Session: 28-06 Structure Characterization and Identification

Paper Number: 126043

126043 - Mechanical Properties of the Support Structure With Recoverable Stiffness 

The loss of fan blades in aircraft engines can cause significant imbalance in the rotor system. A fusible structure design similar to a fuse is often used at the front support point of the fan to ensure the safety of engine operation and aircraft flight. However, the damage to the support structure is irreversible, which will increase the working load of the remaining two bearings. To overcome the shortcomings of fused structures, this paper proposed a new type of support structure with high stiffness, high damping, and high impact resistance, which combines chiral structures with NiTi shape memory alloy ( NiTi-SMA ) materials and has recoverable stiffness.

The support structure with recoverable stiffness was designed by the chiral single cell structures and foldable squirrel cage structures. The mechanical properties of chiral single cell structures with different topological configurations were studied, and the analytical model of the support structure was established. The mechanical properties of the support structure were studied through finite element simulation and the analytical model, and mechanical properties tests of chiral single cell structures and support structures were conducted.

As the core actuator of the supporting structure, the chiral unit cell structure was designed using NiTi-SMA. When an impact occurs, the actuator undergoes compression deformation and undergoes phase transformation, resulting in a rapid decrease in stiffness, thereby reducing the support stiffness. This allows the rotor to decrease to the windmill speed at a lower critical speed, and absorbing impact energy while achieving vibration reduction. During the rotational speed stage of the windmill speed, the vibration energy of the rotor decreases, heating the actuator to restore its original shape and stiffness, thereby restoring the stiffness of the support structure and improving the operational stability of the rotor system.

The simulation calculations of chiral cells showed that the chiral cell structure has good energy absorption characteristics. As the compression displacement increases, the tangential stiffness of chiral cells rapidly slopes down, and the range of stiffness changes is large. After comparative analysis of different indicators, chiral single cell structure with quadrilateral topological structures was selected as actuators.

An analytical model for the stiffness of the support structure article was established. The model established a lumped parameter model for the single cell structure, thereby establishing a macroscopic stiffness characterization model for the entire support structure. This model only takes the mechanical properties of a single cell structure as input and can consider the effects of friction and plastic deformation. The influence of the number of cells on the support stiffness and stiffness uniformity was studied. The results showed that the model can accurately calculate the support reaction force and stiffness of the support structure under different compressive displacements, with an initial tangent stiffness error of 1.7% compared to the simulation model. A support structure with an even number of single cell structures exhibits good stiffness uniformity in different directions.

The mechanical properties of stiffness recoverable structures were investigated through experiments on the mechanical properties of chiral single cell structures with different configurations and quasi-static loading tests on supporting structures. The results show that the chiral single cell structures have good energy absorption properties. In terms of stiffness recovery, the compression of a single cell structure leads to phase transformation hardening, resulting in a higher stiffness after recovery than the initial stiffness.

The quasi-static compression test results of the recoverable support structure show that the stiffness will rapidly decrease after compression, with a stiffness reduction ratio of 61.81%. The support stiffness of the repairable support structure after recovery will be greater than the support stiffness before compression, and the stiffness recovery ratio can reach 114%. In terms of damping effect, the loss factor of the structure reaches above 0.12, when the compressive displacement is greater than 0.3mm.

Presenting Author: He Sun Beihang University

Presenting Author Biography: HeSun, PhD student at Beihang University, mainly engaged in research on blade dry friction damping and intelligent rotor support structures.

Authors:

He Sun Beihang University
Dayi Zhang Beihang University
Qicheng Zhang Beihang University
Cheng Yang Byd Auto Industry Company Limited