民用飞机主起落架断离销结构设计及断离失效分析

Structure design and breakaway failure analysis of fuse-pin for civil main landing gear

起落架在承受过载工况时应能够实现与机体安全快速分离,为了明确民用飞机主起落架应急断离销断离槽结构对其断离载荷的影响,分别设计外槽、长外槽、内槽和长内槽4种断离槽结构,仿真分析断离结构对断离销断离载荷的影响;试验对比分析内、外槽结构的断离销断离载荷和失效模式。结果表明:断离销破坏失效从断离槽内部扩展至外部,断离载荷随受剪截面积的增加而增加,且呈现线性变化趋势;通孔销断离载荷随受剪截面积的变化量(剪切强度系数)最大,外断离槽销次之,内断离槽销最小;内断离槽销受剪切截面积和整体尺寸的影响最小,断离载荷容易控制;断口形貌显示外断离槽销为韧性断裂失效,内断离槽销则表现出脆性断裂失效,内断离槽销的设计符合民用飞机主起落架应急断离适航设计要求。

The landing gear should be able to achieve safe and rapid separation from the aircraft body under overload conditions.To clarify the effect of breakaway groove on the breakaway load of emergency fuse-pin for civil main landing gear,a series of FEM simulations are conducted to study the influence of structural changes of breakaway groove on the breakaway load for outer-groove,long outer-groove,inner-groove and short inner-groove emergency fuse-pin.The breakaway load and failure mode are comparatively analyzed between inner-groove and outergroove emergency fuse-pin by experimental tests.The results show that the breakaway failure of fuse-pin is extended from inside to outside.The breakaway loads increase with the increasing of the sectional area and exhibit a linear relationship.The breakaway load variation with the sectional area(shear strength coefficient) of through-hole pin is the maximum,followed by outer-groove pin,and the inner-groove pin is the minimum.Compared with other pins,the breakaway load of inner-groove pin is easy to control and less affected by sectional area and overall size.The fracture morphology is changed from ductile fracture of outer-groove pin to brittle fracture of inner-groove pin.Accordingly,the design of inner-groove pin meets the aviation regulations requirement for civil main landing gear.