| Being a lightweight aluminum alloy,magnesium aluminum alloy has a low density,high strength,good processing properties and the characteristics of good welding performance,which has been widely applied in aviation,shipbuilding,automobile manufacturing and other fields.Through the research on the fracture characteristics of magnesium aluminum alloy,it can provide effective support and reference value for the later design and optimization of aluminum alloy engineering components.At present,the research on the dynamic fracture characteristics of light magnesium aluminum alloy is still in the initial stage.Due to the limitations of measurement technology,there are still many problems to be solved.Therefore,the research on the fracture characteristics of magnesium aluminum alloy is of great significance,which can lay a foundation for further defining the dynamic fracture properties of light magnesium aluminum alloy.In this paper,5A06 aluminum alloy is taken as the experimental object,and the fracture characteristics of the material are studied based on the experimental method.The fracture process of 5A06 aluminum alloy was obtained by digital image correlation technology,the strain distribution was analyzed,and the microcosmic failure mode of 5A06 aluminum alloy was studied.The influence of experimental parameters on dynamic fracture toughness of 5A06 aluminum alloy was further investigated by numerical simulation,and the stress distribution and crack propagation were analyzed.The main research contents of this paper are as follows:(1)Static tensile tests were conducted on specimens at different temperatures to determine the mechanical properties of them.It is found that with the increase of temperature,the elasticity modulus,yield strength,maximum tensile strength and fracture strength of the specimen decreased continuously,while the maximum elongation,maximum section shrinkage and fracture strain increased continuously.(2)Quasi-static three-point bending experiments were conducted on three-point bending specimens with prefabricated cracks at different temperatures to determine the static fracture toughness at different temperatures and explore its relationship with temperature.It was found that when the temperature increased from room temperature to 300°C,the static fracture toughness decreased to 51% of that at room temperature.(3)The modified split Hopkinson pressure bar apparatus combined with digital image correlation system used to carry out the three-point bending dynamic fracture experiment on specimens.The effects of loading rate and prefabricated crack length on dynamic fracture toughness were determined.Digital image correlation technique was used to obtain full strain measurement,and the failure mode of fracture surface was studied by scanning electron microscopy.It was found that when the loading rate increased by 14%,the dynamic fracture toughness increased by about 15%.When the prefabricated crack length increased by 40%,the dynamic fracture toughness decreased by about 50%.The stress and strain concentration appeared at the crack tip when the crack started,the stress distribution on the specimens surface showed "butterfly shape",The microscopic fracture mode of the specimen was the fracture of precipitated phase.(4)The finite element analysis software ABAQUS was used to simulate the quasi-static three-point bending fracture and to explore the influence of different prefabricated crack lengths on the static fracture toughness.It was found that the prefabricated crack length increased by 40% and the static fracture toughness decreased by 52%.Numerical simulation of dynamic three-point bending fracture was carried out to study the stress distribution and crack growth,and the experimental results were verified.The influence of loading rate and prefabricated crack length on the dynamic fracture toughness was consistent with the experimental results.The error between the dynamic fracture toughness and the experimental results were 7.17% and 7.66%,respectively. |
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