PSI - Issue 10

K.G. Raptis et al. / Procedia Structural Integrity 10 (2018) 33–40 K.G. Raptis and A.A. Savaidis / Structural Integrity Procedia 00 (2018) 000 – 000

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Table 4. Loads acting on HPSTC and resulting maximum stress

Horizontal Load component HPSTC P u (N)

Total Load (normal to tooth) at HPSTC, P (N)

Maximum Stress σ max ( ΜΡα)

Test Number

Load application angle α΄ ( ο )

Gear 1

Gear 2

1 2 3 4

18N 28N 22N 28N

28N 18N 28N 22N

18.558 19.780 20.933 19.438

182.377 193.498 189.049 200.170

192.381 205.630 202.408 212.269

3.066 3.108 3.012 3.167

Fig. 11 (left) and 12 (right). Tests 1 and 2

Fig. 13 (left) and 14 (right). Tests 3 and 4.

In order to compare the stress, which was experimentally determined by means of photoelasticity (Table 3) and numerically estimated by means of FE (Table 4) stress, it should be normalized (Townsend (1992)), as:



bm bmcos α

  κ σ σ σ P

(2)

P

u

where σ u is the dimensionless stress, σ the real stress (MPa), b the tooth width (mm), m the gear module (mm), P the normal load acting on tooth at HPSTC (N), P u the horizontal component acting normally to the tooth symmetry axis (N) and α΄ the load angle with respect to the horizontal axis in degrees. Besides failure at the crucial section, it has been generally observed that due to fatigue caused by the high pressure acting in the region of the rolling cycles of the gears (whole load transferred by a single tooth of the pinion), cracks are