Hasil untuk "Mechanics of engineering. Applied mechanics"

Mohan Kumar Tumkur Sadashivaiah, Sharnappa Joladarashi, Satyabodh Madhav Kulkarni

The current investigation focused on the Finite element analysis (FEA) study on the outcome of sandwich composite's low to high-velocity impact responses. The sandwich structure comprises jute, natural rubber as skin, and epoxy/ natural rubber as a core, mixed with sand as a filler (0%-40%) material for bonding skin, and core B-stage cured natural-based prepreg is employed. The structure is impacted with a low velocity of 10 m/sec, an Intermediate of 50 m/sec, a high-velocity impact of 100m/sec, and ballistic velocity impact of 350 m/sec. Based on the results in terms of energy absorption, filler plays a vital role in increasing energy absorption capabilities for all configurations. The sandwich structure with rubber as the core offers better energy absorption capability because of its flexible nature. For further study, sandwich structures with a 40% sand filler were examined, with a velocity limit of 350 m/s. Varying the core thickness from 5 to 20 mm revealed that increasing the core thickness and filler composition in both configurations results in 0.37% for FR40F and 1.70% for FE40F higher energy absorption. Rubber core sandwiches outperformed epoxy core, suggesting the potential utility of rubber and sand-filled cores in ballistic-loaded sandwich structures.

Xin Wang, Ze Xu, Yulan Liu et al.

The elastoplastic mechanical behavior of Zircaloy-4 (Zr-4) cladding, coated with chromium (Cr) or FeCrAl on its surface, is explored under the coupled effects of multi-field coupling. Utilizing the Finite Element Software ABAQUS, simulations are conducted to calculate the evolution of stress and strain over two complete fuel cycles. Comparisons are drawn between the coated and uncoated Zircaloy-4 cladding materials. The results indicate that the application of surface coatings significantly mitigates stress levels in the cladding during the first fuel cycle. During the second fuel cycle, all three types of cladding exhibit relatively minor plastic strain, which is attributed to the unloading and reloading process between cycles. Notably, the plastic zone propagates from the interior to the exterior of the cladding. When compared to traditional Zircaloy-4 cladding, the coated cladding exhibits improved elastoplastic mechanical behavior. The operational mechanism of the coating for different stresses in cylindrical coordinates and its response to unloading and reloading cycles are also investigated. Specifically, the coated claddings exhibit an evident delay in reaching full plasticity compared to uncoated claddings. Furthermore, FeCrAl coating material initially shows good performance, and it needs to be verified in more aspects in the future. Results and Conclusions in this paper can provide reference and guidance for future experiments.

Sumit Sunil Kumar, Travis Leadbetter, J. Brandon McClimon et al.

Abstract The solution rheology of a fully synthetic, monodisperse mucin that mimics the glycosylated domains of natural mucins, poly(β‐Gal‐Thr)22, is studied to systematically explore relationships between polymer structure, solution conditions, and rheological properties. Using standard cone‐plate rheometry, shear thinning is observed over a range of concentrations, with an apparent yield stress—typical for gels—evident at the highest concentrations. This is surprising given the dilute, weakly interacting nature of the solutions and the lack of observable structure in cryogenic electron microscopy and particle tracking microrheology. However, interfacial rheometry demonstrates that the gel‐like behavior is attributable to a thin structured layer at the air–water interface, without any bulk gelation. This is attributed to an interfacial layer formed by inter‐mucin H‐bonds that yields when sheared. A computational model using kinetic Monte Carlo (kMC) simulations qualitatively reproduces the yield stress response of such a network through an intermolecular bonding potential. An analytical model of stochastic bond formation and breaking, validated by the kMC simulations, demonstrates that having multiple bonding sites per mucin with a force‐dependent debonding rate aligns with experiments, consistent with intermolecular interactions for other mucin proteins. This suggests that in mucin solutions, gelation may begin at the air–water interface, and emphasizes the need for multitechnique validation when exploring structural cues of mucus gelation through rheometry.

Masoud Rabeti, Omid Jahanian, Ali Akbar Ranjbar et al.

In this paper, the influence of equivalence ratio on the low-temperature reaction heat release (LTR-HR) and high-temperature reaction heat release (HTR-HR) of homogeneous charge compression ignition engine has been experimentally and numerically examined. The numerical study was performed using zero-dimensional (0D) single-zone model by considering the chemical kinetic of fuel combustion. Annand, Woschni, Hohenberg, Chang (Assanis), and Hensel semi-empirical heat transfer models were employed in the 0D single-zone simulations. In this study, the in-cylinder pressure, rate of heat release, LTR-HR and HTR-HR were investigated. The Hensel heat transfer model was the only model that predicted the combustion in all of the operating conditions. The Hohenberg model properly recognized the effects of equivalence ratio changes on the HTR-HR.

Ashish Kumar Singh, Rakesh Behera, Andrei Shishkin et al.

Abstract The most common fillers for syntactic foam development are glass microballoons or fly ash cenospheres. However, the need for improved properties and reduced cost requires exploring other possibilities. In this work, syntactic foams of vinyl ester resin reinforced with expanded glass particles (EG) were fabricated and compressive properties of the composites were studied. The foam EGS was reinforced with smaller particles of size 0.04–0.125 mm in 15, 30, and 45 vol.% and EGL had larger particles of size 0.25–0.5 mm in 15 and 30 vol.%. Compression testing reveals that 45 vol.% smaller particles enhance the modulus of the EGS foam by up to 48% with a 3.4% reduction in yield strength compared to neat resin. Strain rate sensitivity was observed in both the modulus and yield strength values for all composites. Composite EGS with 15 and 30 vol.% filler showed better strength and modulus than the neat resin at 0.01 s−1 strain rate, which is an overall improvement in the material. When compared with the literature data, the foams made in the present work have the highest compressive strength and modulus for the same density.

La Kolo, Firdaus Firdaus, Paulina Taba et al.

The synthesis of MCM-48 containing surfactants (CTAB and Triton X-100), ZnO, and CaO aimed to find a potential heterogeneous catalyst in the esterification of Calophyllum inophyllum oil to biodiesel. This research is important in the production of biodiesel from vegetable oils with more than 2% free fatty acids (FFA), such as Calophyllum inophyllum oil using heterogeneous catalysts. Synthesis of heterogeneous catalysts, MCM-48 and ZnO-MCM-48-CaO (ZMC), using the hydrothermal method at various calcination temperatures was conducted to find the optimum calcination temperature for the reaction. The activity of the catalyst in the reaction was determined using acid-base titration methods and GC-MS. The MCM-48 catalyst calcined at 650 °C (MCM-48/650) had a catalytic activity of 35.74% and was selective for converting linoleic acid in Calophyllum inophyllum oil to biodiesel. In addition, this catalyst was also capable of cracking the compounds contained in Calophyllum inophyllum oil into suitable hydrocarbons for biodiesel. In the esterification of vegetable oils, four heterogeneous catalysts (MCM-48/550, ZMC/550, ZMC/650, and ZMC/750) had the potential to replace conventional catalysts (H2SO4), particularly in the generation of biodiesel from Calophyllum inophyllum oil.

Vesović Mitra, Radulović Radoslav

The production industries have repeatedly combated the problem of system modelling. Successful control of a system depends mainly on the exactness of the mathematical model that predicts its dynamic. Different types of studies are very common in the complicated challenges involving the estimations and approximations in describing nonlinear machines are based on a variety of studies. This article examines the behaviour and stability of holonomic mechanical system in the the arbitrary parameter sets and functional configuration of forces. Differential equations of the behaviour are obtained for the proposed system on the ground of general mechanical theorems, kinetic and potential energies of the system. Lagrange’s equations of the first and second kind are introduced, as well as the representation of the system in the generalized coordinates and in Hamilton’s equations. In addition to the numerical calculations applied the system, the theoretical structures and clarifications on which all of the methods rely on are also presented. Furthermore, static equilibriums are found via two different approaches: graphical and numerical. Above all, stability of motion of undisturbed system and, later, the system that works under the action of an external disturbance was inspected. Finally, the stability of motion is reviewed through Lagrange–Dirichlet theorem, and Routh and Hurwitz criteria. Linearized equations are obtained from the nonlinear ones, and previous conclusions for the stability were proved.

Radivojević Dušan S., Mirkov Nikola S., Maletić Slobodan

This paper presents two Machine Learning models that classify time series data given from smartwatch accelerometer of observed subjects. For the purpose of classification we use Deep Neural Network and Random Forest classifier algorithms. The comparison of both models shows that they have similar performance with regard to recognition of subject's activities that are used in the test group of the dataset. Training accuracy reaches approximately 95% and 100% for Deep Learning and Random Forest model respectively. Since the validation and recognition, reached about 81% and 75% respectively, a tendency for improving accuracy as a function of number of participants is considered. The influence of data sample precision to the accuracy of the models is examined since the input data could be given from various wearable devices.

<正>Journal of Measurement Science and Instrumentation （CN14-1357/TH,ISSN 1674-8042） is published by North University of China.It is a comprehensive academic journal,aiming to present scientific research papers in the fields of measurement science and instrumentation,including general principles,technologies and instrumentation of measurement and control applied to such academic and industrial fields as mechanics,electric and electronic engineering,magnetics,optics,chemistry,biology,and so on.

Nae-Hyun KIM

For a cooling or heating coil of a building air conditioning system, large diameter tubes (over 12.7 mm) with wave fins are frequently used. Furthermore, there have been attempts to apply oval tubes to the heating or cooling coils. In this study, nine samples - three herringbone wave fin/round tube, three smooth wave fin/round tube and three smooth wave fin/oval tube samples - were tested under dry condition. All of the samples had the same original tube diameter (12.7 mm). For the smooth wave fin samples, fins were identical, and for the round tube samples, fin corrugation angles were almost the same. Tests were conducted varying the frontal air velocity from 1.0 to 4.0 m/s. Results showed that the round tube samples yielded higher conductance per volume (ηo ho Ao / Vo ) than the oval tube sample. Similarly, the smooth wave fin samples yielded a higher conductance per volume than the herringbone wave fin samples. At one row configuration, however, a significant difference among samples existed between the heat transfer conductance per volume and the heat transfer coefficient, and the reason was explained by the difference in fin efficiency between the round and the oval geometry. The pressure drops of the round tube samples were larger than those of the oval tube samples. Similarly, the smooth wave fin samples yielded larger pressure drops than the herringbone wave fin samples. A performance evaluation revealed that the smooth wave fin samples yielded larger heat transfer conductances per volume than the herringbone wave fin samples at the same pumping power per volume.