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Combined approach for integrity assessment of welded joints with multiple defects
No full textPresence of various types of defects is an unavoidable issue when it comes to welded joints. Typicalapproach to dealing with this problem includes the effects of individual defects, without consideringthecombined influence of several different defect types on the integrity of a welded joint. Research whichwill bepresented here includes the initial steps and the development of a method for analysing the effects of multipletypes of welded joint defects, using a number of different approaches - with the main focus on experimentsand numerical simulations based on the finite element method. This research, inspired by real problemsencountered in engineering practice, initially focused on the geometry of welded joints with defects, asanimportant factor in terms of stress concentration, which could decrease the load-bearing capacity of aweldbya significant margin. As the methodology continued to develop, experimental tests were included, inordertoprovide input data for the numerical models, and to verify their accuracy. The experimental part of thisresearch was further improved by combining it with stereometric monitoring methods - mainly Digital ImageCorrelation (DIC). In this way, a more detailed insight into the behaviour of welded joints with defectswasobtained, providing an extensive and reliable base of information, which could be used by and comparedtothe numerical simulations. In the more recent experimental and numerical analyses, the welded joint itself for consideredinmoredetail, by observing each of its regions - the parent material (PM), the weld metal (WM) and the heat affectedzone (HAZ) - in terms of mechanical properties. The goal was to include different values of yieldstress, tensile strength and deformation for each individual zone, which would correspond to the experimentallydetermined values. For the HAZ, it was not possible to experimentally obtain these values, hence aniterativemethod was developed to determine them using the FEM models, by comparing the results with DICimages. Metallurgical aspects were also an important factor which was included in these analyses, as knowledgeabout what kind of microstructures occurred in each region during welding was crucial in determiningtheexpected mechanical properties of the HAZ. Due to specific conditions during welding (in order toobtainrelevant defects), it was assumed that the microstructures would deviate from those obtained under regularconditions. Taking all of the above into consideration resulted in a quick, effective and reliable methodofdetermining the influence of multiple defects on the structural integrity of welded joints. Next step, whicharecurrently underway, include the application of this methodology to a different combination of materials-namely a welded joint between a ferritic steel and an austenitic stainless steel
Reliability-based approach for structural integrity assessment of a bucket wheel excavator
No full textExisting studies dealing with structural strength of bucket wheel excavators (BWE) include a traditional approach that does not take into account the whole structural response of the object, but only considers the maximum response at the single location. To solve this issue, this paper proposes assessment of the structural response of BWE SchRs 630 that separates structural from mechanical failures, and predicts the reliability of the design. Firstly, stress results from finite element analysis for different loading scenarios are obtained. Three loading scenarios are included: (i) working load and steel weight (deadweight); (ii) steel weight; (iii) steel weight and inertial forces induced by slew drive breaking. In that way the whole in-service cycle of the BWE would be covered. Stresses and the yield criteria are treated as random variables in order to produce their probability density functions, which are compared to evaluate structural response. Monte Carlo method is used for the calculation of the structure’s probability of failure and consequently, reliability and reliability index. That means that the whole structure response is described using one single value − probability of failure. Also, the analysis has shown that the probability of failure starts to rise more rapidly for the reduction factor (RF) below the 0.6–0.7 range. This study confirms design code recommendation value for the criterion of yield stress limit reduction factor RF = 0.67. In addition, assessment of potential cracks was performed to obtain overall structural integrity assessment (OSIA) of the structure. Based on those results, reliability can be increased by small local improvements
Temporary changes in the flexural properties of 3D-printed ABS specimens
No full textThis study investigates the environmental aging effects on 3D-printed Acrylonitrile Butadiene Styrene (ABS) produced using Fused Deposition Modeling (FDM) and Digital Light Processing (DLP) techniques. The materials in filament (FDM) and resin (DLP) forms were exposed to UV light, humidity, and temperature fluctuations over two months. Mechanical testing via three-point bending and Fourier Transform Infrared Spectroscopy (FTIR) were employed to assess the impact of these environmental factors. Results showed notable mechanical strength and structural stability differences between the FDM-printed filament and DLP-printed resin ABS under aging conditions. The filament-based ABS exhibited superior mechanical properties, retaining its strength over time, while the resin-based ABS degraded significantly shortly after printing. Despite exposure to ambient environmental conditions, the chemical composition of both materials remained stable throughout the research period
APPLICATION OF GENERATIVE DESIGN AND DIGITAL IMAGE CORRELATION FOR PART OPTIMIZATION AND MECHANICAL TESTING
No full textGenerative design has emerged as a transformative approach in engineering, enabling the creation of highly optimized components with complex geometries that are well-suited for additive manufacturing (AM). This study examines the integration of generative design, AM and digital image correlation (DIC) for iterative part optimization and mechanical performance validation. By leveraging generative design algorithms, parts can be optimized for weight reduction, material efficiency, and structural performance. The rapid prototyping capabilities of AM facilitate swift fabrication of both original and redesigned components, allowing for direct comparison through experimental testing. DIC, as a noncontact full-field measurement technique, plays a pivotal role in validating numerical models by capturing detailed strain distributions under various load conditions. This paper presents a comprehensive framework that highlights the interdependence of these technologies, reviews
challenges and advances, and outlines future directions for refining the mechanical design cycle through enhanced data-driven workflows
Application of Pipe Ring Notched Tensile (PRNT) Specimens to Fracture Mechanics Testing of Ductile Metallic Materials
No full textThis paper presents the results of experimental and numerical analysis of fracture
mechanics testing of ductile metallic materials using a non-standard procedure with PRNT
(pipe ring notched tensile) ring-shaped specimens, introduced in previous publications
through analysis of 3D-printed polymer rings. The main focus of this research is the
determination of the values of the plastic geometry factor ηpl since the specimen is not a
standard one. Toward this aim, the finite element software package Simulia Abaqus was
applied to evaluate the J-integral (by using the domain integral method) and the F-CMOD
curve so that the plastic geometry factor ηpl can be evaluated for different values of the
ratio of crack length to specimen width (a0/W = 0.45 ÷ 0.55). In this way, a procedure and
the possibility of practical implementation on the thin-walled pipelines are established
NUMERICAL SIMULATION OF ISOTHERMAL RAREFIED GAS FLOW BETWEEN TWO PLATES
No full textpo Ugovoru 451-03-136/2025-03/ 200105 оd 04.02.2025. god
Drying Kinetics and Stability of Fatty Acids in Grape Pomace Seeds Under Mild Thermal Conditions
No full textGrape pomace, a significant by-product of the wine industry, is rich in
health-promoting compounds, including polyunsaturated fatty acids,
dietary fiber, and polyphenols, and holds strong potential for use in
functional foods and nutraceuticals. This study investigates the effects of
low-temperature convective drying at 40°C on the drying behavior and
fatty acid composition of grape seeds from ten Vitis vinifera L. cultivars.
To model the drying process, six thin-layer drying models were applied.
Among them, the Logarithmic model provided the best fit for most
cultivars, showing excellent agreement between predicted and
experimental drying curves. Effective moisture diffusivity values varied
considerably among cultivars, reflecting differences in pomace structure
and seed composition. Fatty acid analysis via gas chromatography
revealed that polyunsaturated fatty acids—particularly linoleic acid—were
the predominant lipid class in fresh grape seeds. After drying, a moderate
reduction in polyunsaturated fatty acids was observed, accompanied by a
corresponding increase in saturated fatty acids. Despite these changes,
certain cultivars, such as Prokupac and Merlot, retained favorable
nutritional profiles. The results support the application of mild drying
protocols to preserve the functional quality of grape seeds while improving
energy efficiency. This research contributes to the sustainable valorization
of grape pomace and highlights its potential applications, such as
functional oil ingredients, antioxidants in skincare, and encapsulated
nutraceutical formulations.Contract No. 451-03-137/2025- 03/200116 and Contract No. 451-03-137/2025-03/ 20010
EVALUATING THE STRUCTURAL INTEGRITY OF NOVEL DECKHOUSES ON TANKER SHIPS UNDER EXTREME CONDITIONS
No full textThis paper assesses the structural integrity of atypical superstructures mounted on the decks of two sister sea-going tankers under extreme load conditions. Namely, each tanker features a pair of deckhouses which are welded onto the existing deck structure girders, exposing them directly to harsh environmental loads. These deckhouses, designed as ‘ad hoc’ solutions resembling land-based structures with similar applications, serve as storage for ballast water treatment systems, added due to insufficient internal technical space within the existing ship structure. Given the lack of fully developed regulations for assessing the structural integrity of novel and atypical ship structures, classification rules typically require a direct structural assessment to ensure their structural integrity. Therefore, this study uses the finite element method to analyse extreme design load scenarios faced by these structures, including seawater loads from waves, wind loads, accelerations due to ship motions, and static loads from the structures’ and internal equipment weights. Besides identifying critical areas, the findings reveal that the initially proposed deckhouse structures failed to meet the criteria for certain scantling arrangements and demonstrate how variations in scantlings affect the overall structural response. Based on these insights, general recommendations for modifying the deckhouse structure are proposed.Contract No. 451-03-137/2025-03/20010
RISK ASSESSMENT IN VAT PHOTOPOLYMERIZATION: ENHANCING SAFETY IN THE AUTOMOTIVE INDUSTRY
No full textAdditive Manufacturing (AM), or 3D printing, is revolutionizing production by building parts layer by layer, offering a significant reduction in material waste compared to traditional subtractive methods. This technology allows the creation of complex geometries that are often difficult or expensive to produce using conventional means. Among the seven process categories defined by ISO/ASTM 52900-21, vat photopolymerization stands out for its precision and ability to fabricate highly detailed parts. Vat photopolymerization techniques, such as stereolithography (SLA) and digital light processing (DLP), cure liquid photopolymer resins with ultraviolet or visible light. This process yields parts with excellent surface finish and accuracy, making it particularly valuable in the automotive industry. Here, vat photopolymerization accelerates prototyping of intricate parts like lighting systems, dashboards, and ventilation components, helping to shorten design cycles and foster innovation. However, the process involves health and safety risks. Photopolymer resins may contain toxic chemicals, and exposure to their vapours or direct skin contact can be harmful. The curing process exposes operators to UV or laser radiation, which poses risks of eye and skin injuries. Additionally, the electrical and mechanical components of used 3D printers introduce hazards such as electric shock and burns. This research applies the Kinney risk assessment method to evaluate these hazards by analysing their probability, frequency, and consequence. Using ISO 12100:2010-based checklists, it identifies key risks and recommends mitigation strategies. These include proper storage of resins in cool, ventilated areas, mandatory personal protective equipment (PPE), adequate machine enclosures with ventilation, regular equipment maintenance, and workload management to prevent fatigue. Equally important is comprehensive operator training and the establishment of standardized procedures. The research highlights the need for dedicated safety standards tailored specifically to additive manufacturing technologies. As vat photopolymerization expands in automotive production – from prototyping to functional part manufacturing – industry-specific guidelines are essential to safeguard workers and ensure environmental responsibility. In summary, integrating structured risk assessments in vat photopolymerization supports the safe adoption of AM technologies in the automotive sector. This approach not only protects user health but also enables the continued innovation and efficiency that define modern manufacturing