Papers by Keyword: Structural Modification

Abstract: Modal truncation errors in structural dynamic analysis arise when only a limited number of modes are retained in the modal basis, leading to significant inaccuracies in eigenfrequency predictions and mode shape estimations. This study presents a novel modal reanalysis technique that incorporates residual flexibility terms to account for the contribution of neglected higher-order modes, thereby reducing truncation errors without increasing the system's degrees of freedom in structural dynamic modification problems. The study presents an efficient modal reanalysis technique that is less expensive and more accurate, which can be used to evaluate the natural frequencies and mode shapes of a modified structure. The uniqueness of this technique lies in the structure of the formula, which emphasizes the contribution of unknown modes. This contribution can either be calculated for a finite element model or identified through an experimental model test. Numerical tests are provided to demonstrate the effectiveness of this method. High-quality results can still be obtained even if the modifications made to the structure are significant.

Abstract: Electric vehicles (EVs) have a significant advantage in terms of energy efficiency and environmental friendliness. In lithium-ion batteries, silicon is seeking more attention than graphite-based anodes due to its high storage capacity. However, it faces severe structural degradation due to volume expansion which is responsible for fast capacity degradation. In the present study, the core shell is developed with the core as silicon and titania as shell (Si@TiO₂) and utilized it as an anode in the 2016-coin cell. The material characterization (FE-SEM, TEM, EDS, XRD and XPS) of this developed core-shell material is recorded to confirm its elemental composition and structural validation. The electrochemical performance is measured using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) test. Cyclic voltammetry profiles reveal the stable lithiation and delithiation process. Initial specific capacity of ≈3180 mAh/g is reported, capacity retention of 61% for the developed core-shell while 34% for the bare silicon is noted over 100 cycles. The proposed method (peptization technique) for the development of core-shell nanoparticles is also compared with the sol-gel approach. The result shows an increment of 5% in capacity retention after 100 cycles by following the peptization technique.

Abstract: Superlattice formation in thin layers of oxidizing crystals and the effect of near-surface proton saturation on structure ordering, formation and periodical distribution of quantum wells have been discussed. The paper shows, it is necessary to develop non-Euclidean approach to the crystal’s internal geometry and consider, in consecutive order, the question of the four-dimentional Riemannian space into three-dimentional Eucliden space interpretation (R_E interpretation).

Abstract: The results on protonation in solutions and melts of salts and acids, as well as structural changes associated with the formation of nanocomposition structure of materials are presented. It is shown by structural methods that proton localization is invariant to the volume in the protonated layer and is accompanied by changes between oxygen distances, enlargement of the unit cell and transition to the rhombic phase. Having the maximum crystal-chemical activity, protons create a hexagonal lattice in accordance with the features of equipotential pictures of their nonequilibrium electrostatic fields. The increase in the integral intensity of reflexes observed on neutronograms of protonated LiNbO₃ (102), (111), (113) it is associated with the ordering of protons in the hexagonal oxygen sublattice of the initial phase.

Abstract: Al-Si eutectic cast alloys are widely used in aeronautical and automobile industries where significantly high strength, toughness and wear resistance are required. This class of cast alloys exhibit relatively low corrosion resistance in brine environments. The mechanical properties of the alloy system mainly depend upon the shape of Si rich eutectic phase, which mainly has acicular geometry. In present research, the effect of modified microstructure of 12 wt. % Si-Al alloy on corrosion behavior was studied. The needle like Si rich eutectic phase was modified to disperse spherical structure using rare earth metal halides. The corrosion rate and pitting behavior of modified and unmodified alloy were evaluated in 3.5% NaCl solution by general corrosion for calculated time. It was observed that the corrosion rate and pitting tendency of modified alloy had been appreciably reduced as compare to unmodified alloy. The improvement of corrosion properties were the attributes of changed morphology and distribution of Si rich eutectic phase.

Abstract: Harvesting energy from vibrations has received massive attention due to it being a renewable energy source that has a wide range of applications. Over the years of development, there is always research to further improve and optimise piezoelectric energy harvesters. This paper presents work on improving piezoelectric energy harvesters based on the structural modifications. Four different strategies of structural modification are employed for optimization by using additional beam structure as well as incorporation of rubber layer. This work summarized the optimum performance of the strategies at a resonance frequency of 60 + 2 Hz at 0.25g. The parameters compared among the strategies are voltage, power, PZT power density, spatial power density and specific power density. The results are also compared with other similar work. In general, structure with an addition of silicon rubber beam was found to give the best power density output and produce 253% increase of power ouput as compared to basic PZT energy harvester.

Abstract: We show here that Ni₃Al compound which is widely used as the base metal for advanced multipurpose hot-resistant alloys may be efficiently bulk nanostructured for improving its physical and strength characteristics. Developing the nanostructured component in the bulk of the intermetallic compound is achieved by plastic deformation of an SHS product during its synthesis and crystallization under conditions of thermal explosion of nickel/aluminum powder mixture of stoichiometric composition. It was shown that the nanosize component is formed on the basis of intermetallic Ni₃Al synthesized by SHS under hot forging conditions from nickel/aluminum powder mixed with an inert binder component. Developing the nanosize structural components improves strength of the intermetallic alloy.

Abstract: This study focuses on the prediction of complex eigenpairs of modified asymmetric systems. A method, which combines the reduced basis and the projection technique, is presented to predict the eigenpairs of modified asymmetric systems. The reduced basis obtained using the homotopy perturbation technique only requires the eigensolution of interest such that the modal truncation problem can be avoided. More importantly, the method can be carried out without using the left eigenvectors. The accuracy of the reduced basis approximation can be improved by introducing the projection technique. A rotor dynamic system is used to illustrate the capacity of predicting the changes of eigensolutions.

Abstract: In order to study the random vibration responses of satellite-borne equipment, the finite element model of satellite-borne equipment was established and its random vibration analysis was performed by ANSYS. The results showed that the stress of key part was too large to meet the strength requirement. The structural design was modified based on the stress analysis results. At the cost of adding 1.03% weight, we find the fundamental frequency of the modified model is increased by 14% and the maximum 1˰σ von Mises stress is decreased by 30%, which verify the correctness of the modification method. This analysis and modification method also can be applied to modify other satellite-borne equipments to shorten the development period and reduce the design cost.

Abstract: Quinones are useful compounds as dye compounds and the 1,4-naphthoquinone structure constitutes an essential part of these classes of compounds. The process in constructing 1,4-naphthoquinone for possible screening as dyestuff is described, starting from 1,4-naphthoquinone and hydroxy acid. It provides a novel methodology for the synthesis of the 5-nitro-2-substituted 1,4-naphthoquinones. The products were characterized by IR and ¹H NMR.