PSI - Issue 37

Rogério Lopes et al. / Procedia Structural Integrity 37 (2022) 73–80 R. F. Lopes et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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of the natural frequencies. On the other hand, the wind velocity is a factor that directly affects the frequencies led to reveal a significant raise.

Table 3. Natural frequencies result for TET mesh for rear and front wind pressure when wind hits at 50 (km/h), values are in Hz.

Empty bus

Natural Frequency

2 3 4 5 6

1

Mesh Density

Wind

Pressure

Fine

0.50 0.50 0.50 0.50 0.51 0.50 0.38 0.39 0.38 0.41 0.41 0.41

1.00 1.01 0.99 1.00 1.02 0.99 0.84 0.85 0.83 0.84 0.86 0.84

1.32 1.34 1.32 1.32 1.34 1.32 1.02 1.03 1.02 1.02 1.03 1.03

1.34 1.35 1.35 1.34 1.35 1.35 1.13 1.15 1.13 1.13 1.15 1.13

1.64 1.66 1.64 1.65 1.67 1.65 1.23 1.24 1.23 1.24 1.25 1.24

3.49 3.51 3.50 3.49 3.50 3.50 2.83 2.84 2.84 2.83 2.84 2.84

Medium Coarse

Front

Fine

Medium Coarse

Rear

Full bus

Fine

Medium Coarse

Front

Fine

Medium Coarse

Rear

Table 4. Natural frequencies values in the case if wind hits the bus in different areas at different velocity. Wind pressure ( ⁄ℎ) 1 ( ) 2 ( ) 3 ( ) 4 ( ) 5 ( ) 6 ( ) Null capacity Front 30 0.48 1.01 1.34 1.35 1.64 3.51 50 0.50 1.01 1.34 1.35 1.66 3.51 90 0.59 1.02 1.34 1.35 1.83 3.51 Rear 30 0.48 1.01 1.34 1.35 1.64 3.51 50 0.51 1.02 1.34 1.35 1.67 3.50 90 0.61 1.02 1.33 1.35 1.88 3.50 All 30 0.49 1.01 1.34 1.35 1.65 3.50 50 0.55 1.02 1.34 1.35 1.74 3.50 90 0.68 1.02 1.33 1.34 2.11 3.50 Full capacity Front 30 0.31 0.85 1.01 1.15 1.21 2.84 50 0.39 0.85 1.03 1.15 1.24 2.84 90 0.52 0.86 1.05 1.15 1.37 2.85 Rear 30 0.32 0.85 1.01 1.15 1.21 2.84 50 0.41 0.86 1.03 1.15 1.25 2.84 90 0.54 0.86 1.06 1.15 1.42 2.84 All 30 0.37 0.85 1.02 1.15 1.23 2.84 50 0.48 0.86 1.05 1.15 1.31 2.84 90 0.59 0.86 1.05 1.15 1.58 2.84

2.1. Comparison

In this section, a comparison is made amongst the numerical and analytical results. Considering the medium FE mesh, the bus with the null capacity and no wind affecting the body, Table 5 presents the results obtained for different natural frequencies with a calculated deviation. It must be noted that there is a greater approximation on the values, shown by the smallest deviation in the modes where the structure tends to be more rigid. When the deviation tends to be greater, there is a combination of several vibrational modes, such as torsion and bending, which analytically becomes difficult to calculate combined modes.