Safety factor probabilistic design of composite structures based on reliability

基于可靠性的复材结构安全系数概率设计法

¹ School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
² National Key Laboratory of Strength and Structural Integrity, Xi'an 710072, China
³ 93147 Unit, People's Liberation Army of China, Deyang 618000, China
⁴ National Key Laboratory of Strength and Structural Integrity, Aircraft Strength Research Institute of China, Xi'an 710065, China

Received: 18 December 2024

Abstract

Deterministic safety factor design is difficult to adapt to the characteristics of composite structures with many uncertainty factors and concurrent multiple failure modes, and the design results cannot quantitatively describe the level of risk. In this paper, based on the synergistic reliability analysis of multiple failure modes and the introduction of uncertainty variables such as material, design, load, and so on, the safety factor probabilistic Design(SFPD) method is proposed, in which taking the structural risk level as a constraint, the allowable failure probability is converted into a safety factor to break the correlation barriers between the safety index, safety factor, and structural design. First, the main failure modes of composite structures are considered to decompose the safety indexes, and the allowable failure probability is assigned to each failure mode; second, the reliability model of composite structures is constructed with the allowable failure probability as a constraint, combining the macro-and fine-specular failure criterion, and the ultimate load is inverted through structural optimization, to make the structure safety coefficient lower and reduce the weight of the structure under the condition of meeting the safety indexes; and finally taking the typical wall plate structure of civil aircraft as the case verification object, the weight reduction of 7% for the skin and 4% for the whole structure is realized under the premise of ensuring the structural safety, and the reasonableness and feasibility of the safety coefficient reduction from 1.5 to 1.4 are verified.

摘要

确定性安全系数设计难以适应复合材料结构不确定性因素多、多失效模式并发的特点, 设计结果也无法定量化描述风险大小。基于多失效模式协同可靠性分析, 引入材料、设计、载荷等不确定性变量, 提出安全系数概率设计法(safety factor probabilistic design, SFPD), 以结构风险等级为约束, 将允许失效概率转换为安全系数, 打破安全性指标、安全系数和结构设计之间的关联壁垒。考虑复合材料结构的主要失效模式分解安全性指标, 为各失效模式分配允许失效概率; 以允许失效概率为约束条件, 结合宏观和细观失效准则构建复合材料结构可靠性模型, 通过结构优化反推极限载荷, 使结构在满足安全性指标要求条件下, 降低安全系数并减轻结构质量; 以民机典型壁板结构为案例验证对象, 在保证结构安全的前提下实现了蒙皮质量减少7%、整体结构质量减少4%, 并验证安全系数由1.5降为1.4的合理性和可行性。