Light emission during impact stressing of a particle layer

The mechanical stress detection technique was developed based on light emission properties of ZnS:Mn particles. The light emission properties of ZnS:Mn particles were characterized by the use of the impact tester that includes a stressing tool, photomultiplier and a contact time measurement system. The mechanical stressing of particles was caused by the impact of a metallic ball, dropped from different heights. At impact, the metallic ball achieves direct contact with the upper surface of the metallic anvil. This allows the measurement of the contact time by means of the electrical current that flows between the anvil and the metallic ball during contact time. The stress, caused at the collision, is transmitted through a metallic anvil to the layer of particles and produces the deformation of particles. The applied stress was detected using a piezoelectric sensor. It was shown that the ZnS:Mn particles generate the light during the action of the loading force. After removal of the loading force the light emission from the particle layer disappears in a few microseconds. The measurement was carried out using different ranges of applied forces. In this way, it was shown that the particle layer exhibits a high damping factor and failure resistance. One of the possible applications of these sensor systems based on light emission properties of ZnS:Mn particles is structural health monitoring.