Strength Analysis of the Marine Weapon’s Construction

Due to the modernization of warships, it was necessary to carry out strength calculations for the newly assembled devices, for which there were no detailed technical requirements. The authors try to present and harmonize the requirements for naval military structures. The lack of experimental verification of newly built systems was indicated. Therefore the finite element method was used to determine the durability of the critical design elements. There is no explicit reference load in the literature, so the authors present a general solution to one of the worst cases. The work presents the cannon structure elements exposed to damage during the underwater explosion load, using the proposed methodology. The proposed method is sufficient to calculate individual ship cases. However, in the case of hull strength analysis, more complex algorithms should be used

Analysis of the pressure wave parameters caused by TNT underwater explosion forced on the hull of minehunter

The paper presents the parameters of the pressure wave incident on minehunter hull structure modeled on the simplified vessel hull of Kormoran II project. The pressure wave is caused by the sea mine explosion on wet board of the ship and propagates in the sea. To describe the pressure wave procedure pressure formulas which can be implemented on programs CAE based on the Finite Element Method (FEM) was used. The way of modeling short – term issues using FEM and constitutive equations describing the explosion of TNT in the sea was described. Naval mines used by the Polish Navy were characterized. Equivalents of selected explosives in relation to the TNT were posted. Geometry of mine destroyer was mapped as a shell – beam model. The results of the pressure wave incident on the hull as a function of charge weight and the location of the epicenter of the explosion was presented. Formulated conclusions and comments

Analysis of the pressure wave parameters caused by TNT underwater explosion forced on the hull of minehunter

The paper presents the parameters of the pressure wave incident on minehunter hull structure modeled on the simplified vessel hull of Kormoran II project

Determining the Trajectory of the Crane Block Using the Finite Element Method

The paper discusses determining crane block trajectories using the finite element method (FEM). The mathematical formulation for air resistance of hooks’ block is presented with kinematic analysis of the block. The three crane blocks are considered: without wind deflector, with a spherical deflector and a cylindrical fairing. The hook block was assumed as a physical pendulum. The FEM analysis is provided with the hook block movement consideration. Movement trajectories of hook blocks for different wind speeds is depicted and the results are. At the end of the paper, the conclusions are provided with the directions of future research

The Use of Aluminium Alloy after High Plastic Deformation for Joining Riveted Structures

This paper presents the results of a static and dynamic tensile test of an Al7.5Mg aluminium alloy taken from round bars made in the technology of hydrostatic extrusion. It is planned to use the Al7.5Mg aluminium alloy for joining riveted structures. Based on the obtained results, the nominal and true characteristics of the Al7.5Mg aluminium alloy, depending on the strain rate in the range from 0 to 2000 s−1, were developed. The failure criterion for tension was determined. The material characteristics were approximated by the Johnson–Cook equation, which can be used in CAE (computer-aided engineering) programs to simulate the impact processes. FEM (finite element method) simulation of the impact of the hammer on the part of the riveted aircraft structure was performed. The FEM simulation results were compared with the experimental results on a drop hammer to verify the material model. The following results were obtained: yield strength Re = 395.3 MPa; strength limit Rm = 523.1 MPa at deformation 0.067; Young’s modulus E = 7.9 × 104 MPa. The AL7.5Mg alloy after hydro-extrusion has favourable plastic and strength properties

Material Properties of HY 80 Steel after 55 Years of Operation for FEM Applications

The paper presents the results of testing the properties of HY 80 steel from the hull of a Kobben class 207 submarine after 60 years of operation in extreme sea conditions. Steels from the HY family in the post-war period were used to build American and German submarines. For the obtained fragment of steel from the hull of the Polish submarine ORP Jastrząb (ORP-Boat of the Republic of Poland), static tensile tests were performed on an MTS testing machine. Dynamic tensile tests were carried out on a rotary hammer for the strain rate in the range of 500~2000 s−1. Results: Based on the obtained results, the Johnson–Cook model and the failure parameters of HY 80 steel in terms of the finite element method (FEM) were developed. Conclusion: This model can be used to simulate fast-changing processes such as resistance of structures to collisions, shelling, and the impact of pressure waves caused by explosions in water and air related to submarines

Algorithm describing pressure distribution of non-contact TNT explosion

[b]Abstract[/b]. The aim of this study is to develop a computational algorithm, describing the shock wave pressure distribution in the space induced by non-contact TNT explosion. The procedure describes pressure distribution on a damp surface of the hull. Simulations have been carried out using Abaqus/CAE. The study also shows the pressure waveform descriptions provided by various authors and presents them in charts. The formulated conclusions convince efficiency of the algorithm application.[b]Keywords:[/b] Underwater explosion, shock wave, CAE, TNT, Kobben class submarin

Determination of material characteristics necessary for modelling of marine structures exposed to small-calibre bullet

The article presents the results of tests of impact properties of steel 1.3964 used on the construction of modern mine destroyers. Ships of this type, like any other military unit, may be exposed to small-calibre projectiles. Firing can be done, for example, from aircraft, drones or pirate units. The thickness of the plates used in the ship’s construction does not guarantee effective resistance to the projectile calibre 7.62 mm for all compartments of such ships. Thus, it is possible to modify the existing structure or apply additional solutions that will ensure a certain level of ballistic resistance. Solutions of this type are necessary in order to maintain the stability and buoyancy of the ship at the current level. During the tests, a stress-strain curve for steel 1.3964 was obtained, then the Johnson-Cook plasticity and damage model was proposed, which was used in the FEM simulation. The task was modelled as non-linear considering the deformation of both the sample and the projectile. The simulation was prepared in the CAE program, and then verified by an experiment on the shooting range. The results were presented in the form of diagrams and deformation figures, and were compared with photographs of samples and velocities after the specimen

Environmental impact of the explosion of the Nord Stream pipelines

Armed conflicts have, in addition to severe impacts on human lives and infrastructure, also impacts on the environment, which needs to be assessed and documented. On September the 26th 2022, unknown perpetrators deliberately ruptured the two gas pipelines Nord Stream 1 and 2 with four coordinated explosions near a major chemical munition dump site near the Danish island of Bornholm in the Baltic Sea. While the massive release of natural gas into atmosphere raised serious concerns concerning the contribution to climate change—this paper assesses the overlooked direct impact of the explosions on the marine ecosystem. Seals and porpoises within a radius of four km would be at high risk of being killed by the shockwave, while temporary impact on hearing would be expected up to 50 km away. As the Baltic Proper population of harbour porpoises ( Phocoena phocoena ) is critically endangered, the loss or serious injury of even a single individual is considered a significant impact on the population. The rupture moreover resulted in the resuspension of 250000 metric tons of heavily contaminated sediment from deep-sea sedimentary basin for over a week, resulting in unacceptable toxicological risks towards fish and other biota in 11 km 3 water in the area for more than a month