and the strain energy stored in the pole, the force and torque applied by the athlete, and the pole design. Although the pole vault literature is vast, encompassing several fields such as medicine, sports sciences, mechanics, mathematics, and physics, the studies agree that pole vault performance is basically influenced by the energy exchange between the vaulter and pole. Ideally, as the athlete clears the crossbar, the vaulter mechanical energy must be composed of high potential energy and low kinetic energy, guaranteeing the high vertical component of the vault. Moreover, the force and torque applied by the vaulter influences this energy exchange and these factors thus must be taken into consideration in the analysis of performance. This review presents the variables that influence pole vault performance during the run up, take off, pole support, and free flight phases.
Sports biomechanics
Julien Frere Maxime L'hermette Jean Slawinski Claire Tourny-chollet
122072160
Reduction to the pole at low latitudes by Wiener filtering
Using simple estimates of the signal and noise power from gridded magnetic data, we design regulated frequency domain operators for reduction to the pole at low magnetic latitudes. These operators suppress the artifacts along the direction of the magnetic declination associated with the conventional reduction to the pole procedure, with negligible increase in computational load. The new procedure is applied to produce high quality reductions to the pole for noisy low latitude synthetic data and for magnetic data from the Dixon Seamount.
Richard O Hansen Robert Pawlowski