Study on Structural Optimization Design of Critical Load-Bearing Screws for Airborne External Store Locking Mechanism

doi:10.3969/j.issn.1009-086x.2026.04.011

Abstract

Abstract:

The load-bearing screw connects the airborne external shell and the locking mechanism casing， which are two non-directly contacting components， through the connecting beam components. It is the critical load-bearing component of the locking mechanism and is subjected to a large combined bending and shear load during operation. In view of the fracture fault of the load-bearing screw in the locking mechanism during the missile-carrying flight of a certain type of aircraft， a physical and chemical analysis of the fracture of the load-bearing screw was first conducted， determining that the failure mechanism was fatigue damage. Then， to address the design defects of the load-bearing screw in the initial state， two structural optimization schemes of a relief groove state and a plain shank state were proposed from the design perspective. Fatigue life simulation analysis and experimental verification were conducted on the load-bearing screw before and after optimization. The distribution trend of the calculated values was consistent with that of the test values， and the fatigue life of the optimized load-bearing screw greatly increased from 308 cycles to 3 800 cycles. Compared with the relief groove state， although the fatigue life of the plain shank state was improved， the improvement was limited. Considering the time cost and economic cost of the design improvement， the relief groove state was selected as the final improvement scheme. Through internal and external field test verification， the improvement measures were proved effective， and the same fault did not occur again.

Key words: load-bearing screw, fatigue life, aircraft store, structural optimization, finite element analysis, fatigue test

摘要：

承力螺钉将机载外挂壳体与锁制机构壳体这2个非直接接触的构件通过连接梁组件进行连接，是锁制机构的关键承力部件，在工作过程中承受较大的弯剪复合载荷。针对某型载机挂弹飞行时出现锁制机构承力螺钉断裂故障的问题，对承力螺钉断口进行理化分析，确定失效机理为疲劳破坏。针对初始状态承力螺钉的设计缺陷，从设计角度提出了退刀槽状态和光柱状态2种结构优化方案。针对优化前后的承力螺钉开展了疲劳寿命仿真分析和试验验证，得出计算值与试验值的分布趋势一致，且优化后承力螺钉疲劳寿命从308次大幅提高至3 800次，光柱状态相对退刀槽状态，虽然疲劳寿命有所提高，但提高程度有限。综合考虑设计改进的时间成本和经济成本，选择退刀槽状态作为最终的改进方案。经过内外场试验验证，验证了改进措施有效，未再发生同样的故障。

关键词: 承力螺钉, 疲劳寿命, 机载外挂, 结构优化, 有限元分析, 疲劳试验

CLC Number:

TJ762.2

Wanyuan LIU, Xiangqiu LIU. Study on Structural Optimization Design of Critical Load-Bearing Screws for Airborne External Store Locking Mechanism[J]. Modern Defense Technology, 2026, 54(4): 103-111.

刘万远, 刘相秋. 机载外挂锁制机构关键承力螺钉结构优化设计研究[J]. 现代防御技术, 2026, 54(4): 103-111.

Figures/Tables 18

Fig. 1 Schematic diagram of load-bearing screw installation

Fig. 2 Appearance of faulty part

Fig. 3 Macroscopic morphology of fracture surface

Fig. 4 Morphology of fracture initiation zone and propagation zone

Fig. 5 Fatigue striations in fracture propagation zone

Fig.6 Simulation model

Fig.7 Connection form of load-bearing screw in initial state

Fig.8 Stress distribution contour map of load-bearing screw in initial state

Fig.9 Life distribution contour map of load-bearing screw in initial state

Fig.10 Connection form of load-bearing screw in relief groove state

Fig.11 Stress distribution contour map of load-bearing screw in relief groove state

Fig.12 Life distribution contour map of load-bearing screw in relief groove state

Fig.13 Connection form of fixing thread in plain shank state

Fig.14 Stress distribution contour map of load-bearing screw in plain shank state

Fig.15 Life distribution contour map of load-bearing screw in plain shank state

Fig.16 Test fixture

Fig.17 Diagram of fatigue test device

Table 1 Comparison of calculated and test values for fatigue life of load-bearing screws in different states

	试验值/次	计算值/次	对数相对误差/%
初始状态	308	201	7.45
退刀槽状态	3 800	3 428	1.25
光柱状态	5 000	4 615	0.94

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