Visualization of impact force using pressure sensitive paper "Prescale"

To characterize damage and deformation in an impacted area of structure caused by foreign objects, it is fundamentally needed to measure the acting force and its pressure distribution over the area. In the present investigation, we attempt to visually identify the impact force by means of the pressure sensitive paper 'Prescale' which is a combination of papers coated by micro-capsules containing coupler and developer, and is currently used for measuring the quasi-statically applied force on the bodies in contact. A split-Hopkinson pressure bar method was used to evaluate the sensitivity of the paper under impact loading. Dynamic impression marked on the paper was digitized by a scanner, and the color density was measured by the FPD901 electronic densitometer system. It was found that the pressure sensitive paper instantaneously responded even for the impact loading of which duration was several hundred microseconds, while the sensitivity was significantly reduced when compared to the quasi-static loading. As for an example, we applied the method to evaluate the impact force in the dynamic response of a golfball and discussed the results