Surface interactions of soccer balls

A soccer ball interacts with a variety of surfaces during a game usually under varying environmental conditions; however there has been limited research in this area. This thesis reports a series of investigations aimed at developing an improved understanding of the surface interaction between a soccer ball and surfaces of interest. The main aims were to quantify the . friction between the ball and surface, to assess the effect of changing the contact conditions and investigate whether the design of a ball could be optimised to perform consistently in dry and wet conditions. Experimental and computational approaches were used in partnership to analyse the impact and rebound behaviour of soccer balls. For the experimental approach, high speed video was used to record the bounce of a ball projected on to a surface with no initial spin and a Robotic Leg was used to assess the kicking action. In both cases the resultant spin, angle and velocity of the impact were measured. The finite element (FE) models of the ball were taken from previous research and used to simulate the above experimental scenarios. Further development of the ball models enabled the sub-modelling and analysis of soccer ball surface textures under realistic loading conditions. The dry and wet condition was found to influence the ball impact more than any other variable. The contact angle between the ball and surface was also found to be significant, however the addition of a surface texture to the soccer ball was only found to have a larger effect at lower velocity impacts and for kicking. After investigating the complex contact conditions (sliding speed and contact pressure) a friction tester was developed to test ball and surface materials with initial tests providing some similar findings to actual ball impacts. A constant coefficient of friction was also found to be sufficient to model the soccer ball impact within FE at a single velocity over a full range of contact angles. A developed FE ball model was created to determine localised loading conditions of the outer panel foam layers where prototype textures could be analysed and compared.