Material Properties of a two-piece golf ball are determined by the viscoelastic split Hopkinson bar(SHB) technique and used to the optimization analysis of golf clubhead. Strain histories of the incident, reflected and transmitted waves on the input and output bars, resulting from SHB tests on cylindrical specimens of cover and core material of the golf ball, are resolved into frequency components by Fourier Transformation. Then, in frequency domain waveforms at measurement points are corrected to those at the interfaces between a specimen and bars. The complex compliance of each material is determined by calculating strain-stress ratio in the frequency domain, and 3-element viscoelastic models are subsequently identified based on variations of the complex compliances. Using the determined viscoelastic properties of the materials of the two-piece golf ball, the shape optimization of a clubhead is investigated by simulating the collision of the viscoelastic golf ball with the golf clubhead numerically. The basis vector approach is utilized to the find the optimal thickness distribution of the clubhead approximately to maximize the driving distance of the ball. The basis vectors are created manually and automatically from eigenmodes. The numerical examples are given to show the validity of this approach.
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