World Journal of Mechanics
ISSN / EISSN : 2160049X / 21600503
Current Publisher: Scientific Research Publishing, Inc, (10.4236)
Total articles ≅ 294
Latest articles in this journal
World Journal of Mechanics, Volume 10, pp 1-10; doi:10.4236/wjm.2020.101001
Abstract:This study is concerned with 12-MW capacity turbochargers on diesel power generators. These are generators equipped with 18 cylinders. Our previous studies  showed that the processing of vibration signature collected from a power generator is very complex, insomuch the dominant vibration remains the one originating from explosion frequency in the diesel generator cylinders, with a fairly high number of cylinders. This vibration drowns out all other possible vibrations, which can expose defects. The study at hand is focused on turbochargers with 20,940 rpm, while the rotation speed in the diesel engine is 600 rpm only. With the turbocharger rotating at very high speed, it results in severe mechanical constraints on the rotor shaft in the turbocharger and its related organs (turbine blades). The wear of turbine blades can result in breakdowns in the turbocharger. This article is an attempt to early detect defaults in turbine blades based on vibration signature that can be experimentally determined. We noted in our investigations that a diesel engine and its turbochargers do not bear the same mechanic loads. While the diesel engine is the seat of violent shocks brought about by explosions in cylinders, the turbochargers are driven by the action of exhaust gas from explosions, without being affected by explosion shocks. The study found that explosion frequency in the diesel engine cylinders, which disrupted the vibration signals in the diesel engine and alternator, did not impact on the vibration signals in the turbocharger. We experimentally determined, following several campaigns of measurements, a vibration signature on the turbochargers under study, which corresponds to a defect in turbine blades.
World Journal of Mechanics, Volume 9, pp 147-162; doi:10.4236/wjm.2019.96010
Abstract:The present study aims to the development of Out of Autoclave (OoA) Carbon Fiber Reinforced Polymers (CFRPs) with increased interlaminar fracture toughness by using MWCNTs. The introduction of MWCNTs into the structure of CFRPs has been succeeded by using carbon nanotube-enriched sizing agent for the pretreatment of the fiber preform using an in-house developed methodology that can be easily scaled up. The positive effect of the proposed methodology on the interlaminar fracture toughness of the CFRP laminate was assessed by the increase of Mode I and Mode II interlaminar fracture toughness of the composites. Different wt% MWCNTs concentrations were used (namely 0.5%, 1%, 1.5% and 2.5%). It was found that the nanomodified composites exhibit a significant increase of the interlaminar critical strain energy release rate GIC and GIIC of the order of 103% and 62% respectively, in the case of 1.5 wt% MWCNTs weight content. Scanning Electron Microscopy (SEM) of the fracture surfaces of CFRP samples revealed the contribution and the associated synergistic mechanisms of MWCNTs to the increase of the crack propagation resistance in the case of nano-modified CFRPs compared to the reference material.
World Journal of Mechanics, Volume 9, pp 177-190; doi:10.4236/wjm.2019.97012
World Journal of Mechanics, Volume 9, pp 191-204; doi:10.4236/wjm.2019.98013
Abstract:In this work, the Hamiltonian of the four-body problem is considered under the effects of solar radiation pressure. The equations of motion of the infinitesimal body are obtained in the Hamiltonian canonical form. The libration points and the corresponding Jacobi constants are obtained with different values of the solar radiation pressure coefficient. The motion and its stability about each point are studied. A family of periodic orbits under the effects of the gravitational forces of the primaries and the solar radiation pressure are obtained depending on the pure numerical method. This purpose is applied to the Sun-Earth-Moon-Space craft system, and the results obtained are in a good agreement with the previous work such as (Kumari and Papadouris, 2013).
World Journal of Mechanics, Volume 9, pp 205-231; doi:10.4236/wjm.2019.99014
Abstract:We have performed sequential studies on new types of soft rubber for their application as artificial skin in robots and haptic sensors. Based on a proposed electrolytic polymerization method and novel adhesion technique for rubber and a metal that utilizes a metal complex hydrate, we have developed an MCF rubber sensor. This sensor uses a magnetic compound fluid (MCF), natural rubber (NR-latex) or chloroprene rubber latex (CR-latex), and requires the application of a magnetic field. The potential application of the developed sensor in various engineering scenarios and our daily lives is significant. In this regard, we investigated the effects of γ-irradiation, infrared radiation, microwaves, and a thermal source on the MCF rubber sensor. We established that the MCF rubber is effective enough to be used for power generation of broadband electro-magnetic waves from γ-rays to microwaves, including the range of the solar spectrum, which is the typical characteristic obtained in the present investigation. The remarkable attribute is that the MCF rubber sensor dose is not degraded by γ-irradiation. We also demonstrated the effectiveness of the MCF rubber sensor in energy harvesting.
World Journal of Mechanics, Volume 9, pp 233-243; doi:10.4236/wjm.2019.910015
Abstract:We developed a planetary-type rod mill that can improve the comminution working efficiency, prevent the generation of soil dust, and make it easy to clean the used jars. Clods are broken by this device into fine-grained soil particles with sizes of less than 2 mm in diameter within 2 min. One objective of this study is to evaluate the performance of the mill by observing the fragmentation process of the clods. The process is visualized experimentally via a high-speed camera installed on a rotating jar of the device. The breakage of the clods in the rod mill is considered morphologically according to the crushing patterns obtained by previous studies. The rod moves together with the clods in the jar. Therefore, violent collisions are not thought to be a major reason for the breakage of the clods. The surfaces of the clods are first scraped and then appear to become fragile. However, if there are no rods in the jar, the clods never break into small pieces. Therefore, it is likely that collisions with the rod trigger the catastrophic fragmentation of the clods into small pieces. This suggests that the design of the device could be modified to improve its performance in the near future.
World Journal of Mechanics, Volume 9, pp 245-258; doi:10.4236/wjm.2019.911016
Abstract:Explosive synchronization (ES), as one kind of abrupt dynamical transitions in nonlinearly coupled systems, has become a hot spot of modern complex networks. At present, many results of ES are based on the networked Kuramoto oscillators and little attention has been paid to the influence of chaotic dynamics on synchronization transitions. Here, the unified chaotic systems (Lorenz, Lü and Chen) and Rössler systems are studied to report evidence of an explosive synchronization of chaotic systems with different topological network structures. The results show that ES is clearly observed in coupled Lorenz systems. However, the continuous transitions take place in the coupled Chen and Lü systems, even though a big shock exits during the synchronization process. In addition, the coupled Rössler systems will keep synchronous once the entire network is completely synchronized, although the coupling strength is reduced. Finally, we give some explanations from the dynamical features of the unified chaotic systems and the periodic orbit of the Rössler systems.
World Journal of Mechanics, Volume 9, pp 259-266; doi:10.4236/wjm.2019.912017
Abstract:In this short article, the upwind and central compact finite difference schemes for spatial discretization of the first-order derivative are analyzed. Comparison of the schemes is provided and the best discretization scheme for convection dominated problems is suggested.
World Journal of Mechanics, Volume 9, pp 1-16; doi:10.4236/wjm.2019.91001
World Journal of Mechanics, Volume 9, pp 17-28; doi:10.4236/wjm.2019.92002