壳板径向初挠度对内外环肋圆柱壳结构强度的影响分析

Influence Analysis of Initial Radial Deformation on Structural Strength of Cylindrical Shell with Internal or External Ribs

用参数化有限元法模拟壳板径向初挠度的分布,通过系列计算和应力系数的对比,研究局部内凹、外凸和整体椭圆度对圆柱壳结构强度的影响。考虑纵向弯曲载荷的贡献,提出了附加弯曲应力的一种估算方法,其结果与有限元接近且偏安全,可用于结构校核及结构加强。跨中壳板局部内凹使弯曲应力急剧上升,而中面应力则变幅较小。局部凹、凸产生的附加弯曲应力方向相反、大小相当,f/t相同时,外凸对应的合成弯曲应力明显小于内凹。局部凹凸度幅值对壳板强度的影响呈非线性,凹陷中心的σ20随f/t提高先缓慢增加而后下降,椭圆度幅值的影响是线性的但很小。

Programs have been written to calculate and analyze the influence of concave, convex and ellipse on structural strength of ring-stiffened cylindrical shell. A convenient method is proposed to estimate additional bending stress due to local convex, which gives a safer solution than FEM and is helpful to form a strengthening plan. Comparison of dimensionless stress factors shows that bending stress would dramatically increase due to local convex, while change of amplitude of membrane stress is relatively small. Additional bending stress due to local convex and concave has almost same values but opposite directions. Therefore, bending stress due to convex is smaller than the one due to concave when the amplitude f/t keeps the same value. Influence of local convex and concave on structural strength is nonlinear. Circumferential membrane stress at the concave center would first increase slowly with f/t, then decline when f/t is big. However, influence of initial elliptical shape on structural strength is linear and less significant than that of local convex or concave of the cylindrical shell.