(\lambda_0, \lambda_1, \lambda_2, \lambda_4) via numerical integration over frequency range.
[ E[D] \textDK = f_p , C^-1 \int 0^\infty S^b , p_\textDK(S) , dS ] | Method | Accuracy (broadband) | Computational cost | Best suited for | |----------------|----------------------|--------------------|---------------------------| | Narrowband | Poor (conservative) | Very low | Nearly sinusoidal stress | | Wirsching-Light| Moderate | Low | Offshore/wind structures | | Dirlik | High (error <10%) | Moderate | General random vibration | | Zhao-Baker | High | Moderate | Bimodal spectra | 5. Practical Procedure for Spectral Fatigue Analysis Step 1: Obtain stress PSD From finite element analysis (modal or direct frequency response) or experimental measurements (strain gauge + FFT). vibration fatigue by spectral methods pdf
Damage is then:
| Method | Damage per sec | Lifetime (hours) | |---------------|----------------|------------------| | Time-domain RF| (3.2 \times 10^-8) | 8680 | | Narrowband | (7.1 \times 10^-8) | 3910 (underest.)| | Dirlik | (3.5 \times 10^-8) | 7930 (error 8.6%)| Damage is then: | Method | Damage per
[ E[D] = f_0 , C^-1 \left( \sqrt2\lambda_0 \right)^b \Gamma\left(1 + \fracb2\right) ] C^-1 \int_0^\infty S^b
[ E[D] = f_0 , C^-1 \int_0^\infty S^b , p_\textRayleigh(S) , dS ]