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PublicationDeformation and optimization of double tube under bending loads(Praise Worthy Prize, 2020)A comparison of optimization values for empty aluminum circular tubes and double circular tubes containing foam under flexible loading is presented in this paper. Thin-walled tube is widely used in the vehicle structure for impact mitigation especially on the vehicle door. In this study, AA6063 T6 aluminum alloy tubes were filled with foam with both ends supported and subjected to quasi-static bending. Finite Element (FE) modeling and analysis has been performed using finite element software. The developed FE model has been experimentally validated and good agreements have been observed between experiment and simulation results. The deformation of the tube under bending load was studied with variations in thickness (t) and diameter (d) of the tube wall. The design of various objective optimization (multi objective optimization) is developed with considering two crashworthy performance that conflicting each other namely Peak Crush Force (PCF) and energy absorption per unit mass (SEA). In order to fulfill these purposes, Radial Base Function (RBF) and Non-dominated Sorting Genetic Algorithm (NSGA II) are adopted. It was observed that double circular tube containing foam exhibit higher energy absorption than that of an empty double circular tube. As such, this structure could be recommended as a power absorbent component such as a side beam on a vehicle door.
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PublicationMechanical properties and microstructural behaviour of microwave sintered WC–Co(Springer, 2019)Abstract: Cemented carbides have been of great interest within industrially manufacturable hard materials for their mechanical properties. Microwave sintering is known for its application on a range of hard materials. Although it has been widely used, its effect on grain growth of materials still requires clear understanding. Three different types of particle size, ranging from 1–3 µm to 100 nm were used for microwave sintering where temperature was used in this study within the range of 1000–1400 °C, while pressure during initial compaction of powder particles was kept constant. The maximum hardness was observed in the order of nearly 1800 Hv for submicron samples, sintered at 1250 °C. Fracture toughness on the samples reached a maximum of 16 MPa √m for micron samples sintered at 1400 °C. Grain growth in all samples was not more than 1–3 µm, even without the presence of any commercial grain growth inhibitors as part of the composition. Line scanning between grains demonstrates the presence of homogenous Co, confirming good mechanical behaviour. The microstructural features associated to the sintering process have also been focused as part of the study, highlighting some challenges in the research. Graphic Abstract: Line scanning of WC (1–3 μm)–7.5 wt% Co (1–3 μm) sample, microwave sintered at 1400 °C[Figure not available: see fulltext.].
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PublicationParametric evaluation of electrical discharge coatings on nickel-titanium shape memory alloy in deionized water(Elsevier, 2020)Nickel-titanium shape memory alloy (NiTi) has a unique capacity to restore its initial shape after deformation, which is highly applicable to orthopaedic implantations, especially for the minimization of invasive surgeries. The high nickel content of this alloy can lead to unfavourable effects on the human body upon dissolution; thus, a reliable barrier of coatings on the NiTi surface is required to alleviate the nickel migration and increase its biocompatibility. In this paper, analyses of a titanium oxide layer development on NiTi surface using electrical discharge coating (EDC) process is presented. The recast layer thickness, crater sizes, and surface roughness were characterized based on five parameters; polarity, discharge duration, pulse interval, peak current, and gap voltage. The results show that the discharge duration is the most significant parameter to influence all responses, followed by peak current. The surface characteristics of the EDC substrate is depending on the crater formations and is highly correlated with the discharge energy intensity. As a result, appropriate parametric conditions of the electrical discharge coating process can enhance the NiTi surface for future medical applications, without compromising the shape memory effect.
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PublicationEffect of porosity, pore size, and pore-opening size optimized on the sound absorption coefficient of aluminum foam(Institute of Noise Control Engineering, 2023)Metal foams are interesting as sound absorbers because of their strength, low mass, high hardness, and damping. To foam fabricationmore accurate and achieve higher sound absorption coefficient (SAC), the effective parameters should be optimized. In earlier study (DOI: 10.32604/sv.2021.09729), the parameters of porosity percentage (Ω), pore size (D) and pore opening size (d) were optimized by the authors. In this study, we intend to investigate the effect of optimizedΩpercentage, D size and d size on the SAC of aluminum foam in the frequency 0 to 8000 Hz with the thicknesses of 5, 10, 20, and 30 mm. The genetic algorithm was performed employing the Lu model, using MATLAB software. According to the results, the optimum values of Ω, D, and d at different frequencies and thicknesses are not constant. That is, at any given thickness and frequency, there are specific optimum amounts. This study provides a way to improve the SAC performance of porous metal materials for various and targeted applications.
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PublicationProposal of an alternating bending technique for evaluating low‐to‐high cycle fatigue of structural steels(Wiley, 2020)This paper proposes an alternating bending technique for evaluating fatigue life in the low‐to‐high cycle fatigue regime. A method was developed for estimating the stress, elastic strain, and plastic strain ranges of a plastically deformed specimen subjected to alternating bending with consideration of stress and strain distributions. To evaluate its effectiveness, fatigue testing was conducted using a specimen made of a steel used for pressure vessels. The stress, elastic strain, and plastic strain ranges could be obtained during cyclic bending. The elastic strain amplitude life and plastic strain amplitude life curves were linear in a log–log plot in the low‐to‐high cycle fatigue regime. Hence, the fatigue life under alternating bending could be evaluated using the proposed strain‐based approach. However, these curves could not be predicted using equations with parameters obtained from tensile testing, such as the universal slope method, due to the strain gradient in the specimen.
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