Highlights The dynamic response of aluminum alloy plates repeatedly impacted by a rigid impactor has been investigated experimentally and theoretically. The permanent deformations of an impacted plate increase with each additional impact, and reach the largest values when the surface crack reaches the other side of the plate. The load-carrying capacity of a plate with a surface crack is sensitive to the crack length especially when the crack is shorter than the impactor diameter. The load-carrying capacity of a plate with a surface crack is also sensitive to the depth of the surface crack. Within the scope of the test program, the surface cracks had rather moderate influences on the permanent deformations. The analytical formulae of Jones was modified with the stresses determined based on the true stresses. Discussions were also given to some assumptions in this refined analytical formula. AbstractThis paper investigates the behavior of aluminum plates with and without initial cracks under repeated impacts. Three series of repeated impact tests were conducted to study the behaviors of circulate plates that do not have any cracks (series B), have surface cracks with varying length (series L), and have cracks varying depths (series D). A hammer was dropped from the same height with a constant initial striking energy 60J for all tests. For each test specimen, the hammer was dropped nine times to simulate the scenario of repeated impacts. It was observed that plates with larger cracks carried smaller impact forces and assumed larger deformations. When the crack length was larger than the diameter of impactor, the responses of aluminum alloy plates became less sensitive to the crack length. With the increase in impact number, the effects of crack lengths and depths on dynamic behavior of aluminum alloy plates became much more significant. Predictions using a rigid-plastic theoretical model were compared with these test results, and discussions were given to the assumptions of this theoretical model. With the stresses determined based on the true strain-stress curve obtained by standard tension test, the refined analytical formula provides better predictions that agree well with the lab tests.
Ships and offshore structures are often exposed to various types of repeated impact loads, such as wave slamming, floating ice impacts and ship collisions which will cause large deformation or even fracture. With imperfections due to the process of construction or damage caused by accidents, the load carrying capacity of structures will decrease. This paper investigates the load carrying capacity of aluminum alloy plate with an initial crack under repeated impact loads by means of experiments and numerical simulations. In the experiments, the prepared specimens with crack and without crack are impacted repeatedly up to plate perforation by releasing a hemispherical-headed cylindrical hammer. Numerical simulations are carried out with ABAQUS/Explicit software. The numerical models are built according to the actual experimental conditions. Comparison of the numerical predictions with the experimental results shows reasonable agreement. It is found that aluminum alloy plates under repeated impacts are sensitive to initial cracks. The fracture mode and plastic deformation of aluminum alloy plates can also be affected.
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