Dynamic Compression of Metals

Dynamic compression

Stu­dy­ing the beha­vi­or of metals during a high-speed dyna­mic com­pres­si­on event has always been chal­len­ging due to the com­plex test set up and fast data cap­tu­re rates requi­red. Curr­ent­ly, very litt­le lite­ra­tu­re is available regar­ding defor­ma­ti­on beha­vi­or at strain rates of  10 to 500s-1. Uti­li­zing high-speed came­ras, the Vic-3D HS sys­tem can be used to quan­ti­fy the sur­face dis­pla­ce­ments and strains in three dimen­si­ons over the enti­re field with gre­at pre­cis­i­on. Digi­tal Image Cor­re­la­ti­on (DIC) has gai­ned wide­spread popu­la­ri­ty over recent years in such high-speed appli­ca­ti­ons due to its high accu­ra­cy, fle­xi­bi­li­ty and ease of use.




Dynamic compression2In this exam­p­le, a 6mm dia­me­ter cylind­ri­cal spe­ci­men was com­pres­sed at a strain rate of 50s-1. The Vic-3D HS sys­tem was used to cap­tu­re the  sur­face dis­pla­ce­ments and  strains on  the  spe­ci­men during the event. A ran­dom speck­le pat­tern is appli­ed to the spe­ci­men that allows the ana­ly­sis soft­ware to easi­ly track the defor­ma­ti­on to sub-pixel accu­ra­cy. Alt­hough the high- speed came­ras are capa­ble of much hig­her cap­tu­re rates, for this test they were set to an appro­pria­te frame rate of 14,400fps to maxi­mi­ze spa­ti­al reso­lu­ti­on while acqui­ring an ade­qua­te num­ber of images during the event. The came­ras were post-trig­ger at a reso­lu­ti­on of 1024 x 400 pixels. After the event, the images are trans­fer­red to the computer’s  hard  dri­ve, and  then  post-pro­ces­sed using Vic-3D ana­ly­sis software.

Images cour­te­sy of Amos Gilat & Jere­my Seidt at Ohio Sta­te University.