由于有限元模型精度的限制，在以往初步结构设计中难于开展耐久性分析，这样会在结构设计中埋下疲劳寿命不足的问题，增加结构细节设计的难度，甚至引发结构超重问题。针对这一问题，在飞机结构的变精度模型技术和细节疲劳额定值方法的基础上，提出了静强度与耐久性综合约束下的初步结构设计方法，将耐久性设计分析工作从详细结构设计后期提前到初步结构设计阶段，并以某一折叠机翼为研究对象，在其结构选型与布置中就对关键结构（内外翼连接耳片）中的应力进行控制，通过多工况优化设计保证了连接耳片的疲劳裕度大于零，这样可以有效地减少详细结构设计中由于疲劳寿命不足而引起的多次迭代设计，并有助于获得更轻量化的结构设计。
The accuracy limit of the finite element model makes durability analysis difficult to conduct in the classic preliminary structure design, leading to the potential problem of fatigue life shortage, increasing the difficulty in structural detail design, and even resulting in structure overweight. To address this problem, we propose the strength/durability preliminary structure design method based on the variable fidelity model technology and detail fatigue rating method. Durability analysis is advanced from the late structural detail design phase to the preliminary structure design phase. A folding wing is studied in this paper, and the stress level of the critical location (the joint between the inner and outer wings) is controlled based on the requirements of strength and fatigue. Multi-case optimization is conducted to ensure that the fatigue margin is larger than zero. Consequently, iteration design caused by fatigue life shortage is limited, and lighter weight structure design can be obtained more conveniently.
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