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Shape Factors of Elastomers
Shape Factor is a term of art used in the design of elastomer products.
It has the virtue of being an easily developed mathematical expression. It quantifies the unique ability of elastomers to react to an applied force by bulging at 90 degrees to the direction of application of the force.
A "high" shape factor indicates a minimal ability to deform. A "low" shape factor indicates a soft material with a high ability to deform. Implicit in a low shape factor is a low spring rate and the capability to have a low natural frequency.
The Shape Factor is calculated by developing the ratio of the average contact surface (one side) divided by the perimeter area. As such, it can be developed for any shape that can be mathematically described. However, a few standard shapes cover over 90% of all needs.
Product properties developed using the Shape Factor methodology have a nominal accuracy of +/-15%. More precise product properties require physical testing or Finite Element Analysis (FEA).
Calculating Deflection / Natural Frequency / Spring Rate
Sorbothane offers "Design Guide," a Windows-based design program. In addition, a paper version of the Design Guide is available upon request from the factory.
