Abstract:
This thesis presents a simulation using LS-DYNA to predict the acoustical output from a golf ball impacting a golf driver head, employing a coupled finite element analysis (FEA) and boundary element method (BEM) solver. The BEM solver utilizes the integral form of Helmholtz's acoustic wave equation to determine sound pressure levels at specific points in space. The modeling approach was validated by first simulating a golf ball impact on a titanium plate, a simpler system for which experimental data was collected using a custom-built air cannon, an anechoic chamber, and acoustic measurement equipment. The titanium plate and its support structure were modeled and meshed using TrueGrid, while the golf ball was based on a three-layer model from prior research. The paper details the process of mesh convergence for both the plate and the ball to ensure the accuracy of the FEA model. The FEA results for the plate showed a promising correlation with the experimental data, leading to the application of the same methodology to a generic 350cc golf driver head model. The driver head simulation, which consisted of 3300 shell elements, was set to fire a ball at the center of the clubface, and the sound was predicted at a point two feet behind the head. The driver head simulation took over 100 hours to compute, and its BEM prediction showed little correlation with actual recorded impact sounds from commercial drivers when comparing frequency response functions. This discrepancy was attributed to simplifications made to reduce computational time, such as not including the sound produced by the golf ball itself. Despite this, the simulation did manage to predict some of the peak frequencies that were observed in the experimental data, partially validating the BEM solver's capability for impact simulations. The conclusion is that while the BEM solution can be a useful tool for characterizing and optimizing the acoustics of different driver heads, the complex nature of the impact makes it difficult to efficiently and accurately predict the true sound. The study also highlights that using FEA can help in the design and optimization process by identifying the frequencies a driver head will produce under specific loading conditions, allowing designers to steer a product towards a more desirable sound.
