Damage-modified nonlinear viscoelastic constitutive equation and failure criterion are introduced and the three-dimensional incremental forms are deduced based on the updated Lagrangian approach. A simple tensile test...Damage-modified nonlinear viscoelastic constitutive equation and failure criterion are introduced and the three-dimensional incremental forms are deduced based on the updated Lagrangian approach. A simple tensile test model and a split Hopkinson pressure bar model are built to verify the accuracy of the subroutine implemented within the non-linear finite element program LS-DYNA. A numerical model of bird strike on windshield is established to study the responses of windshield under three different bird velocities at three sites. The bird is represented by a cylinder with a hemisphere at each end and the contact-impact coupling algorithm is used in this study. It is found that the implemented subroutine can properly describe the mechanical behavior of polymethyl methaerylate under low and high strain rates and large deformation, and can be used validly.展开更多
The collision process of a flying bird and the aircraft windshield was simulated by using movable cellular automata ( MCA) method to improve the structure design of aircrafts. The simulation results show that the whol...The collision process of a flying bird and the aircraft windshield was simulated by using movable cellular automata ( MCA) method to improve the structure design of aircrafts. The simulation results show that the whole strike process is performed in 4. 8 ms,the critical strike velocity for an aeronautic glass windshield is 360 km/h,the windshield vibrates and deforms in the collision,and after absorbing the kinetic energy,its temperature increases. The simulation results coincide with the experiment data better. It is clear that MCA method has more advantages than the usual methods of continuum mechanics.展开更多
基金National Natural Science Foundation of China (50375124) Hi-tech Research and Development Program of China (2006AA04Z401)
文摘Damage-modified nonlinear viscoelastic constitutive equation and failure criterion are introduced and the three-dimensional incremental forms are deduced based on the updated Lagrangian approach. A simple tensile test model and a split Hopkinson pressure bar model are built to verify the accuracy of the subroutine implemented within the non-linear finite element program LS-DYNA. A numerical model of bird strike on windshield is established to study the responses of windshield under three different bird velocities at three sites. The bird is represented by a cylinder with a hemisphere at each end and the contact-impact coupling algorithm is used in this study. It is found that the implemented subroutine can properly describe the mechanical behavior of polymethyl methaerylate under low and high strain rates and large deformation, and can be used validly.
文摘The collision process of a flying bird and the aircraft windshield was simulated by using movable cellular automata ( MCA) method to improve the structure design of aircrafts. The simulation results show that the whole strike process is performed in 4. 8 ms,the critical strike velocity for an aeronautic glass windshield is 360 km/h,the windshield vibrates and deforms in the collision,and after absorbing the kinetic energy,its temperature increases. The simulation results coincide with the experiment data better. It is clear that MCA method has more advantages than the usual methods of continuum mechanics.
文摘机场鸟类群落的多样性及变化是机场鸟击防控关注的重点,了解机场飞行区鸟类多样性与周边景观格局的关系可以为机场鸟击防控提供科学指导。2022年1—12月,每月对成都天府国际机场东、西跑道的鸟类进行调查,运用景观指数量化两跑道外1 km、2 km、3 km 3个尺度内的景观特征,以研究两跑道外不同范围景观格局对场内鸟类组成和多样性的影响。结果发现:(1)西跑道的鸟类多样性和3个尺度的景观多样性均较东跑道高;(2)西跑道林鸟和水鸟类群的多样性显著高于东跑道;(3)在3个尺度范围内,东跑道外农田的平均斑块面积均显著大于西跑道,东跑道农田对整体景观具有较强的主导性。推测两跑道外农田生境的差异可能对整体景观格局产生了影响,从而造成了东、西跑道鸟类多样性的差异。研究揭示场外景观格局对场内鸟类群落的塑造有重要作用,为机场外的景观管理提供了建议,与此同时还要加强重点区域和重要季节的巡查,以提前化解鸟击风险。
