Numerical Analysis On Strength Of Airliner Ditching

The case about ditching is increasing with the development of the Sea-Crossing flight, greater speed entering into the water and strong impact can cause the structure deformation and damage of the plane body in ditching.In the process, plastic deformation caused by water load refer to complicated nonlinear problem.the study of ditching, especially the structure deformation and damage of the plane body not only have great importance on the calculating floating time in the late ditching and the design of the plane body, but also have profound significance to the all Civil aviation safety.The plane's damaged department and the damaged area in the process of ditch were simulated by LS-DYNA, taking fluid solid coupling in numerical calculation. Then numerical analysis on strength at the bottom and regular analysis were given.The main content is as follows:1. Created the ditching model.The ditching model was created in CATIA according to the radio of1:1.Geometric cleaning and grid partition were accomplished in HYPERMESH.The water and empty material grid was completed in ANSYS, then appropriate initial boundary condition was given.Finally a K-file for solution of explicit dynamic was obtained.2. Obtained pressure at the bottom of plan in the process of ditching.The work was accomplished by the numerical calculation of rigid model, getting the pressure changing at the bottom of plan, obtaining the pressure value and distribution, comparing with the pressure hatch by experimental method using pressure sensor, carrying on pressure characteristic analysis, to provide the basis for relevance to the strength model.3. Validated the numerical calculation of the strength model in the process of ditching.The work was accomplished by using strength model, taking fluid solid coupling, calculated several working conditions with different mass, different velocity, different attitude angle with LS-DYNA, obtaining the bottom damage condition containing the bottom stress variation in the cloud, the damaged area and so on.4. Obtained the result of numerical calculation with strength model and the regular analysis.It was found that maximum stress and damaged area at the bottom of plane increased with the increase of mass, and the maximum stress and damaged area were less in the condition with10°attitude angle.By choosing appropriate pressure area, compareing the damage characteristic in strength model with the pressure characteristic in rigid model, the area from4atm to7atm was regarded as the appropriate pressure area.So it was accomplished the replacement of strength model by rigid model and obtained the damaged area and proportion.