Two-dimensional cushioning characteristics of sports surfaces

Abstract

To evaluate sports surfaces, organizations often adopt vertical force attenuation or deformation and horizontal friction tests. Impact attenuation of sports surfaces is especially important for injury prevention. Although the mechanical tests are reproducible and the criteria for these tests are very strict, they have an issue of ‘particularity’: that is, the material behaviour may change when the mechanical properties of the drop mass spring systems are changed. To avoid this, we proposed an evaluation method using a mathematical surface model and computer simulation in previous studies that examines vertical properties only, while a two-dimensional impact test device for examining the two-dimensional cushioning characteristics of sport surfaces using a parallelogram linkage was proposed in previous studies. In this study, the data acquired from the two-dimensional device was confirmed by high-speed video. We then conducted two-dimensional impact tests – 69 trials, including 5 slip trials – using a variety of impact intensities and impact angles. The conclusions are as follows: 1) The impact force and the displacement acquired from the device were reliable even in slip trials; 2) When comparing the impulse of non-slip trials and slip trials, horizontal cushioning was observed in the slip trials, especially in the higher drop height group; 3) Even in non-slip trials, two-dimensional cushioning of impulse was observed; and 4) The impact friction test used in this experiment is significantly different from the popular friction tests and can provide new knowledge about the cushioning and friction characteristics of sports surfaces.

Keywords:

• Two-dimensional cushioning
• sport surface
• impact test
• parallelogram linkage
• friction

Acknowledgements

The authors would like to express their thanks to Oku En-tout-cas Co., Ltd. for their valuable contributions to the study.