It is estimated that in Europe more than one million accidents occur at work annually as a result of lack of friction between shoes and floors. The costs due to days lost at work and medical treatment are valued at 1.5 billion ECU annually. Obviously there is a need to develop harmonised CEN standards for measuring slip the resistance properties of safety, protective and occupational footwear for professional use. This study was focused on bridging the gap between biomechanical test methods involving human subjects and mechanical slip test methods in order to improve the validity and reproducibility of the current draft standard for professional footwear (CEN/TC161/WG3 N22 Rev1, 1996).
The first objective was to define a test protocol based on a detailed comparison of the results of biomechanical and mechanical tests. The second objective was to check the reliability of the test protocol in a ring test and to use the findings of the ring test to propose amendments to the current draft standard as discussed in the European working group CEN/TC161/WG3.
The gap between mechanical tests and (subjective) biomechanical tests has always been large. As a result of this project this gap bas been reduced and is understood more clearly. However, the gap partly remains unbridged mainly due to the fact that in mechanical tests limited test parameters have to be chosen for practical reasons. This leads to satisfying correlations between mechanical and biomechanical results for some parts of the slipping situations, whereas other parts show poor correlations. From the interlaboratory ring test it appeared that three mechanical devices eventually succeeded in reaching the proposed test conditions. The correlation between the test results with those machines were generally acceptable (about 0.85). The correlation between results with other machines were generally poor (about 0.70). It was finally concluded that the following test conditions and parameters have to be strictly defined and met accurately: the shoe attachment and positioning, the normal force, the sliding velocity and the calculation of the dynamic coefficient of friction as a time-average. Based on definitions for these test conditions and parameters as suggested by the project partners, the European working group has already proposed a new draft standard (CEN/TC161/WG3 N23).
A series of mechanical and biomechanical tests was carried out in order to obtain detailed information about the mechanical circumstances that take place during the slip process and to find the most simplified mechanical test conditions, still leading to results that correlate well with the biomechanical test results. The relevant test conditions and parameters were used to formulate a new test protocol based on the current draft standard. Next, the project partners performed an interlaboratory ring test, using six different mechanical test devices and three different (subjective) biomechanical test methods. The new test protocol was verified by comparing and analysing the ring test results. Based on the findings in this study, the project partners proposed amendments to the current draft standard.
Funding SchemeCSC - Cost-sharing contracts
5684 ZC Best
NN16 9JH Kettering