Friction coefficient is based on Amonton’s first law of friction, which states that the friction force, Ff, is directly proportional to the normal load, FN. A friction coefficient, µ, can then be defined by:

friction coefficient

Friction coefficients vary several orders of magnitude across material systems.


Friction coefficients are measured with a tribometer. Most modern tribometers apply a known normal load by mass or a measured normal load by an external loading system with a force transducer to measure the normal load. Friction forces are measured, and a friction coefficient can be determined. Schmitz et al. and Burris and Sawyer address the difficulties of measuring friction coefficient and the uncertainties associated with it [1, 2]. They conclude that misalignments with the transducer and the frictional and normal forces can produce errors, but these errors can be compensated by finding the instrument-related uncertainty of coefficient of friction and by performing sliding reversals to average out the error associated with the misalignment.

1. Schmitz, T.L., et al., The difficulty of measuring low friction: Uncertainty analysis for friction coefficient measurements. Journal of Tribology-Transactions of the Asme, 2005. 127(3): p. 673-678.
2. Burris, D.L. and W.G. Sawyer, Addressing practical challenges of low friction coefficient measurements. Tribology Letters, 2009. 35(1): p. 17-23.


Undergraduate Research Positions Available

Research Opportunities

Oportunity for hands on research experience.

Now Accepting Applications.

In the Tribology Laboratory, undergraduates will do experimental research focused on interfacial interactions of condensed matter. This includes studying the fundamental origins of friction, wear, surface deformation and adhesion on complex surfaces and materials ranging from cells to nanocomposites in environments ranging space to kilometers under water.

Active research includes analysis of materials that recently returned from the international space station, evaluating wear of dinosaur dental fossils, developing and patenting ultra-low wear polymer nanocomposites, studying and designing biocompatible and bio-inspired polymeric and hydrogel materials, and collaborating internationally on the physics of soft matter interactions. This research in tribology is at the intersection of mechanical engineering, materials science and surface physics.

Nanomechanical and Tribological Properties on Hadrosaurid Dinosaurs

Nanomechanical and Tribological Properties on Hadrosaurid

Prof. Greg Sawyer, Greg Erickson and Brandon Krick measured nanomechanical and tribological properties on hadrosaurid (duck-billed dinosaur) dental fossils from the American Museum of Natural History. Using custom instruments, we measured tissue hardness and wear rates that were preserved in the 65 million year old tooth. These properties are preserved in fossilized teeth because apatite mineral content is the major determinant of dental tissue hardness. Measured tissue wear rates were used to simulate the formation of hadrosaurid tooth chewing surfaces using a 3-D wear simulation. The simulation results in a surface profile nearly identical to a naturally worn hadrosaurid dental battery. The model revealed how each tissue (of differing wear rates) contributed to the formation of sophisticated slicing and grinding features in these reptiles tens of millions of years before mammals evolved analogous chewing capacity. This capacity to measure wear-relevant properties preserved in fossils provides a new route to study biomechanics throughout evolution. See Journal papers:
Science, October 5, 2012, pp.98-101.

Experiments back from the International Space Station

Space Tribometers and Samples back for analysis

Materials on the International Space Station Experiments Space Tribometerd

Materials on the International Space Station Experiments (MISSE) Space Tribometers were the first ever active tribometers directly exposed to the Low Earth Orbit Environment

The Tribology Laboratory at Lehigh University is under construction

The lab as of May 2013

The lab as of July, 3rd 2013

The main laboratory is located in Lehigh's Packard Laboratory.