ursor ▁to ▁the ▁development ▁of ▁high - speed ▁rail ▁systems . ▁Im aging ▁a ▁concrete ▁beam ▁before ▁and ▁after ▁application ▁of ▁a ▁compress ive ▁pre - load ▁confir ms ▁that ▁the ▁use ▁of ▁a ▁S tere o D IC ▁system ▁is ▁an ▁effective ▁and ▁accurate ▁non - contact ▁approach ▁for ▁meas uring ▁small ▁surface ▁stra in ▁fields . ▁S tere o D IC ▁measurements ▁provide ▁essential ▁data ▁to ▁reli ably ▁estimate ▁the ▁transfer ▁length ▁and ▁confirm ▁that ▁the ▁entire ▁concrete ▁portion ▁of ▁the ▁beam ▁has ▁the ▁required ▁compress ive ▁stress ▁to ▁maintain ▁compression ▁throughout ▁service ▁life . ▁ ▁The ▁ad hes ion ▁of ▁un c ured , ▁un id irection al ▁composite ▁to ws ▁that ▁are ▁ad her ed ▁to ▁a ▁similar ▁composite ▁to w ▁using ▁autom ated ▁fi ber ▁pla cement ▁( AF P ) ▁processing ▁can ▁be ▁tested ▁using ▁S tere o D IC . ▁A ▁temperature ▁and ▁wear - res istant ▁pattern ▁is ▁ad her ed ▁to ▁composite ▁to ws ▁and ▁then ▁the ▁de form ations ▁of ▁the ▁to w ▁is ▁measured ▁as ▁it ▁is ▁he ated ▁and ▁bond ed ▁during ▁AF P ▁processing . ▁A ▁modified ▁double ▁cant ile ver ▁beam ▁ad hes ive ▁spec imen ▁based ▁on ▁the ▁work ▁of ▁H ög berg ▁can ▁be ▁used ▁to ▁obtain ▁the ▁tra ction - separ ation ▁law ▁to ▁be ▁used ▁in ▁coh es ive ▁zone ▁model ing ▁law ▁of ▁the ▁to w - to - t ow ▁bond ▁layer . ▁ ▁Rec ogn ition ▁ ▁The ▁Society ▁for ▁Ex perimental