Dynamic Characteristics Measurements of a Car Wiper Blade

Dynamic characteristics of a rubber car wiper blade, that are the viscoelasticity under impact load and the dynamical friction, have been accurately evaluated by means of an optical method. In the method, force is generated and measured as the inertial force acing on a mass. A linear air bearing is used to realize a linear motion with sufficiently small friction acting on the mass, i.e. the moving part of the linear bearing. The inertial force acting on the mass is calculated from the velocity of the mass. The velocity is determined highly accurately by means of measuring the Doppler shift of the frequency of the laser light beam reflecting on the mass using an optical interferometer. The viscoelasticity of the wiper blade under impact load is determined by means of colliding the mass with it. The kinetic friction acting between the wiper blade and glass plate is determined by means of pressing the wiper blade onto the glass plate attached on the upper surface of the mass, whose initial momentum is given manually. Using the developed instrumentation, both the viscoelasticity under impact load and the dynamical friction of the wiper blade are easily and accurately determined based on the definition of force.