Structural Optimization of AerMet100 Steel Torsion Spring Based on Strain Fatigue

Abstract

The torsion spring of a carrier-based aircraft landing gear is a key component, which is normally manufactured out of AerMet100 ultra-high-strength steel. The takeoff and landing performance is greatly influenced by its bearing capacity and structural durability. To carry out the structure anti-fatigue design, it is necessary to investigate the influence of the spring structure features on its fatigue life, based on which the strain fatigue analysis and parameter optimization design of the torsion spring are executed. Through the finite element analysis conducted with ABAQUS, it was determined that there exists serious stress concentration in the relief groove. Based on the theory of strain fatigue, the fatigue life of the torsion spring was obtained, and the fracture position and lifecycle were consistent with the test results. A structure optimization platform based on a parametric method was established. Samples were selected through the DOE (design of experiment), and a surrogate model was established based on RBF (radial basis functions), followed by optimization using MIGA (multi-island genetic algorithms). With the parameter optimization of the relief groove, the structure was reconstituted and reanalyzed. From the simulation results, the peak strain was reduced by 30.7%, while the fatigue life was increased by 86.2% under the same loads and constraints. Moreover, laboratory tests were performed on the torsion spring after reconstruction, which showed that the fatigue life increases by 85.6% after optimization. The method presented in this paper can provide theoretical support and technical guidance for the application and structural optimization of ultra-high-strength steel structures.

Keywords

• ultra-high-strength steel
• torsion spring
• strain fatigue
• structural optimization
• FEM