Comparative assessment of implicit and explicit finite element solution schemes for static and dynamic civilian aircraft seat certification (CS25.561 and CS25.562)

摘要

Due to the competitive nature of airline industry and the desire to minimiseaircraft weight, there is a continual drive to develop lightweight, reliable andmore comfortable seating solutions, in particular, a new generation slimeconomy seat. The key design challenge is to maximise the “living space” forthe passenger, with strict adherence to the ‘Crash Safety Regulations’.Cranfield University is addressing the needs of airliners, seat manufactures andsafety regulating bodies by designing a completely novel seat structure coinedas “Sleep Seat”. A generous angle of recline (40 degree), movement of “SeatPan” along the gradient, fixed outer shell of the backrest, and a unique single“Forward Beam” design distinguishes “Sleep Seat” form current generationseats. It is an ultra-lightweight design weighing 8kg (typical seat weight is 11kg).It has to sustain the static (CS 25.561) and dynamic (CS25.562) “Emergencylanding” loads as specified by “Certification Specifications (CS).Apart from maintaining structural integrity; a seat-structure must not deform,which would impede evacuation, should absorb energy so that the loadstransferred to Occupants are within human tolerance limits and should alwaysmaintain survivable space around the Occupant. All these parameters, whichincrease a life-expectancy in a ‘survivable’ crash, can be estimated using eitherexperimental testing or virtual simulation tools such as “Finite Element Analysis(FEA). Design of the “Sleep Seat” is still in its conceptual phase and thereforeexperimental testing for all the design iterations involved is unrealistic, given ameasure of the costs and timescales involved.Therefore focus of research is to develop practical and robust FEmethodologies to assess static and dynamic performances of a seat-structureso as to compare different design concepts based on their strength, seatinterface loads (a limit defined by strength of aircraft-floor), maximumdeformations and cross-sectional forces ... [cont.].