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.