Abstract
Aircraft lug joint is the key part of load transfer. In order to improve the safety of lug joint, on the premise of meeting the design requirements of static strength and fatigue, the composite connection lug structure design technology of different metal materials is proposed in this paper. Firstly, the damage safety design and life reliability analysis of the lug structure are studied theoretically. Secondly, based on the concept of damage safety design and the design principle of deformation coordination, the design method of composite connection lug with deformation coordination is proposed, and the thickness ratio of single ear is 0.8:1:0.8. Finally, the reliability of the composite lug is analyzed. The results show that the structural design scheme of aluminum-titanium composite ear piece can meet the requirements of static strength and damage tolerance, and compared with the conventional ear structure, the failure probability of structure mission life is greatly reduced when the weight of the composite connection lug is only increased by 4.9%. The proposed method can effectively guide the structural design of composite ear piece.
Highlights
分析,分析结果从检查门槛值和重复检查间隔来体 现。 根据《 民机结构耐久性与损伤容限设计手册》 第五章[15] 应力强度因子中的 J41 对应的无衬套对称 直耳片模型,对结构进行损伤容限分析,裂纹扩展寿 命模型为线性累加模型( Walker 公式),寿命计算方 法为变量分离法。 本文假设钛-铝混杂耳片结构损 伤容限方面有 2 种失效模式: 以铝作为第一路径,2 种材料的初始裂纹都为 1.27 mm[16],假设铝板先失效且 2 层铝板同时失效, 裂纹扩展第一阶段为钛板在初始裂纹 1.27 mm 条件 下,持续目标寿命 67 200 FC 这一过程。 裂纹扩展
于常规单耳的检查门槛值和剩余强度较低,但是二 者的剩余强度均小于等于剩余强度许用值,满足剩 余强度要求;检查门槛值均满足疲劳损伤检查门槛 值 24 000 FC 的设计目标。 同样的,检查间隔也满 足疲劳损伤重复检查间隔 14 400 FC 的设计目标, 因此所提方案满足损伤容限设计要求。
Aeronautical Manufacturing Technology, 2017(5) : 96⁃99 ( in Chinese)
Summary
单传力路径耳片无论是结构设计、疲劳寿命影 响因素还是安全性评估的研究在国内外均取得了较 丰硕的成果。 如李维娜通过静力学的相关分析,针 对常规的耳片接头提出了比较完善的设计准则和评 估方法[2] ;徐明波基于损伤容限分析对耳片结构进 行了 优 化 设 计[3] 。 针对不同材料, 徐茂和李辉等[4⁃5] 分别对 7055 铝合金耳片接头和钛合金耳片结 构的力学性能进行了分析。 在疲劳寿命研究方面, Boljanovic 给出了 疲劳载荷下耳片的计算模型[6] ; Maksimovic 从裂纹扩展方面对耳片疲劳寿命进行了 分析[7] ;另外,Andrea 对重复检查下的飞机结构安 全性评估给出了较为完善的分析流程[8] 。 对于按 破损安全设计的耳片接头,国外学者 Abraham 给出 了一种合理选择结构检查门槛值和检查间隔的方 法, 同时考虑了不同材料参数对失效概率的 影响[9] 。 受的载荷一般很大,为了提高耳片接头的安全性,本 文基于破损安全理念提出了复合连接耳片设计技 术,主要包括结构设计和可靠性分析 2 个方面,如图 1 所示。 结构设计方面首先根据破损安全设计理念 和变形协调设计原则,参考国内某飞机接头的单耳 尺寸,根据铝和钛的弹性模量,给出了 3 层“ 铝-钛- 铝” 复合单 耳的厚度比例参数; 其次开展了该方案 在给定载荷条件下的静强度分析,保证铝耳片、钛耳 片在极限载荷下都不出现破坏,即满足结构静强度 要求;然后对含裂结构进行损伤容限分析与评定,判 断是否满足剩余强度载荷要求和检查间隔要求。 可 靠性分析方面主要是根据损伤容限分析结果对单耳 结构进行寿命可靠性评估,并与对应的常规单耳结 构相比,判断是否能够满足质量和失效概率的目标 要求,如果不满足,则需要调整结构的尺寸参数,如 果满足,则得到复合耳片的设计方案。 值 24 000 FC、疲劳损伤重复检查间隔 14 400 FC) , 采取图 2 所示的“铝-钛-铝” 复合单耳,2 层铝板厚 度相同,布置在外侧,钛板布置在中间。 耳片几何参 数含义如图 3 所示,具体尺寸大小如表 1 所示。
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