排序方式: 共有27条查询结果,搜索用时 15 毫秒
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Abdelkader Nour Samir Lecheb Nouredine Chikh M. Ouali Si-Chaïb 《Journal of Mechanical Science and Technology》2011,25(7):1629-1636
This work concerns the characterization of the thermodynamic behavior of the superalloy Airsist 215 (PN 3601669-7) containing
cobalt. Such superalloys are used in aeronautical construction, in the hot parts of the turbine. They are frequently used
for the production of the paddles. The parts in service are subjected to dynamic solicitations and thermal fluctuations over
the course of time. They are responsible for modification and degradation of material properties. This can lead to the appearance
of cracks and, in the long term, to the rupture of these parts. In this paper, a preliminary physical study is made on the
appearance of the cracks, followed by experiments using shocks at ambient temperature and under a heating situation which
simulates combustion. It is found that these dynamic loads have a significant impact on the development of the cracks that
appear on the segments of the turbine nozzle. The study is devoted to the elastic shock of Hertz-Boussinesq extended to viscoelastic
bodies by direct convolution of Riemann-Stielges. The interest resides in the local convolution and the distribution of stresses
in the contact zone. The shock excitation method includes a deduced force in the load and disload phases. This force is an
impulse which approaches a Dirac function. The sample can be modeled approximately by a system of one degree of freedom for
natural frequency, damping and transfer function. The spectral response of the specified shock allows calculation of the damping.
Every point of this spectrum gives the response for the linear system of the transfer function. Then, viscoelastic shock parameters
are deduced. 相似文献
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Jan Gmys Rudi Leroy Mohand Mezmaz Nouredine Melab Daniel Tuyttens 《Concurrency and Computation》2016,28(18):4463-4484
In this paper, the focus is put on multi‐core branch‐and‐bound algorithms for solving large‐scale permutation‐based optimization problems. We investigate five work stealing (WS) strategies with a new data structure called integer–vector–matrix (IVM). In these strategies, each thread has a private IVM allowing the local management of a set of subproblems enumerated using a factorial system. The WS strategies differ in the way the victim thread is selected and the granularity of stolen work units (intervals of factoradics). To assess the efficiency of the private IVM‐based WS approach, the five WS strategies have been extensively experimented on the flowshop scheduling permutation problem and compared with their conventional linked‐list‐based counterparts. The obtained results demonstrate that the IVM‐based WS outperforms the linked‐list‐based one in terms of CPU time, memory usage and number of performed WS operations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Samir Khamel Nouredine Ouelaa Khaider Bouacha 《Journal of Mechanical Science and Technology》2012,26(11):3605-3616
The main of the present study is to investigate the effects of process parameters (cutting speed, feed rate and depth of cut) on performance characteristics (tool life, surface roughness and cutting forces) in finish hard turning of AISI 52100 bearing steel with CBN tool. The cutting forces and surface roughness are measured at the end of useful tool life. The combined effects of the process parameters on performance characteristics are investigated using ANOVA. The composite desirability optimization technique associated with the RSM quadratic models is used as multi-objective optimization approach. The results show that feed rate and cutting speed strongly influence surface roughness and tool life. However, the depth of cut exhibits maximum influence on cutting forces. The proposed experimental and statistical approaches bring reliable methodologies to model, to optimize and to improve the hard turning process. They can be extended efficiently to study other machining processes. 相似文献
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Shuohong Gao Xingchen Yan Cheng Chang Xinliang Xie Qingkun Chu Zhaoyang Deng Bingwen Lu Min Liu Hanlin Liao Nouredine Fenineche 《金属学报(英文版)》2022,35(9):1439-1452
This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H c ), remanence ( B r ), and power losses ( P 相似文献
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Mohamed Khemissi Babouri Nouredine Ouelaa Mohamed Cherif Djamaa Abderrazek Djebala Nacer Hamzaoui 《Journal of Failure Analysis and Prevention》2017,17(5):905-913
The recent increase in machining productivity is closely related to longer tool life and good surface quality. In the present study, an experimental technique is proposed to evaluate the performance of a cemented carbide inset during the machining of AISI D3 steel. The aim of this technique is to find a relationship between the vibratory state of the cutting tool and the corresponding wear during machining in order to detect the beginning of the transition period to excessive wear. A spectral indicator named spectral center of gravity, SCG, is proposed to highlight the three phases of tool wear using the spectra of the accelerations measured. Very promising results are obtained which can be used to underpin an industrial monitoring system capable of detecting the onset of transition to excessive wear and alerting the user of the end of the tool’s life. The purpose of this study is to review the vibration analysis techniques and to explore their contributions, advantages and drawbacks in monitoring of tool wear. 相似文献
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Ghazi Otmanine Nouredine Bentahar Mohamed Otmanine 《Petroleum Science and Technology》2016,34(7):693-701
The global demand for petroleum products is increasing year by year quantitatively and qualitatively. Besides the clear products supplied by the fractionation of crude oil, there are a number of heavy petroleum products obtained from the secondary treatment, which are not the proper use; they are often used as components of fuel oil. Now, all the refineries are equipped by hydrotreating facilities aimed to transform these fractions heavy in market value of products most important. Consequently, the choice of adequate processes is a major challenge for oil refineries. The objective of this work is to value these heavy cuts by the catalytic cracking process, which is the most suitable method and is the only one existing in Algeria. 相似文献
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Morteza Kheradmandi Mehdi EhsanRené Feuillet Nouredine Hadj-Saied 《Electric Power Systems Research》2011,81(1):1-9
This paper investigates various approaches to relieve the transient stability constraint in restructured power systems. The approaches adopted fall into two broad categories: those based on eliminating the constraint in the least-cost way and those based on eliminating with the least possible rescheduling. The latter group can, on the other hand, emerge in the form of a pool-protected policy in which the bilateral contracts are rescheduled to maintain the stability or in the form of a contract-protected policy in which the realizable bilateral contracts are maximized while minimizing the rescheduling in pool market. Transient energy function (TEF) method is used as a tool to calculate the sensitivity of energy margin to the variations in the magnitude of generation and load. The effectiveness of the method is illustrated by case studies on Western System Coordinating Council (WSCC) 3-machine 9-bus power system and on the 10-machine 39-bus New England test system and the results are compared. The results are also verified by time domain simulations. 相似文献
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