PERFORMANCE OF INDUSTRIAL FLUIDLASTIC™ MOUNTS AND FEASIBILITY FOR HELICOPTER SEAT APPLICATION

Open Access
Author:
Santo, Angela N
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Christopher Rahn, Thesis Supervisor
  • Mary I Frecker, Honors Advisor
Keywords:
  • helicopter
  • fluidlastic
  • helicopter seat
  • whole body vibration
  • pilot injury
Abstract:
Negative health and performance effects are becoming increasingly important issues attributed to excessive vibrations in helicopter seats. Foam seat cushions are currently used for vibration reduction, but to further resolve these issues other methods of vibration mitigation are being explored. Fluidlastic™ technology is used in many other vibration applications due to its tunable performance at desired frequencies of operation. Industrial Fluidlastic™ mounts, designed as cab mounts in semi-trucks, provide high damping at one tunable frequency along with low damping and superior isolation at a different tuned frequency. In this thesis, the performance of industrial Fluidlastic™ mounts is compared to the performance of foam cushions currently used on helicopter seats. The results are assessed at the frequencies of interest for a Sikorsky Blackhawk helicopter, mainly four times the blade passage frequency (4/rev = 17.2 Hz). A supplemental frequency of interest is the natural frequency of the human spine (10 – 12 Hz) because excessive vibrations at this frequency could be the cause of some of the negative health effects. An experimental test stand is designed and fabricated to test the dynamic response of the mounts and the seat cushion. The test stand consists of a Ling shaker, two load cells that measure input and output force, and a LabVIEW control and data acquisition system. It is found that the mount offers a nearly 250% improvement over the cushion alone at the mount’s isolation frequency, but the cushion performs better near the spinal natural frequency range. Models are developed and validated with the experimental data to determine the generalized behavior of the Fluidlastic™ mount and the cushion, and allow predictions and comparisons of performance at different preloads, internal dimensions and mount characteristics. From these models, a fluid mount redesign is proposed in order to tune the mounts to isolate vibrations at the Blackhawk 4/rev frequency and increase damping at the spinal natural frequency range. It is determined from this research that Fluidlastic™ mounts are a viable method of helicopter seat vibration reduction and should be further investigated.