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31.
32.
结构静动力屈曲问题研究进展 总被引:19,自引:0,他引:19
近几十年来,结构的静动力屈曲问题一直是力学工作者极为关注的一个前沿课题.本文总结和综述了这一研究领域的几个基本问题:屈曲问题的分类、动态屈曲问题的特点及其特征量;介绍了屈曲问题的处理方法和目前已取得的成果;总结评述了人们关心的热点问题;屈曲问题的模型分析和实验技术、动态屈曲判别准则. 相似文献
33.
研究了一类含平方、立方非线性项的两自由度系统的全局分岔。首先应用多尺度法求解其平均方程 ,然后通过一系列变换得到一个近似可积的两自由度系统。应用能量 相位准则 ,确定了在哈密顿共振时Silnikov轨道存在的条件。通过数值计算验证了此条件。 相似文献
34.
本文采用俞茂宏双剪统一屈服准则求解部分均匀荷载下简支圆板的塑性极限,已有的最大主应力准则、Tresca准则,Mises准则的解答均是该解答的特例或线性逼近。该解答可以适合于多种工程材料,具有普遍性和适用性,从得出的解析解和图示中可得出一些新的有益的认识 相似文献
35.
A structural health assessment (SHA) methodology is developed using data acquired from structural health monitoring (SHM) system installed on long-span bridges. A set of fatigue criteria has been proposed for pre-determining the global state of the bridge structure failure due to fatigue. This involves finding the threshold of fatigue initiation, below which the rate of fatigue damage may be undetectable under current technology or it is economically unfeasible. The state-of-art for large structures corresponds to the initiation of macro-cracks caused by the accumulation of damage generated by actual service loads for the case of bridges. In what follows, consideration is given to developing fatigue crack growth criterion based on the concept of the continuum damage mechanics (CDM). Fatigue accumulative is included in the model where a fatigue limit for multi-axial stress state is considered. The proposed criterion advocates the evolution of micro-crack growth up to the stage of macro-crack formulation. Considered are the loading histories that correspond to normal traffic loading for highways and railways, incidental or accident loadings such as those caused by typhoons and effective environmental loadings. The potential sites of damage are determined are discussed. The proposed criterion is applied to analyze the fatigue damage of the Tsing Ma Bridge with online strain history data acquired by the SHM system that is permanently installed in the bridge. 相似文献
36.
37.
Cheng Pinsan 《Acta Mechanica Sinica》1991,7(3):235-242
In this paper, a nonlocal theory of fracture for brittle materials has been systematically developed, which is composed of
the nonlocal elastic stress fields of Griffith cracks of mode-I, II and III, the asymptotic forms of the stress fields at
the neighborhood of the crack tips, and the maximum tensile stress criterion for brittle fracture. As an application of the
theory, the fracture criteria of cracks of mode-I, II, III and mixed mode I–II, I–III are given in detail and compared with
some experimental data and the theoretical results of minimum strain energy density factor. 相似文献
38.
G. V. Galatenko 《International Applied Mechanics》2007,43(7):745-753
The generalized Dugdale crack model is used to formulate two-parameter failure criteria for the cases of quasibrittle state
and developed plastic zones at a mode I crack tip. The failure criteria relate the fracture strength characteristics and the
stress mode at the crack tip through the plastic constraint factor. The critical state of bodies with cracks under uni-and
biaxial loading is analyzed in the cases of plane stress and plane strain using the Tresca and von Mises yield criteria. A
small-scale yield criterion, which is an analytic relation between the critical stress intensity factor and T-stresses, is established
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 47–57, July 2007. 相似文献
39.
Upper bound limit analysis of active earth pressure with different fracture surface and nonlinear yield criterion 总被引:7,自引:0,他引:7
Conventional calculations of static and seismic active earth pressures of soils on a retaining wall are formulated assuming the soils obeying a linear Mohr–Coulomb yield criterion. However, experimental evidences show that the strength envelopes of almost all geomaterials are nonlinear in nature over a wide range of normal stresses. In this paper, the strength envelope of the backfill behind a retaining wall is considered to follow a nonlinear yield criterion. A simple method is proposed for calculating the static and seismic active earth pressures acting against a retaining wall using a nonlinear yield criterion. This method is based on the upper bound theorem of limit analysis. Both translational and rotational fracture surfaces are employed in the formulation for calculating active earth pressures. Quasi-static representation of earthquake effects using a seismic coefficient concept is adopted for seismic active earth pressure calculations. Instead of using directly the actual nonlinear yield criterion, a linear Mohr–Coulomb yield criterion, which is tangential to the nonlinear yield criterion, is used to formulate the active earth pressure problem as a classical nonlinear programming problem. A nonlinear sequential quadratic programming algorithm is used to search for the maximum solution. In order to assess the validity of the proposed method, values of active earth pressures for different values of seismic coefficients and nonlinear parameters in the yield criterion are calculated and compared with solutions obtained using an extended Rankine’s active earth pressure theory. For the case of static active earth pressure, the upper bound solutions using the present method with a translational fracture surface are equal to the extended Rankine’s theoretical solutions and are slightly smaller than those obtained using the present method with a rotational fracture surface. For the case of seismic active earth pressure, numerical results obtained using the present method with a rotational fracture surface is very close to the extended Rankine’s theoretical solutions. A study is conducted to investigate the effects of the parameters in the nonlinear yield criterion on the active earth pressures. 相似文献
40.
基于微面有效应力矢量的各向异性屈服准则 总被引:1,自引:0,他引:1
基于微面模型,定义损伤变量为微面上有效承载面积的减少. 将Kachanov的一维有效
应力概念推广到三维,提出微面有效应力矢量的概念. 根据微面的有效应力矢量,将无损材
料的宏观应力张量及不变量与微面应力矢量的积分关系拓展到有损材料,得到了有损材料的
宏观有效应力张量及其不变量与宏观名义应力张量、微面面积损伤组构张量之间的关系. 将
无损材料的以应力张量不变量表示的Drucker-Prager准则推广到有损材料,建立了含缺陷
材料的各向异性屈服准则. 对有损材料,宏观有效应力张量与Murakami的有效应力张量具
有相同的形式,各向异性强度准则与Liu等提出的扩展Hill准则有相同的形式,当不考虑
静水应力对屈服的影响时,它与Hill准则具有相同的形式. 相似文献