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COD阻力曲线的单试样三曲线分析法 总被引:1,自引:0,他引:1
在三曲线分析的基础上,提出了一种新的单试样测定 COD 阻力曲线的方法和步骤,编制了计算机应用程序。用三曲线法测定了 C—Mn 钢,Cr-Mo 钢和一种焊缝金属的 COD 阻力曲线,与标准的多试样法实验结果符合较好。该方法使用方便经济。有推广使用的价值。 相似文献
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单试样三曲线法测定J积分阻力曲线及条件起裂值 总被引:1,自引:0,他引:1
用单试样三曲线法测定了16MnR 钢和某一焊缝金属的 J 积分阻力曲线及其条件起裂值,与标准的多试样测定结果基本吻合.实验表明,单试样三曲线的关联分析反映了带裂纹的三点弯曲试样的宏观断裂物理过程,裂纹的延性扩展符合幂函数规律. 相似文献
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模态局部化及频率曲线转向现象研究的几何理论 总被引:8,自引:1,他引:8
根据复平面映射理论,详细讨论了结构振动系统的固有频率曲线在复平面的几何特点.研究表明,频率曲线重合和转向现象实际上可进行统一的几何描述.复参数平面中支点的形成是解释局部化现象和曲线转向现象的基础.利用近频摄动理论中的缩聚方法将系统降维,大大拓宽了这一几何方法的使用范围.计算实例验证了理论分析所得的结果.该文是对M.S,Tri-antafyllou等近期工作的改进与推广. 相似文献
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本文研究了线弹性的圆截面压杆在刚性井壁的曲线井中的屈曲问题。压杆两端为铰支,杆和井壁之间的摩擦力忽略不计,失稳前假设压杆位于曲线井的较低侧。分析了压杆屈曲时的几何变形条件,导出了压杆的曲率,变形能和各项外力势的表达式,用最小势能原理导出压杆失稳的微分方程和边界条件。引入梁单元,用有限单元法求得了压杆失稳时的临界压力和杆轴线状态。结果显示,临界压力随着压杆自重和曲线井半径的增加而增加。自重为零时,杆轴线为半个正弦曲线;自重不为零时,杆轴线为振荡的曲线,且振荡主要集中在压杆顶部。 相似文献
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假设曲线纤维的方向角沿板的长度方向按照线性规律变化,导出了纤维曲线铺设时的参考路径,将参考路径沿板的宽度方向平移可得一种曲线纤维增强复合材料单层板,当这种纤维曲线铺设的单层板对称铺放时即可得相应的曲线纤维增强复合材料层合板.基于弹性薄板的小挠度理论,建立了曲线纤维增强复合材料层合板自由振动问题的基本方程,采用微分求积法进行数值求解,得到了层合板的自振频率及相应的振型.与已有文献计算结果的比较,验证了本文计算结果的正确性.通过数值算例分析了微分求积法求解本问题时的收敛性,研究了纤维铺放路径和边界条件的不同对曲线纤维增强复合材料层合板频率及振型的影响,研究结果可为该种结构的设计提供一定的参考. 相似文献
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一维封闭冻结风积土冻胀曲线的分形性质 总被引:1,自引:0,他引:1
通过分析风积土冻胀的特征,提出采用分形插值方法研究一维封闭冻结风积土的冻胀问题.通过理论研究和对实测曲线的分析,结果表明冻胀曲线具有良好的自相似性,可以利用分形理论对冻胀曲线进行描述.分维体现了冻胀曲线的复杂性及非线性特征,这对进一步认识风积土的冻胀过程有着很重要的作用。 相似文献
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利用Stribeck润滑曲线理论分析和薄膜润滑试验考察了不同表面粗糙度的钢球与圆盘点接触及钢滑块与圆盘面接触摩擦副的润滑状态,通过改变圆盘转速获得了包含薄膜润滑状态的Stribeck曲线.结果表明:在Stribeck曲线上可以划分出薄膜润滑状态,其位于摩擦系数谷底附近;薄膜润滑的产生及其区间大小同圆盘表面粗糙度密切相关;圆盘表面粗糙度较小时更易形成薄膜润滑状态,而圆盘表面粗糙度较大时薄膜润滑状态不明显;光滑表面对应的Stribeck曲线谷底较宽,相应的薄膜润滑区间亦较宽. 相似文献
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廖世俊 《应用数学和力学(英文版)》2008,29(2):223-228
A new modification of false position method for solving nonlinear equations is presented by applying homotopy analysis method (HAM). Some numerical illustrations are given to show the efficiency of algorithm. 相似文献
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给出了弹性力学三维问题的离散算子差分法 ,讨论离散算子差分法在三维问题中的特点 ,意在为该方法的进一步发展提供依据 ,为应用弱形式进行数值求解的研究提供参考。本文从弹性力学平衡方程更为一般的弱形式出发 ,给出了含边界参数的弱形式方程。由该方程不仅可以得到有限元法 ,还可得到离散算子差分法。给出了两个八结点块体单元 ,虽然单元中位移函数是非协调的 ,不需特殊处理便可保证离散格式收敛 ,并对单元位移有十分好的反映能力。 相似文献
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A new efficient numerical method for three-dimensional hydrodynamic computations is presented and discussed in this paper. The method is based on the operator splitting method and combined with Eulerian–Lagrangian method, finite element method and finite difference method. To increase the efficiency and stability of the numerical solutions, the operator splitting method is employed to partition the momentum equations into three parts, according to physical phenomena. A time step is divided into three time substeps. In the first substep, advection and Coriolis force are solved using the explicit Eulerian–Lagrangian method. In the second substep, horizontal diffusion is approximated by implicit FEM in each horizontal layer. In the last substep, the continuity equation is solved by implicit FEM, and vertical diffusion and pressure gradient are discretized by implicit FDM in each nodal column. The stability analysis shows that this method is unconditionally stable. A number of numerical experiments have been performed. The results simulated by the present scheme agree well with analytical solutions and the other documented model results. The method is efficient for 3D shallow water flow computations and fully fits complicated configurations. © 1998 John Wiley & Sons, Ltd. 相似文献
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L. F. Yang Q. S. Li A. Y. T. Leung Y. L. Zhao G. Q. Li 《European Journal of Mechanics - A/Solids》2002,21(6):104
Linear and non-linear peaky fuzzy numbers and their arithmetic operations are constructed for the analysis of engineering structures with fuzzy characteristic quantities. Fuzziness of the corresponding quantities is consistently incorporated into the functional of the total potential energy. A set of deterministic recursive equations is obtained as the alternative expressions of the fuzzy variational principle by means of the second-order perturbation technique. The fuzzy Ritz method and the fuzzy finite element method are presented as the applications of the fuzzy variational principle. Accordingly, the roundabout procedures frequently used in the formulations of the fuzzy finite element method are avoided. A benchmark problem of a bending beam with fuzzy Young's modulus under fuzzy external loading is solved by the developed fuzzy numerical methods. Numerical examples show that results determined by these two fuzzy methods are both little conservative, and are in good agreement with those obtained by the analytical method. Moreover, the fuzzy Ritz method or the fuzzy finite element method can provide more valuable information than the conventional deterministic methods. 相似文献
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T. MINYARD Y. KALLINDERIS 《International Journal of Computational Fluid Dynamics》2013,27(1-2):119-136
Abstract This paper presents a hybrid spectral/finite volume method for steady-state compressible viscous flows. The method is evaluated for accuracy via test cases for various Mach numbers. The domain is divided into a viscous region and an inviscid region. The viscous region uses the full Navier-Stokes equations, while the inviscid region employs the Euler equations. A high order Chebyshev collocation spectral method is developed for the viscous region to resolve boundary layers. This method avoids the dense grids needed by finite-volume methods to resolve the viscous areas. A low order finite-volume method based on a Lax-Wendroff type scheme is employed for the inviscid region. A special interface formulation is developed for coupling the spectral with the finite-volume method. Comparisons with analytic results as well as convergence histories are presented. 相似文献
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Numerical modeling of wave interactions with coastal structures by a constrained interpolation profile/immersed boundary method 下载免费PDF全文
A high‐order difference method based multiphase model is proposed to simulate nonlinear interactions between water wave and submerged coastal structures. The model is based on the Navier–Stokes equations using a constrained interpolation profile (CIP) method for the flow solver, and employs an immersed boundary method (IBM) for the treatment of wave–structure interactions. A more accurate interface capturing scheme, the volume of fluid/weighed line interface calculation (VOF/WLIC) scheme, is adopted as the interface capturing method. A series of computations are performed to verify the application of the model for simulations of fluid interaction with various structures. These problems include flow over a fixed cylinder, water entry of a circular cylinder and solitary waves passing various submerged coastal structures. Computations are compared with the available analytical, experimental and other numerical results and good agreement is obtained. The results of this study demonstrate the accuracy and applications of the proposed model to simulate the nonlinear flow phenomena and capture the complex free surface flow. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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An axisymmetric elastic problem is solved by a heterogeneous numerical scheme of the alternating Schwarz method based on the finite- and boundary-element methods. The Schwarz method and the modified scheme are compared. A relaxation parameter is used to accelerate the iterative process 相似文献
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SHPB数据处理中的二波法与三波法 总被引:15,自引:1,他引:14
分析了传统的分离式霍普金森压杆测试数据处理方法(二波法)及其他被提出的改进方法的误差及优缺点,给出了传统二波处理方法在不同被测材料情况下所带来的误差。分析结果表明,基于绝对时间下的试件应力及应变计算的三波处理法具有最好的可信度且能最大程度地避免数据处理过程中的人为因素。传统二波法在不同测试情况下均不是优选的方法。对于三波测试无法进行的情况,也提出了一种简化三波处理方法。 相似文献
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提出了一种不可压缩流体与弹性薄膜耦合问题的特征线分裂有限元解法. 首先, 给出了流场和结构的控制方程. 然后, 对流场、结构以及流固耦合的具体求解过程进行了描述. 其中, 流场求解采用改进特征线分裂方法和双时间步方法相结合的隐式求解方式, 并利用艾特肯加速法对每个时间步的迭代收敛过程进行了加速处理;结构部分的空间离散和时间积分分别采用伽辽金有限元方法和广义方法, 并通过牛顿迭代法对所得非线性代数方程组进行了求解;流场网格的更新采用弹簧近似法;流场、结构两求解模块之间采用松耦合方式.最后, 采用该方法对具有弹性底面的方腔顶盖驱动流问题进行了求解, 验证了算法的准确性和稳定性.此外, 计算结果表明艾特肯加速法可以显著地提高双时间步方法迭代求解过程的收敛速度. 相似文献