2.1装配应力产生过程2.2装配应力对强度影响分析

飞机装配本质上是按照设计和技术要求，将大量飞机零件和紧固件进行组合、连接，逐步装配为组合件、部件及整机的过程。由于零件数量巨大、构型多样，装配关系复杂，而且，由于零件加工过程尺寸公差、装配过程中的形位公差，零件加工过程中残余应力释放，在飞机主机装配过程中，各类误差累积，导致结构间存在装配间隙。在紧固件作用下，产生装配应力。装配应力作为预应力一直存在于飞机结构中，改变结构应力状态，使其偏离设计点，进而影响飞机结构完整性，甚至危及飞行安全。本文基于飞机结构应力状态，分析了装配应力对结构强度的影响，主要在于降低疲劳寿命和导致应力腐蚀开裂两方面，并进行了试验验证。试验表明，随着装配间隙增加，结构产生应力腐蚀裂纹概率及裂纹数量急剧增加，实际工程中，应考虑工艺水平及成本等因素，严格控制装配间隙以降低由此产生装配应力影响飞机结构强度品质。

Research on the Influence of Assembly Clearance on Aircraft Structural Strength

In essence, aircraft assembly is the process of assembling and connecting a large number of aircraft parts and fasteners according to the design and technical requirements, and gradually assembling them into assemblies, components and the whole machine. Due to the large number of parts, various configurations and complex assembly relations, and due to the dimensional tolerance, geometrical tolerance and residual stress release during the processing of parts, in the assembly process of aircraft main engine, various kinds of errors accumulate, resulting in assembly clearance between structures. Under the action of fastener, the assembly stress is produced.Assembly stress always exists in aircraft structure as prestress. It can change the state of structure stress and make it deviate from the design point, thus affecting the integrity of aircraft structure and even endangering flight safety. Based on the stress state of aircraft structure, this paper analyzes the influence of assembly stress on the structural integrity, mainly in reducing the fatigue life and leading to stress corrosion cracking, and carries out the test verification. The test shows that with the increase of assembly clearance, the probability of stress corrosion cracking and the number of cracks increase sharply. In practical engineering, the technology level and cost should be taken into account, and the assembly clearance should be strictly controlled to to reduce the resulting assembly stress that affects the strength of aircraft structures.