Experimental investigations on the mechanical responses of fully clamped circular plates with prefabricated crack at room temperature and low temperature have been conducted. Initial cracks with different lengths were prefabricated by the electrical discharge machining method. Low ambient temperature was created by the liquid nitrogen in a low-temperature chamber, and a dropping hammer was dropped from the same height with a constant impact energy of 5 J to carry out the repeated impact. Experimental test results show that the prefabricated crack has a significant influence on the mechanical behavior of the thin plates. The maximum impact force decreases with increase of the crack length, and the threshold impact number until fracture decreases with increase of the crack length. It is also observed from the test results that the maximum impact force increases with decrease of the temperature, while threshold impact number until fracture and the plastic permanent deformation decreases due to the brittleness of the material in low temperature. The present investigations provide useful insight into the failure mechanism of the clamped thin plate with initial crack under low-velocity repeated impacts in low temperature, which will lead to a guideline for research and design of marine structures in the arctic area.

This paper addresses a simplified analytical method for evaluating the impact responses of the stiffeners in a ship side shell subjected to head-on collision by a bulbous bow. The stiffeners are classified as the “central stiffener” and the “lateral stiffener” according to their relative position to the bulbous bow. In analytical predictions, it is assumed that the flexural bending of the central stiffener and plate occurs simultaneously. However, the deformation mode of the central stiffener outside the indenter contact region is simplified as linear to derive its deformation resistance. The curved deformation mode of the lateral stiffener is proposed to calculate the deformation resistance and to consider the interaction effect with the plate, which can cause the plate to fracture earlier. Model tests with three specimens (one unstiffened plate for reference and two stiffened plates) quasistatically punched by a conical indenter are performed to validate the proposed analytical method. Resistance-penetration curves and damage shapes for the three specimens are obtained. The experimental results illustrate the effects of the stiffeners on the deformation resistance and fracture initiation of the stiffened plate and the influence of stiffener tripping on the lateral resistance. Moreover, the experimental and analytical predicted results correspond well, suggesting that the proposed analytical method can accurately predict the crashworthiness of a ship side shell subjected to bulbous bow collision.

Engineering structures in aviation and marine experience complex loads and are often affected by repeated impact loads. The damage accumulated from deflection in the process of repeated impact will often seriously affect the safety of the structure. In this research, the low-velocity repeated impacts behavior of corrugated core structures was investigated through experimental methods. A series of low-velocity repeated impact tests were carried out to study impact resistance, taking into account the effects of varied impact sites and impact energy levels and the effects of different impact locations and different levels of impact energy. It is also observed from the test that the upper panel played a crucial role and experienced the coupling mode of the local indentations and global bending deformations during the repeated impacts tests. Three different failure modes were observed when changing the impact energies and impact locations. Moreover, the “pseudo-shakedown” phenomenon was also found when the energy of the impacts is 10 J on the short span. The present surveys provide a reliable method and insight into the dynamic response of the aluminum corrugated core structures when subjected to low-velocity repeated impacts, which could be a significant guideline for the investigation and lightweight design of shipping and aviation.