Design of indenter rig for measuring seat cushion dynamic stiffness

Abstract

Vibration induced on the car floor is transmitted to human body through seat structure, affecting both comfort and health. Seat structure components are mainly comprised of rigid frame and seat cushion. Previous studies have shown and suggested that the indenter is preferable option for replacing human subject in seat vibration experimental work when assessing the seat cushion dynamic characteristics. Indenter method offers more control, cheaper and less time intensive compare to other methods such as passive dummies, sandbag, and rigid mass. This paper proposes a design of indenter testing rig to measure the dynamic stiffness of seat cushion material. The rig was designed to operate at frequencies between 2 to 100 Hz and applied load of maximum 50 kg. The size of bed is proposed to be able to fit the size of standard sedan car seat. Modal analysis was conducted on indenter rig structure design to ensure the suitability of the design. Structural frame was designed to fit the mounting of the shaker used in this study. Six modes shapes were extracted from the modal analysis and its corresponding frequencies ranging from (121.63Hz – 507.3Hz). The lowest natural frequency for the proposed design of indenter testing rig occurs in the first mode of vibration with peak displacement of 174.04mm. From this result, it can be concluded that the proposed design met the criteria set and produces a fundamental frequency of greater than the operating range of the rig.