ISSN: 0090-3973
Page Count: 6

The Nonvibrating Kelvin Probe and Its Application for Monitoring Surface Wear

Zanoria, ES
Post-doctoral research associate,Oak Ridge National Laboratory, Metals and Ceramics Division,TN,

Hamall, K
Graduate research assistant,The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology,GA,

Danyluk, S
Graduate research assistant,The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology,GA,

Zharin, AL
Belarussian Powder Metallurgy Association,

(Received 18 March 1996; accepted 23 August 1996)

Abstract

This paper reports on the design and development of the nonvibrating Kelvin probe that could be used as a noncontact sensor for tribological damage. This device detects surface charge through temporal variation in the electron work function of a material. Experiments are performed to demonstrate the operation of the probe on a rotating aluminum shaft. The probe, made of lead, is placed adjacent (<0.5-mm distance) to the shaft. The two surfaces, which are electrically connected, form a capacitor. Benchmark experiments on the variation of the work function with changes in surface chemistry were performed by coating a segment along the shaft circumference with a colloidal silver paint. As the shaft rotated, the probe senses changes in the contact potential difference with the shaft surface, due to the compositional variation. The temporal variation in the contact potential difference induces a current in an external electrical circuit. This current is amplified and converted to a voltage signal. The magnitude of the signal decreases asymptotically with the electrode-shaft distance and increases linearly with the rotational frequency, as expected. These results are consistent with the theoretical. Preliminary tests to detect mechanical surface damage, using the probe, were also done. These results show that the Kelvin probe can distinguish geometrical features on the surface.

Keywords:
surface wear, work function, Kelvin probe

Paper ID: JTE11484J
DOI: 10.1520/JTE11484J
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