The purpose of this research project was to examine the effects of normal force and to conduct a preliminary investigation into the effects of changes in circuit power on contact resistance under fretting conditions. Examination of changes in normal force was undertaken to verify the correct operation of a fretting machine. An initial step toward understanding the effects of increased voltage is accomplished by comparison of contact resistance under fretting conditions at two different electrical power levels. The lower power condition was supplied by a four wire milliohmeter, passing a maximum current of 10 μA at 1000 Hertz using an open circuit voltage of 20 milliVolts. A higher power condition used 10 Volts to pass 0.2 Amperes through a 50 Ω resistor in series with the point of contact. Under fretting conditions, an increase in normal force resulted in a lower and more stable contact resistance pattern. At the higher power condition, an accelerated increase in contact resistance was observed as fretting cycles increased. An examination of the wear tracks produced under the higher power condition with a white light profilometer revealed an unusual surface morphology.
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