Fretting wear, tests

A further level of complexity arises because fretting wear tests show wear constants, k, which appear to vary with slip amplitude. However, it seems possible that, in fact, k is independent of the true slip amplitude but that workers may have erroneously neglected the effects of friction and elasticity on the actual slip within the contact. This would give the trend shown by Vingsbo and Soderberg [16] and by Baker and Olver [17]. Further experiments would be needed to resolve this point. 

ASTM International has a number of standard test methods for erosion, cavitation, and fretting wear. 

Conventional wear test configurations can be adapted to fretting. Ball-on-flat, block-on-ring, and crossed cylinders can be modified so that the sliding motion can be made oscillatory and the amplitude small (less than 100 tm). 

ASTM D 4170-97 Standard Test Method for Fretting Wear Protection by Lubricating Greases, Annual Book of ASTM Standards, Vol. 05.02, ASTM International, West Conshohocken, PA. 

Fretting wear D4170 Test Method for Fretting Wear Protection al Lulnicating Greases Mass 1< ratio... 

The friction coefficient and the specific wear rate of the nanocomposites were determined by sliding wear tests on a block-on-ring apparatus against a 100 Cr 6 (German standard) steel ring as the counterpart. A pressure of 1 MPa and a velocity of 1 m/s were used over a duration of 20 h for each sample. Additional wear tests of the composite systems were carried out under fretting test conditions against a ceramic ball as the counterpart. 

The uncertainties in calculating specific wear rates from in-service data are discussed, as well as the data from laboratory tests which attempt to simulate particular modes of wear (eg abrasion, fretting). 

FIGURE 19. Volumetric wear at ball, disk and total wear, determined in Fretting tests with HIPed Si3N4 ball against Si3N4-BASand HIPed Si3N4 disks for comparison ... 

The above test methods do not exactly simulate the actual fretting conditions. The surface damage produced by the test should be compared to the damage on parts damaged in service. If there is significant difference between scar morphologies, the wear mode may not be correctly simulated in the test. Corrections can be made in contact geometry, contact stress, and amplitude and velocities of movement. 

Standard Test Method for Measuring Fretting Corrosion of Osteosynthesis Plates and Screws Standard Test Method for Cavitation Erosion Using Vibratory Apparatus Standard Terminology Relating to Wear and Erosion... 

Endurance tests in a High Pressure Loop to examine wear-out and fretting issues. 

Of the earlier experiments, 3 and 4 were tests of wire wrapped fuel pins which featured In the fuel design at that time. Experiment 3 failed by local dryout downstream of a wire wrap at a position Just above the peak rating. This, together with adverse heat transfer test results and fretting behaviour, led to the change to wear pads and spacer grids. Most of the more recent irradiations, apart from experiment 12, have used NH, dosed coolant. No excessive cruddlng has been seen In any of the series, and deposition appears to... 

The present reference design has shown no evidence of any fretting damage on wear pads in tests up to 2000 hours. Early tests showed some distortion of grid ferrules and these were strengthened (thickness Increased from 0.010 in... 

Figure 9, Wear rate of epoxy/Si02 nanocomposites vs. particle content (amine catalyst) (a) fretting test, (b) block-on-ring test.

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