 Fracture toughness is measured using a notched and pre @-@ cracked rectangular specimen , of which the dimensions are specified in standards , for example ASTM E23 . There are other means of estimating or measuring fracture toughness by the following : The <unk> impact test per ASTM A370 ; The crack @-@ tip opening displacement ( <unk> ) test per BS 7448 @-@ 1 ; The J integral test per ASTM <unk> ; The <unk> drop @-@ weight test per ASTM <unk> . 
