1 Photoelastic experiment general process 1. The model outer ring model adopts epoxy resin type material with high sensitivity, small mechanical creep, good transparency and mechanical processing. Since the wedge-shaped curve of the outer ring of the roller type overrunning clutch is the Archimedes spiral, the processing is difficult, so the special manufacturer of the clutch is broached by a broach. Since the outer ring of the overrunning clutch is relatively small, the model is made the same size as the real object.

1. 2 working condition simulation outer ring is the active part of the overrunning clutch. Since the photoelastic experimental model stress freeze is performed in an oven, it is difficult to achieve the actual working condition of the clutch. This problem has caused many researchers to do nothing.

Through repeated consideration and design, the clutch condition simulation is finally determined: the outer ring is fixed and simplified by mechanics, and the load is transmitted from the heart wheel (sleeve) to the outer ring through the roller; the torque is loaded by the disc, the pulley, the nickel chrome Wire and so on, the torque is scaled by weight. This mechanical similarity simulation is in line with the actual working conditions of the outer ring.

In the production of the photoelastic model, the model needs to be annealed since the initial stress is accumulated during the curing process and during turning and broaching.

2 experimental results

After the frozen outer ring model is sliced ​​and photographed on a photoelastic instrument, the outer ring model stress fringe pattern is obtained.

3 Determine the stress concentration factor

For parts such as the outer ring, the geometrical features are similar to those of the curved bar, so the stress concentration factor is calculated by the empirical formula.

a = 1 + n 1 - n 2 n 1 + n 2 where: a stress concentration factor; n 1 maximum fringe value on the concave side; n 2 maximum fringe value on the convex side.

Using a photoelastic instrument to measure n 1 = 8. 093, n 2 = 3, the outer ring stress concentration factor is calculated as a = 1. 411.

4 Conclusion

It is intuitive and convenient to measure the stress concentration factor of mechanical parts with complex shapes by photoelastic method, which is worthy of promotion.

(Finish)

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