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Four-Ball Wear Test: ASTM D 2266 describes a test method using three hard steel balls in a locked position. A fourth ball is rotated against the three stationary balls, producing a wear scar on each of the three balls, the average wear scar diameter. This test is run at light loads. Seizure or welding does not occur.

Four-Ball EP Test: ASTM D 2596 describes a similar test as the Four-Ball Wear Test except that the loads are much higher. The load at which the balls weld together is referred as the weld load. EP Lubricant additives result in a high load-carrying ability.
 Berekening van de contact temperatuur als gevolg van wrijving1.
 F N K1 W/mK
 n rpm K2 W/mK
 D mm k2 10-6 m2
 µ  H GPa
  (default waarde kogellagerstaal)
 F N  v m/s  r mm
 Ar /An  rj 10-6 m    
 dTbulk °C  dT'flash °C  dT °C
1Ashby, M.F., Abulawi, J., Kong, H.S., 1991, "Temperature maps for Frictional Heating in Dry sliding", Tribology Transactions, Vol.34, Number 4, October 1991, pp577-587.
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