This study presents a comprehensive analysis of aeroelastic stability in multi-stage turbine rotors mounted on nonlinear supports. A high-fidelity dynamic model is developed by coupling the structural behavior of a rotating shaft–disk–blade assembly with quasi-steady aerodynamic forces. The system incorporates nonlinear stiffness and damping in the bearing supports, and the governing equations of motion are derived using the Lagrangian method. Aerodynamic forces are modeled using cascade theory for incompressible subsonic flow and integrated with structural dynamics through coordinate transformation. The resulting nonlinear system is solved using the Runge-Kutta method, and its stability characteristics are investigated via bifurcation diagrams and Poincaré maps. A detailed parametric study is conducted to examine the influence of aerodynamic parameters, structural parameters and support characteristics on rotor response. Results show that nonlinear supports significantly alter stability boundaries, reduce critical flutter speeds, and introduce multi-periodic dynamic behavior. These findings provide valuable insights into the design and tuning of support systems to enhance the dynamic robustness of turbomachinery.

Hot rolled 40Cr and W6Mo5Cr4V2 steels were diffusion-welded by using a 4-staged process including uniaxial 50 kN compression at 1200 oC in 10-5 mbar vacuum with following cooling down to room temperature. Structural 40Cr and high-speed tool W6Mo5Cr4V2 steels are dissimilar, since they are different (i) in content of host Fe element and alloying Cr, W, V, Mo elements, (ii) in phase composition (40Cr steel is single-phased and W6Mo5Cr4V2 steel is multi-phased), (iii) in microstructure (homogeneous inclusions-less microstructure is characteristic for 40Cr steel, composite microstructure consisting of matrix Fe-based phase with metal (W, V, Mo) carbides is characteristic of W6Mo5Cr4V2 steel), and (iv) in grain structure (40Cr steel is coarse-grained with grain ~100 µm size and W6Mo5Cr4V2 steel is fine-grained with grain size of several µm). Phase composition, microstructure and grain structure of the steels are retained after welding. Diffusion redistribution of Fe, Cr, W, V, Mo atoms results in forming the diffusion zones with different widths (several µm for W, V and Mo, ~25 for Cr and ~15 µm for Fe). Resulting concentration Cr profiles are typical for diffusion from limited sources and could be satisfactorily described by diffusion coefficient equal to ~1.1∙10-14 m2∙s-1 (the coefficient is weighted over the entire temperature range from 1200 oC to room temperature). Within the diffusion Cr and Fe zones, the Vickers microhardness decreases from ~2000 HV (for W6Mo5Cr4V2 steel) to ~530 HV (for 40Cr steel). During room-temperature tensile tests, the diffusion-welded steels were always fractured not in the diffusion joint but in 40Cr steel.

This research pioneers the development of an innovative approach for refining dental implant fixture surfaces using the SLA+Anodizing method. Leveraging a rich dataset encompassing 68 distinct implant surface treatment states, the study employs an Artificial Neural Network (ANN) to predict crucial parameters such as surface roughness and cellular viability. Through meticulous training and validation, the ANN demonstrates a remarkable 3% error rate in comparison to experimental results, underscoring its precision. The methodology extends beyond prediction, facilitating the optimization of implant surfaces for enhanced osseointegration. Experimental validation, including Atomic Force Microscopy and Molecular Cytotoxicity Tests, corroborates the accuracy of the ANN predictions. The study pioneers a transformative era in dental implantology, introducing a tailored and adaptable approach that bridges gaps in understanding the intricate interplay between surface modifications and biological responses. This work sets the stage for a paradigm shift in dental science, emphasizing precision, personalization, and elevated standards of care.

Selective laser melting (SLM) is considered to be a highly significant additive manufacturing (AM) technology, with the capacity to produce complex shapes that would be difficult to achieve using other methods. However, the broad application of this method is limited by problems like harmful microstructures and porosity, especially during the processing of aluminum alloys. Laser shock peening (LSP) provides a promising approach to reduce the adverse effects linked to aluminium SLM. This research examines how a critical LSP parameter, specifically the number of impacts, influences AlSi10Mg parts produced by SLM. The results were assessed with porosity, microstructure, and microhardness. Results show a 72% reduction in porosity. Furthermore, microstructural analysis revealed discernible grain refinement, accompanied by enhanced hardness. Tensile testing further confirmed the effectiveness of LSP, showing increases in both ultimate tensile strength and yield strength. These results suggest that LSP can effectively address the limitations of the SLM process for demanding applications when used as a post-processing technique.

For the past 19 years, high entropy alloys (denoted as HEAs) have piqued the interest of many researchers due to their unique properties. Sputtering High Entropy Alloys on bulk materials, on the other hand, have been widely utilized due to their low cost of manufacture. This paper reviews the most recent trends and advancements in sputtered HEA coatings, thin film research, and development. Firstly, HEA coating and thin films were introduced. Then, a look at sputtering technologies and procedures is presented, followed by a summary of recent research on sputtered HEA thin films, properties, and applications. From reviewed literature, it can be deduced that HEAs that include the full nitride element have greater mechanical and elastic properties, and HEAs generally have the potential for structural, industrial, biomedical, and energy applications. Finally, it is suggested that new stable HEA films and coating research initiatives with various materials be undertaken to widen its applications.

For several offshore installations, especially those for exploration of offshore resources, such as Floating Production Storage and Offloading (FPSO), the stability of subsea pipelines and exploration risers are closely related to the mooring system. High performance polymeric fibers have been used in recent decades for offshore mooring, more recently polyester has been challenged by advancement in ultra-deep waters due to its considerable elongation. A candidate fiber for lower elongation mooring systems is high modulus polyethylene (HMPE). The work describes mechanical characterization procedures in high modulus polyethylene fibers envisioning the possibility of offshore mooring systems made entirely with HMPE, which allow deeper water depths, as well as stability to the pipelines. As a result, the fiber is suitable for mechanical strength and linear tenacity. It still shows good performance in abrasion resistance, and loss of inelastic portions in cyclic loads. However, the behavior in creep, due to its slightly high strain rates, restricts its use, but recent fibers known as "Low creep" can be studied, allowing complete mooring systems made with HMPE.

Composite marine structures are crucial for maritime and aerospace applications due to their strength-to-weight ratio and corrosion resistance. To ensure their reliability and durability, a methodology to predict the damage criticality and service life of composite marine T-joints is essential. Finite Element Analysis (FEA) has emerged as a powerful tool for preliminary design and structural evaluation of complex structures, reducing the need for extensive experimental work and leading to substantial cost savings. This research project aims to conduct a comprehensive FEA of composite T-joints, considering alternative skin, core, and infill materials. Structural analyses under various loading conditions will evaluate overall deflection and stress levels, aiming to enhance the design and reliability of composite marine constructions, ultimately improving their performance and extending their service life in demanding maritime and aerospace environments.

This study investigates the tensile behavior and crack repair of aluminum using fiberglass-reinforced composite patches. Tensile testing compared uncracked, pre-cracked, and repaired aluminum specimens. Pre-cracking by hole drilling decreased strength and ductility from stress concentrations. Composite patching recovered strength, with 4-ply laminates optimal. Uncracked samples failed by necking, pre-cracked by crack growth, and repaired by adhesive detachment. Results demonstrate composite patching effectively restores strength to cracked aluminum by mitigating stress concentrations when appropriately designed. Finite element modeling simulated stress reduction after patching. This work provides experimental data on composite patch performance for metal crack repair and confirms the approach as an effective strengthening technique, although further optimization is needed.

This paper aims to investigate the impact of vehicle velocity on the rollover stability of a fully loaded tractor semi-trailer during lane changes and turning. Specifically, the study focuses on velocities ranging from 30 km/h to 60 km/h. The investigation found that vehicle velocity is a critical parameter that can affect the potential for rollover during lane changes or turning. The results showed that to ensure the vehicle moves steadily and does not roll over during these maneuvers, the steering angle must be controlled and kept within certain limits. The study provided specific recommendations for maximum steering angles at different velocities. For instance, to ensure stability when the vehicle is moving at 60 km/h, the maximum steering angle should be less than 4 degrees. Similarly, at 50 km/h, the maximum steering angle is recommended to be less than 6 degrees, and at 44 km/h, it should be less than 8 degrees. At lower speeds, the recommended maximum steering angle increases, with the maximum recommended angle at 36 km/h being 12 degrees. These findings highlight the importance of carefully controlling vehicle velocity and steering angle to minimize the risk of rollover accidents. By providing specific recommendations for different velocities, this study can inform the design and safety testing of vehicles to improve their stability and safety during lane changes and turning.

The article presents an analysis of the stress state of workpieces during upsetting of workpieces with an additional shear. For the analysis, the slip line method and the finite element method were used. A schematic diagram of upsetting in dies with “floating” elements, contributing to the implementation of additional shear, reduction of barreling, inhomogenous deformation and contour tensile stresses, is presented. The analysis of the research results showed that during upsetting of workpieces with additional shift forces, tensile stresses on the side surface of the workpieces decrease, which excludes the appearance of cracks on the side surface of the samples, especially when processing low-plastic alloy steels and alloys, and also reduces the barreling of the side surface.