﻿ 船体直翼桨区域结构疲劳时域分析
 舰船科学技术  2001, Vol. 44 Issue (6): 34-39    DOI: 10.3404/j.issn.1672-7649.2022.06.007 PDF

Fatigue analysis for ship's cycloidal propeller region based on time domain
WANG Wei, GUO Jian-jie, XU Zhi-ting, LI Cong
Marine Design and Research Institute of China, Shanghai 200011, China
Abstract: Aiming at the structural fatigue problem in the region of cycloidal propeller, the calculation process of structural response in time domain under the vibration load and wave load was discussed based on the stress superposition. Furthermore, a fatigue analysis approach based on time domain was proposed. By a fatigue damage analysis for a ship, the influence of the loads on the fatigue life was compared. The results show that the both loads account for a large proportion of the structural fatigue damage. The influence of wave load on structural fatigue is dominant near the center longitudinal plane, and the influence of vibration load induced by the main engine on the base plate is prominent, reaching 50% of the total fatigue damage value, and the resonance fatigue problem cannot be ignored. The research provides a reference for the structural fatigue design of ship’s cycloidal propeller region.
Key words: fatigue analysis     cycloidal propeller     vibration load     time domain
0 引　言

1 疲劳时域分析方法 1.1 疲劳时域分析方法流程

 图 1 疲劳时域分析方法流程 Fig. 1 Flow diagram of fatigue time domain analysis
1.2 激振载荷时历分析

1）激励力的时域信号拟合公式如下：

 $\begin{split} F\left( t \right) = {A_0} + {A_1}\cos (2\text{π} {f_1}t - {\varphi _1}) + {A_2}\cos (2\text{π} {f_2}t - {\varphi _2})。\hfill \\ \end{split}$ (1)

2）盘外脉动压力拟合公式如下：

 $P\left( t \right) = \sum\limits_{i = 1}^n {{\alpha _i}\cos \left( {{\omega _i}t + {\varepsilon _i}} \right)。}$ (2)

1.3 波浪载荷时历分析

 $\begin{gathered} \varPhi \left( {x,y,z,t} \right) = \left[ { - Ux + {\varPhi _S}\left( {x,y,z} \right)} \right] + \hfill \\ {Re} \left\{ {\left( {{\phi _I}\left( {x,y,z} \right) + {\phi _D}\left( {x,y,z} \right) + {\phi _R}\left( {x,y,z} \right)} \right){e^{i\omega t}}} \right\} 。\hfill \\ \end{gathered}$ (3)

 $p - {p_0} = - \rho gz - \rho \frac{{\rm{{\partial}} \Phi }}{{{\partial} t}} - \frac{1}{2}\rho {\left| {\nabla \Phi } \right|^2}。$ (4)

 ${G_{\eta \eta }} = \frac{{H_s^2}}{{4\text{π} }}{\left( {\frac{{2\text{π} }}{{{T_z}}}} \right)^4}{\omega ^{ - 5}}\exp \left( {{{ - }}\frac{1}{\text{π} }{{\left( {\frac{{2\text{π} }}{{{T_z}}}} \right)}^4}{\omega ^{{{ - }}4}}} \right)。$ (5)

 $\mathop {{\omega _i}}\limits^ \wedge = {\omega _{i - 1}} + ({\omega _i} - {\omega _{i - 1}}) \times {n_{rand}}。$ (6)

1.4 疲劳应力响应计算

 $\sigma \left( t \right) = {\sigma _e}\left( t \right) + {\sigma _w}\left( t \right)。$ (7)

 ${\sigma _w}\left( t \right) = \sum\limits_{i = 1}^n {{a_i}{\sigma _{_i}}\cos ({\omega _i}t + {\varepsilon _i})}。$ (8)
1.5 疲劳累计损伤计算

 ${S_{eq}} = \frac{S}{{2\left(1 - \dfrac{{{S_{m} }}}{{{\sigma _b}}}\right)}}。$ (9)

 $D = \frac{\delta }{A}\sum\limits_i {\sum\limits_j {\frac{{{\alpha _i}{T_d}{P_{ij}}}}{T}{n_i}S_{ij}^m} } 。$ (10)
2 直翼桨区域结构疲劳分析算例 2.1 有限元模型

 图 2 有限元模型 Fig. 2 Finite element model

 图 3 盘面关联点选取 Fig. 3 Correlation points on the disk surface
2.2 疲劳热点选取

 图 4 疲劳热点位置分布 Fig. 4 Distribution of fatigue hotspots
2.3 载荷计算

 图 5 激振力拟合时历 Fig. 5 Time history of excitation force

 图 7 脉动压力拟合时历 Fig. 7 Time history of pulsation pressure

2.4 热点应力计算

 图 8 激振载荷作用下应力响应时历 Fig. 8 Time history of stress response under vibration load

 图 9 波浪载荷作用下应力响应时历 Fig. 9 Time history of stress response under wave load

 图 10 载荷联合作用下的应力响应时历 Fig. 10 Time history of stress response under combined loads

 图 11 总应力统计结果 Fig. 11 Statistical results of total stress
2.5 疲劳损伤计算结果

3 结　语

1）基于时域分析方法，将激振载荷和波浪载荷下的结构应力响应时历曲线叠加再分析，可以较为合理地模拟直翼桨区域在真实环境下的疲劳损伤情况；

2）激振载荷对直翼桨基座支撑构件翼板与基座盘面焊缝位置处疲劳损伤影响最大，局部位置达到总损伤值的50%，在设计过程中需考虑该位置共振疲劳的影响；

3）在靠近船体中线面的位置，波浪载荷对直翼桨区域结构疲劳影响占主导地位。

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