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Ice is a strain rate-dependent material showing ductile and brittle behavior and can play a critical role in maritime operations. Particularly in propeller-ice interactions, with high strain rates, ice fails brittle. Such interactions not only induce potential damage to the propeller, but also have a significant impact on the entire drive train of vessels in ice. The determination of ice-induced loads on propellers is a significant challenge, as direct measurements are usually not possible and indirect measurements are contaminated and superimposed with various other signals. Therefore, this paper delves into the domain of dynamic finite element simulations focusing on the interaction between ice and ship propellers in connection with dedicated small scale experiments. Experiments emulating propeller-ice milling-type interactions have been employed to enhance the knowledge of propeller-ice interaction and ice as a material. These experiments serve as input to refine the numerical model, which is a state-of-the-art Mohr-Coulomb Nodal Split (MCNS) ice material model. The aim is to determine the ice loading on the propeller numerically and to compare the experimental results with the simulation. These simulations in combination with the experiments provide insight into complex propeller-ice dynamics and enable investigating the applicability of the MCNS model for propeller-ice simulations. The discussion includes the observed phenomena, emphasizing the propagation of brittle fractures and their effects on the propeller. In summary, this study comprehensively explores propeller-ice interactions through finite element simulations. This research contributes to the understanding of ice-induced mechanical challenges in the maritime realm by considering the brittle behavior of ice.

Ships that are navigating in ice covered waters are at risk of colliding with icebergs or ice floes, which can lead to severe damage to the ship‘s hull in certain conditions. Predicting these loads is of great importance for the design and safety of ships. Ice loads are driven by a range of parameters, including ice properties such as the compressive strength, the geometry of the ship's hull and values related to the interaction (e.g. impact velocity). Classification rules and requirements for polar vessels account for these parameters to a certain extent. However, sea ice exhibits not only variability of its properties but also the geometry of the ice shows a high degree of diversity: icebergs and ice floes exist in multiple different shapes. Therefore, this paper addresses the ice-structure interaction process, focusing on the influence of the initial ice contact shape and its impact on the local load. Additionally, the paper explores the feasibility of pinpointing geometric parameters of the ice responsible for influencing these loads. Ultimately, understanding which ice shape in contact poses the greatest risk would be valuable for improving numerical simulations for the worst case scenario and, consequently, enhancing the safety of ships in ice-prone environments. To achieve this, a comprehensive drop tower test campaign on a small-scale has been conducted at the test facilities of the Hamburg University of Technology. In these experiments, single impacts of differently shaped ice specimens against a rigid 50 mm steel plate in normal direction were investigated. In the experiments, a drop hammer was released from a predefined drop height to realize a brittle failure of the ice at an interaction velocity of about 2000 mm/s. This falls within the lower range of ship-ice interaction speeds. The drop hammer fell onto the ice specimen which was positioned centered underneath the drop hammer. The investigated specimen geometries were cylindrical shapes of 200 mm diam

The interaction of waves and ice is of significant relevance for engineers, oceanographers and climate scientists. In-situ measurements are costly and bear uncertainties due to unknown boundary conditions. Therefore, physical laboratory experiments in ice tanks are an important alternative to validate theories or investigate particular effects of interest. Ice tanks use model ice which has down-scaled sea ice properties. This model ice in ice tanks holds disadvantages due to its low stiffness and non-linear behavior which is not in scale to sea ice, but is of particular relevance in wave-ice interactions. With decreasing stiffness steeper waves are required to reach critical stresses for ice breaking, while the non-linear, respectively non-elastic, deformation behavior is associated with high wave damping. Both are scale effects and do not allow the direct transfer of model scale test results to scenarios with sea ice. Therefore, the alternative modeling approach of Model Ice of Virtual Equivalent Thickness (MIVET) is introduced. Its performance is tested in physical experiments and compared to conventional model ice. The results show that the excessive damping of conventional model ice can be reduced successfully, while the scaling of the wave induced ice break-up still requires research and testing. In conclusion, the results obtained are considered a proof of concept of MIVET for wave-ice interaction problems., The interaction of waves and ice is of significant relevance for engineers, oceanographers and climate scientists. In-situ measurements are costly and bear uncertainties due to unknown boundary conditions. Therefore, physical laboratory experiments in ice tanks are an important alternative to validate theories or investigate particular effects of interest. Ice tanks use model ice which has down-scaled sea ice properties. This model ice in ice tanks holds disadvantages due to its low stiffness and non-linear behavior which is not in scale to sea ice, but is of particular relevance in wave-ice interactions. With decreasing stiffness steeper waves are required to reach critical stresses for ice breaking, while the non-linear, respectively non-elastic, deformation behavior is associated with high wave damping. Both are scale effects and do not allow the direct transfer of model scale test results to scenarios with sea ice. Therefore, the alternative modeling approach of Model Ice of Virtual Equivalent Thickness (MIVET) is introduced. Its performance is tested in physical experiments and compared to conventional model ice. The results show that the excessive damping of conventional model ice can be reduced successfully, while the scaling of the wave induced ice break-up still requires research and testing. In conclusion, the results obtained are considered a proof of concept of MIVET for wave-ice interaction problems.

High Frequency Mechanical Impact (HFMI) is one of the post-weld treatment methods. In this study, comparative axial fatigue tests were conducted on as-welded and HFMI-treated welded transverse attachment details. The test results demonstrated the efficiency of HFMI-treatment in fatigue life extension of cracked welded structures, providing that the existing crack size is less than 1.2 mm. Cracks were created in some specimens through fatigue testing before HFMI-treatment, while other specimens were not subjected to any fatigue loading prior to treatment. Many of the treated specimens ran-out after 10 million cycles of loading when tested at a stress range of 150 MPa. Therefore, the stress range was increased to 180 MPa or 210 MPa. No remarkable difference was found between the fatigue strength of the crack-free and the cracked treated specimens. It was found that the induced compressive residual stress can exceed the material yield limit, and reach a depth larger than 1.5 mm in most of the cases. The induced compressive residual stress, the local material hardening, the increase in weld toe radius, the change in crack orientation and the shallowness of the crack size were the causatives of the obtained long fatigue lives of the HFMI-treated specimens. Besides, linear elastic fracture mechanics calculations were conducted to predict the fatigue lives of as-welded and HFMI-treated details. The results were in agreement with the experiment. Moreover, the calculations showed that the initial crack size, the clamping stress and the induced compressive residual stress were the main factors behind the scatter in fatigue lives.

Fatigue cracks have appeared as a significant issue for joints and connections in existing steel structures in the last decades. Therefore, those are a major inspection and maintenance matter for any steel structure's operator. This emphasises the importance of using a reliable detection method to determine the crack size and assessing the severity of such a crack on the structural integrity of a structure. In this article, the effectiveness of strain measurement in detecting fatigue cracks in transversal non-load carrying welded attachment subjected to out of plane axial loading is studied. Numerical analysis and experimental investigations allowed to correlate the decrease in strain measured by attached gauges to the crack depth at the weld toe. In addition, different strain evolution patterns were found during fatigue testing, and the fracture surfaces of the specimens were observed to interpret these patterns. Moreover, the crack position with respect to the weld toe surface was predicted via strain measurements.