## OPTIMIZATION OF FUSELAGE OPENING ZONE OF CIVIL AIRCRAFT

YIN Kaijun,1), SU Yanfei, ZHANG Yinli

The First Aircraft Institute of the Aviation Industry Corporation of China, Xi'an 710089, China

Received: 2019-12-6   Revised: 2020-02-22   Online: 2020-06-20

Abstract

The cabin door openings are usually arranged in the fuselage for civil aircraft, resulting in fuselage stiffness discontinuity. In view of the structural stiffness and the transmission of the load, the paper studies the opening structure of the fuselage: clarifying the factors affecting the stiffness of the opening structure and optimizing the opening angle and the size of the reinforcing structure. The above research shows the direction and the method of the design and the reinforcement of the opening structure in the preliminary design stage of the opening structure of the aircraft fuselage.

Keywords： fuselage ; stiffness ; opening angle ; optimization analysis

YIN Kaijun, SU Yanfei, ZHANG Yinli. OPTIMIZATION OF FUSELAGE OPENING ZONE OF CIVIL AIRCRAFT. MECHANICS IN ENGINEERING[J], 2020, 42(3): 289-293 DOI:10.6052/1000-0879-19-342

## 2 机身开口区优化分析方法

### 2.1 机身开口区刚度分析计算

2.1.1 机身开口区刚度计算模型简化

### 图1

\begin{align} \delta_0 = \delta_{\rm mp} + \frac{F_{\rm ch}}{s_{\rm ch}} + \frac{F_{\rm gk}}{s_{\rm gk}} \end{align}

2.1.2 刚度计算

\begin{align} S_y ={}& \int\nolimits_A {zd A} + \sum\limits_i {A_i} z_i = R^2\delta_0 (\cos \gamma - \sin \beta) +\notag\\ & A_{\rm jq} R (\sin \gamma - \cos \beta) \end{align}

\begin{align} A = \int\nolimits_A {d A} + \sum\limits_i {A_i} = \delta_0 R\Big(\frac{3}{2}{\pi} + \beta - \gamma\Big) + 2A_{\text{jq}} \end{align}

\begin{align} z_{\rm c} = \frac{S_y}{A} \end{align}

\begin{align} I_y = \int_A {z^2d A + \sum\limits_i {A_i z_i ^2}} \end{align}

\begin{align} I_{y\rm c} = I_y + z_{\rm c}^2 \cdot A = \frac{1}{2}R^3\delta_0 \cdot (B_1 + B_2 ) \end{align}

\begin{align} & B_1 = \frac{3}{2}{\pi} + \beta - \gamma + \frac{1}{2}\sin 2\gamma + \frac{A_{\rm jq}}{R\delta_0}(\sin ^2\gamma + \cos ^2\beta) \\\end{align}
\begin{align} & B_2 = \frac{\left[ {\cos \gamma - \sin \beta + \dfrac{A_{\rm jq}}{R\delta_0}(\sin \gamma - \cos \beta)} \right]^2}{\dfrac{3}{2}{\pi} + \beta - \gamma + 2\dfrac{A_{\rm jq}}{R\delta_0}} \end{align}

2.1.3 模型验证

### 2.2 机身开口区强度分析计算

(1)在纯气密载荷工况下,蒙皮环向拉应力$\sigma_t$小于控制拉伸应力$[\sigma]$

\begin{align} \sigma_t = \frac{PR}{\delta_{\rm mp}} \leq [\sigma ] \end{align}

(2)对于未开口区蒙皮在35%极限载荷下不发生压缩弹性失稳

\begin{align} \sigma_{\rm cr} \geq 0.35\sigma \end{align}
\begin{align} \sigma_{\rm cr} = \frac{K_\text{e} \pi ^2E}{12\left( {1 - \mu ^2} \right)}\left( {\frac{\delta_0}{S_{\rm ch}}} \right)^2 \end{align}
\begin{align} \sigma = \frac{M_{\max}}{I_0} \end{align}

\begin{align} I_0 = R^3\delta_0 {\pi} \end{align}

\begin{align} \delta_0 ^3 \geq \frac{4.2M_{\max} (1 - \mu ^2)S_{\rm ch} ^2}{ER^2{\pi}^3K_\text{e}} \end{align}

\begin{align} EI_1 \geq \frac{M_{\max} \cdot (2R)^2}{16 000 S_{\rm gk}} \end{align}

(3)对于开口区蒙皮在35%极限载荷下不发生剪切弹性失稳

\begin{align} \tau_{\rm cr} \geq 0.35\tau \end{align}
\begin{align} \tau_{\rm cr} = \frac{K_{\rm s} \pi^2E}{12\left( {1 - \mu ^2} \right)}\left( {\frac{\delta_0}{S_{\rm ch}}} \right)^2 \end{align}
\begin{align} \tau = \frac{F_Z \cdot S_y}{I_{y\rm c} \cdot 2R} \end{align}

\begin{align} \frac{S_y}{I_{y\rm c}} \leq \frac{40R}{7F_Z}\tau_{\rm cr} \end{align}

### 2.3 开口角度及加强桁梁面积优化分析

\begin{align} \varDelta = \frac{I_{y\rm c}}{A} \end{align}

\begin{align} \left.\begin{array}{l} \dfrac{\partial \varDelta}{\partial \gamma} = 0 \\[3mm] \dfrac{\partial \varDelta}{\partial A_{\rm jq}} = 0 \\ \end{array} \right\} \end{align}

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