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 km3 water in the area for more than a month.

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.

Three-Dimensional Smooth Particle Hydrodynamics Modeling and Experimental Analysis of the Ballistic Performance of Steel-Based FML Targets.

In this paper, shields made of 1.3964 stainless steel bonded to a fiber laminate were subjected to ballistic impact response of 7.62 × 51 mm LPS (light projectile with a lead core) projectiles. Additionally, between the steel sheet metal and the laminate, a liquid-filled bag was placed, which was a mixture of ethylene glycol (C2H6O2) with 5 wt.% SiO2 nanopowder. Numerical modeling of the projectile penetrating the samples was carried out using the finite element method in the Abaqus program. The elasto-plastic behavior of the projectile material and the component layers of the shields was taken into account. Projectile penetration through glycol-filled bag has been performed using the smooth particle hydrodynamics technique. The morphology of the penetration channel was also analyzed using a scanning electron microscope. For the shield variant with a glycol-filled bag between the steel and laminate plates, the inlet speed of projectile was 834 m/s on average, and 366 m/s behind the sample. For the variant where there was no glycol-filled bag between the steel and laminate plates, the inlet and outlet average velocities were 836 m/s, after 481 m/s, respectively. Referring to the steel-glycol-laminate and steel-laminate variants, it can be concluded that the laminate-glycol-laminate is more effective.

Small Caliber Bulletproof Test of Warships' Hulls.

The article presents the characteristics of 1.3964 steel and the results of firing a 7.62 mm projectile with a steel core. A simplified Johnson-Cook material model for steel and projectile was used. Then, a FEM (finite element method) simulation was prepared to calibrate the material constants and boundary conditions necessary to be used in simulations of the entire hull model. It was checked how projectile modeling affects the FEM calculation results. After obtaining the simulation results consistent with the experimental results, using the model of a modern minehunter, the resistance of the ship's hull to penetration by a small-caliber projectile was tested.