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Hockey as a game has been the subject of little research. The authors of this paper outline a modified rigid body model of the hockey stick impact, using coefficient of restitution (COR) values that take into account different ball and stick properties. Field data was taken from a number of players, including two internationals, giving a wide range of data for comparison. Basic physical properties were recorded for a selection of hockey sticks, and COR data was acquired for different hockey balls using a range of impact velocities. It was found that the COR of hockey balls decreases with increasing approach velocity, and that balls of a different construction exhibit a wider range of response at high velocity. The top end carbon fibre stick tested here hits a ball around 6% faster than a wooden stick under the same conditions. The modified rigid body model successfully predicts ball departure velocity to within 3% of experimental data across a wide range of velocities. [ABSTRACT FROM AUTHOR]

The traction force of studded boots on artificial turf was studied using a friction sled pulled by a constant speed motor. The traction of 6 and 12 mm cylindrical studs were studied on an artificial surface with grass fibre lengths of 50 mm and filled with rubber crumb and sand. It was found that the traction force increased with the number of studs and became approximately constant if more than six studs were used. Doubling the stud length more than doubled the traction. A simple model of traction was developed, in which the total traction was equal to the plate friction plus the ploughing traction of the studs. The ploughing traction increased and the plate friction decreased with the number of studs, due to lift that was generated by each stud as the sled moved across the surface. The theory ovelpredicted the traction for large numbers of studs, probably because leading studs shielded following studs, thus reducing the shear strength of the surface. [ABSTRACT FROM AUTHOR]

The surface on to which a bowler projects a ball in the game of cricket is termed the pitch and is a source of great concern to players, commentators and spectators alike. The pitch is a carefully prepared strip of natural turf of fundamental importance to the play of the game. In order to ascertain why the cricket ball rebound varies from pitch to pitch, a study was conducted to further the understanding of the cricket ball impact. The cricket ball impact is oblique and previous studies have shown both the ball and pitch to deform significantly during impact. This study presents a normal impact model capable of simulating both the deformation of the ball and the pitch. The model provides a firm platform on which the more complex oblique impact may be considered. High speed video measurements validated the normal impact model on both a first class cricket pitch and a soft artificial surface. [ABSTRACT FROM AUTHOR]

An impact hammer was designed that incorporated an accelerometer to measure impact response and a set of light-gates to measure impact velocity. This system was capable of consistent drop tests that provided the necessary data to characterise a range of normal impacts. A parametric study was carried out to assess the effect of variables including mass, contact velocity and impact hammer shape. The contact kinetic energy was found to be the control parameter in the loading phase of contact and allowed predictions of maximum force and displacement, independent of mass. The impact mass was found to be the control parameter for the unloading phase of contact, allowing predictions of the damping behaviour of the surface. Mass-spring-damper modelling was performed to quantify these effects and predict surface behaviour during impact. Modelling was carried out for two different sports surfaces, an acrylic tennis court and an athletics track. To validate the model, normal impacts were carried out between a rigid ball and the athletics track, monitored using a high speed video camera. The model successfully predicted the coefficient of restitution and displacements for a range of impacts. [ABSTRACT FROM AUTHOR]