▁the ▁practice ▁of ▁supporting ▁one ▁end ▁of ▁a ▁bridge ▁on ▁roll er ▁bear ings ▁to ▁allow ▁for ▁thermal ▁expansion . ▁ ▁His ▁work ▁on ▁fat igue ▁marks ▁the ▁first ▁system atic ▁investigation ▁of ▁S - N ▁Cur ves , ▁also ▁known ▁as ▁W öh ler ▁curves , ▁to ▁character ise ▁the ▁fat igue ▁behaviour ▁of ▁materials . ▁Such ▁curves ▁can ▁be ▁used ▁to ▁minim ise ▁the ▁problem ▁of ▁fat igue ▁by ▁lower ing ▁the ▁stress ▁at ▁critical ▁points ▁in ▁a ▁component . ▁W öh ler ▁showed ▁clearly ▁that ▁fat igue ▁occurs ▁by ▁crack ▁growth ▁from ▁surface ▁defect s ▁until ▁the ▁product ▁can ▁no ▁longer ▁support ▁the ▁applied ▁load . ▁The ▁history ▁of ▁a ▁f ract ure ▁can ▁be ▁understood ▁from ▁a ▁study ▁of ▁the ▁f ract ure ▁surface . ▁He ▁developed ▁appar atus ▁for ▁repeated ▁loading ▁of ▁railway ▁ax les , ▁mainly ▁because ▁many ▁acc idents ▁were ▁caused ▁by ▁sudden ▁fat igue ▁f ract ure . ▁The ▁presentation ▁of ▁his ▁work ▁at ▁the ▁Paris ▁Ex position ▁in ▁ 1 8 6 7 ▁brought ▁it ▁to ▁a ▁wide ▁international ▁audience . ▁▁ ▁W öh ler ▁was ▁an ▁advoc ate ▁of ▁state ▁standard isation , ▁testing ▁and ▁cert ification ▁of ▁iron ▁and ▁steel . ▁ ▁He ▁died ▁in ▁Hannover ▁in ▁ 1 9 1 4 . ▁ ▁References ▁ ▁Further ▁reading ▁ ▁External ▁links ▁ ▁Category : 1 8 1 9 ▁birth s ▁Category : 1 9 1 4 ▁death s ▁Category : G erman ▁engine ers <0x0A> </s> ▁An ▁ear then ▁floor , ▁also