Apparatus

The apparatus was deisigned to use simple ceramic specimens while reproducing most of the operating conditions of a ring/cylinder interface at temperatures to 650 C. The specimen configuration is shown in Figure 1. The two cylinder specimens are flats measuring 13 x 32 x 125 mm. One flat is fixed, while the other is mounted on a slideway to permit applying contact loads

up to 50 N/mm and is adjustable to maintain parallelism between the flats. For a comparison of ring contact loading, the peak ring loading on a typical diesel engine is approximately 35 N/mm. The ring specimens are 19 mm long and 3.2 mm thick. A 32 mm-radius crown is ground on the ring specimen to provide a cylinder-on-flat initial contact geometry. The ring specimen holders are pivoted at the center to provide alignment along the length of their contact surfaces. A chamber around the specimens is used to control the atmosphere and temperature. The exhaust from a 4.5 kW diesel engine is passed through the chamber to provide an atmosphere similar to that of actual service. The ring specimens are attached to one of thé pistons of a motored 4-cylinder engine to provide the reciprocating motion. The stroke is 106 mm, and the speed is variable from 500 to 1500 rpm. Dynamic friction is calculated from the current applied to the electric clutch on the variable speed drive. A summary of the testing conditions is presented in Table 1.

Table 1. Summary of Testing Conditions

Sliding Contact:

Dual flat-on-flat

"Cylinder" Specimens:

13 x 32 x 127 mm

"Ring" Specimens:

3.2 x 19 x 19 mm

"Ring" Crown Radius:

32 mm

Motion:

Reciprocating,

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