Helicopter Rescue Hoist Bracket Topology Optimization Design And Analysis

The helicopter has become important equipment used in life and property rescue in modern society. Rescue hoist system is one of the key equipment in rescue helicopters and its working load is complex. The structure design greatly affects the operation convenience, safety and reliability for the hoistman and lifeguard in the rescue process. Based on ergonomics, topology optimization, modal, fatigue analysis theory and ANSYS Workbench software, this paper optimizes and analyzes the helicopter hoist bracket structure so as to improve its operational convenience, dynamic and fatigue characteristics. The main contents are as follows.Firstly, on the basis of analyzing the helicopter rescue conditions and characteristics of the working load, this paper establishes the force analysis model of the hoist and bracket, and gives five typical stress conditions, which lays the foundation of the hoist bracket design. Based on ergonomics, combining with the hoistman and lifeguard body standard in China, this paper designs the structural size and shape of the hoist bracket, and uses ANSYS Workbench software to analyze its structural strength under five typical working conditions. The analysis results show that the maximum deformation and stress of the hoist bracket occurs at the condition of inclining backward 30°load. The maximal values of the stress and deformation are 246.37 Mpa and 1.25 mm, which meet the structural requirements.Secondly, based on topology optimization theory and ANSYS Workbench software, rescue helicopter hoist bracket topology optimization design can be accomplished. The case analysis shows that the weight of the hoist bracket decreases by 12.5% when the stress and deformation meet the structure requirement, which will help improve the dynamic performance of the helicopter, and reduce the fuel consumption and cost.Thirdly, this paper utilizes the ANSYS Workbench software to analyze the modal characteristics of the rescue helicopter hoist bracket after topology optimization. The first six order modal and vibration after exerting constraints on the hoist bracket are extracted, and contrasted with the vibration frequency of the helicopter rotor. The results show that the minimum frequency value is 475.24 HZ, accurred by first-order transverse plane-swinging, and the helicopter rotor frequency is 24 HZ. The vibration frequency of the bracket and the rotor meets the condition of not occurring the resonance.Finally, this paper obtains the hoist bracket S-N curve based on modifying the material S-N curve of the hoist bracket by introducing the fatigue strength factor and using the Goodman curve. The modification considers the influences of the shape, size, surface quality, loading conditions and the mean stress. Then the bracket S-N curve is input into ANSYS Workbench and the life curve and safety factor nephogram are obtained. The results show that when the rescue helicopter hoist bracket is exerted pulsating cyclic loading, whose wave peak value is working limit value, the cycles are more than 107 times. So the hoist bracket has infinite life, and meets the requirements of the fatigue strength.