Maritime University of Szczecin

The paper presents the results of model tests related to the process of forming a pipeline arc using the mechanical bending method with a new flexible mandrel design. The introductory section outlines the problems associated with the pipeline manufacturing process and the methods and tools used to shape bent pipeline sections, in particular the so-called mandrel bending. The shortcomings of the currently used cold pipe bending methods and the need to search for new solutions in this area are pointed out. The main part of the paper consists of the results of model tests of deformations and stresses resulting from the process of forming a mechanically bent pipeline arc using the proposed version of the mandrel, which has the properties of flexible adaptation to the shape of the formed pipe while maintaining radial stiffness. The model studies included an analysis of the values of deformations and stresses occurring in the cross-section of a bent pipe arc depending on changes in the design parameters of the flexible mandrel using the finite element method. Based on the obtained test results, the design parameters of the flexible mandrel were determined, thanks to which the stresses in the cross-sections of the bent pipe section caused using the mandrel are within the limits imposed by normative recommendations, while eliminating the ovalisation of the cross-section of the shaped pipe. This demonstrates the practical usefulness of the proposed flexible mandrel with a new design. The innovative nature of the proposed solution is determined by the fact that the mandrel is characterised by flexible susceptibility to bending deformation, while maintaining radial rigidity. The presented flexible mandrel also allows pipes to be shaped using traditional methods without the need for specialised and expensive mandrel bending machines.

The aim of this study is to demonstrate that popular measurement techniques-visual inspection, mechanical tools (digital calliper and steel linear ruler) and modern photogrammetry-can be used to detect shrinkage in 3D prints produced using fused deposition modeling (FDM) technology. The choice of the appropriate technique can be made objectively. Measurement techniques and their interrelationships have been the subject of much discussion and numerous scientific articles. They can be described using various criteria, which are often competitive and mutually exclusive. To avoid bias when selecting the measurement method, a multi-criteria decision-making tool-the analytic hierarchy process (AHP) was used. The results obtained in this study provide a quantitative decision-making framework for researchers selecting measurement methods in FDM quality control. The AHP analysis showed that decision-makers with the profile of a university researcher and lecturer tend to disregard visual inspection techniques and choose mechanical tools or photogrammetry, despite differences in the assessment of the importance of individual criteria characterising a given method. The key criteria for this profile of decision-makers were: measurement system precision (C2) and the overall ability of the technique to detect shrinkage (C8). The least important criteria were: the time-consumption of the measurement and the potential for automation of the measurement technique (C9). The analysis of weight aggregation (using a linear rule) and sensitivity analysis showed that decision-makers with the profile of a research and teaching staff can rely on the results presented in this study.

This study evaluates the quantitative effects of laser cladding technology on the refurbishment of valve cages and exhaust valves in a Deutz TBD645 internal combustion engine. Laser powder cladding with Inconel 625 alloy is applied to GGG40 cast iron, and process parameters are optimized to minimize Fe dilution. The method enables low dilution, a homogeneous crack-free microstructure, reproducible valve seat geometry, and stable surface roughness after machining. Quantitative results indicate that laser cladding reduces unit repair costs by 70-80%, while total overhaul expenses decrease by 40-60%. For exhaust valve refurbishment, yearly savings of EUR 125,000-200,000 are achievable for fleets repairing 50-80 components per year. Despite process costs of EUR 250-383/kg, economic benefits remain strongly positive due to reduced downtime and extended component lifetime. The results confirm that laser cladding is an effective method for marine engine overhauls, delivering measurable economic benefits and supporting circular economy objectives in line with IMO 2030 and EU Green Deal targets.

This paper focuses on the analysis of post-weld forming of 8 mm thick sheet metal, with particular reference to the influence of the weld zone, heat affected zone, and residual stresses on the course of the forming process and deformation characteristics. Experimental tests were carried out on steel specimens joined by active gas shielded welding. After the welds were made, the specimens were subjected to stamping tests. Observations revealed significant differences in the strain distribution in the weld regions compared to the parent material, which manifested itself as increased stress concentration and a tendency to initiate microcracks, especially in the heat affected zone. Variable hardness gradients and tensile stresses acting perpendicular to the weld line proved to be particularly significant. Successful post-weld pressing of thick plates requires not only optimisation of the parameters (forces, punch radius, process speed) of the forming process but also appropriate preparation of the weld itself by controlling the heat affected zone structure, applying stress-relieving heat treatment, or preemptively removing the layer with microcracks in the future pressing area. Particularly for thicknesses above 6-8 mm, local differences in mechanical properties become crucial for maintaining material continuity and avoiding cracks. This article highlights the importance of an integrated approach to the design of post-weld sheet metal stamping technology, in which not only the geometry of the tool but also the previous stages of blank preparation, the quality of the welded joint and the structural characteristics of the material in the transition zones play an important role.

This article presents new probabilistic approach to assessing the risk of collisions between ships and bridges, focusing specifically on the incident involving the container ship Dali and the collapse of the Francis Scott Key Bridge in Baltimore. Current risk models are significantly limited, particularly given the evolution of navigation practices and the adoption of ultra-precise positioning systems. The proposed method enhances predictive capability by incorporating three categories of technical ship failure: loss of power supply, failure of the main engine, and malfunction of the steering gear. A simulation-based reconstruction of the Dali incident was conducted using the NTPro 6000 full-mission bridge simulator. This reconstruction forms the basis for an in-depth analysis of four critical components: (1) the probable technical cause(s) of the accident; (2) key stakeholders and influencing factors in the risk profile of ship-to-bridge interactions; (3) engineering and procedural options for mitigating bridge strike incidents; and (4) expert assessment of feasible preventive measures, particularly those available to maritime pilots. The study includes the results of a targeted survey of maritime professionals, including pilots and captains. The survey aimed to evaluate the effectiveness of current preventive protocols and to identify potential gaps in training, coordination, and technical response in emergency situations. The findings provide valuable insights into the dynamics of maritime accidents in confined waters and propose a structured approach to enhancing risk assessment methodologies through the use of realistic failure scenarios and expert-informed analysis.