  The Tribomechadynamics Research Challenge (TRC) was a blind prediction of the
vibration behavior of a thin plate clamped on two sides using bolted joints.
The first bending mode's natural frequency and damping ratio were requested as
function of the amplitude, starting from the linear regime until high levels,
where both frictional contact and nonlinear bending-stretching coupling become
relevant. The predictions were confronted with experimental results in a
companion paper; the present article addresses the experimental analysis of
this benchmark system. Amplitude-dependent modal data was obtained from phase
resonance and response controlled tests. An original variant of response
controlled testing is proposed: Instead of a fixed frequency interval, a fixed
phase interval is analyzed. This way, the high excitation levels required
outside resonance, which could activate unwanted exciter nonlinearity, are
avoided. Consistency of testing methods is carefully analyzed. Overall, these
measures have permitted to gain high confidence in the acquired modal data. The
different sources of the remaining uncertainty were further analyzed. A low
reassembly-variability but a moderate time-variability were identified, where
the latter is attributed to some thermal sensitivity of the system. Two
nominally identical plates were analyzed, which both have an appreciable
initial curvature, and a significant effect on the vibration behavior was found
depending on whether the plate is aligned/misaligned with the support
structure. Further, a 1:2 nonlinear modal interaction with the first torsion
mode was observed, which only occurs in the aligned configurations.
