﻿ 船体应力释放孔的优化
 舰船科学技术  2023, Vol. 45 Issue (24): 33-37    DOI: 10.3404/j.issn.1672-7649.2023.24.006 PDF

Optimization of stress release hole for ship hull
ZHANG Si-hang, LUO Ren-jie, XIE Xiao-long, LI Liu-yang, MA Tian-shuai
Marine Design and Research Institute of China, Shanghai 200011, China
Abstract: For some ship structure areas with serious stress concentration, their peak stress can be reduced by means of arranging a stress release hole. In order to improve the peak stress at concerned locations as far as possible, the shape and size optimization of stress release hole is carried out. The shape, size and location parameters are selected as design variables, opening boundary, manufacturing practice and stress level of non-optimization area are selected as constraints, and minimizing stress utilization factor of optimization area is selected as objection. Based on the Isight software platform, parametric procedure of stress release hole is integrated. After solving the optimization with genetic algorithm, an optimal design of stress release hole can be obtained.
Key words: stress release hole     shape optimization     size optimization     Isight integration
0 引　言

1 优化模型

1.1 数值算例

 图 1 某散货船槽形横舱壁纵剖面结构及折角点处应力水平 Fig. 1 The longitudinal section structure and stress level at the bending point of the trough shaped transverse bulkhead of a bulk carrier

 图 2 应力释放孔的形状、尺寸及位置等优化设计参数 Fig. 2 Optimization design parameters for the shape, size, and position of stress relief holes
1.2 数学模型

 $\left\{ \begin{array}{l} {\rm{Find}}\quad X = {[a,b,d,\theta ]^{\rm T}}，\\ {\rm{Min}}\quad f(X) = \max({f_{{\rm{weld}}}}(x),{f_{{\rm{nonweld}}}}(X))，\\ {\rm{s.t}}.\left\{ \begin{array}{l} 30 \leqslant a \leqslant140，\\ 40 \leqslant b \leqslant160，\\ 35 \leqslant d \leqslant100，\\ 15{\rm{^\circ }} \leqslant\theta \leqslant100^\circ，\\ {{b}} > a + 10，\\ \theta - a\tan \left( {\dfrac{{\dfrac{a}{2} + 20}}{{d + \dfrac{b}{2}}}} \right) \geqslant 10{\rm{^\circ }}，\\ \theta + a\tan \left( {\dfrac{{\dfrac{a}{2} + 20}}{{d + \dfrac{b}{2}}}} \right) \leqslant105{\rm{^\circ }}，\\ {{k}_{{\rm{nopt}}}}(X) \leqslant1。\end{array} \right. \end{array} \right.$ (1)
 $\left\{ \begin{array}{l} {\rm{Find}}\quad X = {[c,d,\theta ]^{{\rm{T}}}}，\\ {\rm{Min}}\quad f(X) = \max({f_{{\rm{weld}}}}({\rm{X}}),{f_{{\rm{nonweld}}}}(X))，\\ {\rm{s.t}}.\left\{ \begin{array}{l} 30 \leqslant c \leqslant90，\\ 35 \leqslant d \leqslant100，\\ 15{\rm{^\circ }} \leqslant\theta \leqslant100{\rm{^\circ }}，\\ (d + c)\cdot\sin(\theta ) - c > 25，\\ (d + c)\cdot\sin(115{\rm{^\circ }} - \theta ) - c > 25，\\ {{k}_{{\rm{nopt}}}}(X) \leqslant1。\end{array} \right. \end{array} \right.$ (2)
 $\left\{ \begin{array}{l} {\rm{Find}}\quad X = [{{\rm{m}}_{\rm{1}}}{\rm{,}}{{\rm{m}}_{\rm{2}}}{\rm{,s,d,}}\theta {{\rm{]}}^{\rm{T}}}，\\ {\rm{Min}}\quad f(X) = \max({f_{{\rm{weld}}}}(X),{f_{{\rm{nonweld}}}}(X))，\\ {\rm{s.t}}.\left\{ \begin{array}{l} 30 \leqslant{m_1} \leqslant80，\\ 30 \leqslant{m_c} \leqslant80，\\ 10 \leqslant s \leqslant100，\\ 35 \leqslant d \leqslant100，\\ 15{\rm{^\circ }} \leqslant\theta \leqslant100{\rm{^\circ }}，\\ (d + {m_1})\cdot\sin(\theta ) - {m_1} > 25，\\ (d + {m_1})\cdot\sin(115{\rm{^\circ }} - \theta ) - {m_1} > 25，\\ (d + {m_1} + {\rm{s}})\cdot\sin(\theta ) - {m_2} > 25，\\ (d + {m_1} + {\rm{s}})\cdot\sin(115{\rm{^\circ }} - \theta ) - {m_2} > 25，\\ {{k}_{{\rm{nopt}}}}{{(X)}} \leqslant1。\end{array} \right. \end{array} \right.$ (3)

2 优化求解

2.1 模型参数化

2.2 Isight集成

 图 3 Isight关于应力释放孔优化模型的计算流程 Fig. 3 The calculation process of Isight's optimization model for stress release holes
2.3 优化求解

3 优化结果及分析 3.1 计算结果

 图 4 椭圆应力释放孔优化模型目标函数变化曲线 Fig. 4 Objective function variation curve of optimization model for elliptic stress release hole

 图 5 圆形应力释放孔优化模型目标函数变化曲线 Fig. 5 Objective function curve of optimization model for circular stress release hole

 图 6 大小圆应力释放孔优化模型目标函数变化曲线 Fig. 6 Objective function variation curve of optimization model for large & small circular stress release hole
3.2 结果分析

1）对于3个应力释放孔优化模型，经过优化求解后，目标函数值即优化区域结构的归一化屈服利用因子，相对初始值均有一定程度的下降，相对于无应力释放孔时下降程度更大，同时非优化区域结构的应力水平也有一定程度的下降；

2）对于椭圆应力释放孔优化模型，初始设计虽然可以降低优化区域结构的应力峰值，但非优化区域结构的应力水平略有增加，不满足约束条件，经优化求解后，优化区域和非优化区域结构的应力水平均有降低；

3）对于圆形应力释放孔优化模型，初始设计下优化区域结构的屈服利用因子比无应力释放孔时更大，说明初始设计值不尽合理，经优化求解后，屈服利用因子下降明显；

4）3种应力释放孔优化模型相比较而言，大小圆应力释放孔优化模型的最优解降低应力峰值的效果最为明显，相比不设置应力释放孔而言，显著降低了优化区域的屈服利用因子，在不增加重量的前提下，结构安全性大幅提升。

 图 7 最优椭圆应力释放孔的应力 Fig. 7 Best result for elliptic stress release hole

 图 8 最优圆形应力释放孔的应力 Fig. 8 Best result for circular stress release hole

 图 9 最优大小圆应力释放孔的应力 Fig. 9 Best result for large & small circular stress release hole
4 结　语

1）对于应力释放孔的设计，在各设计参数未经优化前，一方面，可能使得优化区域结构的屈服利用因子比无应力释放孔时更大，起到负面作用；另一方面，也可能导致虽然降低了优化区域结构的应力峰值，但会提高非优化区域结构的应力水平，顾此失彼。因此，对应力释放孔进行形状优化和尺寸优化十分必要。

2）本文构建的船体应力释放孔优化模型可行，通过优化求解可得到最优的应力释放孔开孔形式，大幅降低关注区域结构的应力峰值和水平，在不增加结构重量的情况下，提高结构的安全性。本文提出的3种应力释放孔优化模型具备一定通用性，只需对部分模型参数稍作修改，可应用于其他船体结构部位。

3）3种应力释放孔优化模型相比较而言，大小圆应力释放孔优化模型的最优解降低应力峰值的效果最为明显，特别是相比不设置应力释放孔而言，显著降低了优化区域结构的屈服利用因子，同时非优化区域结构的应力水平也相应降低。

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