Weight Optimization of Fork and Axle of Main Landing Gear for an Unmanned Aerial Vehicle by Finite Element Analysis

Unmanned Aerial Vehicles (UAV) are being deployed in military, law enforcement, search & rescue, scientific research, environmental & climate studies, reconnaissance and other commercial and non-commercial applications on a large scale. A design and development of landing gear system has been taken up for a UAV. This paper presents the design optimization of structural components of Wheel-Brake & Fork assembly pertaining to the Main Landing Gear (MLG) for a UAV. The wheel, fork, axle and brake unit constitute the wheel assembly. The wheel-brake assembly is assembled with the strut assembly and forms the Landing gear system. The Fork is the connecting member between the shock strut and the axle containing the wheel-brake assembly. As the fork and axle are subjected to shock loads while landing, the strength of these components are very much essential to withstand the dynamic loads. Reducing the weight of the fork and axle helps better maneuverability of flight and lesser fuel consumption. Hence, a weight optimization of the landing gear has been taken up. The major technical challenges for weight reduction is modifying the design for the same strength and to achieve compactness of the whole landing gear. The optimization process was carried out iteratively to achieve the maximum possible weight reduction by using Finite Element Analysis (FEA).

A CAD model was created using Creo-parametric and converted into FE model by ANSYS 14.0. The element convergence study was carried out using higher order elements. The loads were estimated for various landing conditions as prescribed by the Federal Aviation Regulation (FAR) standards. In accordance with calculated loads, boundary conditions were applied on the FE model and an optimized geometry for the fork and axle has been achieved. In the present analysis, Aluminum Alloy T6 condition and High strength alloy steel are used for Fork and axle respectively. With the modified layout, a 30 percent weight reduction was achieved and a reserve factor of 1.2 was maintained for both fork and axle. The optimization study has successfully yielded a compact, weight reduced fork and axle.