Scientific Journal of Gdynia Maritime University

ANALYSIS OF STRENGTH PROPERTIES OF SELECTED MATERIALS FOR 3D PRINTING

2025-10-23T06:51:45+00:00

3D printing is now becoming an integral part of technological development worldwide. The growing popularity of additive techniques means that more and more money is being spent on them, and their applications are gradually extending into more areas of life. Incremental manufacturing makes it possible to produce both prototypes and finished spare parts, the properties of which are comparable, and often almost identical, to components currently in use. With this technology, it is possible to create components with complex geometries without having to invest in costly, advanced mass production. 3D printing technologies make it possible to construct three-dimensional objects based on successive layers of material. Testing of the additive-printed samples was carried out using an orthogonal plan, in which factors are selected so that each is different from the others. This means that during the experiments, the influence of the individual parameters could be assessed independently, without interference from other variables. As part of the study, specimens were prepared and subjected to a static tensile test. The test models were printed with five different infill densities: 20; 40; 60; 80; and 100. After testing, the results obtained were collated in the form of graphs illustrating, among other things, the tensile strength of the Young’s modulus values and the percentage strain. These data were then analysed and described in detail for all selected materials. The highest tensile strength value was obtained for the PET-G material with 50.09 MPa at 100% infill. The lowest tensile strength value was achieved by the ASA material – 23.43 MPa at 20% infill. The highest Young’s Modulus value was achieved by the ASA material – 1924 MPa at 100% infill. The lowest value of the Young’s Modulus was obtained for the PET-G material – 934 MPa at 20% infill. The material and the infill density have no significant effect on the deformation value. The results showed that changing the infill density has an effect on the strength properties.

ANALYSIS OF THE CAUSE OF TRIBOLOGICAL DAMAGE TO VALVE ROCKERS IN A DIESEL ENGINE

2025-10-28T07:52:25+00:00

This describes the consequences of a Volvo V70 diesel engine failure, as well as the development of this failure and its immediate cause. The engine was damaged 68 km after the timing belt had been changed. Preliminary analysis demonstrated strong material wear at the rocker arms of the exhaust valves, while not showing a similar wear on the intake side. Analysis of the timing belt replacement process shows that when the prescribed repair procedure is not followed, the timing system on the floating wedge can be set incorrectly and this may cause the exhaust valves to collide with the pistons. The collision caused cyclic overload in the friction nodes between the valves and rocker arms, resulting in engine damage. The aim of this paper is to indicate possible methods for determining the actual causes of tribological damage in internal combustion engine components. In addition, it is intended to serve as an example of the consequences that may result from non-compliance with the service instructions.

EVALUATION OF THE EFFICIENCY OF OXYGEN ABSORBERS DURING STORAGE

2025-08-12T09:03:21+00:00

Oxygen absorbers allow for the effective extension of the shelf life of food products. A necessary condition is the correct selection of the absorber for the size of the packaging and its correct operation. Oxygen absorbers have a factory-declared minimum sorption capacity, but manufacturers do not declare the period during which this parameter will be maintained. The lack of information on the period for maintaining the original parameters of oxygen absorbers means that users do not know how long from the date of production they can still use the absorbers so that they provide optimal protection for the products packed with them. The aim of the work was to assess the sorption properties of absorbers after a specified period of storage in the original bulk. Sorption capacity was determined using a non-invasive, fluorescent method of measuring oxygen. The obtained results were compared with the results obtained for brand new oxygen absorbers of the same type. Additionally, the properties of packaging materials (i.e. thickness, composition, oxygen transmission rate) from which the factory packaging of the tested absorbers was made were determined, as well as the effect of the type of packaging on maintaining sorption capacity.

SAILING ACTIVITY IN SEA YACHT HARBOURS OF THE SOUTHERN BALTIC COAST

2025-11-14T14:35:48+00:00

The objective of this paper is to compare the yachting in three regions on the southern coast of the Baltic Sea: Vorpommern in Germany and West Pomerania and Pomerania in Poland (Zachodniopomorskie and Pomorskie Provinces, respectively). A survey of sail and motor yacht captains was completed during voyages with landings to one of the ports considered in the paper. The size, propulsion type and form of ownership of the yachts, the size and structure of the crew, as well as the length of voyages and time in port were studied. The results are shown in diagrams, broken down by the three regions of interest. The results and conclusions reached can be applied to the design and improvement of sea marina services and provide the foundation for developing concepts for further research and analysis. The research material was collected as part of the South Coast Baltic marketing initiative project.

A PRACTICAL APPROACH TO ASSESS THE OXIDATIVE STABILITY OF COSMETIC BUTTERS: QUALITY CONTROL PERSPECTIVE

2025-08-12T10:26:33+00:00

Oxidative stability is an important parameter determining the quality of fat products. The oxidation time (OT) of cosmetic butters measured using RapidOxy can be predicted using simple equations based on unsaturated fatty acid / saturated fatty acid content (UFA/SFA), calculated oxidizability (CoxV) and calculated iodine values (CIV). This predictive capability increases the efficiency of the quality control processes for these products. Similar predictive relationships also exist for other fat-based products, such as oils. This simple but innovative approach to assessing the oxidative stability of fats is quick, eliminates chemical reagents and minimizes waste production, making it both cost-effective and environmentally friendly. It is in line with the idea of green chemistry and sustainable development, making it the preferred technique in modern chemical analytics.

SUSTAINABLE COSMETIC PRODUCTS BASED ON NATURAL PLANT OILS

2025-08-18T18:57:16+00:00

An analysis was carried out of the market choice of leave-on cosmetic care oils available on the Polish market. The study aimed to analyze market trends and evaluate the chemical composition of cosmetic oils in terms of sustainability aspects. The analysis revealed a clear trend towards the use of more sustainable plant oil-based raw materials, the development of waterless formulas, multifunctionality, and minimalism formulations. The largest group in the market offer consists of cosmetic universal (multipurpose) oils as well as hair care oils. A total of 98 natural plant oils and fats were identified in the analyzed products’ composition, often used as substitutes for mineral or silicone oils, with the most popular being sunflower oil, almond oil, jojoba oil, argan oil, and soybean oil.

THE COMMODITY ASPECTS OF USING OAT BRAN AND WHEAT BRAN IN COSMETIC SCRUBS

2025-11-04T10:29:14+00:00

The aim of the research was an attempt to apply waste raw materials (oat bran and wheat bran) to cosmetic scrubs. On the basis of literature reports and our own research, original formulations were developed for cosmetics containing the additives in question as an abrasive. The developed cosmetics were in an anhydrous form and contained vegetable fats and skin-sensitive surfactants. Only upon use did they come into contact with water and form an emulsion that, after abrading the epidermis, took care the skin. The reference point in the evaluation was a high-quality commercial product. The functional properties of the obtained cosmetic prototypes were evaluated: stability, viscosity, yield point, skin moisturization, and sensory analysis of the developed formulations. Based on the study, it was found that scrubs containing the addition of oat bran had more favourable rheological and sensory properties, and showed a higher degree of skin moisturization two hours after washing the product off the skin, compared to a commercial product.

MOTIVATIONS AND BARRIERS TO THE UTILIZATION OF SIDE-STREAMS FROM PELAGIC FISH PROCESSING FOR FOOD PURPOSES: THE POLISH AND NORWEGIAN PERSPECTIVE

2025-08-30T17:20:31+00:00

Pelagic fish side-streams are nutritionally rich raw materials that are currently utilised for fishmeal, fish oil, and pet food. This study examined the motivators and barriers to using fish processing side-streams for human consumption in Poland and Norway.

In Norway, the prospect of increased revenue and profit emerged as the primary motivator for enhanced side-stream utilization, whereas in Poland the highest-rated motivators were environmental benefits and waste reduction. Market-related factors were identified as the main barrier in Poland, whereas financial constraints were the primary issue in Norway.

Industry representatives confirmed the technical feasibility of recovering valuable nutrients from side-streams but emphasized the need for proven technologies, investment security, and sufficient market demand to justify the new initiatives.