The Influence of the Structural Stiffness of Dynamic Test Fixturing on Seat-to-Airframe Interface Loads for Lightweight Wall-Mounted Crashworthy Troop Seats

摘要

The influence of structural stiffness of the wide multi-seat fixture and the effects of specific placement of the seat on the fixture as well as the fixture on the test sled became an important issue for NAVAIR when the results of initial multi-seat tests of wall-mounted troop seats indicated a marked difference in magnitude of the reaction loads measured at the seat-to-airframe interface dependent upon whether the seat was located on the left or right side of the fixture. NAVAIR developed and conducted an experimental test series to quantify the magnitude of the effects of the fixture design and occupant placement. In addition, finite element modeling and modal analysis of the fixture as well MADYMO? modeling and simulation of the seat and occupant were used to study and analyze the results of the test series and the possible effects of fixture stiffness of the measured reaction loads at the seat-to-airframe attachments. The effect of load variance with seat position on the side-by-side fixture was successfully reproduced in test. Based on the results of testing and analysis, this variance was determined to have been an affect of the asymmetries in the side-by-side fixture design coupled with the fixture-to-sled anchor plate mounting configuration. These asymmetries resulted in a corresponding asymmetric structural modal response when the sled was impacted by the force of the HYGE piston during the conduct of the dynamic test events. When the mass to fixture weight ratio was too low, the response of the fixture was such that for the particular design and construction of the tested seat and restraint system, failures occurred within the design envelope of the seat.