CCEFP Researchers Develop Novel Model of Rod Seals to Predict Performance, Especially Leakage of Hydraulic Fluid

Achievement date: 
2013
Outcome/accomplishment: 

Researchers at the Center for Compact and Efficient Fluid Power (CCEFP), an NSF-funded Engineering Research Center (ERC) headquartered at the University of Minnesota, have focused on the important seals between rods and housings of linear hydraulic actuators, which are critical elements in a hydraulic system. The researchers developed a numerical viscoelastic model that can predict key seal performance characteristics, especially leakage and friction. (Viscoelastic materials exhibit both viscous and elastic characteristics when undergoing deformation.)

Impact/benefits: 

This new model provides both a tool and physical understanding that enable development of seals to eliminate or substantially reduce leakage from fluid-power components, such as actuators, valves, and pumps. Benefits to the fluid-power industry and to the environment are significant.

Explanation/Background: 

It is widely recognized that leakage of hydraulic fluid into the environment must be significantly reduced or eliminated. Rod seals are intended to prevent leakage, but until recently the fundamental physics of seal operation have not been well understood. Prior to this model, seals were developed through empirical means, using trial-and-error techniques. Previous models treated the seal material as elastic, reacting instantaneously to changes in the sealed pressure within the actuator. However, CCEFP researchers found that the polymeric materials used for seals are viscoelastic and have a delayed reaction to pressure changes. Because the seals have memory, their behavior depends on past history. Viscoelastic effects are taken into account in the new model.