Four-ball wear test machine

A four-ball wear test machine is used to determine a coefficient of friction of lubricants." Three metal balls having diameter of 12.7 mm are clamped together and the fourth ball of the same diameter is rotated on these balls under pressure of 98.1 N with a speed of 600 rpm for 10 min. The temperature of the test lubricant is 75°C. At the end of the 10 min interval, the coefficient of friction is measured. The measurements are repeated for successive 10 min intervals until frictional trace indicates incipient seizure. 

ASTM D5183-05(2011) Standard Test Method for Determination of the Coefficient of Friction of Lubricants Using the Four-Ball Wear Test Machine. 

Some of these carboxylic acid salts, such as 3-iodo-4-methosxybenzoic acid, have been reported to have load-bearing capacities in an aqueous solution of 0.98 (megapascal) MPa at 200 rpm with a four-ball type lubrication oil testing machine [4], A four-ball wear test (ASTM D-4172) is a test used in the petroleum industry that determines the wear characteristics of a lubricant. In this test, three balls are clamped together, covered with the lubricant being analyzed, and rotated with a fourth ball under a load. Inputs can be varied by temperature, pressure, revolutions per minute, and duration. 

The flash temperature is also related to types of tribomachines. Each type of machine has its specific type of contact geometry and style. For example, on a four-ball lubricant testing machine, the flash temperature is totally different from that of a sliding pin on disk. The A7max temperature for a standard four-ball wear contact may be calculated from a Blok equation 18... 

Wear spot diameter under conditions of hydrodynamic friction and critical seizure load were determined on a four-ball friction testing machine with steel balls of 0.017 mm diameter and a rotation speed of 1 500 rev/min [2]. 

When tested in the four-ball machine, solutions of sulfur in petroleum oils of moderate viscosity or in white oil raise the critical load for the onset of severe, destructive wear, which is designated as "antiseizure" action in the technological idiom of the four-ball test. Davey [54] found a significant increase in the critical initial seizure load from 834 N (85 kg) for a petroleum base oil to 1275 N (130 kg) for elemental sulfur dissolved in the oil. Sakurai and Sato [55] observed a 3.2-fold increase in the load-wear index (mean Hertz load) for a 0.5 weight-percent solution of elemental sulfur relative to that of the uncompounded white oil. The load-wear index is a specialized result of the four-ball test that can be taken as indicative of the average antiseizure behavior of the lubricant. Mould, Silver and Syrett [56] reported a load-wear index ratio of 3.08 for 0.48% sulfur in white oil relative to that of the solvent oil, and also an increase in the initial seizure load from 441 N to 637 N (45 kg to 65 kg) and in the 2.5-second seizure-delay load from 490 N to 833 N (50 kg to 90 kg). 

A direct comparison of the additive behavior of neutral phosphates and phosphites in the four-ball test under relatively mild conditions is reported in the work of Goldblatt and Appeldoorn [43]. The data shown in Table 11-15 are their findings for 3% of the additive dissolved in a heavy white oil and run in the four-ball machine for 15 minutes at 1200 rpm. In wet air all the phosphates show about the same wear im.provement under a 10 kg load over wear with the base oil in dry argon there is no significant improvement. Tributyl phosphite functions consistently poorer in the wear test than either triallyl or triphenyl phosphite, whose behavior is not significantly different from that of the corresponding phosphates. All the additives improve the performance of the... 

The relation between structural types in silicones and wear or friction control has been studied from several points of view. Brown [16] prepared a series of methyl alkyl polysiloxanes whose properties are shown in Table 17-8. The results of their wear testing in the four-ball machine is seen in Fig. 17-5. The sharp drop in wear as the size of the... 

The tribological properties of Cu nanoparticles were determined on an MRS-lOA four-ball test machine at 1450 rpm in ambient conditions. The 12.7-mm-diame-ter balls used in the test were made of bearing steel (composition 0.95%-1.05% C, 0.15%-0.35% Si, 0.24%-0.40% Mn, <0.027% P, <0.020% S, 1.30%-1.67% Cr, <0.30% Ni, and <0.025% Cu) with a Rockwell hardness (Rc) of 61-64. The base oil was chemically pure liquid paraffin (LP), which has a distillation range of 180°C-250°C and density of 0.835-0.855 g/cm. Before each test, the balls and specimen holders were ultrasonically cleaned in petroleum ether (normal alkane with a boiling point of 60°C-90°C) and then dried in hot air. At the end of each test, the wear-scar diameters (WSD) of the three lower balls were measured on a digitalreading microscope to an accuracy of 0.01 mm. Then the average wear-scar diameter from the three balls was calculated. 

FIGURE 10.6 (See color insert following page XXX.) Effect of load on wear-scar diameter (four-ball test machine additive concentration in liquid paraffin (LP) 0.1% speed 1450 rpm test duration 30 min). 

---