Non-linear viscoelastic properties of golf balls

Based on a stress relaxation following the logarithmic law, a wide variety of golf balls was analyses as to viscosity constant (the multiplier of LNt), the stiffness parameters at different cross head speeds, conventional Atti and Riehle numbers, and first peak frequency of impact sound. The Atti number correlated highly with the peak frequency. Solid core golf balls are more viscous than wound balls. The force-deflection curve of solid core balls follows a parabolic function, the one of wound balls an exponential function. Based on the logarithmic law, the stifffiess can be extrapolated linearly with respect to the logarithm of deflection rate, and peak forces and contact time were calculated at an impact speed of 50 m/s.