Relaxation damping in oscillating contacts

If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect "relaxation damping". The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential motion with superimposed high frequency normal oscillations, the system acts as a tunable linear damper. Generalization of the results for macroscopically planar, randomly rough surfaces is discussed.Comment: 5 pages, 4 figure

Experimental Tests of Discrete Strengthened Elements of Machine-Building Structures

Computer simulation and bench tests of components and full-scale structures of internal combustion engine are performed in order to evaluate discrete and continual strengthening technology. The contact pressure distributions, friction coefficients, wear, roughness and hardness of the contacting surfaces of the tested machine parts were determined. The numerical characteristics that determine the effectiveness of such combined strengthening method are established. Conceptual fundamentals of discrete continual strengthening have been developed. Positive effects in the “load – contact – friction – wear” chain were found due to the proposed strengthening method. The positive effect of the coordination of micro and macroscale processes and states of loaded parts, which are strengthened by the discrete and continuous method, is also established. It is confirmed that the entire set of tribo-mechanical characteristics is improved with such strengthening, in contrast to traditional methods, an application of which results in improvement in some characteristics at the cost of the others

Relaxation damping in oscillating contacts

If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect "relaxation damping". The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed

A Dialogue about the Impacts of Mass Digitization Projects

There are many approaches to thinking about the economic impact of digitization initiatives such as the Google partnership with the University of Michigan. For example, there will be impact on the local economy, as Google hires staff and develops a presence in the area. Due to the high profile of this partnership, the State will be seen as more of a center of technological development and innovation, and will attract businesses in the technology sector. State government may change its approach to funding libraries and universities as a result of the mass digitization. Finally, the digitization itself will have a broad impact on national and even international economy, as this content becomes available. This partnership will spark changes in scholarly communications, publishing, and education, as discussed in other panels, and all of these issues will have economic aspects.University of Michigan University Library & National Commission on Libraries and Information Science; held March 10 and March 11, 2006 in Rackham Auditorium, University of Michigan, Ann Arbor.http://deepblue.lib.umich.edu/bitstream/2027.42/57306/6/mdp-economics.movhttp://deepblue.lib.umich.edu/bitstream/2027.42/57306/5/pohrt.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/57306/4/varian.pd