飞机蒙皮仿生耦合强化裂纹扩展规律与阻滞机理研究

The integral fuselage connecting technology for aircraft skin and stringer has been one of the most important light-weight technology on modern advanced aircraft. Due to the lack of rivet hole, the integral fuselage cannot refuse the crack keeping grow just as fabricated technology does. It has weak ability on damage tolerance. Thus, to reveal the crack growth laws and crack blockage mechanism for aircraft skin is one of the most research area for improving its damage tolerance ability. Based on fatigue crack restraining principle of nature biological prototype, bionic coupled strength face which adapt to the aircraft skin scale is designed and prepared by laser alloying. Considering the mechanism of residual thermal stress into substrate regional stress, which induced by bionic unit processing, bionic coupling strengthening crack propagation simulation model is established, and then characteristic parameters for crack tip stress field is identified. Based on the crack growth test, crack propagation rate prediction model for aircraft skin bionic coupling strengthen surface is established, evolution mechanism between aircraft skin service performance and microscopic parameters is revealed. This program could provide a new crack prevention method for aircraft skin, and is also available to improve the damage tolerance ability for aircraft skin.

飞机蒙皮与桁条骨架之间的整体式壁板连接技术是现代飞机轻量化设计的关键之一。整体式壁板由于缺乏装配式铆接技术固有的止裂结构—铆钉孔，导致其损伤容限能力差，因此开展飞机蒙皮裂纹扩展规律与阻滞机理研究意义重大。本项目基于自然界抗疲劳生物原型止裂功能原理，设计与飞机蒙皮尺度相适应的仿生耦合强化功能表面并采用激光合金化进行制备。纳入仿生单元体加工诱导的残余热应力对基体区域应力作用机制，建立仿生耦合强化裂纹扩展仿真模型，实现裂尖应力场表征参量的有效甄别。继而通过裂纹扩展试验，发展飞机蒙皮仿生耦合强化裂纹扩展速率预测模型，构建仿生耦合下各微观拘束障碍参量与飞机蒙皮服役性能之间的形性演化机理。本项目研究将为飞机蒙皮提供一种新的裂纹阻滞方法，进而提高飞机蒙皮损伤容限能力。

近年来，整体式飞机蒙皮逐渐取代装配式以此来减轻整机的重量。但是，整体式壁板由于缺乏装配式铆接技术固有的止裂结构—铆钉孔，导致其损伤容限能力差，因此本项目开展了飞机蒙皮裂纹扩展规律与阻滞机理研究。基于自然界抗疲劳生物原型止裂功能原理，采用数字图像处理的方法提取了植物树叶，蜻蜓翅膀等生物特征，利用激光熔覆、激光喷丸等技术制备了仿生单元耦合体。通过实验以及有限元等方法证明了基于仿生学的激光熔覆、激光喷丸的方法可以进一步提高飞机蒙皮的抗裂性能。主要原因是裂纹在扩展时路径会出现偏折现象，这意味着需要消耗更多的能量来确保裂纹可以扩展，从而飞机蒙皮寿命得到延长。激光熔覆、激光喷丸等技术所引入的残余压应力是提升飞机蒙皮裂纹阻滞能力的关键。此外，基于BP神经网络以及蒙特卡洛法建立了适用于仿生激光喷丸的剩余疲劳预测模型，可以准确的预测试样的疲劳寿命。