Development of a Sprag Wear Test Procedure for Evaluating the Antiwear Performance of ATF's

Friction and wear are extremely important issues in micromachined surfaces in design applications that allow rubbing. A polysilicon surface-micromachined inchworm device has been developed to obtain detailed in-situ information on these properties under well-controlled loading conditions. Here, we investigate the inchworm operational wear and the evolution of friction coefficient as a function of the number of imposed wear cycles. A test procedure was developed to monitor various functional parameters such as the travel distance of the inchworm under an imposed drag force for a fixed number of steps and the friction coefficient. While subject to this drag force, the travel distance decreased gradually until the foot of the device became permanently lodged in the grooves created by the wear-track. Meanwhile, it was found that the friction coefficient increased from 0.2 on a virgin surface to 3 when the accumulated number of wear cycles reached around 200,000. The friction test itself was found to interact with the wear processes. By minimizing the number of friction tests performed during the wear test, the operational life of the device was extended well beyond 700,000 cycles. Microscopic observation of the wear surfaces revealed that the early wear is characterized by the blunting of the sharp peaks on the poly silicon grains and then flattening of this fine wear debris on the surface. Evidence of plastic deformation was inferred by the spread of the wear debris over several grains. With increased number of wear cycles, material removal through scratches induced by the wear debris was observed. The device failure occurred due to a large volume of material removal (severe wear) in localized regions.

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Development of a Valve Train Wear Test Procedure for Gasoline Engine Oil

10.4271/940794 ◽

1994 ◽

Author(s):

Kenji Hanada ◽

Yasuhiro Murakami ◽

Yusuke Shoji ◽

Hisamoto Aihara ◽

Atsushi Hirose

Keyword(s):

Gasoline Engine ◽

Test Procedure ◽

Wear Test ◽

Valve Train ◽

Engine Oil

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Benefits from Computerized Adaptive Testing as Seen in Simulation Studies

European Journal of Psychological Assessment ◽

10.1027//1015-5759.15.2.91 ◽

1999 ◽

Vol 15 (2) ◽

pp. 91-98 ◽

Cited By ~ 10

Author(s):

Lutz F. Hornke

Keyword(s):

Measurement Error ◽

Computerized Adaptive Testing ◽

Test Procedure ◽

Adaptive Testing ◽

Parameter Estimates ◽

Simulation Studies ◽

Computerized Adaptive Test ◽

Item Banks ◽

Item Parameters ◽

General Reliability

Summary: Item parameters for several hundreds of items were estimated based on empirical data from several thousands of subjects. The logistic one-parameter (1PL) and two-parameter (2PL) model estimates were evaluated. However, model fit showed that only a subset of items complied sufficiently, so that the remaining ones were assembled in well-fitting item banks. In several simulation studies 5000 simulated responses were generated in accordance with a computerized adaptive test procedure along with person parameters. A general reliability of .80 or a standard error of measurement of .44 was used as a stopping rule to end CAT testing. We also recorded how often each item was used by all simulees. Person-parameter estimates based on CAT correlated higher than .90 with true values simulated. For all 1PL fitting item banks most simulees used more than 20 items but less than 30 items to reach the pre-set level of measurement error. However, testing based on item banks that complied to the 2PL revealed that, on average, only 10 items were sufficient to end testing at the same measurement error level. Both clearly demonstrate the precision and economy of computerized adaptive testing. Empirical evaluations from everyday uses will show whether these trends will hold up in practice. If so, CAT will become possible and reasonable with some 150 well-calibrated 2PL items.

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