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Search Results: 1 - 10 of 24761 matches for " Arc-Length Method "
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Post-Buckling Behavior of Laminated Composite Cylindrical Shells Subjected to Axial, Bending and Torsion Loads  [PDF]
Yengula Venkata Narayana, Jagadish Babu Gunda, Ravinder Reddy Pinninti, Markandeya Ravvala
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.34019
Abstract: In present work, post-buckling behavior of imperfect (of eigen form) laminated composite cylindrical shells with different L/D and R/t ratios subjected to axial, bending and torsion loads has been investigated by using an equilibrium path approach in the finite element analysis. The Newton-Raphson approach as well as the arc-length approach is used to ensure the correctness of the equilibrium paths up to the limit point load. Post-buckling behavior of imperfect cylindrical shells with different L/D and R/t ratios of interest is obtained and the theoretical knock-down factors are reported for the considered cylindrical shells.
基于共旋列式的空间梁的稳定性分析
王振,孙秦
固体力学学报 , 2014,
Abstract: 基于独立于单元的共旋列式(EICR),将一种几何线性的无剪切锁死的Timoshenko梁单元扩展用于空间梁结构的几何非线性分析。考虑到三维分析中发生大转动时转动顺序的不可交换性,也即转动自由度不能作为向量采用加法规则更新,采用了四元变量来存储和更新转动自由度,使得共旋列式适用于位移任意大和转动任意大但应变很小的几何非线性分析。同时改进了Riks弧长法使之适用于带有大转动的三维几何非线性分析。给出了几个数值算例,结果表明本文方法具有较高的计算精度和效率。
多跨碰摩转子系统分析的降维增量谐波平衡法
姚红良,丛艳,许琦,闻邦椿
- , 2015, DOI: 10.12068/j.issn.1005-3026.2015.07.017
Abstract: 摘要 多跨碰摩转子系统所建有限元动力学模型自由度很多,严重降低响应预测时的计算效率.为了提高计算效率,同时保证计算精度,提出结合固定界面模态综合法的降维增量谐波平衡法.首先利用固定界面模态综合法降低多跨碰摩转子系统的自由度数目,再利用增量谐波平衡法求解降维后系统的稳态响应,最后还原回原系统的响应.该方法不仅能够直接获得稳态解,还可以与弧长法相结合从而求得非稳定解.对双跨转子系统进行仿真试验,结果表明该方法在主模态数较小时即可保证计算精度并且具有很高的效率.
Abstract:The finite element model of multi-span rubbing rotor system has a large number of degrees of freedom,which affects the efficiency of the numerical simulation seriously. To overcome this problem and remain the accuracy of numerical simulation at the same time, a new dimension-reduced incremental harmonic balance method combining the fixed interface component mode synthesis method was presented. Firstly, the degree of freedom was reduced by the fixed interface component mode synthesis method, and then the incremental harmonic balance method was applied to obtain the stable state response of the dimension-reduced system, and at last the response of the original rotor system can be obtained. The method can not only get the stable state solution directly, but also be combined with the arc-length method to obtain the unstable state response. The results show that a two-span rotor system can reach good accuracy and high efficiency with few dominant modes.
非线性有限元方程组的弧长延拓算法
Arc-Length Continuation Algorithm for Nonlinear Finite Element Equations

殷有泉,邸元,姚再兴
- , 2017, DOI: 10.13209/j.0479-8023.2017.072
Abstract: 摘要 研究工程结构因构件屈曲和材料软化导致的稳定性问题, 就需要追踪结构的平衡路径。当采用非线性有限元进行分析时, 传统的牛顿迭代法会在极值点和分叉点处失效, 而弧长延拓方法能很好地解决这一数值计算难题。针对结构稳定性非线性有限元分析程序的编制, 给出弧长延拓算法牛顿迭代的标准格式和两种实用的迭代格式, 并讨论它们之间的关系。通过一个边坡稳定性的有限元分析, 验证了实用迭代格式的有效性。
Abstract Stability analysis of engineering structures requires tracing equilibrium path of the structure when member’s buckling or material softening occurs. In nonlinear finite element analysis, the traditional Newton method fails at limit point and bifurcation point. The arc-length continuation method can overcome these numerical difficulties. To develop a nonlinear finite element code for stability analysis, the standard iteration formulation of Newton method is presented for the arc-length continuation method. Two practical formulations of the arc-length continuation method and their relationships with the standard form are also discussed. The applicability of the practical formulation is examined by the finite element analysis of stability for a slope.
焊接残余应力对Y型相贯节点极限承载力影响分析
Analysis on Influence of Welding Residual Stress on Ultimate Bearing Capacity of Y-joints

高占远,郭彦林
- , 2016,
Abstract: 采用ANSYS的热?步峁辜浣玉詈稀⑸?死单元技术模拟Y型相贯节点的焊接过程;将牛顿-拉普森法和弧长法结合,求解Y型相贯节点极限承载力,给出求解流程;分析支管外径与主管外径比、支管倾角、主管径厚比等几何参数对Y型相贯节点极限承载力的影响,将考虑和不考虑焊接残余应力的计算结果进行对比分析。研究结果表明:焊接残余应力降低了Y型相贯节点的极限承载力;支管外径与主管外径比β越大,主管的径厚比γ越小,支管倾角θ越小,则Y型相贯节点极限承载力降低越多;结构设计时,保证强度和安全的前提下选择合适的支管外径、主管壁厚和支管倾角,可减小焊接残余应力对Y型相贯节点极限承载力的影响。
The welding process of Y-joint was simulated by using thermal structure indirect coupling and birth-death element in ANSYS. Combined Newton-Raphson method and arc-length method, the ultimate bearing capacity of Y-joints was solved, and solution flow was given. The influence of geometric parameters such as the ratio of diameter of branch pipe and diameter of pipe, angle of branch pipe, ratio of diameter and thickness of pipe, on the ultimate bearing capacity of Y-joints with considering welding residual stress was analyzed. Ultimate bearing capacities of Y-joints with welding residual stresses and without welding residual stresses were compared and analyzed. The results show that the ultimate bearing capacity of Y??joint is reduced by welding residual stress; because values of the βare larger, or values of the γ are smaller, or values of the θare smaller, the ultimate bearing capacity of Y-joint is more reduced. In structural design, to ensure the strength and safety of structure, choosing the suitable diameter and angle of branch pipe, wall thickness of pipe, the effect of welding residual stress on ultimate bearing capacity of Y-joint can be reduced
Numerical solution techniques for structural instability problems
E. Armentani,C. Calí,G. Cricrí,F. Caputo
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: The purpose is to overcome numerical problems arising in structural instability numerical computations for equilibrium configurations corresponding to increasing loads on structures having points of instability or more generally large non linearity.Design/methodology/approach: The used numerical methodology was the finite element method with the particular technique of non linear transient dynamic analysis. In such way dynamic equilibrium paths, which are able to lead to required corresponding static ones, can be obtained.Findings: A methodology to develop this kind of analyses as well as a procedure to set some initial parameters and to check the accuracy of the solution have been investigated and pointed out.Research limitations/implications: In the future it will be possible to apply the investigated numerical procedure to other practical cases.Originality/value: We have overcome the limitations in the use of the Newton-Raphson classical method when load control conditions are considered. We also emphasise the practical limits of the Arc Length technique, which requires consistent formulations of the element stiffness matrix in non-linear field; this kind of high precision is often not available in the common FE codes.
Bundle Block Adjustment with 3D Natural Cubic Splines
Won Hee Lee,Kiyun Yu
Sensors , 2009, DOI: 10.3390/s91209629
Abstract: Point-based methods undertaken by experienced human operators are very effective for traditional photogrammetric activities, but they are not appropriate in the autonomous environment of digital photogrammetry. To develop more reliable and accurate techniques, higher level objects with linear features accommodating elements other than points are alternatively adopted for aerial triangulation. Even though recent advanced algorithms provide accurate and reliable linear feature extraction, the use of such features that can consist of complex curve forms is more difficult than extracting a discrete set of points. Control points that are the initial input data, and break points that are end points of segmented curves, are readily obtained. Employment of high level features increases the feasibility of using geometric information and provides access to appropriate analytical solutions for advanced computer technology.
与k折对称点有关的解析函数族的一些新子族
CERTAIN NEW SUBCLASSES OF ANALYTIC FUNCTIONS WITH RESPECT TO k-SYMMETRIC POINTS

作者,石磊,王智刚
- , 2016,
Abstract: 本文引入了两类与k折对称点有关的解析函数族的新子族.利用从属理论,得到了这些函数族的积分表示、系数不等式、覆盖定理、弧长估计等结果.所得结果推广了一些相关文献的结论.
In this article, we introduce two new subclasses Rms (b,k,λ) and Kms (α,b,k,λ,δ) of analytic functions with respect to k-symmetric points. By using the principle of subordination, we obtain the integral representations, coe-cient inequalities, covering theorems and arc-length estimates for these function classes, which would provide extensions of those given in earlier works
Research on Optimal Parametrization of Bézier Curve
Bézier曲线最优参数化研究

GUO Feng-hua,YANG Xing-qiang,
郭凤华
,杨兴强

计算机科学 , 2005,
Abstract: A rational reparametrization function is used, compared with Mobius transformation, the function is very simple. Rational reparametrization of a polynomial curve is characterized by a single degree of freedom. Like Mobius transformation, further research shows the "optimal" reparametrization in this faminly(that comes closest under the L_2 norm to arc-length parametrization) can also be identified by solving a quadratic equation. The function is proved to reach the same result with Mobius transformation as identifying the "optimal" parametrization of the same polyno- mial curve.
岩石应变软化本构模型建立及nr-al法求解研究
王军祥,姜谙男
岩土力学 , 2015,
Abstract: 针对岩土工程材料应变软化问题及有限元对其数值计算时切线刚度矩阵负定造成求解困难的问题进行研究。建立了基于drucker-prager(d-p)强度准则的岩石弹塑性应变软化本构模型,本构积分算法采用一种完全隐式返回映射算法,它具有无条件稳定和精确的特点,详细论述了如何进行本构模型的程序化求解;考虑弧长法在判断切线刚度矩阵正定性导致效率低的缺点,在弹塑性增量有限元方程的迭代计算中尝试采用newton-raphson法和arc-length法(nr-al法)联合迭代求解的思路,即在结构未达到极限荷载前采用nr迭代法,而当结构接近极限荷载时转换为al法控制迭代,从而使结构越过峰值点进入软化区直至破坏,nr-al法汲取了2者迭代求解中具有的优势;利用c++语言对所建应变软化模型的本构求解和弹塑性增量有限元方程迭代求解过程给予程序实现,应用所编程序进行数值计算,分析了d-p理想弹塑性模型、应变软化模型、应变硬化模型计算的应力-应变曲线的区别,同时将应变软化模型计算结果与试验数据进行了对比。研究结果表明:所建应变软化本构模型可以较好地模拟岩石材料的峰后软化特性,能够揭示峰后应变软化特性和破坏机制,同时nr-al法能够求解由于应变软化造成的负刚度问题,也克服了单独使用弧长法时判断切线刚度矩阵正定性效率低的缺点。
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