Response Spectra and Expected Fatigue Reliability: A Look at Hydroelectric Turbines Behavior

When we look at the fatigue reliability of a structure, its dynamic response will be closely related to the sensitivity to material properties both in terms of crack propagation and limit state. In this paper, we have identified 2 types of response spectra for hydroelectric turbines. The type 1 spectrum is simpler and was the first encountered. The type 2 spectrum is more complex and contains more Low Cycle Fatigue (LCF) stress cycles compare to type 1. Hence, reliability decreases faster for similar parameters values. For each spectrum, 3 scenarios have been identified. In this paper, we first present the simple typical response spectra expected, the reliability model and its relation to life expectancy with regards for High Cycle Fatigue (HCF). Next, we propose families of response spectra based on the observed data from in situ measurements. This is followed by a discussion on the sensitivity to material properties. Finally, we suggest specific guidelines and recommendations. We believe that a better knowledge of the structure response spectra with respect to fatigue reliability will help turbine operators and manufacturers to maximize the overall reliability of their equipment.