Lucerne University of Applied Sciences and Arts
As part of a research project together with the company Stöckli Swiss Sports AG, the Lucerne University of Applied Sciences and Arts has developed a virtual ski model. The goal was to simulate the complete heating-press process by means of FEM simulations. Skis are quasi-symmetrical multilayer composites, bonded by an adhesive. Since the adhesive curing depends on heat and pressure, the skis are heat-pressed. This production step gives the ski its shape and stiffness, and thus determines the characteristics and the quality of a ski. The proper simulation of the process of curing was an essential part in simulating the complete process. In a preliminary work, the focus was therefore on the simulation of the curing behavior of the adhesive and the development of a curing-contact model.
The simulation of the heat-press process consists of three steps, conducted with ANSYS Mechanical. A thermal-transient simulation of the ski generates the nonstationary temperature field, including the surrounding press bed. Depending on the temperature change, position and time, the calculation of the adhesive curing behavior is computed in a separate intermediate step, performed with ANSYS APDL commands. In a concluding nonlinear static-mechanical simulation, the heat-press process is simulated using the temperature field, the curing behavior of the adhesive and other parameters, resulting in the final shape of the ski and the residual stresses. The successful validation of the temperature field, the deflection curve and the bending stiffness by measurements emphasize the level of maturity of the developed ski model. The simulation model generated major insights. Problematic zones in the ski and press bed were identified. The greatest potential is in the large number of possible parameter studies for all kinds of geometry and process parameters. The use of simulation in the development of new skis and processes in ski manufacturing can save costs by requiring significantly fewer physical prototypes. Furthermore, such models help to explore the effectiveness of completely new and unconventional approaches in ski design.