PSI - Issue 12

C. Braccesi et al. / Procedia Structural Integrity 12 (2018) 224–238 C. Braccesi et al. / Structural Integrity Procedia 00 (2018) 000–000

7

230

Experiment Numeric model

30

25

Output PSD [(m/s 2 ) 2 /Hz] 10 15 20

5

0

550

600

650

700

750

800

850

900

Frequency [Hz]

Fig. 3. Comparison between numerical and experimental acceleration PSD

800

Kurtosis= 7.36 Skewness=0.00031

600

400

200

0

-200

Amplitude [N]

-400

-600

-800

0

50

100

150

200

250

300

Time [sec]

Fig. 4. Input stationary non-Gaussian signal with k u = 7 . 36

Table 2. Comparison between input and output kurtosis. Nr. Signal type

Theoretical

Experimental Output stress k u

Numerical

Input k u

Output stress k u

1. 2. 3. 4.

Gaussian stationary

2.96 5.43 7.36 7.08

2.79 2.78 2.85 6.18

3.21 3.05 3.26 6.55

Non-Gaussian stationary Non-Gaussian stationary Non-Gaussian non-stationary

the system response is non-Gaussian with a kurtosis close to that of the excitation. It is therefore evident that, under these excitation conditions, the use of a frequency-domain approach for the fatigue damage estimation would lead to inaccurate results.