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The Fracture Research of Hexagonal Duralumin Nut

The microstructure, fracture surface topography and mode of hexagonal nut cracked in assembling under air pressure were analyzed with optical microscope and scanning electronic microscope, which are made in contrast with that of hexagonal nut cracked in man-made. The research results show that the man-made fracture of nut was of dimple shape and cracked in toughness mode, which accorded with the fracture behavior of 2Al2 duralumin material. The air-pressure fracture of nut was of right shape and cracked in brittle mode. The fracture mechanism is concluded that crack fountain is formed in surface of nut because of scoring during assembling and then the crack expands rapidly, leading to brittle fracture of the nut.