New United States Army Centrifuge Structurally Analyzed with the Help of Algor Software

The centrifuge, diagrammed above, is located at the U.S. Army Corps of Engineers Waterways Experiment Station in Vicksburg, Mississippi. It is currently being commissioned and will be used for geotechnical, structural, hydraulic, environmental, cold regions and coastal engineering research.

Gary Butler of the U.S. Army Corps of Engineers in Vicksburg, Mississippi, has been using Algor software as part of ongoing stress analysis of the new U.S. Army Centrifuge.

The U.S. Army Centrifuge has a radius of 6.5 meters a design performance envelope that includes a maximum payload carrying capacity of 8,000 kg (17,600 lb) at 143 g and 2,000 kg (4,400 lb) at 350 g. At maximum g-levels, this centrifuge is designed to operate at speeds of 240 RPMs while maintaining the safest of operating conditions.

The U.S. Army Centrifuge and its laboratory facility will be operated by the engineers at the Waterways Experiment Station (WES), and will be used for geotechnical, structural, hydraulic, environmental, cold regions and coastal engineering research.

The Testing Platform

A critical component of the U.S. Army Centrifuge is its swinging platform. The platform's function is to carry the testing apparatus during centrifuge operation. As enumerated earlier, these payloads may reach masses up to 8000 kg. During centrifuge operation, the force transmitted to the platform from the payload increases proportionally with the rotational g-level.

Due to these enormous forces, a routine structural stress analysis of the platform is performed before most tests. A finite element model of the platform was developed to enable WES engineers to make a quick evaluation of its structural integrity under specific loading conditions before any centrifuge testing begins. Results of all analyses are documented and stored for future reference.

The centrifuge platform is analyzed for each experiment. The picture to the right shows the complete platform model. On the left is a quarter section analyzed with appropriate boundary conditions.

Physical Modeling

The Waterways Experiment Station has been involved in the use of centrifuge testing for several decades. Initially, centrifuge testing was applied primarily in the area of weapons effects, but has since been employed to assess a variety of engineer problems such as liquification, erosion and earthquakes.

For example, scientists construct testing packages that contain scaled models of the structure in question. These packages may also contain soil, rock and water. The centrifuge experiment may replicate what would happen to the structure during an earthquake or embankment failure. The engineers can then extrapolate to make predictions about real-world cases. Other experiments may be conducted to determine how long pollution may take to "migrate" into a water source, or the rate at which a coastline erodes.

In many cases, full-scale testing of an environmental system is expensive and time consuming. Centrifuge testing offers a feasible alternative to this process by scaling the important factors such as size and time.