Grönqvist Raoul, Hirvonen Mikko, Rajamäki Erkki, Matz Simon
Liberty Mutual Research Center for Safety and Health, Hopkinton, MA 01748, USA. raoul.gronqvist@occuphealth
Accid Anal Prev. 2003 Mar;35(2):211-25. doi: 10.1016/s0001-4575(01)00105-1.
A previously developed test rig was used as starting point for designing a portable slip meter with two new features. First, an inflatable pneumatic test wheel, consisting of six slider units, was introduced as the impacting contact element relative to floor surface. Second, an inductive trigger was built into the system to facilitate a precise timing of the slider-floor contact during the test. This new test rig was designed to measure transitional friction properties of contaminated floor surfaces during simulated heel strike, which is considered the most critical phase of gait from the slip and fall point of view. Another objective was to quantify the validity and reliability of this test method in the laboratory, but not yet in the field. The measurement process was evaluated on eight wet and oily floor surfaces (vinyl and ceramic tile floorings) using two slider materials (plain, profiled), two normal loads (100, 200 N), and two sliding velocities (0.15, 0.30 m/s) as independent variables. The outputs of the portable slip meter, in terms of transitional friction coefficients, were compared to force platform-based friction values and to slip resistance values obtained with a slip simulator apparatus for laboratory testing of shoes and floor surfaces. The outputs were also evaluated against slipperiness ratings made by three male subjects in paired comparison trials, in which the subjects walked over eight wet floor surfaces wearing shoes with the plain soling material. The results showed that test option 200 N and 0.15m/s led to optimum validity despite its tendency to promote frictional vibrations (stick-slip) in the contact surface. Compared to the lower sliding speed, the higher speed reduced both stick-slip and measurement bias. Test option 200 N and 0.30 m/s was the most reliable one in this experiment. It yielded lower friction coefficients than any other test option and reduced the likelihood of underestimating slip and fall hazards. The results implied that the minimum friction coefficient was 0.25 for preventing a fall on wet floor surfaces, whereas the limit for preventing a slip was in the range 0.30-0.35. Transitional friction measurement was found to be a valid and reliable indicator for slip resistance. A more accurate control of the normal force during testing is needed for actual field use of the test method.
一个先前开发的试验台被用作设计一种具有两个新特性的便携式滑度计的起点。首先，引入了一个由六个滑块单元组成的可充气气动测试轮，作为相对于地面的冲击接触元件。其次，在系统中内置了一个感应触发器，以便在测试过程中精确计时滑块与地面的接触。这个新的试验台旨在测量模拟脚跟撞击过程中受污染地面的过渡摩擦特性，从滑倒和跌倒的角度来看，这被认为是步态中最关键的阶段。另一个目标是在实验室中量化这种测试方法的有效性和可靠性，但尚未在实际场景中进行。使用两种滑块材料（普通的、异形的）、两种法向载荷（100 N、200 N）和两种滑动速度（0.15 m/s、0.30 m/s）作为自变量，在八个湿的和有油污的地面（乙烯基地板和瓷砖地板）上评估测量过程。便携式滑度计的输出结果，以过渡摩擦系数表示，与基于力平台的摩擦值以及使用用于鞋类和地面表面实验室测试的滑度模拟器设备获得的防滑值进行比较。输出结果还与三名男性受试者在配对比较试验中给出的滑度评级进行评估，在该试验中，受试者穿着带有普通鞋底材料的鞋子走过八个湿地面。结果表明，200 N和0.15 m/s的测试选项尽管倾向于在接触表面促进摩擦振动（粘滑），但仍导致最佳有效性。与较低的滑动速度相比，较高的速度减少了粘滑和测量偏差。200 N和0.30 m/s的测试选项在本实验中是最可靠的。它产生的摩擦系数比任何其他测试选项都低，并降低了低估滑倒和跌倒危险的可能性。结果表明，在湿地面上防止跌倒的最小摩擦系数为0.25，而防止滑倒的极限在0.30 - 0.35范围内。发现过渡摩擦测量是防滑的有效且可靠指标。在实际现场使用该测试方法时，测试过程中需要更精确地控制法向力。
