Fig.8. Fan blade fatigue test system.
The essence of test was to measure the strain based on the stress and
strain values of different measuring points on the structure surface.
The real-time stress values could be calculated through LabVIEW that was
a graphical program compilation platform developed by America national
instrument company NI, and NI dynamic and static stress and strain
analysis system.
In order to determine the position of the measuring point, the strain
should be selected in the position of greater stress or easy to damage.
In this paper, the stress state of the impeller structure was calculated
by using the finite element method, and partitioned the fan. To ensure
the accuracy of the measured data, the root paint of the blade was
removed. Finally, six of the blades were selected to stick strain gauge
and the strain gauge was pasted on the root of the blade to measure the
stress in the X-direction, as shown
in Fig. S2.
The other end of the high-temperature wire joined up the terminal of the
rotor side of the high-speed slip ring. Meanwhile, the terminals of the
corresponding stator side were connected to the wire, and attached to
the response channel of the NI scxi-1317 junction box in a uniform
order. Then, the junction box was installed into the NI pxi-6224 strain
data acquisition card that had been placed in the card slot of NI
pxi-1042q chassis. The speed photoelectric sensor was placed on the
shaft end of the fan to collect speed signal, which was connected to NI
data acquisition card successively. After all the instrument was linked,
the initial measurement was calibrated by LabVIEW software.