"I worked with Altair ProductDesign for roughly one year attempting to correlate a composite lay-up finite element model of a tennis racquet, built in HyperWorks, to its real world counterpart. I was very impressed with Altair’s knowledge, hard work, quick response, and attention to detail. At the conclusion of the study, we were able to predict and verify within 4% error at least four important performance characteristics of the tennis racquet. We believe this will give us an advantage of speed to market in future product designs"
– Bob Kapheim, Design Engineer, Wilson Labs
Modeling of Tennis Racquets in a Virtual Environment
While exploring developments in FEA, Wilson Labs Design Engineer Bob Kapheim became familiar with Altair's HyperWorks® software and Altair ProductDesign engineering services. He learned that the Altair ProductDesign team would perform software simulation and test correlation for Wilson without them having to first invest in the software.
While composites simulation technology was relatively new and advanced for the Wilson Labs racquet team and the sporting goods industry in general, Altair has worked extensively on composites simulation methods within industries such as aerospace that have been routinely employing the technology. With this mature offering and experience base, it was fairly simple for Altair to adapt the technology to the composites simulation of tennis racquets. "To my knowledge, we’ve never made as much progress as we have working with Altair. We knew Altair would be a good partner for us because they were able to demonstrate exactly how their software would work for an engineer – that was significant for us. And they worked with us to show how their product could tackle what we are looking to do." said Mr. Kapheim.
The initial part of the work was done with a finite element model build based on the provided geometry representing the Outer Mold Line (OML) of the racquet that was undrilled, ungripped and without a handle.
Modeling of the laminate was kept at a simplified level. For each ply, the lay-up document was reviewed to understand the ply location, and then surfaces were trimmed and organized. Ply thicknesses were assigned, as were material properties. Loads and boundary conditions were also applied. Several analyses were performed using Altair’s structural analysis and optimization software OptiStruct® and results were validated to correlate with physical test data. Altair’s engineers successfully modeled today’s tennis racquet in a virtual environment. Testing and analyses demonstrated the close correlation between a virtual model’s behaviors and real life behaviors.
The project inspired a high degree of confidence that HyperWorks brings the accuracy required to model the tennis racquets in a virtual space, and that virtual simulation as a resource is far more efficient than manual techniques.
Meeting the Metrics
For all the performance metrics expected by the Wilson Labs racquet team (mass, center of mass, dynamic stiffness, static stiffness) the results showed an error percentage of less than 4%. The mass showed an error within 3%, center of mass in 2%, frequency being the dynamic stiffness was in 1% error, and the static stiffness was in 4% error, demonstrating results that were far better than expected up front.
"I worked with Altair ProductDesign for roughly one year attempting to correlate a composite lay-up finite element model of a tennis racquet, built in HyperWorks, to its real world counterpart. I was very impressed with Altair’s knowledge, hard work, quick response, and attention to detail. At the conclusion of the study, we were able to predict and verify within 4% error, at least four important performance characteristics of the tennis racquet. We believe this will give us an advantage of speed to market in future product designs," concluded Mr. Kapheim.