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.

This article reports on the failure analysis of the geothermal steam pipe. Macro and micro examination of failed pipelines was studied using optical and scanning electron microscopy. The energy-dispersive spectroscopy studied the elemental composition of the corroded surface. Further, the study measured the pipe thickness on the failed pipeline section. Visual examination showed a significant thinning of the outer section of the failed pipe to 3 mm from 12.7 mm of the original pipe. The chemical composition results show that the steel meets the minimum requirements for API 5L Grade B steels used in steam pipelines for geothermal power plants. The microstructural analysis of the investigated steel shows that the steel had pearlite and ferrite phases. The steel failure mechanism was due to erosion-corrosion, which caused localised wall thinning near the drain port and elbow section. The study recommends creep-resistant steel for the drain port and elbow for geothermal power plant application.

This paper presents an experimental study to investigate some of the thermal and strength behaviors of a new mortar material which was prepared by adding some of the residues of agricultural Iraqi biomass materials such as wood sawdust, reed, corn cobs, and their blending. These biomass materials are available in plenty of amounts in Iraq / Karbala City. These materials are blended with sand and cement, which are raw materials for mortar preparation, in different percentages to produce new types of mortar. The major focal area of interest is to identify the likelihood of applying these products as external wall insulating material to minimize heat transfer from outside to a building. Thermal conductivity, water absorption and skeletal density, and compressive strength at 7 and 28 days of the new mortars was also determined in the work. Comparing the performances obtained it was found that the new mortar containing wood sawdust had the highest compressive strength values While the best improvement in heat insulation was recorded in the mortar containing corn cobs compared to the other types. The results presented here prove that this mortar can be recommended for building purposes, specifically for exterior wall cladding. It provides good thermal resistance and improves the fortification of building walls; it also affords an added benefit of being cheaper and therefore fashionable for construction related uses.

In order to monitor the surface condition of the conveyor belt in the process of running, a method of beam structure light irradiation based on machine vision is adopted. A spring-type mechanical vibration damping device is designed to improve the focusing quality of the camera, and an algorithm is proposed to solve the selection of spring parameters under different flutter amplitudes. Yolov7 deep learning algorithm was adopted and ACmix attention mechanism was introduced to identify the surface cracks of conveyor belt. The experimental results show that the improved YOLOV7-ACmix algorithm can effectively improve the accuracy and generalization ability of image recognition.

The need for a lack of three-phase energy for the operation of an electric winch that is used to empty infrastructure constructions such as (houses, buildings, among others). The scientific article aims to replace the electric generator used in an electric winch for infrastructure construction, implementing the design of an electrical system through the use of a frequency inverter, this new alternative will reduce costs when using the electric winch. Analytical methods were used and it was checked in the Autodesk Inventor program, obtaining optimal results in the solution, the established methodology is technological-explorative, since the problem was identified, and the possible solutions had to be investigated, when establishing the new solution, it began to be designed and manufactured. Once completed, it was incorporated and assembled into the electric winch, where the respective tests were carried out, being effective at 95%, since the power of the network is unstable where there are ranges where the current is raised and lowered, being an inconvenience for the machine to work at 100%, but it is being used for different activities and needs in construction. The results obtained by adding up all the costs that concern each system of the electric winch for construction: the use of the electrical system is S/ 392.98, the use of the electric generator is S/ 831.60 per day and manually it is S/ 580.00 per day. In summary, by using a frequency inverter in the solution, it allows us to prolong the useful life of the motor, preventing deterioration and unnecessary stoppages that cause downtime, it helps us to reduce energy consumption with a more efficient use, matching the demand of the application, avoiding current peaks and voltage drops, above all, it allows us to regulate the frequency according to the need, configure the acceleration and deceleration to avoid stops and sudden starts of the engine.

The current work presents a finite element analysis (FEA) based investigation of the structural steel pipe with internal corrosion defects. A total of 27 different geometrical conditions for internal corrosion defect were considered using 3 different internal pressures of 2.2 MPa, 4.5 MPa, and 6 MPa. The validation of the FEA model was carried out using the analytical solution for failure pressure using radial and hoop stresses. The failure pressure of the uncorroded pipe was 11.5 MPa. In contrast, for pipe with internal corrosion defect having the largest defect depth (1.7 mm), largest length (454 mm), and sharpest geometry (width of 26 mm), the failure pressure from FEA was 6 MPa. The remaining strength at this boundary condition was 0.521. The radial stress influences the strain in wall thickness which was 8.8 mm and much less as compared to other dimensions of pipeline which diminishes the material's ability to resist the failure pressure. The Von-Mises stress accumulation inside the interface increases the stress intensity (K) distribution at the vicinity of the internal corrosion defect geometry vis-à-vis lowers the K-distribution just outside of the internal corrosion defect. The largest factor of safety (FOS) of 2.11 was obtained at threshold boundary conditions considering fatigue limit as the optimum stress. It is then suggested that the FOS for the "break-before-leak" leak model can be anywhere between 2.11 to 1.45 and hence the pipeline cannot burst into rapture.

Offshore moorings play a key role in the stability of maritime structures such as floating oil production platforms. This study focuses on polyamide as a promising alternative for offshore moorings due to its mechanical characteristics and degradation resistance. Initially, characterization tests are carried out to determine the polyamide’s linear density, the rupture strength, and the linear tenacity. Following, impact tests are carried out on polyamide samples, using a methodology based on a free fall mass effect. The analysis of the results includes statistical data filtering and the parameterization of curves to correlate the number of impact cycles to the applied load. Furthermore, the effect of the accelerated hydrolysis on polyamide is investigated, subjecting the samples to an aging process in fresh water for 180 days at 65°C. The results are analyzed to evaluate the effect of the hydrolysis on the resistance to impact cycles. It was concluded that, in general, polyamide shows a promising ability for energy absorption and impact resistance, with the potential for its use in offshore moorings. However, it is necessary to consider the hydrolysis effect on the degradation of its mechanical properties over time. This study contributes to the advancement of knowledge about the performance of polyamide in marine environments, providing important insights for the design and maintenance of offshore mooring systems, and also contemplating an exploratory study for its material's behavior.

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.

Additive manufacturing by direct metal fabrication represents one of the fastest-growing areas in material science and manufacturing. Modern manufacturing demands that parts be engineered to have high strength, be lightweight with complex geometrical details, and be suitable for operation upon completion. A very good example of such engineering-manufacturing involves the design and manufacturing of turbine blades for energy efficiency. On the other hand, topology-optimized lattice structures have huge potential and flexibility available to designers operating in the area of designing lightweight structures and high-strength ones at the same time, in contrast to solid form structures. The key issues involved in the research include designing graded density structures made from different lattice architectures for dense materials by characterization of the thermo-mechanical properties for a number of lattice settings in Gyroid, Diamond, Schwarz, Lidinoid, Split P, and Neovius lattices for varied parameters. This paper questions how appropriately the design structure functions in high-speed-rotating elements, such as turbine blades. The current research work will be aimed at the design, finite element analysis for simulation, and manufacturing through additive manufacturing of the turbine blades, considering several designs and lattice structures that satisfy the requirements of lightweight construction and high strength. A detailed preliminary design study has already been performed with the aim of justifying the idea presented in this paper and to create an initially validated basis. It therefore presents findings from the design of different lattice structures, supported by simulations that explain the potential, extent, and limitations of the proposed paper with regard to its general scope.

Lightweight structures tend to be susceptible to vibration, which can lead to fatigue and failure. Piezoelectric shunt damping is an efficient technology that converts mechanical energy into electrical energy and dissipates it through shunt circuits without requiring external power. This study models several piezoelectric patches coupled to different shunt circuits on a thin plate, utilizing Rayleigh-Ritz modal analysis to examine patch parameters including size, position, and distribution. Optimization demonstrates that effective patch-circuit topologies correspond with structural mode shapes, resulting in maximum vibration reduction. The findings introduce a fresh technique to enhance vibration control which improves structural reliability and performance.