Date of Award
MS in Mechanical Engineering
A simulation was created using LS-DYNA® to determine the acoustical properties of a golf ball and golf driver head impact. LS-DYNA® has a coupled finite element analysis (FEA) and boundary element method (BEM) solver that uses the integral form of Helmholtz’s acoustic wave equation to deliver predicted sound pressure levels at predetermined acoustic points. Validation of the modeling was done on a simple plate donated by Titleist Golf. The plate was modeled and meshed using TrueGrid and impacted by a three layer golf ball model derived from “Tanka’s” paper on multilayered golf balls. The final converging model consisted of 10,900 solid fully integrated elements between the ball, plate, and plate support structure. The result was compared to experimental data taken by an air cannon and anechoic chamber that housed strain and acoustical measurement equipment. The sound level predictions from the model showed a promising correlation with experimental data and the focus switched to a golf driver head response during impact.
The same ball developed from Tanaka’s paper was used to impact a 350cc generic golf driver head. The driver head consisted of 3300 fully integrated shell elements throughout the model. The top of the hosel was fixed during the simulation to simulate the connection to the golf shaft. The ball was fired at the center of the driver’s face and the predicted sound was determined for a point two feet behind the driver head. The BEM prediction of the driver head model showed little correlation with actual recorded impact sounds provided by Cleveland Golf when comparing frequency response functions. These differences could arise from assumptions and simplifications made to speed up the impact simulation. The sound produced from the golf ball after impact was one such factor was not included. Due to the complex shape of the driver head and the total number of elements involved, the numerical solution took upwards of 100 hours to finish. Adding the golf ball sound would greatly increase computational time and not contribute significantly to the overall predicted sound. Although the BEM solution can be used to characterize different driver heads, the impact is too complicated to efficiently and accurately predict the true impact sounds.