新しい衝撃曲げ試験法による動的破壊強度じん性の評価(<小特集>衝撃小特集)

概要

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A novel impact bend test procedure is described for determining the dynamic fracture-initiation toughness, K_<Id>, at a loading rate K^^・_1 of the order of 10^6MPa√<m>/s. The split Hopkinson pressure bar techinque was used to measure dynamic loads applied to a fatigue-precracked bend specimen. The dynamic stress intensity factor history for the bend specimen was evaluated by means of a dynamic finite element code. The onset of crack initiation was detected using a strain gage near a crack tip. The K_<Id> values was determined from the critical dynamic stress intensity factor at crack initiation. A series of dynamic fracture tests were performed for a Ti-6246 alloy and a 7075-T6 aluminum alloy. The K_<Id> values obtained for both the aoolys were compared with the corresponding values obtained under quasiststic losding conditions. The fracture surface morphology was examined with the help of a scanning electron microscope to rationalize the apparent differences in the measured fracture-initiation toughness in response to the change in loading rate. Furthermore, the validity of the K_<Id> determination was confirmed by measurements of the crack tip plastic zone size inthe interior of the fracture specimens based on the microhardness tests.
社団法人日本材料学会の論文
1990-12-15