page_title: Stribeck curve
section_title: History
hierarchical_section_title: Stribeck curve / History
caption_attribution_description: Typical “Stribeck” curves obtained by Martens showing coefficient of friction as a function of pressure in kgf/cm² (even if it looks like kg/mm²) at v = 0.5 m/s using water quenched, hardened steel shaft 99.6 mm diameter and 70.2 mm long, running in bearing shell made from “Rotguß” (red brass, a Cu-Sn-Zn cast alloy) with “Rüböl” (rape oil). The parameter lines represent temperature in °C.
context_page_description: The Stribeck Curve is a fundamental concept in the field of tribology. It shows that friction in fluid-lubricated contacts is a non-linear function of the contact load, the lubricant viscosity and the lubricant entrainment speed. The discovery and underlying research is usually attributed to Richard Stribeck and Mayo D. Hersey, who studied friction in journal bearings for railway wagon applications during the first half of the 20th century; however, other researchers have arrived at similar conclusions before.
context_section_description: Richard Stribeck's research was performed in Berlin at the Royal Prussian Technical Testing Institute (MPA, now BAM), and his results were presented on 5 December 1901 during a public session of the railway society and published on 6 September 1902. Similar work was previously performed around 1885 by Adolf Martens at the same institute, and also in the mid-1870s by Robert Henry Thurston at the Stevens Institute of Technology in the U.S. The reason why the form of the friction curve for liquid lubricated surfaces was later attributed to Stribeck – although both Thurston and Martens achieved their results considerably earlier – may be because Stribeck published his findings in the most important technical journal in Germany at that time, Zeitschrift des Vereins Deutscher Ingenieure (VDI, Journal of German Mechanical Engineers). Martens published his results in the official journal of the Royal Prussian Technical Testing Institute, which has now become BAM. The VDI journal provided wide access to Stribeck's data and later colleagues rationalized the results into the three classical friction regimes. Thurston did not have the experimental means to record a continuous graph of the coefficient of friction but only measured it at discrete points. This may be the reason why the minimum in the coefficient of friction for a liquid-lubricated journal bearing was not discovered by him, but was demonstrated by the graphs of Martens and Stribeck.
  The graphs plotted by Martens show the coefficient of friction either as a function of pressure, speed or temperature (i.e. viscosity), but not of their combination to the Hersey number. Schmidt attempts to do this using Marten's data. The curves' characteristic minima seem to correspond to very low Hersey numbers in the range 0.00005-0.00015.
caption: A typical Stribeck curve obtained by Martens[6]
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