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排序方式: 共有419条查询结果,搜索用时 109 毫秒
271.
提出了基于有限元软件ANSYS的激光焊接钢质夹层甲板板格结构强度计算的子模型方法。分别对考虑激光焊接焊缝缺陷的I型夹层板格结构的壳单元计算模型和体单元子模型进行强度分析,并与全部体单元模型的芯层与上下面板连接处及面板中部处应力分布计算结果进行对比,验证壳单元计算模型和子模型方法用于计算夹层甲板板格强度的正确性。计算结果表明,对强度特征关注区域,可建立多个体单元子模型,确定子模型边界影响区域范围,从而可较为准确地评估夹层甲板板格结构强度特性,包括焊缝处应力分布。壳单元计算模型可获得较为精确的板格变形值,但无法考虑激光焊接焊缝缺陷,获得的焊缝处最大应力值明显偏小。 相似文献
272.
A series of collapse analyses is performed applying nonlinear FEM on stiffened panels subjected to longitudinal thrust. MSC.Marc is used. Numbers, types and sizes of stiffeners are varied and so slenderness ratio as well as aspect ratio of local panels partitioned by stiffeners keeping the spacing between adjacent longitudinal stiffeners the same. Initial deflection of a thin-horse mode is imposed on local panels and that of flexural buckling and tripping modes on stiffeners to represent actual initial deflection in stiffened panels in ship structures. On the basis of the calculated results, buckling/plastic collapse behaviour of stiffened panels under longitudinal thrust is investigated. The calculated ultimate strength are compared with those obtained by applying several existing methods such as CSR for bulk carriers and PULS. Simple formulas for stiffened panels, of which collapse is dominated fundamentally by the collapse of local panels between longitudinal stiffeners, are also examined if they accurately estimate the ultimate strength. Through comparison of the estimated results with the FEM results, it has been concluded that PULS and modified FYH formulas fundamentally give good estimation of the ultimate strength of stiffened panels under longitudinal thrust. 相似文献
273.
采用有限元/边界元方法针对加筋结构,研究了损伤对振动与声辐射特性的变异特性。将损伤模型引入结构有限元分析中,针对各向同性损伤单元模型中,采取刚度各向整体弱化的方法分析;对于各向异性损伤单元模型中,采用Kachanov理论,分别引入了x和y两个方向的弹性损伤折减系数。基于Mindlin板理论,建立描述健康和损伤的4结点有限壳单元模型,采用有限元方法计算结构振动特性与表面动力响应。基于4结点二维线性边界元模型,根据Rayleigh积分可以计算结构振动向外辐射的声压,进而可以得到辐射声功率和辐射指向性。为了研究损伤结构处于空气或水中不同损伤位置和大小对结构振动及声特性的影响,文章建立了含损伤结构的动力与声辐射分析方法,就各种损伤对结构振动频率、振动模态与声辐射模态、辐射阻尼、辐射功率与指向性的影响进行了数值模拟。通过对典型算例分析,得出了相应的结论,在评价损伤对船舶与海洋结构物常用的加筋结构声辐射特性影响方面做出了一定的探索。 相似文献
274.
A series of finite element analyses are conducted to investigate the influence of boundary conditions and geometry of the model on the predicted collapse behaviour of stiffened panels. Periodic and symmetric boundary conditions in the longitudinal direction are used to calculate the ultimate strength of stiffened panels under combined biaxial thrust and lateral pressure. The calculated ultimate strength of stiffened panels are compared with those by different FEM (finite element method) code and are assessed. The periodic boundary condition in the longitudinal direction for two spans or bays model provides an appropriate modelling to a continuous stiffened panel and can consider both odd and even number of half waves and thus, is considered to introduce the smaller model uncertainty for the analysis of a continuous stiffened panel. 相似文献
275.
HUANG Sheng WANG Pei-sheng HU Jian 《船舶与海洋工程学报》2007,6(2):6-11
The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with constant source and doublet distribution. Each panel's corner coordinates were calculated by spline interpolation between the main parameter and the blade geometry of the propeller. The integral equation was derived using the Green Formula. The influence coefficient of the matrix was calculated by the Morino analytic formula. The tangential velocity distribution was calculated with the Yanagizawa method, and the pressure coefficient was calculated using the Bonuli equation. The pressure Kutta condition was satisfied at the trailing edge of the propeller blade using the Newton-Raphson iterative procedure, so as to make the pressure coefficients of the suction and pressure faces of the blade equal at the trailing edge. Calculated results for the propeller in steady inflow were taken as initialization values for the unsteady inflow calculation process. Calculations were carried out from the moment the propeller achieved steady rotation. At each time interval, a linear algebraic equation combined with Kutta condition was established on a key blade and solved numerically. Comparison between calculated results and experimental results indicates that this method is correct and effective. 相似文献
276.
277.
278.
全方向推进器非定常水动力性能的面元预报方法 总被引:3,自引:0,他引:3
研究了全方向推进器非定常水动力性能的面元预报方法,基于螺旋桨面元法建立了全方向推进器的非定常水动力性能计算的数学模型,对全方向推进器的非定常水动力性能进行了数值预报。采用了关于扰动速度势的基本积分微分方程,并采用双曲面元以消除面元间的缝隙。用Newton-Raphson迭代过程在桨叶随边满足压力Kutta条件。在计算面元的影响系数时,应用Morino导出的解析计算公式加快了数值计算的速度。为避免数值求导中的奇异性,用Yanagizawa方法求得物体表面上的速度分布。本文计算结果与日本水池模型试验结果、升力线方法计算结果及升力面方法计算结果进行了对比。 相似文献
279.
280.
A 3-d seakeeping code uses first-order Rankine panels with special numerical integration on the ship's hull and Rankine point
source clusters above the free surface. The code computes the motions of the ship in regular waves of small height (linearized).
The steady flow is captured without simplification by solving the fully nonlinear wave-resistance problem first. A special
treatment of the surge motion considers the influence of periodic quantities on thrust and resistance, and improves surge
motion predictions. Radiation and open-boundary conditions are enforced by staggered grids. Results for the ITTC standard
test case S-175 containership agree well with experiments except for very long waves. The importance of capturing the three-dimensional
steady flow contributions is also demonstrated. 相似文献