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Three commercial hockey balls, two with mixed cork, wool and polymer cores and one which was hollow, were tested dynamically using ball rebound and ‘hardness’ tests. The load / deformation behaviour of selected ball types was determined at low deformation rates (0.02 − 2 mm s−1) using a Zwick Z100 universal tester and at high deformation rates (16 − 24 m s−1) using a gas cannon and steel target. In addition, cylindrical samples taken from the core were compression tested (using the same slow deformation rates, also on the Zwick Z100) to determine their tangential modulus variation with strain and deformation rate as well as their viscoelastic energy losses. The trends shown during impact tests were consistent with those in the low strain rate compression tests and these correlated with the materials properties and dimensions. Lower impact speed behaviour was associated with deformation being dominated by the cover, whilst higher deformation rates gave significant differences in ball behaviour due to the composition and dimensions of their cores. These differences were, however, demonstrated in the core compression testing indicating that the core materials play a greater role as the speed of the shots increases and deformation spreads beyond the cover. The qualitative relationships between ball construction at deformation behaviour at varying speeds is also summarised.

The performance of golf balls during various shots occurs under a range of strains and strain rates, which results in varying ball stiffness and energy loss responses due to the viscoelastic nature of the polymers used in ball construction. Modelling of ball performance is often based on fitting FE models to ball rebound data, although some groups have started to successfully use the material properties of the various components to account for normal impact. The latter approach is more predictive as it allows the potential effects of varying material properties and ball constructions to be estimated before balls are actually fabricated. The normal impact is often represented through a normal coefficient of restitution (CoR), which is strain and strain rate dependent. In oblique impacts the situation is complicated as both normal and tangential forces act with the bending moment of the tangential force causing backspin generation. Modelling of oblique impact will need to be able to predict contact time of the ball on the club face as this is the time during which the tangential force is generating backspin. One route to this contact time could come from the normal part of the impact as the ball centre of mass velocity normal to the face is decelerated and then accelerated. This paper will report results of impacts of a number of commercial ball types with a series of angled plateds at a number of impact speeds. These tests have been analysed in terms of normal and tangential CoR values and show that the normal part of the oblique impact can be treated independently of the tangential. In addition the relationship between backspin rate and loft angle, determined by the tangential component can be characterised using an effective friction coefficient, which has been related to the material properties and dimensions of the cover and sub-surface regions of the golf ball.