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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The experimentally determined results concerning stress and distance of HPSTC from the gear center are provided in Table 3.

Table 3. Experimentally determined stress and HPSTC

Maximum Stress σ (MPa)

Distance HPSTC from gear center r B (mm)

Test Number

Horizontal Load at HPSTC P u (N)

Isochromatic Class N

1 2 3 4

182.377 193.498 189.049 200.170

2 2 2 2

3.048 3.048 3.048 3.048

183.929 285.047 223.880 284.472

Spur gears with identical geometrical characteristics as the ones tested have been designed in Autodesk Inventor. The corresponding relations reported in (Raptis et al. (2010)) have been implemented. After having analytically determined the position of HPSTC the local stress field has been studied by means of a FE program ANSYS. Tooth profile and meshed tooth surface for the 18-teeth gear is shown in Figures 9 and10. The FE model consists of 2-D finite elements, whereas the material properties are typical of polycarbonate material PSM-1 (E=3.5 GPa, v=0.38). The tooth profile has been clamped at its low edge. A finer mesh has been applied in the vicinity of the tooth root. As the tooth is subjected to bending, stress con centration is expected to occur in that region. Thus, finer mesh has been applied in order to accurately capture the steep stress gradient.

HPSTC r B = 183.929 mm

Fig. 9 (left) and 10 (right). Tooth profile and meshed tooth surface of 18-teeth gear

The total load applied along the contact trajectory of the vertical cut of the gear at HPSTC is given by:

u P

(1)

P



cos α'

where: P u is the horizontal component of load acting normally on the tooth at HPSTC and α΄ is the load application angle with respect to the horizontal axis. The values of total load P , horizontal component P u , load application angle α΄ and maximum stress are shown in Table 4. The total load given in Table 4 has been applied in the numerical model in ANSYS, leading to estimation of maximum stress shown in Figs. 11-14.