DETERMINATION OF THE OPTICAL-CONSTANTS OF CAUSTICS UNDER DYNAMIC LOADING USING A CONCENTRATED LOAD

A new technique is proposed for evaluating the optical constants of ca ustics under dynamic loading, In this technique, the optical constants are determined from the caustic pattern under a concentrated load and the dynamic value of the concentrated load, which is obtained using s train gages bonded to the surface of the falling weight. The optical c onstants of caustics c(0) for Several polymers are accurately evaluate d from the caustic pattern formed by a concentrated load acting on a h alf-plane, and the dependence of c(0) on the loading rate is determine d. The results show that the value of c(0) decreases considerably with increasing loading rate in Plexiglas and Araldite D containing 30% so ftening material. On the other hand, the values for polycarbonate, Ara ldite B and Araldite D not containing softening material decrease slig htly with increasing loading rate.