共查询到19条相似文献,搜索用时 531 毫秒
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含凹坑缺陷圆柱壳的数值极限分析 总被引:3,自引:0,他引:3
使用文[1]提出的三维结构塑性极限分析的一般计算方法,我们对含凹坑缺陷的圆柱壳进行了数值极限分析.对凹坑和筒体各种组合的几何参数,本文给出了筒壳极限压力的上限.计算结果与现有的理论、实验和数值解进行了比较.本文调查和评估了各种形状和尺寸的凹坑对筒壳极限承载能力的影响规律,研究了对应于不同凹坑尺寸的筒壳两种典型的破坏模式.根据以上数值结果,本文采用几何参数G来反映凹坑各参数对筒壳极限压力的综合影响,并给出了估计带凹坑筒体极限压力的拟合公式.本文结果对含凹坑缺陷压力容器的安全评估具有重要参考价值 相似文献
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多孔材料塑性极限载荷及其破坏模式分析 总被引:4,自引:1,他引:4
运用塑性力学中的机动极限分析理论,研究韧性基体多孔材料的塑性极限承载能力和破坏模式。以多孔材料的细观结构为研究对象,将细观力学中的均匀化理论引入到塑性极限分析中,并结合有限元技术,建立细观结构极限载荷的一般计算格式,并提出相应的求解算法。数值算例表明:细观孔洞对材料的宏观强度影响明显;在单向拉伸作用下,孔洞呈现膨胀扩大规律;多孔材料破坏源于基体塑性区的贯通。 相似文献
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钢构支架是半潜式钻井平台管道支吊架的主要类型之一,钢构支架的极限强度是管道系统正常工作的重要保障。研究结构极限强度的方法有理论分析、有限元数值仿真和实验分析。在分析极限理论的基础上由静力法计算四种钢构支架试件的极限载荷;利用MSC软件对试件极限载荷进行数值仿真分析,并对有限元模型化技术进行讨论;对试件进行实验极限载荷测试,对比分析了三种方法测得的极限载荷。结果表明,三种分析方法计算得到结构的极限载荷基本一致,对于结构形式较为简单的结构通过理论分析可以得到简化解析解析解;数值仿真分析中采用合理的有限元模型化技术(结构有限元模型、边界、约束等)可得到精度较高的计算结果。 相似文献
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The symmetric Galerkin boundary element method (SGBEM) instead of the finite element method is used to perform lower bound
limit and shakedown analysis of structures. The self-equilibrium stress fields are constructed by a linear combination of
several basic self-equilibrium stress fields with parameters to be determined. These basic self-equilibrium stress fields
are expressed as elastic responses of the body to imposed permanent strains and obtained through elastic-plastic incremental
analysis. The complex method is used to solve nonlinear programming and determine the maximal load amplifier. The limit analysis
is treated as a special case of shakedown analysis in which only the proportional loading is considered. The numerical results
show that SGBEM is efficient and accurate for solving limit and shakedown analysis problems.
Project supported by the National Natural Science Foundation of China (No. 19902007), the National Foundation for Excellent
Doctorial Dissertation of China (No. 200025) and the Basic Research Foundation of Tsinghua University. 相似文献
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Shutao Zhou Yinghua Liu Binjie Ma Chuantao Hou Yatang Ju Bing Wu Kelin Rong 《Acta Mechanica Solida Sinica》2021,34(2):221-236
This paper proposes a numerical solution method for upper bound shakedown analysis of perfectly elasto-plastic thin plates by employing the C1 natural element m... 相似文献
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含缺陷轴对称体的安定与极限分析 总被引:2,自引:0,他引:2
利用静力安全定理得到了计算轴对称体安定与极限载荷的统一格式,采用温度参数法构造安定分析所需的残余应力场,为了克服对工程实际问题进行安定分析时解题规模与计算精度的矛盾,针对轴对称体的特点,采用两种线性化方案对屈服面进行线性化处理,即直接内接法和在降维应力偏量空间中对屈服面的线性化处理,使安定分析转化为一线性规划问题,在简化过程中合理选择线性化方案以便使应力校核点接近精确的屈服面;为了减小计算量,在求 相似文献
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The classical shakedown theory is extended to a class of perfectly plastic materials with strengthening effects (Hall–Petch effects). To this aim, a strain gradient plasticity model previously advanced by Polizzotto (2010) is used, whereby a featuring strengthening law provides the strengthening stress, i.e. the increase of the yield strength produced by plastic deformation, as a degree-zero homogeneous second-order differential form in the accumulated plastic strain with associated higher order boundary conditions. The extended static (Melan) and kinematic (Koiter) shakedown theorems are proved together with the related lower bound and upper bound theorems. The shakedown limit load problem is addressed and discussed in the present context, and its solution uniqueness shown out. A simple micro-scale structural system is considered as an illustrative example. The shakedown limit load is shown to increase with decreasing the structural size, which is a manifestation of the classical Hall–Petch effects in a context of cyclic loading. 相似文献
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将基于Voronoi结构的无网格局部Petrov-Galerkin法与减缩基技术相结合,建立了一种安定下限分析的新方法.为了克服移动最小二乘近似难以准确施加本质边界条件的缺点,采用了自然邻近插值构造试函数.通过引入基准载荷域上载荷角点的概念,消除了安定下限分析中由时间参数所引起的求解困难.利用减缩基技术,将安定分析问题化为一系列未知变量较少的非线性规划子问题.在每个非线性规划子问题中,自平衡应力场由一组带有待定系数的自平衡应力场基矢量的线性组合进行模拟,而这些自平衡应力场基矢量可应用弹塑性增量分析中的平衡迭代结果得到.算例结果证明了提出的分析方法的有效性. 相似文献
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《International Journal of Solids and Structures》2006,43(14-15):4201-4219
There is a range of problems where repeated rolling and sliding contact occurs over a half space of an elastic–perfectly plastic material. For such problems shakedown and limit analysis provide significant advantages over other forms of analysis when a global understanding of deformation behaviour is required. In this paper, a recently developed numerical upper bound method, the Linear Matching Method (LMM), for shakedown analyses is applied to the solution of a problem previously considered by Ponter et al. [Ponter, A.R.S., Hearle, A.D., Johnson, K.L., 1985. J. Mech. Phys. Solids 33 (4), 339–362] for a moving Hertzian contact, with sliding friction. This semi-analytic solution is an upper bound based on certain specific kinematic assumptions. We show that the Ponter, Hearle and Johnson solution is a reasonable approximate solution for a circular contact area but is less accurate for an elliptic contact area. For an elliptic contact area LLM solutions converge to the line contact solution. The effect of the non-coincidence of the direction of travel and slide is also investigated. 相似文献
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《International Journal of Plasticity》2005,21(1):21-42
In this paper, the static shakedown theorem is reformulated making use of the symmetric Galerkin boundary element method (SGBEM) rather than of finite element method. Based on the classical Melan’s theorem, a numerical solution procedure is presented for shakedown analysis of structures made of elastic-perfectly plastic material. The self-equilibrium stress field is constructed by linear combination of several basis self-equilibrium stress fields with parameters to be determined. These basis self-equilibrium stress fields are expressed as elastic responses of the body to imposed permanent strains obtained through elastic–plastic incremental analysis. The lower bound of shakedown load is obtained via a non-linear mathematical programming problem solved by the Complex method. Numerical examples show that it is feasible and efficient to solve the problems of shakedown analysis by using the SGBEM. 相似文献
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A modified shakedown theorem and its solving technique are presented to involve hydrogen embrittlement of steel into limit and shakedown analysis. Firstly, the shakedown theorem for hydrogen embrittled material is derived from a limited kinematic hardening shakedown theorem and hydrogen enhanced localized plasticity mechanism of hydrogen embrittlement. In the presented theorem, hydrogen’s effect is taken into account by the synergistic action of both strength reduction and stress redistribution. Secondly, a novel solving technique is developed based on the basis reduction method, in which the complicated constraints in the resulting nonlinear mathematical programming are released. At last, three numerical examples are carried out to verify the performance of the proposed method and to reveal hydrogen’s effect on the limit and shakedown load of structure. The numerical results are discussed and compared with those from literatures, which proves the accuracy and high efficiency of the introduced solving technique. It is concluded that the proposed theorem can predict the limit and shakedown load of hydrogen embrittled structure reasonably. 相似文献
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Jidong Zhao Scott W. Sloan Andrei V. Lyamin Kristian Krabbenhøft 《International Journal of Solids and Structures》2008,45(11-12):3290-3312
In this paper, shakedown of a cohesive-frictional half space subjected to moving surface loads is investigated using Melan’s static shakedown theorem. The material in the half space is modelled as a Mohr–Coulomb medium. The sliding and rolling contact between a roller and the half space is assumed to be plane strain and can be approximated by a trapezoidal as well as a Hertzian load distribution. A closed form solution to the elastic stress field for the trapezoidal contact is derived, and is then used for the shakedown analysis. It is demonstrated that, by relaxing either the equilibrium or the yield constraints (or both) on the residual stress field, the shakedown analysis leads to various bounds for the elastic shakedown limit. The differences among the various shakedown load factors are quantitatively compared, and the influence of both Hertzian and trapezoidal contacts for the half space under moving surface loads is studied. The various bounds and shakedown limits obtained in the paper serve as useful benchmarks for future numerical shakedown analysis, and also provide a valuable reference for the safe design of pavements. 相似文献