共查询到20条相似文献,搜索用时 328 毫秒
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通过试验和有限元方法分析了单轴压缩下加筋板的失效模式.研究了三种预置损伤位置及四种损伤尺寸的复合材料T型加筋板的线性及非线性屈曲行为,比较了损伤对临界屈曲载荷和最大失效载荷的影响.研究结果表明:损伤位置在桁条间蒙皮时,损伤的尺寸对其临界屈曲载荷和最大失效载荷影响较小;损伤位置在桁条区蒙皮时,加筋板的临界屈曲载荷随损伤尺寸的增加而明显降低,最大降低50%;损伤位置在桁条边凸缘处蒙皮时,加筋板最大失效载荷所受影响随损伤尺寸的增加而明显降低,最大降低25%.从而得到了复合材料加筋板临界屈曲载荷比和最大失效载荷比与损伤位置及尺寸的关系图. 相似文献
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运用大型有限元软件Patran/Nastran分析了大开口复合材料加筋壁板的稳定性,并对不同加筋方式下壁板屈曲特征值和屈曲模态图进行了比较。结果表明:补强提高了大开口复合材料壁板的稳定性,但往往无法达到很好的效果,需要通过加筋改善其稳定性;加筋复合材料壁板稳定性较原有模型有较大提高;加筋大开口复合材料壁板屈曲特征值随筋条距开口中心距离的增加而减小,其屈曲分界线均位于筋条布置处;纵筋大开口复合材料加筋壁板一阶屈曲特征值为2.13,而横筋只达到1.08;纵筋布置对复合材料壁板稳定性影响明显高于横筋布置,可在实际工程应用中适当增加纵筋的布置。 相似文献
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V. S. Nagornyi 《Journal of Applied Mechanics and Technical Physics》2000,41(2):225-230
The physical and mathematical principles of the method of electrogas-and electrohydrodynamic conversion of electrical signals
to pneumatic (hydraulic) signals and vice versa for control of gas and liquid jets and flows in electropneumohydraulic systems
are considered.
St. Petersburg State Technical University, St. Petersburg 195251. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika,
Vol. 41, No. 2, pp. 25–31, March–April, 2000. 相似文献
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Richard E. Whaley 《Experimental Mechanics》1962,2(11):329-334
This paper describes a method of presentation of fatigue data on three commonly used aircraft materials, 2024-T3 and 7075-T6 aluminum alloys and normalized SAE 4130 steel, such that variations in fatigue strength with stress-concentration factor can be shown. Comparisons of the fatigue strengths of 2024-T3 and 7075-T6 aluminum are made for the most useful range of stress-concentration factors. Static-strength results of notched and unnotched specimens of the three materials are presented to show how the strength varies with some parameters of the stress concentration. Comparison of the data with one theory for the strength of cracked specimens was made. 相似文献
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STICTION AND ANTI—STICTION IN MEMS AND NEMS 总被引:6,自引:1,他引:6
赵亚溥 《Acta Mechanica Sinica》2003,19(1):1-10
Stiction in microelectromechanical systems (MEMS) has been a major failure mode ever since the advent of surface micromachining
in the 80s of the last century due to large surfacearea-to-volume ratio. Even now when solutions to this problem are emerging,
such as self-assembled monolayer (SAM) and other measures, stiction remains one of the most catastrophic failure modes in
MEMS. A review is presented in this paper on stiction and anti-stiction in MEMS and nanoelectromechanical systems (NEMS).
First, some new experimental observations of stiction in radio frequency (RF) MEMS switch and micromachined accelerometers
are presented. Second, some criteria for stiction of microstructures in MEMS and NEMS due to surface forces (such as capillary,
electrostatic, van der Waals, Casimir forces, etc.) are reviewed. The influence of surface roughness and environmental conditions
(relative humidity and temperature) on stiction are also discussed. As hydrophobic films, the self-assembled monolayers (SAMs)
turn out able to prevent release-related stiction effectively. The anti-stiction of SAMs in MEMS is reviewed in the last part.
The project supported by the Distinguished Young Scholar Fund of NSFC (10225209), key project from the Chinese Academy of
Sciences (KJCX2-SW-L2) and National “973” Project (G1999033103) 相似文献
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本文针对现代换热设备设计、两相流动与传热研究的需要,介绍了可供科研使用的水和水蒸汽物性计算方法,完善了计算程序。根据超临界锅炉设计中的超临界水的物性计算,两相流研究和换热设备动态特性研究中对物性导数计算的需要,提供了两个算例,并进行了定性分析。 相似文献
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Amit Acharya 《Journal of Elasticity》2011,104(1-2):23-44
A methodology is devised to utilize the statistical mechanical entropy of an isolated, constrained atomistic system to define constitutive response functions for the dissipative driving-force and energetic fields in continuum thermomechanics. A thermodynamic model of dislocation mechanics is discussed as an example. Primary outcomes are constitutive relations for the back-stress tensor and the Cauchy stress tensor in terms of the elastic distortion, mass density, polar dislocation density, and the scalar statistical density. 相似文献
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Jean-François Pinton Guillaume Brillant 《Theoretical and Computational Fluid Dynamics》2005,18(6):413-433
We review several aspects of the propagation of sound in vortical flows. We restrict ourselves to isothermal, humidity-free flows at low Mach number M. Since vorticity plays a major role in vortex-flow interactions we focus on vortical flows. We consider two main canonical situations. The first concerns the transmission of sound. We analyze the evolution of acoustic wavefronts as they propagate across a single vortex. The second situation addresses the scattering of sound waves by nonstationary vortices. We study the evolution of the acoustic pressure emitted in the far field, at an angle with the initial direction of propagation. In this geometry one performs direct spectroscopy of the flow vorticity field. In each case, we review theoretical results and compare with experimental measurements and numerical simulations when available. We also briefly report how the following new acoustic techniques have recently been used to study complex or turbulent flows: time-resolved acoustic spectroscopy, speckle interferometry and Lagrangian particle tracking. PACS 43.25, 43.28, 47.32, 67.40 相似文献
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Francisco J. Montáns Francisco Chinesta Rafael Gómez-Bombarelli J. Nathan Kutz 《Comptes Rendus Mecanique》2019,347(11):845-855
In the past, data in which science and engineering is based, was scarce and frequently obtained by experiments proposed to verify a given hypothesis. Each experiment was able to yield only very limited data. Today, data is abundant and abundantly collected in each single experiment at a very small cost. Data-driven modeling and scientific discovery is a change of paradigm on how many problems, both in science and engineering, are addressed. Some scientific fields have been using artificial intelligence for some time due to the inherent difficulty in obtaining laws and equations to describe some phenomena. However, today data-driven approaches are also flooding fields like mechanics and materials science, where the traditional approach seemed to be highly satisfactory. In this paper we review the application of data-driven modeling and model learning procedures to different fields in science and engineering. 相似文献