Thin-walled structures are interesting for applications in which lightweight structures with high stiffness and high resistance are especially advantageous or even required. The mechanical behaviour of thin-walled structures is, therefore, of high importance. Thin-walled structures which are internally stiffened are of particular importance, as internal reinforcements can be designed to maximize the inertia moment, leading to higher stiffness and strength. The present study investigates the mechanical behavior of sandwich beams using the Finite Element Method (FEM) software ANSYS Mechanical APDL. This study is in the field of solid mechanics, with a specific focus on analyzing structures' non-linear mechanical response. Structural analysis was conducted on internally reinforced hollow-box beams, and a non-linear static analysis was conducted under bending loads. The material considered was structural steel. The models were solved using the iterative Newton–Raphson method. A material curve, obtained from real tensile tests, was input into ANSYS Mechanical APDL software for the FEM simulations considering the plasticity of the material. A load–displacement curve was generated to characterize the non-linear behavior of the models. To ensure high precision in the results, a mesh convergence analysis was carried out. Additionally, a comparison was made between the stiffness characteristics of the different beams and those of conventional hollow-box beams.

This research addresses the need for a sustainable alternative by focusing on the performance evaluation of 3D printed mortar using recycled materials. The overarching problem lies in the environmental impact of conventional construction methods and the lack of comprehensive studies on the viability and sustainability of 3D printed mortar. This project aims to investigate the mechanical and environmental performance of 3D printed mortar while considering its potential to contribute to a circular economy. By conducting a detailed analysis, the study aims to provide insights into the feasibility of implementing 3D printed mortar as a sustainable solution in construction practices, thereby addressing the broader challenges of resource conservation and environmental sustainability in the construction industry. The purpose of studying 3D printing is to develop a technology-based alternative for construction. The methodology of study is to compare the strength of conventional mortars of cubes to 3D printed Mortars by strength performance analysis. In this study brick dust powder was used as partial replacement of cement. The compressive strength achieved for control sample was (24.3MPa) and it increased up to (27.6 MPa) by partial replacement of cement with 10% brick dust powder. The benefits of study of mechanical properties of 3D printed mortar utilizing waste materials are anticipated to result in a range of favourable composite materials. Together, these effects collectively promote construction practices that are both environmentally conscious and economically feasible. After successful testing of developed mortar, this technology can be recommended for housing construction at large scale.

The increasing levels of carbon dioxide emissions have caused a global reconsideration of approaches to addressing global warming. One of the main contributors of these emissions is cement production, which generates high temperatures during its combustion processes. A recent development in construction industry has shown promise during formation of fly-ash based geopolymer composite, offering a potential alternative to traditional Portland cement concrete that could reduce or even eliminate its use, this research focuses on the mechanical performance of fly ash incorporated composites, especially its strength related parameters. The data for this study was obtained from tests conducted on geopolymer concrete specimen created from two different sources of fly ash, each subjected to varying concentrations of sodium hydroxide solution. The compressive strength of geopolymer concrete ranged from values typical of normal-strength concrete to those associated with high strength. The primary emphasis of this paper is on the correlation between different mechanical parameters of geopolymer concrete. Geopolymer concrete requires a combination of cement ingredients and fly ash as replacement. This research is especially relevant to developing countries as it will explore the locally produced fly ash as a raw material for production of geopolymer composite. Development of suitable geopolymer composite can be an alternate construction material for the industry and reduce reliance on conventional concrete. This will also lead to reduction in production of cement and help combat the climate change. The goal of this study is to help the achieve sustainable development goals by developing eco-friendly composite material for construction of sustainable cities.

This study investigates the mechanical behavior of six triply periodic minimal surface (TPMS) structures—gyroid, primitive, diamond, lidinoid, neovious, and splitP—fabricated using stereolithography (SLA) 3D printing with a tough engineering resin. Each structure measures 70x70x70 mm³ and maintains 75% porosity, designed to enhance properties like lightweighting and energy absorption. The resin’s excellent mechanical properties make it suitable for engineering prototypes, mechanical aids, fixtures and medical devices.

Compression tests were conducted at a deformation rate of 2 mm/min to compare the mechanical response of the TPMS structures. Results indicate that, within the same strain range, stress ascends in the elastic zone in the following order: lidinoid, primitive, neovious, splitP, diamond, and gyroid. This sequence highlights the varying mechanical responses under identical testing conditions. While porosity and dimensions remained constant, most structures followed a clear trend where thicker walls resulted in higher stress in the elastic zone. However, neovious, despite having the thinnest walls (0.31 mm), performed unexpectedly well, ranking fourth in stress, surpassing some thicker structures. The wall thickness for other structures ranged from lidinoid (1.17 mm), splitP (1.33 mm), diamond (1.94 mm), primitive (1.31 mm), to gyroid (2.32 mm). The splitP and diamond structures displayed very similar stress-strain behavior, as reflected in their close curves on the stress-strain diagram.

These findings emphasize that while thicker walls generally correlate with increased stress, the geometry of the TPMS structures plays a significant role in mechanical behavior. The unique performance of neovious further underscores that wall thickness alone cannot predict mechanical outcomes. By leveraging advanced TPMS designs and tough resin, this study demonstrates the potential for creating lightweight, robust components for various engineering and medical applications, enhancing stress distribution, energy absorption, and overall mechanical performance.

The fabrication of parts by metal additive manufacturing may reduce environmental impact, cost, lead time, and other factors compared to traditional fabrication processes. In particular, several studies have shown that the fabrication of impellers, one of the key elements of turbomachinery, by wire arc additive manufacturing (WAAM) can improve the fabrication process compared to traditional fabrication methods. However, there are problems that have not been discussed in the analyses conducted in these studies with regard to the relationship with the hydraulic performance of the impeller. As the mechanical design in industrial turbomachinery requires appropriate evaluation and determination of impeller hydraulic performance and fabrication methods, it is important to clarify these relationships for industrial applications of WAAM.
In this study, an analysis was conducted for low-solidity axial-flow impellers with a focus on the number of blades. Two aspects were analyzed for axial flow impellers with different numbers of blades. First, an evaluation of the fabrication method by WAAM in the fabrication of impellers was conducted. Second, the pump performance wass measured for a centrifugal pump with axial-flow impellers installed as an inducer to evaluate the hydraulic performance. In addition, these results were analyzed comprehensively. The conclusion is that there is a trade-off between the fabrication process advantage of WAAM and pump suction performance.

Morphing quadcopters have recently gained unprecedented popularity due to their flight flexibility, geometric reformation, and self-controlled arm management and the diversity of their applications. It has been established that in morphing quadcopter control, morphing formations in flight introduce time-varying parameters into the dynamic models, thereby increasing the complexity of the control problems, in addition to the non-linearity, coupling dynamics, and external disturbances present in the model. Thus, to address these challenges, this research therefore developed a robust backstepping sliding mode controller for morphing quadcopter position and orientation control. In the first stage, a mathematical model of an active morphing quadcopter (a foldable drone) was presented considering five morphing formations (X, H, T, O, and Y). Following the development of the system model, the proposed control method was designed in two stages: a high-performance sliding mode controller (HSMC) for attitude control to ensure chattering-free and fast convergence of the angles of orientation and a backstepping controller applied to position control were developed. Then, Lyapunov stability was used for an analysis of the stability of the closed-loop system. Finally, the robustness and effectiveness of the controller were investigated and benchmarked against a backstepping control approach using the mean square error and the sum of tracking errors as the performance metrics. The simulation results obtained show the effectiveness of the developed controller for the backstepping approach in the presence of parameter variations and external disturbances.

The application of additive manufacturing to the fabrication process of metal parts has the potential to solve some of the problems that have existed in the industry for a long time. On the other hand, it is necessary to guarantee sufficient quality of the fabricated parts. One of the causes of functional degradation of parts fabricated by additive manufacturing is the presence of internal defects such as blowholes. In the case of turbomachinery blade parts, damage to the parts caused by internal defects may result in a noticeable loss of machine performance; therefore, it is necessary to accumulate a great deal of knowledge and make appropriate judgments. For this reason, there is an active discussion on the integrity of parts. A suitable method of additive manufacturing for large parts is wire arc additive manufacturing (WAAM). In addition, X-ray Computed Tomography (CT) scans are often used for the observation of internal defects in metal additively fabricated parts.
The purpose of this study is to clarify the effect of artifacts, which are noise from X-ray CT scans, for the proper evaluation of internal defects in parts fabricated by WAAM. An axial-flow impeller made of general-purpose stainless steel, fabricated by WAAM and machining, was used as a test model. The blades of this impeller were observed for internal defects by X-ray CT scanning. Suitable imaging results and imaging results affected by artifacts were obtained by changing the imaging conditions. These results were used to consider the effects of artifacts on the imaging results. In conclusion, it was shown that artifacts may cause a misidentification of internal defects in parts fabricated by WAAM.

The space propulsion market has experienced steady growth in recent years, driven by increasing demand for solutions that enhance satellite autonomy, versatility, economy, payload capacity, and readiness to fly. Key trends, initiated 25 years ago with CubeSats, include system miniaturization and modularization. These trends highlight the need for simple, small, high-performing solutions characterized by streamlined procedures and rapid maneuvers, which are required to optimize mission costs and lead times. Traditional chemical and electric space propulsion technologies, such as those based on hydrazine and its derivatives or Hall-Effect Thrusters, are being surpassed by cheaper, more powerful, and leaner systems that emphasize sustainable and safer green propellants, according to the current and future global policy initiatives.

This paper presents an extensive and critical overview of innovative propulsion system solutions, already existing or currently under development, which meet these criteria. It analyzes commonalities and differences among space propulsion technologies in terms of mission goals, satellite size, architectures, and performance parameters, as well as key points of departure from traditional systems. It investigates solutions utilizing green propellants, focusing on those based on water, especially water electrolysis propulsion technology.

This overview aims to provide a comprehensive definition of stakeholder expectations in the current space propulsion scenario, serving as input to the design process of an innovative water electrolysis propulsion system.

Tubular structures play a crucial role in renewable energy and the oil and gas industry, particularly in offshore applications. Over time, these structures face significant load, emphasizing the importance of addressing the degradation of tubular joints for sustained operation. Carbon fibre-reinforced polymers (CFRP) offer promising solutions for rehabilitation, yet existing literature primarily focuses on SCF at the crown/saddle points, which is sufficient only for determining fatigue life under uniplanar loads, leaving a gap in SCF along the weld toe. This study aims to bridge this gap by investigating the fatigue design of CFRP-reinforced tubular KT-joints subjected to axial loads at 24 positions along the weld toe. Our research highlights the remarkable potential of CFRP in reducing stress concentration factors (SCFs) in KT-joints, with the degree of reduction correlating with reinforcement layers and elastic modulus. We also uncover the critical role of fibre orientation in optimising stress distribution, particularly when wrapping CFRP around the brace axis with fibres perpendicular to the weld toe. Through 1679 simulations encompassing various geometric and reinforcement configurations, we analyse stress fields at the chord-brace interface under axial compression. Leveraging this data, we employ artificial neural networks to develop empirical models, enabling rapid estimation of CFRP's impact on fatigue life. These models provide precise approximations of hot-spot stress (HSS) in CFRP-reinforced KT-joints under axial load, with less than a 10% difference from simulation results, facilitating accurate fatigue life predictions akin to established methodologies for unreinforced tubular joints.

For offshore jacket constructions, circular hollow sections (CHS) have been widely used due to their exceptional performance in compression and high torsional resistance. Specifically, CHS have direction-independent stiffness and drag characteristics, which provide the structure with added stability under various marine environments. Hence, CHS are commonly chosen and welded to form tubular joints. Due to the complex geometry of the joints, the environmental loads, and the corrosion and aging of the structure, the joints are prone to fatigue cracks which can lead to crack propagation. The fatigue cracks and crack propagation can be investigated by analyzing the stress intensity factor (SIF) of the crack. If the SIF exceeds the fracture toughness of the joint, the crack will propagate. To alleviate this issue and prevent crack propagation, the application of composite reinforcement has been receiving traction in the industry due to its ability to provide in-service maintenance windows, besides its renowned capability to enhance the structural integrity of affected offshore structures. However, the effect of composite reinforcement on the SIF of fatigue-cracked tubular T-joints has been insufficiently explored. Therefore, this study aims to conduct a numerical parametric study on a semi-elliptical cracked tubular T-joint to investigate the effect of crack size, crack location, and composite reinforcement on the SIF under various basic loadings.