High Speed Impact Simulation And Optimization Design Of Wing Anti Bird Impact Structure

Bird strike of aircrafts are increasing threat to flight safety.On the one hand,bird strike accident has caused economic losses of hundreds of millions of yuan around the world every year,on the other hand,experience cost of bird strike is extremely expensive.Therefore,finite element simulation technology represented by Smoothed Particle Hydrodynamics(SPH)method plays an important role in design and improvement of aircraft bird strike resistance.Basing on SPH method,bird strike process and deformation mechanism of a typical tail structure was studied in this paper,furthermore,influence of strike position and direction to structure stress,deformation,energy and material failure behavior were studied.On the basis of the above works,Two improvement design schemes in terms of structure and material were proposed.In this paper,a numerical verification of bird strike algorithm was made at first.Simulation results show that SPH algorithm can simulate initial shock regime,release regime,steady flow regime and termination regime during bird strike on a rigid flat plate.The relative error of peak pressure in impact center between numerical simulation and experimental data recorded in literature is about 4.3%.Next,a typical leading-edge structure stress,strain,pressure,displacement and energy response as well as weakness in bird strike resistance were analyzed using bird model verified before.Besides,various impact conditions such as impact position and direction were studied,simulation results show that impact speed along normal direction of target has influence in pressure distribution while speed along tangent direction relate to element failure,and leading-edge outer skin is main energy absorbing part while front beam plays the role of supporting structure,but during oblique striking,front beam provide torsion stiffness as well.According to simulation result above,two improved designs in terms of structure and material were considered,namely addition of unidirectional support plate structure and the use of fiber-metal composite materials,respectively.Structure of support plate decreases damage to leading-edge outer skin by cutting bird body and evacuate impact kinetic energy while fibermetal composite structure helps to lose structure weight by about 10%,as well as to improve structure stiffness,thus the maximum deformation decreased to 25% of original one.Next,comparative analysis of deformation mechanism,leading-edge curvature,skin thickness,configurations of fiber-metal material and different plies were carried out.Results show that the compressive fiber model and tensile matrix model are main damage model during bird strike,while tensile matrix seems to be more serious.In some cases,reduction of curvature radius of leading-edge is helpful to improve structure stiffness,but when curvature is too small,the tensile matrix damage area may increase.The analysis results show that reasonable laminate layers’ orientation design can significantly improve leading-edge structure bird strike resistance.At last,comparative analysis of tail whole structure assembled with modified leading-edge structure and simplified structure was made.Results show that calculation method and improved scheme adopted in this paper are effective,the results of finite element analysis are reasonable and reliable.The results of this paper may provide reference in damage tolerance design of aircraft structure.