_ This article proposes a shaft system transient stress estimation method based on the Houbolt method. First, based on a lumped parameter model, the transfer matrix method is used to conduct steady-state torsional vibration analysis of the propulsion shafting in the frequency domain, identifying potential resonance risk points. Subsequently, transient angular displacements at resonance speeds are solved using the Houbolt implicit integration algorithm, and dynamic stresses in shaft segments are calculated in real time by combining material mechanics theory. Finally, real ship test validates that the error between theoretical results and measured data is less than 5%, confirming the effectiveness and accuracy of the mathematical model and computational approach. This study provides an algorithmic foundation for potential instantaneous stress monitoring in digital twin systems of marine propulsion systems. Keywords torsional vibration; ship shafting; transient stress; test verification
_ This study presents a comprehensive comparative investigation of the buckling and ultimate strength behavior of flat and curved plates subjected to longitudinal compression, utilizing nonlinear finite element analysis (FEA) with NASTRAN, ABAQUS, and ANSYS and benchmarking the results against the established rules of major classification societies including American Bureau of Shipping (ABS), Bureau Veritas (BV), Det Norske Veritas (DNV), and Germanischer Lloyd (GL). The parametric analysis was conducted on plates with an aspect ratio of 3.0, thicknesses ranging from 10 to 25 mm, widths from 800 to 1000 mm, and curvature radii from 3000 to 10;000 mm (corresponding to flank angles of 5°–45°), encompassing the typical geometric configurations found in large LNG carrier hull structures. The findings reveal that for flat plates, FEA predictions demonstrate excellent correlation with classification society rules, with mean ratios of FEA to rule-based strengths between .988 and 1.036, coefficients of variation below 5%, and coefficients of determination R2 exceeding .985, confirming the adequacy of existing empirical methods for flat plate assessment. Keywords ship structure; buckling; regulations and standards; longitudinal strength; structural analysis
_ The angle of deck edge immersion, which is related to both intact and damage stability, is a crucial factor in the safety of a vessel. This article presents a direct calculation method for determining the angle of deck edge immersion for an onboard loading computer. In this approach, the deck edge line points and a section model database are established by cutting the stereolithography model of the ship hull in the vertical and longitudinal directions. In addition, the polygon offset algorithm and the Sutherland-Hodgman polygon clipping algorithm are employed to calculate the volume and center of buoyancy. Furthermore, a simplified Newton Iteration Method is used to solve the system of equilibrium equations for the free trim of the ship at given heel angles. Finally, the results of the model are validated with three recently constructed vessels. The proposed method provides a reliable and efficient means of calculating the angle of deck edge immersion for efficient calculation by an onboard loading computer. Keywords angle of deck edge immersion; ship floating state; Newton Iteration Method; loading computer
_ In most of the high-speed planing hulls, the hydrodynamic forces are greater than the hydrostatic forces. With an increase in speed, the rate of increase in drag is greater in such vessels. Studies have developed energy-saving devices, such as stern flaps, wedges, hull vanes, and trim tabs, to reduce drag and trim on high-speed crafts. The investigation and design method for high-speed vessels with stern appendages is important to understand their performance. The approach for predicting the motion of such hulls plays a crucial role. Several studies have been done over the past on hydrodynamic analysis of high-speed vessels mounted with stern devices. The focus of this paper is to review the existing investigations on hydrodynamic studies of high-speed vessels mounted with a stern interceptor. Comprehending the robustness and constraints of these approaches will help designers and researchers to select the best method for the effective design of the stern appendage and examine its performance. An extensive study is made and presented on existing experimental and numerical techniques. Mounting stern appendages for high-speed vessels and their hydrodynamic performance vary for each case. Keywords planing hull; stern appendages; experimental method; numerical approach
_ This study develops a stochastic load model for ship structures that accounts for the temporal correlation of wave-induced load pulses and the stochastic process governing voyage duration. The distribution of the extreme values of the still water bending moment and its combination with wave-induced bending moment is formulated using a stochastic renewal process, accounting for the possible nonexponential distribution of voyage duration and the associated uncertainty across different ship operations. The correlated wave-induced loads are modeled as a stochastic Markov process, and closed-form expressions are derived to estimate the extreme value distribution of the load combination. The applicability and accuracy of the proposed approaches are investigated for an Aframax tanker under full load conditions, and the results obtained are compared with those of existing formulations. In addition, the impact of different stochastic processes, voyage duration models, and wave correlation on the extreme value distribution of ship structural loads is investigated. The proposed approaches are straightforward and can be readily adopted in practical engineering applications for probabilistic load modeling of ship structures. In addition, they can be extended to perform reliability analysis of ship hull girders at the ultimate limit state by incorporating a statistical description of the structural capacity. Keywords still water load effects; wave-induced load effects; stochastic process; temporal correlation; load combination
