SMA损伤对航空发动机变形齿单齿力学性能的影响

Effects of SMA Damage on Mechanical Property of Variable Geometry Single Chevron of Aero Engine

航空发动机变形齿(Variable geometry chevron,VGC)是一种由形状记忆合金(Shape memory alloy,SMA)驱动的锯齿形航空动力学装置,其固定在发动机外涵道尾部呈环状分布,在飞机起飞和降落时能够通过弯曲变形扰动发动机外涵道气流,达到降低噪声的目的。然而,在反复使用过程中,VGC的循环弯曲变形必然会导致材料出现损伤,甚至会出现功能性疲劳或结构性疲劳现象,进而对发动机性能造成不可预知的影响。鉴于此,本工作拟开展SMA损伤对航空发动机VGC力学性能的影响研究。在已有SMA本构模型的基础上,引入损伤因子,建立含有损伤的SMA本构模型,编写有限元子程序,仿真分析SMA的损伤对VGC力学性能的影响。研究结果表明,随着SMA损伤程度增大,VGC的尖端挠度增大、最大等效应力减小。研究结果可为VGC的安全性运营提供指导。

The aero engine variable geometry chevron(VGC)is a saw-tooth aerodynamics device driven by shape memory alloy(SMA)beams,which is fixed in the tail of the engine bypass and distributed in a ring.It can disturb the airflow in the engine bypass through bending deformation during take-off and landing to reduce the noise.However,in the process of repeated use,the cyclic bending deformation of VGC will inevitably lead to material damage,and even functional or structural fatigue,which will cause unpredictable effects on aero engine performance.In view of this,this work intends to carry out the research on the influence of SMA damage on the mechanical behaviors of aero engine VGC.Based on the existing SMA constitutive model,the damage factor was introduced to establish the SMA constitutive model with damage,the finite element subroutine was written,and the effect of SMA damage on the mechanical behaviors of VGC was simulated and analyzed.The results show that as the degree of SMA damage increases,the tip deflection of VGC increases and the maximum Mises stress decreases.Guidance for the safety operations of VGC can be provided from the research results.