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针对用换铰法确定体系振动自由度时所遇到的问题,提出了换铰时对弹簧支座、抗弯刚度为∞的杆件以及定向支座的处理方法.应用此方法,具有任何支座和杆件的结构都可以用换铰法正确地确定其振动自由度数目. 相似文献
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将单位支座位移法推广应用于超静定结构的未知支座反力计算,建立并证明了相应的退化虚位移方程,推导指出超静定结构支座反力的影响线即为相应单位支座位移所引起的位移曲线。而且,展示了几个求解超静定梁支座反力的算例.本文工作可供大学生和教师们在结构力学相关知识的学习和教学中借鉴参考. 相似文献
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针对用换铰法确定体系振动自由度时所遇到的问题,提出了换铰时对弹簧支座、抗
弯刚度为$\infty$的杆件以及定向支座的处理方法. 应用此方法,具有任何支座和杆件的
结构都可以用换铰法正确地确定其振动自由度数目. 相似文献
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换铰法是结构力学中用于判定独立线位移未知量的一种方法,但经典的换铰法对约束的考虑并不全面,从而导致该方法在使用时存在一定的局限性。针对换铰法的局限性,提出了修正的换铰法,该方法考虑了各种约束以及无穷刚性杆的影响,从而在原理上更全面地体现了"铰化"和受弯直杆假定。算例表明,修正的换铰法可正确应用于复杂情形下独立线位移未知量的判定,并且在考虑参与质量后,该方法还可应用于较复杂的振动自由度判定问题。 相似文献
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SUN Xufeng 《力学与实践》2019,41(1):91
换铰法是结构力学中用于判定独立线位移未知量的一种方法,但经典的换铰法对约束的考虑并不全面,从而导致该方法在使用时存在一定的局限性。针对换铰法的局限性,提出了修正的换铰法,该方法考虑了各种约束以及无穷刚性杆的影响,从而在原理上更全面地体现了“铰化”和受弯直杆假定。算例表明,修正的换铰法可正确应用于复杂情形下独立线位移未知量的判定,并且在考虑参与质量后,该方法还可应用于较复杂的振动自由度判定问题。 相似文献
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提出了用Maple编程绘制无铰拱影响线的解析法.绘制了抛物线无铰拱在单位竖向移动载荷作用下,3个多余未知力的影响线;指定截面上的弯矩,剪力和轴力的影响线;支座水平约束力,垂直约束力及约束力矩的影响线.实例表明,利用Maple强大的符号运算功能,使用解析法绘制无铰拱影响线,速度快,方法简单,能同时给出影响线的解析表达式. 相似文献
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从矩阵位移法看有限元应力精度的损失与恢复 总被引:15,自引:0,他引:15
矩阵位移法在计算杆端力时须叠加一个“固端力”项,而在有限元法中结点(应)力是直接对位移求导获得的,丢失了“固端力”一项,致使应力的精度大为下降.其实,对于一维有限元,同样可以对结点力叠加一个“固端力”项,使结点内力的精度与位移不相上下,而且这一做法几乎可以直接推广到半解析的有限元线法的二维问题中.本文简要介绍这一最新研究的思路、做法和一些初步的数值结果. 相似文献
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Lewis Wheeler 《Journal of Elasticity》1971,1(2):121-124
In recent separate investigations, Kirchhoff's classical uniqueness theorem of elastodynamics has been extended in two ways. Gurtin and Toupin generalized the theorem to encompass bodies possessing an elasticity tensor that obeys the semi-strong ellipticity condition, whereas the author has extended the theorem to unbounded regions. These two results are brought together in the present paper.
Resume Dans deux études récentes, le champ d'application du théoréme classique de Kirchhoff sur l'unicité de l'élastodynamique a été élargi de deux manières différentes. Gurtin et Toupin l'ont généralisé pour inclure les corps possédant un tenseur d'élasticité obéissant à la condition d'ellipticité demi-forte, alors que le présent auteur l'a étendu aux régions non finies. Ces deux résultats ont été combinés dans la présente communication.相似文献
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P. L. Fuhr D. Huston J. G. Beliveau P. J. Kajenski W. B. Spillman 《Experimental Mechanics》1991,31(2):185-188
An optical technique has been developed whereby two angles and linear displacement can be simultaneously measured in a noncontact fashion. The method depends upon the properties of diffraction gratings with linear variation of period along their length and photodetection using CCD arrays. The grating is attached to a structure at a point of interest while all other system components are placed at a remote location. Experimental results obtained using this technique are presented and compared with theory. 相似文献
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In this paper the linear stability of immiscible displacement in porous media is examined by numerical methods. The method of matched initial value problems is used to solve the eigenvalue problem for displacement processes pertaining to initially mobile phases. Both non capillary and capillary displacement in rectilinear flow geometries is studied. The results obtained are in agreement with recent asymptotic studies. A sensitivity analysis with respect to process parameters is carried out. Similarities and differences with the stability of Hele-Shaw flows are delineated.This is a revised version of paper SPE 13163, presented at the 59th Annual Technical Conference of the Society of Petroleum Engineers, Houston, Texas, 16–19 Sept. 1984. 相似文献
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Chang and Slattery (1986, 1988b) introduced a simplified model of dispersion that contains only two empirical parameters. The traditional model of dispersion (Nikolaevskii, 1959; Bear, 1961; Scheidegger, 1961; de Josselin de Jong and Bossen, 1961; Peaceman, 1966; Bear, 1972) has three empirical parameters, two of which can be measured in one-dimensional experiments while the third, the transverse dispersivity, must be measured in experiments in which a two-dimensional concentration profile develops. It is found that nearly the same linear stability behavior results from using either model. 相似文献
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Calvin H. Wilcox 《Journal of Elasticity》1979,9(3):221-243
Uniquencess theorems are proved for the fundamental boundary value problems of linear elastostatics in bodies of arbitrary shape. The displacement fields are required to have finite strain energy in bounded portions of the bodies and satisfy the principle of virtual work. For bounded bodies, the total strain energy is finite and uniquencess is proved without additional hypotheses. In particular, no restrictions other than the energy condition are placed on the field singularities that may occur at sharp edges and corners. For unbounded bodies, uniqueness can be proved as in the bounded case if the total strain energy is finite. Sufficient conditions for this are shown to be the finiteness of the strain energy in bounded portions of the body together with the growth restriction % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% GabaqaaiGacaGaamqadaabaeaafiaakeaadaWdraqaaiaabwhadaWg% aaWcbaGaaeyAaaqabaGccaGGOaGaaeiEaiaacMcacaqG1bWaaSbaaS% qaaiaabMgaaeqaaOGaaiikaiaabIhacaGGPaGaaeizaiaabIhacaqG% 9aGaaGimaiaacIcacaqGYbGaaiykaiaacYcacaqGYbGaeyOKH4Qaey% OhIukaleaacqGHPoWvdaWgaaadbaGaaeOCaiaacYcacqaH0oazaeqa% aaWcbeqdcqGHRiI8aaaa!5E73!\[\int_{\Omega _{{\text{r}},\delta } } {{\text{u}}_{\text{i}} ({\text{x}}){\text{u}}_{\text{i}} ({\text{x}}){\text{dx = }}0({\text{r}}),{\text{r}} \to \infty } \] on the displacement fieldu
i
, where r, is the portion of the body that lies between concentric spheres with radiir andr+ and >0.This research was supported by the Air Force Office of Scientific Research. Reproduction in whole or part is permitted for any purpose of the United States Government.Prepared under Contract No. F 49620-77-C-0053 for Air Force Office of Scientific Research. 相似文献
20.
Claude Valle Jean-Marie Souriau Gry de Saxc Danielle Fortun 《Comptes Rendus Mecanique》2004,332(12):1013-1018
We show that the affine structure of the 3-dimensional space is deeply enmeshed with the static laws expression. The relevance of tensorial rules for calculus in mechanics is thus enhanced. The virtual work principle is stated precisely but a little twist is given to the usual statements: the tensorial nature of the so-called virtual displacement vector is asserted to be covariant. To cite this article: C. Vallée et al., C. R. Mecanique 332 (2004).