The frictional temperature rises at the microcontacts of rough surfaces are analyzed by characterizing the surfaces as fractals and assuming Hertzian contacts of spherical asperity tips. The maximum temperature rise of a fractal surface domain in the slow sliding regime, where transient effects are negligible, is expressed as a function of thermomechanical properties, sliding speed, friction coefficient, real and apparent contact areas of the fractal domain, and fractal parameters. The distribution density function of the temperature rise at the real contact area is also determined based on the statistical temperature rise distributions of individual microcontacts and the maximum temperature rise of a fractal domain. This function characterizes the fractions of the real contact area subjected to different temperature rises, and can be used to analyze tribological interactions on dry and boundary-lubricated sliding surfaces.

The limitation of the fractal theory as applied to real surfaces is interpreted, and engineering surfaces are considered as a superimposition of fractal structures on macroscopic regular shapes by introducing the concepts of fractal-regular surfaces and multiple fractal domains. The effects of frictional heating at neighboring microcontacts are analyzed, and a simple solution of the temperature distribution is obtained for contact regions that are appreciably larger than a fractal domain. It is shown that the temperature rise at an elastoplastic microcontact does not differ significantly from that at an elastic microcontact of a similar geometry under the same load. The fractional real contact area subjected to temperature rises greater than any given value is represented by a complementary cumulative distribution function. The analysis yields that the average value and standard deviation of the temperature rise at the real contact area are 0.4 and 0.24 times the maximum temperature rise, respectively. The implications of the theory in boundary lubrication are demonstrated in light of results for ceramic materials.

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Thin flexible sheets of high-permeability FINEMET R foils encased in thin plastic layers have been used to shield various types of 20-cm-diameter photomultiplier tubes from ambient magnetic fields. In the presence of the Earth's magnetic field this type of shielding is shown to increase the collection efficiency of photoelectrons and can improve the uniformity of response of these photomultiplier tubes.