A Novel Computational Model for Traction Performance Characterization of Footwear Outsoles with Horizontal Tread Channels

Abstract

Slips and falls are among the most serious public safety hazards. Adequate friction at the shoe–floor contact is necessary to reduce these risks. In the presence of slippery fluids such as water or oil, the footwear outsole is crucial for ensuring appropriate shoe–floor traction. While the influence of flooring and contaminants on footwear traction has been extensively studied across several outsole surfaces, limited studies have investigated the science of outsole design and how it affects footwear traction performance. In this work, the tread channels of a commonly found outsole pattern, i.e., horizontally oriented treads, was varied parametrically across the widths (i.e., 2, 4, 6 mm) and gaps (i.e., 2, 3, 4 mm). Nine outsole designs were developed and their traction, fluid pressures, and fluid flow rates during slipping were estimated using a mechanical slip testing and a CFD-based computational framework. Outsoles which had wider tread (i.e., 6 mm) surfaces showed increased slip risks on wet flooring. Outsoles with large gaps (i.e., 4 mm) exhibited increased traction performance when slipped on wet flooring (R2 = 0.86). These novel results are anticipated to provide valuable insights into the science of footwear traction and provide important guidelines for the footwear manufacturers to optimize outsole surface design to reduce the risk of slips and falls. In addition to this, the presented CFD-based computational framework could help develop better outsole designs to further solve this problem.