Test Method for High Cycle Friction Testing  Typical loads and speeds use d in the testing were se t to force and speed levels that corresponds to the  drag that the friction materials would experience during a sliding transition. During a clamp move, the friction materials experience force levels up to 6000 N but with the expectation that no sliding will occur.  To characterize the materials’ initial hardness and surface roughness, both values were measured before  any wear testing and recorded for all specimens. DSM requested eighteen material pairs to be tested by USF listed in Tables 1A and 1B.  The interaction of the friction pairs in a piezoelectric motor was simulated using a Universal MicroTribometer with custom fixtures. The lower test specimen (50x12x1.2 mm 3) and fixture were fixed. The  upper test specimen (25x12x1.2 mm3) and fixture provided normal loading and reciprocating sliding  motion using the upper vertical and lateral positioning systems of the tribometer.   Each pair was subjected to the following test procedure:  1. Clean test surfaces with acetone before each test  2. Photograph test specimens and measure surface roughness of test specimens  3. Measure initial friction force with sliding velocity of 0.5mm/s and sliding displacement of 2mm for 3  steps with 1 sec rests in between steps  4. Perform a test sequence on the tribometer for N cycles where N is 100, 500, 10,000, 50,000,  100,000, 200,000, or 300,000, until the test is sto pped due to failure or poor friction response.  a) Set upper specimen near center of contact area of lower specimen  b) Set normal contact force to 44.5 N  (10 lb)  c) Move upper specimen to the left 5 mm at sliding velocity of 7.5 mm/s d) Move upper specimen to the right 5 mm at 7.5 mm/s  e) Repeat steps c thru d for N-1 times  5. Photograph test specimens, measure surface roughness and assess wear of test specimens  Test Results for High Cycle Friction Testing An example of a typical friction coefficient versus time plot for a solid Croblox /g147 sample against a 52100  steel sample is shown in Figure 8. Contrary to conventional thought, each plot in Figure 8 indicates that  the initial breakaway friction (static) is less than the moving friction (dynamic). DSM attributes this  characteristic to the very smooth nature of the interfacing surfaces and their lack of mechanical interaction. Tables 1A and 1B show the te st results for the coated friction in terface materials and solid friction  interface materials respectively. The tungsten carbide (WC) coated specimens against either a Croblox /g147 gage block or a ceramic gage block showed very low friction. The Croblox /g147 is a chromium carbide  material from Starrett Gage Company. The diamond like carbon (DLC) coating also indicated very low  friction against the ceramic gage block. These tests were therefore cancelled after only a few cycles. The  response of the other coated material friction pairs in Table 1A indicate that within 40,000 cycles, the  coating had abraded enough that is was decided to stop the test. The coatings were generally 2 to 5 microns (80 to 200 microinch) thick. Therefore, surface roughness on the order of 2 microns (80  microinch) is an indication that the coating thickness might be completely worn away. Generally, after  abrasion on the surfaces exceeded 2 microns (80 microinch) the test was stopped. The trends indicate  that the surfaces with higher initial coefficient of friction (COF) had greater abrasion after fewer cycles.  8