Adrian Neacsa

This study presents an ASME-based structural assessment of the head–shell junction in a 60 m³ pressurized railway tank wagon subjected to an internal pressure of 0.45 MPa, combining classical shell theory with finite element analysis (FEA) in accordance with ASME Section VIII Division 2 stress categorization and linearization procedures. An analytical model based on the moment theory of shells of revolution was developed to describe displacement and rotation compatibility at the ellipsoidal head–cylindrical shell junction, allowing for the determination of contour interaction loads governing membrane–bending coupling in the discontinuity region. The calculated contour loads (Q₀ = 795 N/mm, M₀ = 13,350 N·mm/mm) indicate localized membrane–bending interactions caused by geometric discontinuity. Finite element simulations using axisymmetric (2D) and full 3D models were evaluated through the ASME VIII-2 stress linearization procedure, enabling comparison between analytical predictions and numerical results. The maximum equivalent stress according to the Coulomb–Tresca criterion reached 115 MPa (2D) and 117 MPa (3D), with less than 2% deviation, confirming the adequacy of the axisymmetric model. Stress linearization shows that the maximum combined primary membrane and bending stress (109.5 MPa) remains well below the ASME allowable limit of 308 MPa, while the discontinuity influence zone extends approximately 120–150 mm from the junction. The results confirm compliance with ASME VIII Division 2 requirements and demonstrate that the combined analytical–numerical approach provides a reliable method for evaluating stress concentration effects in railway tank wagons.

Even the European Union is the international leader regarding the energy transition, the consumers are increasingly affected by overlapping crises affecting income levels and energy prices, as the geopolitical context has become more volatile. The energy poverty is a complex problem that is intricately linked to social, political, and economic elements like low income, skyrocketing energy prices, and inefficient housing. In addition to restricting comfort and well-being, energy poverty exacerbates social inequality, has serious health effects, and impedes the development of a fair and sustainable energy transition. The European Union and its Member States have taken strong action to reduce energy poverty through focused policies and initiatives in recognition of the seriousness of this issue and to assure the access to energy and to improve the energy resilience . Significant challenges still exist, though, necessitating a comprehensive and progressive strategy to guarantee that everyone has access to sustainable, inexpensive, and clean energy. In this study, the authors considered the evolution of some factorial variables that have an influence on the phenomenon of energy poverty at the level of the European Union, using in this sense statistical data taken from official sources, such as Eurostat, from the last 21 years (2004–2024). This analysis is useful to understand the trends and factors that influence energy consumption, energy prices, as well as the population's ability to maintain adequate thermal comfort in homes. This study adds to the expanding conversation on sustainable energy access by revealing the patterns and factors influencing energy consumption, cost, and affordability. It reaffirms the pressing need for an energy system that is resilient, inclusive, and geared to the future—one that enables every home to prosper in a world that is cleaner, fairer, and more sustainable.

Fiber-reinforced polymer (FRP) pipes are increasingly used in pressure piping systems due to their corrosion resistance and favorable mechanical performance; however, the direct experimental validation of design assumptions adopted in international standards remains limited. The objective of this study is to experimentally validate the mechanical response and stress distribution of filament-wound GFRP pipes under representative loading conditions and to assess the consistency of the measured behavior with the allowable-stress design framework of ISO 14692 and complementary ASME and BS codes. In this study, the mechanical behavior of filament-wound glass fiber-reinforced polymer (GFRP) pipes is investigated through a combined experimental program including tensile, bending, and full-scale internal pressure tests. Electrical resistance strain gauges were applied in axial and circumferential directions to directly measure deformation under internal pressure up to 31 bar, allowing experimental stresses to be derived using orthotropic laminate relationships. The results demonstrate a predominantly linear elastic response within the service range, followed by progressive damage initiation at higher load levels, with circumferential stresses consistently exceeding axial stresses, confirming a hoop-dominated response. At the maximum applied pressure of 31 bar, axial and circumferential strains reached approximately ε_a ≈ 1.30 × 10⁻³ and ε_h ≈ 1.60 × 10⁻³, corresponding to experimentally derived stresses of σ_a^exp ≈ 15.3 MPa and σ_h^exp ≈ 18.8 MPa, without catastrophic failure. The novelty of this work lies in the direct integration of full-scale strain gauge measurements with standardized allowable-stress design assumptions, enabling an experimental validation of ISO 14692 that is rarely addressed in existing studies. The experimentally derived stress–strain data show good agreement with theoretical models and provide a direct link between measured behavior and the allowable stress philosophy and design equations defined in ISO 14692 and complementary ASME and BS design codes. The findings validate the applicability of standardized design approaches and provide experimentally grounded support for engineering design decisions in FRP piping systems.

In the course of the 3D printing process, the occurrence of imperfect structures is attributable to the rapid cooling of molten polymer. In this study, gears were manufactured from PA6 using a dedicated 3D printer, and their performance was analyzed using finite element analysis (FEA), validated by wear tests. A subset of the gears was subjected to annealing heat treatments to investigate their influence on the behavior of the material. The novelty of this study lies in the correlation of the effects induced by heat treatment with the stress distribution, wear, and service life of 3D-printed gears. This provides useful information for optimizing polymer gears for engineering applications. This study’s novelty lies in highlighting the influence of heat treatments on wear behaviour and mechanical stress factors, offering new insights into the optimisation of 3D-printed polymer gears.

The article is the result of the question mentioned in its title, namely, whether heat treatments without phase transformation and pressing of parts can improve the physicomechanical properties of metallic materials and alloys. Starting from this hypothesis, the article analyzes the influence of non-phase change thermal treatment TT and plastic deformation (compression) on a steel used for the realization of components in the engineering industry, as presented in the specific standards SR EN-10025 and SR EN-10027. The results of the tensile tests and of the Vickers hardness tests on the specimens made of this material are presented. The results in terms of material ultimate stress σ_u, yield strength S_y, elongation δ, reduction in cross section ψ, as well as those obtained in the Vickers test are summarized in tabular or graphical form. From the research conducted by the authors of this work, it can be seen that the 0.5 × T_m−s (T_m−s—melting-solidifying temperature, K) heat treatment gives the best mix of properties: mechanical strength similar to that of the non-treated material, improved elasticity and ductility, but with a small, negligible reduction in hardness. The results are useful to support the activities of optimal selection of heat treatments and plastic forming for various engineering applications. Heat treatment without phase transformation is essential for improving the mechanical properties of materials used in engineering. This study investigates the impact of heat treatments and plastic deformation on S355J2+N steel, highlighting the increase in yield strength and improvement in ductility. The results show an increase of up to 15% in yield strength and an improvement in relative elongation by 2% for treatments at 0.5 × T_m−s, while hardness remains almost unchanged.

Additive manufacturing technology, also known as 3D printing, has emerged as a viable alternative in modern manufacturing processes. Unlike traditional manufacturing methods, which often involve complex mechanical operations that can lead to errors and inconsistencies in the final product, additive technology offers a new approach that enables precise layer-by-layer production with improved geometric accuracy, reduced material consumption and increased design flexibility. Geometrical accuracy is a critical issue in industries such as aerospace, automotive, medicine and consumer goods, hence the importance of the following question: can the dimensional optimisation of 3D FDM-manufactured parts be a solution for correct design? This paper presents a complex study of model parts printed from four common polymers used in fused deposition modelling (FDM) additive technology, namely ABS (acrylonitrile–butadiene–styrene), PLA (polylactic acid), HIPS (high-impact polystyrene) and PETG (polyethylene terephthalate glycol). The results of the methodology used highlight the dimensional changes that need to be made at the design stage, depending on the direction of printing and the type of geometric elements in the final part.

Additive manufacturing technology, also known as 3D printing, has emerged as a viable alternative in modern manufacturing processes. Unlike traditional manufacturing methods, which often involve complex mechanical operations that can lead to errors and inconsistencies in the final product, additive technology offers a new approach that enables precise layer-by-layer production with improved geometric accuracy, reduced material consumption and increased design flexibility. Geometrical accuracy is a critical issue in industries such as aerospace, automotive, medical and consumer goods, hence the importance of the question: Can the dimensional optimization of 3D FDM manufactured parts be a solution for a correct design? This paper presents a complex study of model parts printed from four common polymers used in Fused Deposition Modelling (FDM) additive technology, namely ABS (Acrylonitrile Butadiene Styrene), PLA (Poly-Lactic Acid), HIPS (High Impact Poly-Styrene) and PETG (Poly-Ethylene Terephthalate Glycol). The results of the methodology used highlight the dimensional changes that need to be made at the design stage depending on the direction of printing and the type of geometric elements in the final part. The results of the methodology used highlight the dimensional changes that need to be made at the design stage depending on the direction of printing and the type of geometric elements in the final part.

This research will investigate how heat treatments affect the behaviour of 3D printed gears made from Polyamide 6 (PA6), a thermoplastic polymer with excellent mechanical properties. However, imperfect structures can result from the 3D printing process, which involves rapid cooling of the molten polymer. Gears were manufactured from PA6 by means of a dedicated 3D printer and their behaviour in gears was then analysed by means of various specific test protocols. Some of the gears were subjected to annealing heat treatments to determine material behaviour, which was a key aspect of this study. Finite Element Analysis (FEA) was used to investigate the effect of heat treatments on the mechanical properties of PA6 thermoplastic material, specifically in the area of 3D printed gear mechanisms. The simulations included both static and transient conditions to determine the influence of different heat treatments on the mechanical properties of PA6. Through the use of comprehensive FEA, the research investigates the deformation, stress distribution and strain rates in 3D printed gears and elucidates the correlation between the mechanical properties and the contact pressure on the tooth flanks during gear operation. As conclusion the study mainly uses numerical simulations based on mechanical characteristics determined in our laboratory. The contribution of the study lies in the novelty of highlighting, through the results obtained, the influence of heat treatments on wear and mechanical stress related factors.

The reduction in GHG emissions has become one of the most important objectives in Europe. One of these clean technologies in the quest for large-scale decarbonisation is the blending of hydrogen and natural gas (H₂NG). The significance of this article lies in conducting a technical–economic analysis that relies on simulating annual consumption patterns. This study focuses on the utilization of H₂NG at different proportions within a distribution network in Bucharest, Romania’s largest city. The paper is a fallow up of another paper and presents a case study for the injection through all four entry points in the city of different percentages of hydrogen and the dynamic of the mix through the gas distribution network. The study found that the variation in H₂ in the network is high and depends on the entry point levels and consumption. An economic analysis was conducted on seasonal real consumption, which confirmed the investment’s profitability.

The increase in demand, and thus the need to lower its price, has kept C-based fuels as the main source. In this context, the use of oil and gas has led to increased climate change, resulting in greenhouse gases. The high percentage of eissions, over 40%, is due to the production of electricity, heat, or/and energy transport. This is the main reason for global warming and the extreme and increasingly common climate change occurrences, with all of nature being affected. Due to this reason, in more and more countries, there is an increased interest in renewable energies from sustainable sources, with a particular emphasis on decarbonisation. One of the energies analysed for decarbonisation that will play a role in future energy systems is hydrogen. The development of hydrogen–natural gas mixtures is a major challenge in the field of energy and fuel technology. This article aims to highlight the major challenges associated with researching hydrogen–natural gas blends. Meeting this challenge requires a comprehensive research and development effort, including exploring appropriate blending techniques, optimising performance, addressing infrastructure requirements, and considering regulatory considerations. Overcoming this challenge will enable the full potential of hydrogen–natural gas blends to be realised as a clean and sustainable energy source. This will contribute to the global transition to a greener and more sustainable future. Several international, European, and Romanian studies, projects, and legislative problems are being analysed. The mix between H2 and natural gas decreases fugitive emissions. In contrast, using hydrogen increases the risk of fire more than using natural gas because hydrogen is a light gas that easily escapes and ignites at almost any concentration in the air.