Model test study on the extrusion action between plate frame structure and ice

Against the backdrop of global warming, shipping activities in the Arctic region are becoming increasingly frequent, and polar vessels inevitably experience ice loads during navigation. Accurately understanding the deformation characteristics and damage failure mechanisms of hull plate structures under ice loads is crucial for ensuring the navigation safety of polar vessels. However, existing research still has significant gaps in areas such as initial hull damage and the repeated action mechanisms of ice loads. Based on this, this study aims to deeply explore the mechanical response characteristics of hull plate structures under ice loads, focusing on key scientific issues such as initial damage effect assessment and repeated ice load mechanisms, providing theoretical and technical support for the anti-ice structure design and safety evaluation of polar vessels.

A repeated compression test of steel hull plates and ice was designed and conducted, using a simplified plate model based on the actual bow shoulder structure, with some specimens pre-fabricated with initial defects to simulate real service damage. During the test, triangular pyramid ice models were prepared using the filling-freezing method. A total of 12 test cases were designed to systematically examine the effects of variables such as plate thickness, stiffener arrangement, defect direction, and position offset. During the test, the plate was pressed vertically at a constant speed of 6mm/min to achieve repeated compression with the ice. High-precision sensors were used to collect displacement, force, and strain data in real time, and the plastic deformation of the structure was measured after each loading cycle to comprehensively capture the structural response characteristics under ice loads.

The results show that plate thickness has a significant impact on structural strength: as the plate thickness increases, the slope of the compression force-displacement curve increases, and the loading displacement at ice failure significantly decreases. Although the arrangement of stiffeners can effectively enhance anti-ice compression strength, their compensation for strength reduction caused by longitudinal defects is limited. Notably, when the defect location coincides with the ice load area, especially for longitudinal defects, significant stress concentration occurs at the root, leading to defect propagation. Comparative analysis revealed that under the same load conditions, transverse defects exhibit higher load-bearing capacity than longitudinal defects. Additionally, defect offset significantly alters stress distribution characteristics: a 200mm longitudinal offset of a longitudinal defect can reduce root stress by about 74%, while a 75mm transverse offset of a transverse defect can increase root stress at one end to 202 MPa and decrease it to 66 MPa at the other end. After the first loading, plastic deformation generally occurred in the plates, with plates of lower initial strength showing more significant strength improvement during the second loading, even potentially surpassing plates with higher initial strength.

The study reveals the structural response characteristics of plate structures with initial damage under repeated ship-ice compression scenarios, providing valuable references for the anti-ice strength design and evaluation of polar vessel structures.