Hasil untuk "Mechanics of engineering. Applied mechanics"

Ahmed TAIBAOUI, Tahar BENMESSAOUD, Cheikh KEZRANE

This numerical analysis investigates the interplay between fluid dynamics and structural mechanics within a horizontal axis wind turbine. Tip speeds ranging from 1 to 8.1 are explored, focusing on blade structural responses at maximum aerodynamic coefficient across Young's modulus values. Visual representations of absolute pressure and velocity magnitude highlight a significant velocity gradient at the minimum tip speed ratio, contrasting with the maximum aerodynamic coefficient case. Examination of relative wind speed vectors uncovers predicted flow separation near the blade's trailing edge at the minimum tip speed ratio. However, for the highest tip-speed ratio, airflow remains attached to the blade across all radial positions. Radial deformation patterns show increasing blade deformation from centre to tip, diminishing with higher Young's modulus. Von Mises stress analysis identifies maximum values at the blade-hub junction and midpoint of the blades, decreasing with increasing Young's modulus values.  Blade tip deflection variation over time reveals initial oscillations followed by stability, with decreasing blade tip deflection values as Young's modulus values increase. A comparison between One-way and Two-way Fluid Structure Interaction simulations indicates higher blade tip deflection values in the Two-way simulations. with a maximum percentage difference of 8.21% observed at the minimum Young's modulus case (5×108 Pa).

Abiodun Ajibade, Mojeed Akolade, Basant Jha

This study integrates the single-phase nanofluid viscosity model into the generalized Buongiorno model to analyze the combined convection of an ammonia-water nanofluid over a vertical flat plate. A key contribution of this work in the field of mass and heat transfer is representing fluid viscosity as a composite function of nanoparticle concentration and temperature, while also achieving the nanofluid hybridization model. The model development assumes that fluid viscosity is directly influenced by nanoparticle concentration, temperature, and buoyancy. It indirectly controls the concentration gradient through the Dufour effect and dissipative heat. This physical phenomenon is addressed to achieve the quantitative improvements necessary for optimizing the design of engineering systems. The mixed convection problem, which incorporates the influences of the Dufour and Soret effects as well as the dynamics of the ammonia-water nanofluid (Sc = 445, Pr = 7.2, Le = Sc/Pr), is modeled over a semi-infinite plate subjected to double-diffusive and convective thermal boundary conditions. The model equations are simplified using an appropriate similarity transformation and are numerically solved via the Spectral Local Linearization Method (SLLM). The results highlight a reduction in fluid viscosity with increasing temperature, which consequently diminishes viscous drag; enhanced momentum and energy fields due to the involvement of the non-linear density–temperature relationship (Λ1);a pronounced effect of the non-linear density-solutal relationship (Λ2), particularly in the constant viscosity model (λ = 0.0), which exhibits significantly higher sensitivity compared to the variable viscosity model (λ = 0.2); increased contributions of dissipative heating with a rising Eckert number (Ec), acting as a thermokinetic effect on fluid flow. Further analysis reveals that, in the presence of Ec = 0.05, the skin friction in the constant viscosity model is reduced by 19.2%, while the Nusselt number, nanoparticle mass transfer, and regular mass transfer increase by 2.4%, 7.7%, and 7.4%, respectively, in the variable viscosity model.

Ali Albu-Rghaif , Hussein A. Abdulkadhim, Latifah Munirah Kamarudin

The Global Positioning System (GPS) represents a significant leap in global navigation satellite systems. This is achieved through continuous localization, reliable navigation, and precise timing for various uses, such as civilian, commercial, and military. Among the multiple signals sent by GPS satellites, the L1C signal greatly enhances structure and performance, boosting user reliability (by employing binary offset carrier modulation to reduce multipath effects) and accuracy (by lengthening the ranging code). It features data and pilot components, enhancing resilience against multipath interference and strengthening the signal under challenging conditions. In this work, an orthogonal single-channel acquisition algorithm for the GPS L1C signal is proposed, and it is utilized to reduce the complexity of a conventional side-by-side/dual-channel configuration. The proposed scheme mathematically combines the data and pilot portions into one orthogonal channel, which approach has been shown to achieve a 3dB gain in signal-to-noise ratio (SNR) with 34% gain in computation complexity over the conventional implementation. The MATLAB-Simulink environment was used to simulate the GPS L1C parameters with a sampling frequency of 16.368 MHz and a dwell time of 10 ms. The simulations were carried out across various SNR levels to evaluate detection probability, and processing time. The results show that the proposed solution preserves detection probability and dramatically increases resource utilization. This work provides the first single-channel orthogonal design for GPS L1C acquisition and is an efficient step towards low-power, high-performance GNSS receivers.

Zhiwu Zhou, Zhifeng Zhao, Julián Alcalá et al.

The safety, longevity, and healthy operation and maintenance of world-class large bridges are a research hotspot that continues to attract attention from academia and industry. In particular, during the sustainable operation period of large and statically indeterminate bridges under various loads and complex environmental conditions, it is necessary to establish an information-based intelligent structural health monitoring and early warning cloud platform system to ensure the safety and economic efficiency of in-service bridges. Through interdisciplinary research in computer science, communication engineering, automation control, and engineering mechanics, this article established a multi-factor complex modal multi-source theoretical model and applied the real-time early warning of bridge monitoring data and the coupling of finite element models to verify the robustness of the intelligent cloud model under the influence of multiple factors on statically indeterminate bridges. This work solves the technical barriers that traditional technical monitoring cannot achieve continuous real-time, spatiotemporal and remote monitoring of statically indeterminate structures, and realizes an intelligent cloud platform model for spatial, direct and automated monitoring, providing scientific and technological guarantees for the healthy maintenance of super-large bridges, and providing theoretical scientific support and paradigms for saving labour and reducing maintenance costs.

Hongxu Guo, Jianjun Wang, Xiangxiang Tu et al.

To enhance the strength and toughness of metallic materials simultaneously over a wide range of temperatures and strain rates, a eutectic high-entropy FCC/Laves composite with a heterogeneous initial microstructure was fabricated by powder plasma arc additive manufacturing. The mechanical behavior of the composite over a wide range of temperatures and strain rates was tested with the aid of an electronic universal testing machine and an improved Split Hopkinson pressure bar. The high-entropy FCC/Laves composite possesses a unique combination of strength and ductility over the selected temperature and strain rate ranges due to the in situ composite nature with both soft high-entropy FCC phase and hard high-entropy Laves phase. Complicated thermal viscoplastic behavior is presented. To reveal the mechanisms of the complicated thermal viscoplastic behavior, microstructure evolution was characterized. The high-entropy Laves phase, as a kind of multi-component intermetallic, defies convention by displaying plastic deformation at room temperature and different strain rates. Superior damage tolerance of the high-entropy FCC/Laves composite can be achieved over the selected temperature and strain rate ranges with the contribution of deformation twin in FCC phase, as well as dynamic recrystallization over high temperature range. Finally, a constitutive description was developed, which is shown to be able to accurately describe the complicated plastic behavior over a wide range of temperatures and strain rates. These findings suggest promising prospects for advanced material design, opening a new avenue to achieve a fine balance between strength and ductility across different conditions.

Idrees Khan, T. Chinyoka, Emad A.A. Ismail et al.

This study examines the complex dynamics of an incompressible, electrically conducting third-grade fluid (TGF) flow through a vertical micro-channel that is filled with porous media. The research utilizes asymmetrical convective cooling, a transverse magnetic field, and exothermic reactions to introduce a comprehensive model. The viscosity of the fluid, which is determined by the Naham-type law, changes significantly with temperature. Additionally, the convective heat transfer rates, which govern the asymmetric convective cooling at the surfaces of the micro-channel, are modeled using Newton's law of cooling, and Modified Darcy law is used to address the porous medium effect. To solve the complex system of nonlinear partial differential equations, we employ computational solutions derived from reliable and efficient finite difference methods (FDM). The method is tested for different time-steps and mesh sizes and it is found that the algorithms reliably produce the same results. Our investigation includes an evaluation of both spatial and temporal convergence of the FDM scheme. The study present qualitative discussions of graphical results, that highlight the impact of various flow parameters integrated into the system. The velocity and temperature profiles increases for higher values of thermal Grashoff number Gr and Reynolds number Re while opposite effect is noticed for increasing values of Hartman number M.

Qihong Huang, Kaituo Zhang, He Huang et al.

The emergent universe provides a possible method to avoid the Big Bang singularity by considering that the universe stems from a stable Einstein static universe rather than the singularity. Since the Einstein static universe exists before inflation, it may leave some relics in the CMB power spectrum. In this paper, we analyze the stability condition for the Einstein static universe in general relativity with k-essence against both the scalar and tensor perturbations. Furthermore, we find the emergent universe can be successfully realized by constructing a scalar potential and an equation of state parameter. Solving the curved Mukhanov–Sasaki equation, we obtain the analytical approximation for the primordial power spectrum, and then depict the TT-spectrum of the emergent universe. The results show that both the primordial power spectrum and CMB TT-spectrum are suppressed on large scales.

Wenlei Zhang, Yang Gao, Yifan Zhou et al.

Adhesives are commonly assessed by two properties: strength and toughness. Here we study how strength and toughness are affected by adhesive thickness. We sandwich gelatin adhesives of various thicknesses between glass substrates. The transparency of the adhesives and substrates enables us to observe crack nucleation and growth. We measure strength by lap shear of samples without precrack, and measure toughness by lap shear of samples with precrack. Our data show a characteristic adhesive thickness, about 0.5 mm. For adhesives below the characteristic thickness, strength is independent of thickness, but toughness increases with thickness. For adhesives above the characteristic thickness, strength decreases as thickness increases, but toughness is a constant. Strength scatters narrowly for samples of a thin adhesive, but broadly for samples of a thick adhesive. By contrast, toughness scatters narrowly for samples of all thicknesses. This work shows the importance of assessing adhesives of various thicknesses.

Ivan Kuric, Jaromír Klarák, Vladimír Bulej et al.

The article discusses the possibility of object detector usage in field of automated visual inspection for objects with specific parameters, specifically various types of defects occurring on the surface of a car tire. Due to the insufficient amount of input data, as well as the need to speed up the development process, the Transfer Learning principle was applied in a designed system. In this approach, the already pre-trained convolutional neural network AlexNet was used, subsequently modified in its last three layers, and again trained on a smaller sample of our own data. The detector used in the designed camera inspection system with the above architecture allowed us to achieve the accuracy and versatility needed to detect elements (defects) whose shape, dimensions and location change with each occurrence. The design of a test facility with the application of a 12-megapixel monochrome camera over the rotational table is briefly described, whose task is to ensure optimal conditions during the scanning process. The evaluation of the proposed control system with the quantification of the recognition capabilities in the individual defects is described at the end of the study. The implementation and verification of such an approach together with the proposed methodology of the visual inspection process of car tires to obtain better classification results for six different defect classes can be considered as the main novel feature of the presented research. Subsequent testing of the designed system on a selected batch of sample images (containing all six types of possible defect) proved the functionality of the entire system while the highest values of successful defect detection certainty were achieved from 85.15% to 99.34%.

Xianguo Li

Fernanda Mendoza, Laura Masgrau

Carbohydrate processing enzymes are of biocatalytic interest. Glycoside hydrolases and the recently discovered lytic polysaccharide monooxygenase for their use in biomass degradation to obtain biofuels or valued chemical entities. Glycosyltransferases or engineered glycosidases and phosphorylases for the synthesis of carbohydrates and glycosylated products. Quantum mechanics-molecular mechanics (QM/MM) methods are highly contributing to establish their different chemical reaction mechanisms. Other computational methods are also used to study enzyme conformational changes, ligand pathways, and processivity, e.g. for processive glycosidases like cellobiohydrolases. There is still a long road to travel to fully understand the role of conformational dynamics in enzyme activity and also to disclose the variety of reaction mechanisms these enzymes employ. Additionally, computational tools for enzyme engineering are beginning to be applied to evaluate substrate specificity or aid in the design of new biocatalysts with increased thermostability or tailored activity, a growing field where molecular modeling is finding its way.

Gilles Dusfour, Dominique Ambard, Patrick Cañadas et al.

Up-to-date, back pain is among the most prevalent health issues and generally takes its origins from lesions of the annulus fibrosus (AF). While the AF ex vivo mechanical properties are increasingly well understood, in vivo data are still missing. In particular, very few studies have precisely measured the residual strains within the AF and thus the in vivo deformation state of the AF is still miss-interpreted and miss-evaluated. In this work, we propose an original and robust method for the AF residual strains quantification via digital image correlation technics. Ten pig annulus fibrosus were extracted from adjacent vertebrae followed by a radial incision to release the residual strains. The operations were filmed and then analyzed by a custom digital image correlation software in order to quantify the circumferential, radial and shear residual deformations. Our results show that residual strains are of the same order of magnitude than the in vivo one. The average circumferential strains are in tension on the outer periphery ([3.32; 5.94]%) and in compression on the inner periphery ([−6.4; −1.69]%). The mean radial residual strains are essentially in compression ([−10.4; 2.29]%). Locally, radial and circumferential residual strains can reach really large values up to 40% of compression. The mean shear strains remain very small (−0.04% ± 2.88%). This study also shows that circumferential and radial residual strains evolve linearly along the radius and non-linearly along the angle. We propose a simple model to predict their spatial variations. Our results and methods will allow the quantification of more realistic in vivo strains and stresses within the human intervertebral disc.

Georgiev Svetlin, Mebarki Karima, Zennir Khaled

We study a class of initial value problems subject to nonlinear partial differential equations of hyperbolic type. A new topological approach is applied to prove the existence of nontrivial nonnegative solutions. More precisely, we propose a new integral representation of the solutions for the considered initial value problems and using this integral representation we establish existence of classical solutions for the considered classes of nonlinear wave equations.

Lei Sun, G. Grasselli, Quansheng Liu et al.

Erik Jonsson, Murat Kantarcioglu, L. Khan et al.

• Chemical & Biomolecular Engineering, Minor (http:// catalog.upenn.edu/undergraduate/programs/chemical-biomolecularengineering-minor/) • Computer Science, Minor (http://catalog.upenn.edu/undergraduate/ programs/computer-science-minor/) • Data Science, Minor (http://catalog.upenn.edu/undergraduate/ programs/data-science-minor/) • Digital Media Design, Minor (http://catalog.upenn.edu/ undergraduate/programs/digital-media-design-minor/) • Electrical Engineering, Minor (http://catalog.upenn.edu/ undergraduate/programs/electrical-engineering-minor/) • Energy & Sustainability, Minor (http://catalog.upenn.edu/ undergraduate/programs/energy-sustainability-minor/) • Engineering Entrepreneurship, Minor (http://catalog.upenn.edu/ undergraduate/programs/engineering-entrepreneurship-minor/) • Materials Science and Engineering, Minor (http://catalog.upenn.edu/ undergraduate/programs/materials-science-engineering-minor/) • Mechanical Engineering and Applied Mechanics, Minor (http:// catalog.upenn.edu/undergraduate/programs/meam-minor/) • Systems Science and Engineering, Minor (http://catalog.upenn.edu/ undergraduate/programs/systems-science-engineering-minor/)

X. Shao, Zhenning Chen, X. Dai et al.

Digital image correlation (DIC) is a well-known technique for non-contact, non-destructive, full-field deformation measurement in experimental solid mechanics. Although DIC has been widely used in science and engineering, the resolution of strain measurement with DIC is limited by imaging resolution and is much lower than that obtained with a strain gauge. To achieve a breakthrough in strain measurement using DIC, a camera array-based DIC method is proposed herein for high-resolution strain measurement. Twenty-five industrial cameras were assembled into a plane array, with each camera capturing a part of the specimen. A novel calibration-based image stitching method is proposed and was applied to these images and their corresponding displacement fields. The strain field was then calculated based on the stitched displacement fields. The use of the camera array greatly improved the measurement spatial resolution of DIC and made high-resolution strain measurement possible. Both static error analysis and four point-bending experiments were performed to demonstrate the feasibility and effectiveness of the proposed method, and a full-field strain resolution of 10 μ ε was achieved.

B. Kalynyak, Y. Tokovyy, А. V. Yasinskyy

Valery N. Varavka, Oleg V. Kudryakov, Alexey F. Mednikov

The approximating model for the definition of the steam turbines blades wear rate under the continuous operation through the droplet-impact erosion is built on the ground of the comparative analysis of the stand test data of the titanium alloy samples.

Andrey N. Leshchenko, Anatoly P. Babichev

The theoretical research on the noise emission process under the ball - and - rod hardening of the bar - and plane - type parts is considered. The analytic dependences of the produced noise spectra are obtained. That is th e basis for making the engineering de cisions on the bringing the acoustic characteristics to the sanitary norms at the design stage of such processes.

Bo Wu, N. Vajragupta, J. Lian et al.