Crash Characteristic For The Cargo Subfloor Structure Of Civil Aircraft

In a survivable crash accident,sub-cargo fuselage section of commercial aircraft firstly contact the ground.Structure components are able to deform and dissipate large kinetic energy of the aircraft,which will maintain the level of deceleration below a tolerable limit and reduce the risks to the passengers.Therefore,the mainly objective is to research the typical failure mode and energy absorption characteristics of the sub-cargo fuselage section under the condition of the crash.The research is of great significance for increasing the crashworthiness of the aircraft and enhancing passengers' survivablity.The crashworthiness of the typical substructure of cargo cabin in transport aircraft is investigated by building an effective analysis method through the experiment and the simulation.The specific research contents are as follows:Firstly,the typical material system usually used in the fuselage structure was selected.The quasi-static and dynamic experiments of the material system were conducted.The parameters used in the finite element model can be obtained from the quasi-static material experiment.The dynamic material experiment show that the tensile rate has no influence on the characteristics of the material.Therefore,there is no need to consider the strain rate effect in the simulation experiment.Secondly,based on the validated material model,the explicit dynamic software,LS-DYNA,was used to establish the finite element model of the substructure under the cargo.After the detailed discussion on the grid partitioning,the material property setting,the contact simulation and the boundary load condition,the finite element model of the sub-cargo substructure can successfully simulate the mechanical behavior of energy absorption in impact load condition.Based on the simulation results,the load transfer path,the deformation mode,the failure mode,the structural impulse response,the energy absorption and the dissipation characteristics of the crash process were identified from the overall and components.Then the section is mainly for researching the impact of the material failure and the connect failure which have different effects on the structure deformation,the force path and the energy absorption contribution.Comparing the crashing characteristics of different failure modes can discover the special influence regular of the different failure models.Discussing the boundary conditions and loading forms of different crash experiments can discover the differences of the test schemes.Finally,combining with the complex and varied impact conditions during the crash process can discover the influences of initial energy and the impact attitude on the crashing characteristics.All the research can provide a guidance for the future verification experiments.The research in this paper is of great significant for the crash experiment of the substructure under the cargo cabin and can also provide a reference for the design and verification of the transport aircraft.