Falling accidents are among the largest and fastest growing sources of occupational injuries. Despite slips representing a plurality of all falling accidents, the technology used to assess the slipperiness of shoe and floor surfaces has remained relatively stagnant over the past two decades. A major limitation in existing slip-testers is that the under-shoe conditions that are experienced during slipping are not replicated in the testing device. Different testing conditions alter the tribological interaction at the shoe-floor interface and affect the coefficient of friction measurement. In addition, current testing methods only measure the coefficient of friction value, which does not provide sufficient information about the critical frictional mechanism to suggest a specific ergonomic intervention. The overall objective of this research is to develop a slip-testing apparatus that 1) mimics a human slip while measuring friction and 2) provides specific information on the shoe-floor interaction that can be used to guide the appropriate intervention. The rationale for mimicking the human slip is that recreating the loading conditions of the shoe during a slip will reproduce the tribological phenomenon at the shoe-floor interface and will lead to more accurate friction measurements;and that collecting additional data related to the tribological interaction will lead to improved ergonomic interventions that reduce slipping accidents. This project aims to establish proof-of-concept for this device through three specific aims.
Specific Aim #1 is to develop a slip-testing device that mimics the under-shoe conditions of a human slip. A device will be developed with three individual degrees of freedom to individually control vertical force, anterior/posterior displacement/velocity and shoe angle. Sensors will simultaneously measure vertical force, sliding speed and shoe angle, which will be used in the closed-loop feedback control. The device will use PID control to track time-series profiles of human slips. Objective #1.1 will be to develop the device so that the coefficient of multiple determinations between human slipping data and the slip-testing data is greater than 0.9. Representative data from human slips will be used to demonstrate the ability of the device to mimic a variety of slipping profiles.
Specific Aim #2 will validate the use of novel fluid pressure sensors to assess the role of tread on the shoe-floor-contaminant interaction. Inadequate tread has been demonstrated to lead to higher hydrodynamic pressures in the shoe-floor interface and lower shoe-floor coefficient of friction. Objective #2.1 will be to quantify the hydrodynamic pressures in order to provide feedback regarding whether a shoe tread intervention is necessary. Two hypotheses are used to test the effectiveness of this technology. Hypothesis 2.1 will test whether the force supported by the fluid is related to friction coefficient and Hypothesis 2.2 will test whether tread affects the fluid coefficient.
Specific Aim #3 will be to assess reliability and reproducibility of the device. This research is expected to be a first step towards developing a device that is the gold standard in assessing slipperiness and that is useful for identifying optimal interventions for reducing slipping accidents.
Slip and fall accidents account for one of the largest sources of occupational injuries and fatalities. Developing technology that accurately assesses slipperiness of shoe-floor- contaminant surfaces and that is useful in developing interventions is critical to reducing these types of accidents. This proposal will improve our slip-testing technology by making it more relevant to human slipping and by identifying situation-specific interventions for improving shoe-floor friction.