Affiliations: Mechanical System Laboratory, School of Mechanical
Engineering, Federal University of Uberlandia, Av Joao Naves de Avila 2121,
Campus Santa Monica, Bloco 1M, Uberlandia, MG, 38400-902, Brazil | Tribology and Materials Laboratory, School of
Mechanical Engineering, Federal University of Uberlandia, Av Joao Naves de
Avila 2121, Campus Santa Monica, Bloco 1M, Uberlandia, MG, 38400-902,
Brazil
Abstract: When the surfaces of two elastic bodies present relative motions
under certain amount of contact pressure the mechanical system can be unstable.
Experiments conducted on elastic bodies in contact shown that the dynamic
system is self-excited by the non-linear behavior of the friction forces. The
main objective of this paper is to estimate the friction force using the
vibrations signals, measured on a reciprocating wear testing machine, by the
proposed non-linear signal analysis formulation. In the proposed formulation
the system global output is the sum of two outputs produced by a linear path
associated in parallel with a non-linear path. This last path is a non-linear
model that represents the friction force. Since the linear path can be
identified by traditional signal analysis, the non-linear function can be
evaluated by the global input/output relationships. Validation tests are
conducted in a tribological system composed by a sphere in contact with and a
prismatic body, which has an imposed harmonic motion. The global output force
is simultaneously measured by a piezoelectric and by a piezoresistive load
cells. The sphere and prismatic body vibrations are measured by a laser Doppler
vibrometer and by an accelerometer respectively. All signals are digitalized at
the same time base and the data is transferred to a microcomputer. The
non-linear signal analysis technique uses this data to identify the friction
force.
Keywords: Non-linear signal analysis, friction force identification, wear, vibration
