Solid-state welding processes, particularly friction-stir welding (FSW), offer significant advantages for joining different aluminum alloys due to their good mechanical performance, energy efficiency, and cost-effectiveness. The FSW of the AA5052-H32 and AA6261-T6 alloys has not been previously reported. In this study, the effects of the main FSW process parameters on the mechanical behavior of different AA5052/AA6261 alloy joints were systematically investigated. A full factorial experimental design was applied, considering the tool rotation speed (900–1800 rpm) and the welding speed (56–252 mm/min) as control factors, along with their ratio (Rs/Ws). The results of the tensile tests reveal that the joint strength is strongly affected by the interaction between the rotation and welding speeds, with the Rs/Ws ratio is identified as a key parameter governing material flow, plastic deformation, and defect formation. The maximum tensile strength, approximately 198 MPa, corresponding to a mechanical efficiency of 84.4%, was achieved at 1800 rpm and 7 rev/mm, a condition that favored effective material mixing and a defect-free interfacial bond (≈162–186 MPa). The microhardness profiles showed a minimum of approximately 40–50 HV within the TMAZ, on the advancing side. In general, clear quantitative relationships were established between the process parameters and the mechanical properties, which allowed for the identification of optimal operating conditions to produce high-quality FSW joints between the dissimilar materials AA5052/AA6261.

Compression helical springs are critical components in pressure control systems. However, classical analytical formulations present significant limitations by not accounting for effects such as contact, friction, and geometric non-linearities, which can lead to substantial errors in stiffness prediction. This study addresses this issue through an experimental and numerical characterisation of a compression helical spring made from EN 10270-1 SH steel, designed for use in pressure control valves. The elastic constant was determined experimentally by means of standardised tensile tests (ASTM E8/E8M), yielding a value of k = 42.38 N/mm and a restoring force of F = 423.80 N. These values were compared with the results of analytical models (classical theory and Wahl's correction) and with finite element simulations under linear and non-linear static configurations with self-contact (code NE3, μ = 0.15). The results show that the classical formulation overestimates stiffness by 8.28%, whilst Wahl's correction underestimates it by 16.26%. Case NE3 provides the closest agreement with the experimental values, confirming its suitability for modelling helical springs under axial load. It was further verified that the spring operates within the elastic regime throughout the entire range of compression analysed. The methodology developed constitutes a reliable tool for the design of such components in pressure-regulation systems.

Las matemáticas un universo lleno de belleza abstracta, un juego lógico perfecto que permiten descubrir realidades externas más allá de lo físico y de lo real, que nos lleva a un resultado inesperado pero que al final tiene lógica. Las matemáticas un arte puro, un lenguaje oculto de realidad que nos lleva a volar la imaginación abstracta para obtener un resultado lógico. Las Ecuaciones diferenciales una de las ramas de las matemáticas aplicadas, que describe como una magnitud cambia en relación a otra, permitiendo modelar un sistema dinámico.

Introduction: In the field of biomedical applications, the use of biodegradable and biocompatible materials is essential. In this context, seafood shell waste represents an innovative and sustainable alternative for the production of biomaterials. This study addresses the use of shrimp and crab exoskeleton waste, which generates an unpleasant odor that affects the quality of life of residents in the center of Ambato city. The study highlights the need to investigate the mechanical properties of these exoskeletons for potential use in biomedicine, specifically in tissue engineering.Objective: The objective of this study is to analyze the mechanical properties of shrimp and crab exoskeletons to evaluate their potential for chitin extraction and subsequent application in the biomedical field.Materials and Methods: For chitin extraction, three types of exoskeleton species were used: brown shrimp, red shrimp, and crab, the most common in the region. The shells were washed to remove impurities, then dried and sieved. The resulting powder was stored in an airtight container. This powder was then used to produce chitin through a chemical process involving deproteinization with NaOH 0.1N and demineralization with HCl 0.1N. The obtained chitin was molded according to ASTM D638-10 and dried at room temperature.Results: The material characterization showed that the obtained chitin had an irregular morphology with particles of different sizes, suggesting a complex structure and a larger surface area. The mechanical properties indicated that the material’s hardness was 88.15 HD, classifying it as relatively hard. Additionally, the roughness measured 5.1 μm, and the tensile strength reached 7.43 MPa for brown shrimp, indicating that the material can withstand a significant amount of stress, making it suitable for biomedical applications.Conclusions: The study demonstrates that shrimp and crab exoskeletons can be effectively utilized to obtain chitin, a biomaterial with mechanical properties suitable for biomedical applications such as tissue engineering. The highlighted properties, such as hardness and tensile strength, confirm its potential to be a useful material in this field.