LAUSR

Abstract Shoes are an essential item in daily life to prevent slip-and-fall accidents and to improve performance in human activities such as walking, running, and jumping. These effects are supported by the friction between the outer shoe soles and the floor. In designing the friction of the outer sole, the wear resistance must be also considered to maintain slip resistance and provide a longer shoe lifetime. Rubber is the most popular material for the outer sole in shoe design, but it is also common to use a cross-linked resin foam on the outer sole to reduce the weight and improve the slip resistance. Ethylene vinyl acetate (EVA) is a popular material for the shoe foam material. In general, cross-linked EVA foam has a non-uniform porosity distribution, and especially near the surface in the low-porosity region called the skin layer. Here, it is considered that the friction and wear behaviors of cross-linked EVA foams can be changed via the skin layer, but the influence of the porosity distribution on the friction and wear behaviors has not been clarified. Using cross-linked EVA foams with a skin layer, this study focused on the foam friction and wear behaviors on a rough surface as a function of the porosity distribution. The friction and wear behaviors were found to depend on the wear surface porosity, which increased with wear progress. In addition, the friction coefficient exhibited a positive and negative correlation with the porosity of the wear surface and the normal force, respectively, while the specific wear rate increased with both parameters. These results are particularly meaningful for designing shoe materials.