Magneto-Rheological Fluid Damper Device design with flexible and superior damping capabilities using simple and inexpensive manufacturing


The Composite and Intelligent Materials Laboratory (CIML), led by Faramarz Gordaninejad, within the University of Nevada, Reno Mechanical Engineering Department focuses on the fundamental understanding of the behavior of advanced materials such as magneto-rheological fluids and magneto-rheological elastomers, as well as the study of electromechanical systems performance for various engineering applications. The CIML also designs, fabricates, and tests prototypes utilizing these materials for shock absorption and vibration control. The below covers six related patents on magneto-rheological fluid shock absorption devices and their features.

Technology Summary

A magneto-rheological fluid (MRF) is a smart material that can change its viscosity, or thickness, in the presence of a magnetic field. Shock absorbers, or dampers, that use MRF are used in the vibration control field because they require no moving internal parts to control damping, reducing the mechanical complexity and cost of the device. Current MRF dampers have several limitations including magnetic requirements which require ferrous materials (containing iron) to be used, making the damper too heavy for weight-sensitive applications. Conventional MRF dampers also have restrictively small dimensional tolerances in the region where the magnetic field is applied, making for difficult and expensive manufacturing methods.

The UNR MRF damper design has increased damping capabilities, can be easily manufactured at a low cost, can be light weight, has a greater flexibility in the design of the damper, and has a fail-safe mode of operation in the event of an electrical system failure. The UNR damper design consists of a moveable piston that contains an MRF, which is housed inside of a chamber. Magnets are attached within the chamber and create a magnetic field which increases the viscosity of the MRF, therefore resisting the flow of the MRF through the passages, and in turn increasing the damping force of the device.

The design includes passages on the outside of the piston which simplify manufacturing and lowers costs. This feature also negates the need for ferrous components to activate the MRF – it allows for a damper constructed from non-magnetic materials (such as aluminum, ceramic, or plastic), ferrous materials, or a combination of both – making a significantly lighter damper. This feature was constructed and tested, and the experimental results provided an increase of more than 100% in damping force (from 200 lb. to 520 lb.).

Another feature of the invention comprises a disk shaped space within the MRF flow path to increase the surface area on which the magnet can change properties of the MRF, again resulting in a much higher damping force.

In a closely related feature, the passages contain two valving regions within the piston. Two valving regions provide greater control of the MRF and potentially enhanced performance compared to devices having only one valving region. Increasing the surface area of the passage can increase the damping capabilities of the device. Even with no electrical current applied to the magnet(s), this feature can still provide significant viscous damper forces across the device, providing a fail-safe mode of operation in the event of an electrical system failure.

Another option is adjustably activated magnets located at various positions along the axial length of the device. These can enhance or modify damper performance by specifically increasing the magnetic field strength at differing physical locations along the damper or along varying lengths of the MRF chamber inside the damper.

The variable volume liquid spring provides for a semi-active device that can dissipate and store energy. As an example, this functionality provides a non-symmetric stroke force where a large energy dissipation stroke can be followed with a softer rebound.

The valve design also provides a low-power MRF annular valve that can work in series or in parallel to a fluid system, internally or externally. The valve facilitates a compact design that requires low electrical input current through a unique configuration of materials and geometry. It does not rely on any mechanical moving parts and manufacturing tolerances, making it inexpensive and less prone to maintenance complications. This MRF valve that was developed and tested validated the design benefits of this device.

The patented UNR MRF damper design can be made of a flexible, resilient, durable, and tough material with high resilience to tearing, abrasion, and puncture. This material enables it to withstand great tension and compression forces both from the interior and exterior of the body, while also having the ability to form into multiple shapes and forms to fit the damper employing the MRF. This design aspect reduces wear on moving parts and better manages variable external forces such as vibration.

Potential Applications

  • Vibration mitigation and energy absorption devices to protect civil infrastructure such as buildings and the decks of bridges under natural hazards, man-made hazards and/or seismic events.
  • Shock absorbers in mechanical systems such as bicycles, motorcycles, automobiles, trucks, trains, airplanes, military transport vehicles, exercise equipment, and sports equipment (i.e. landing gear).
  • Vibration isolation and shock mitigation for laser/optics systems and equipment such as optical tables, bench top platforms, breadboards, support systems, and individual mounts.
  • Vibration control of automation and testing equipment in the semiconductor manufacturing industry, including active- and passive-air isolation workstations. Super isolated workplaces protected from vibrations and disturbances for the precise assembly of sensitive components used in aerospace or bioscience projects.

Opportunity UNR is seeking expressions of interest from parties interested in collaborative research to further develop, evaluate, or commercialize this technology.

IP Status Controllable Magneto-rheological Fluid Device/Damper US Patent No.: 6,471,018; 6,510,929; 6,823,895; 6,971,491; 7,364,022; 7,422,092.

Patent Information:
For Information, Contact:
Dan Langford
Technology Commercialization, Manager
University of Nevada, Reno and Desert Research Institute
Faramarz Gordaninejad
Shawn Kelso